CA1084762A - Thermophilic aerobic digestion process for producing animal nutrients and other digested products - Google Patents

Abstract

THERMOPHILIC AEROBIC DIGESTION PROCESS
FOR PRODUCING ANIMAL NUTRIENTS AND OTHER DIGESTED PRODUCTS
Abstract of the Disclosure Animal waste matter, for example manure produced by hogs, sheep, cattle, chickens and humans is aerobically digested at thermophilic digestion temperatures to produce single cell, proteinaceous material suitable for feeding to animals as part of the animals' nutritive diet. Animal waste matter is introduced into a digesting zone that is sufficiently insulated to prevent any substantial heat loss from the digesting material during the digestion process. An oxygenating gas such as air is introduced into the digesting material during all phases of the digestion.
The digesting material is simultaneously vigorously agitated.
The waste material is placed into the digester at ambient tempera-tures and is contacted with the oxygenating gas at a rate and is agitated at a level effective to cause thermogenic microbial digestion of the materials present in the waste matter. Since the microbial digestion is thermogenic and because the digester is insulated the temperature of the digestion waste material will rise from ambient to thermophilic digestion temperatures. There-after, the digesting mixture is continuously contacted with the oxygenating gas at a rate and is agitated at a level effective to maintain the thermophilia digestion temperatures for a period of at least four days.
In a broader aspect of the present invention, lignocel-lulosic materials, such as woody plants, as well as biochemically degradable organic materials, such as sewage sludges, organic domestic and industrial wastes and animal, vegetable and fruit processing plant wastes, are digested by the thermophilic micro-organisms present in the foregoing process. When the foregoing process has reached thermophilic digestion temperatures, ligno-cellulosic material and biodegradable organic wastes can be placed in the digester, preferably in chipped or finely divided form. The lignin is digested out of the lignocellulosic complex in a period of about four days after placement in the digester, leaving free individual cellulosic cells that can be assimilated by animals. Likewise, biodegradable materials are digested in a similar amount of time. Alternatively, lignocellulosic material or biodegradable material in the form of an aqueous slurry can be placed in a digester with a small quantity of animal waste matter or a thermophilic bacterial culture extracted from the fecal matter digestion process described above. Thereafter the slurry is agitated and aerated in accordance with the foregoing require-ments. The aqueous slurry will gradually rise to thermophilic digestion temperatures and can be maintained at those temperatures to substantially digest the lignin out of the lignocellulosic complex or to digest the biodegradable material, as the case may be.

Description

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19 ¦ Background of the Invention .
20 ¦ The present invention rel.ates to aerobic digestion .
21 Iprocesses that are self generating and self sustaining without 22 Ithe:addition of external heat, and more particularly to such a 23 Ithermophilic aerobic digestion process for producing foodstuffs 24 ¦ for animals from animal waste matter, and in another aspect : .
relates to a thermophilic aerobic digestion process for digestlng : ~:
26: materials containing llgnocellulosic complexes, such as are found:
27 ::.in woody plants, and for digesting other biodegradable waste 28 materi~ls for a~variety of end uses including feeding to animals.
29 In the course o~f primary agricul-tural production, animals are utilized in the conversion of basic feed ingredients :
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into mllk, meat, eggs and relatod high nutrient sources for human consump~ion. In the conversion process, animals eat foodstuf~s such as grass and grain and create byproducts, namely manure, which is presently classed as a waste product and pollutant. The growing human population density in North America and throughout the world has required a more intensive and selective animal production to meet the increasing demand for foodstuffs for human consumption. The result of the higher demand for Eood production is a greater animal population with a concomitant and consequential pollution po~ential caused by an increasing amount o animal waste products created. Moreover, the more intensive animal production facilities are growing in competition with expanding urban deYelopment, compounding the pollution problem, whereas in the past agricultural areas contained small, widely spread farms that did not create a burden on the environment through their waste products.
Presently, as in the past, animal waste products are disposed of by any convenient method. For example, the animal waste products have been spread in untreated form over the land as a fertilizer. As the volume oE animal waste products has increased, the latter disposal method has ~ecome inadequate as the untreated waste product tends t~ contam:inate the surrounding streams and rivers as well as adversely afect the subterranean water. Moreover, it has become increasingly common for the runoff from animal feedlots to gain aocess to the streams and rivers in large quantities, causi~g a serious pollution problem. ;~
~onsequently, interest has been recently spurred toward finding a `~
means to detoxify animal waste products and to render them harm-less to the environment. Even more recently, interest has been deve-loped in creating a foodstuff from the animal waste products that can ~ 1084~6Z
1 be refed to ~nimals as at least a portion of their nutritive

2 diet .

3 Several techniques to detoxiEy animal waste products

4 have been attempted, including forced dryin~ and microbiological di~estion. Drying of the byproducts is a relatively expensive 6 process requiring a significant capital investment in equipment 7 and controls as well as requiring a hi'gh external energy input.
8 Thus, more interest has recently been generated in microbiological 9 digestion processes as there is a potential that a smaller capital ! ' investment and lesser amounts of external energy input will be 11 required.
12 One attempt at microbiologically digesting animal waste 13 products is disclosed in United States Pa'tent 3,462,275 issued to 14 W. D. Bellamy for a waste conversion process and product. Bellamy inoculates animal waste matter with thermophilically active 16 microorganisms from sources such as compost piles and from hot 17 sprin~s and anomalous hot earth areas. Bellamy flocculates 18 animal waste matter by the addition of Elocculating agents to 19 reduce the concentration of inorganic solids and thereafter inoculates the supernatent liquor with a thermophilic aerobic 21 microorganism. Thereafter, the inoculatèd waste product is 22 placed in a thermophilic aeroblc growth chamber and heated to 23 thermophilic digestLon temperatures. ~fter ~igesting for a short 24 perlod of time, the digestecl product is separated into a solid and liquid by centrifuging and filtering. The liquid is disposed 26 of by conventional means while the solid portion is dried and 27 pac]ca~ed for use as an animal foodstuEf. Although the Bellamy 28 process is, on its fac'e, efficacious to produce an animal foodstuff 29 from animal waste matter, it is to be observed that the Bellamy process requires the application of external heat and uses only a 31 very small portion of the inpu-t product.
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It is accordingly a broad object o~ the present invention to providc a thermophilic ~Lerobic di~estlon process for animal waste products, nanlely manure, to produce a protinaceous foodstuff that can be refed to anima]sas part of the animal's nutritive diet. Additional objects of the present invention are to provi~e a thermophilic aerobic digestion process that requires the addition of no external heat; to provide a thermophilic digestion process ;~
that deodorizes the animal waste products and renders them harmless to the environment; to provide a thermophilic ~erobic digestion process that increases the protein content of the digestion product over the protein content of the initial waste product being digested; to provide a thermophilic aerobic digestion process that kills all pathogens in the waste products including coliEorm and salmonella bacteria, virus, worms and larvae and to provide an economical thermophilic aerobic digestion process that requires a minimum capital investment and which therefore can be installed on site at animal production sites.
It is a further broad object of another aspect of the ~;
invention to provide a thermophilic aerobic digestion process that is capable of digesting materials containing lignocellulosic complexes. Other objects of this aspect of the invention are ~o provide a thermophilic aerobic diges~ion proccss tha~ can m~cro-biologically digest lignocellulosic complexes in a very short time; to provide a thermophilically digested product from ligno-cellulosic complexes that does not contain harmful byproducts as yielded in chemical pulping processes and that does not produce the undesirable odor and disposal problems normally associated ;~
with pulping processes; and to provide a thermophilic aerobic digestion process for lignocellulosic complexes that yields a new source o~ nutrients l~n digestible form for ~eeding to animals.

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. .. : .: ; . . . . ~ . . , It is anotller broad object of the present invention to provide a thermophilic aerobic digestion process that is capable of digesting bio-chemically degradable material such as sewage sludges, organic domestic and industrial wastcs, and animal, vegetable and fruit processing plant wastes.
Other objects of this aspect of the invention are to provide a thermophilic aerobic digestion process that can microbiologically digest such biodegrad-able materials in a very short time -to provide a digested product that has an increased protein content relative to the biodegradable material; and to provide a process for stabilizing sewage sludges and other biodegradable material so that they can be disposed of economically and safely.
Summary of the Invention The present invention is directed to a process for thermophilically digesting animal waste matter under aerobic conditions to produce a protein-aceous end product. According to the present invention, there is provided a process for using thermophilic bacterial microorganisms or thermophili-cally digesting an aqueous mixture of a biochemically degradable organic material under aerobic conditions comprising the steps of:
introducing said mixture into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, said mixture comprising `;
nt least about 5 percent by weight of animal fecal matter, based on the total mixture, continuously introducing an oxygenating gas into said mixture and continuouslyJ mechanically and vigorously agitating said mixture while introducing said oxygenating gas, said oxygenating gas being introduced at a rate and said mixture being agitated at a level effective to cause and promote the temperature of said mixture to rise from ambient temperaturesJ through mesophilic temperaturesJ to a temperature o at least 55C without the addition of external heat to said mixture to form a digested productJ said ,, ~
oxygenating gas further being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological ; ;

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oxygen demalld of thc mixture, sa;d mixture being agitated and said gas being introduced adjacent the bottom of said digester, continuing to agitate said mixture at a level and to introduce said oxygenating gas at a rate effective to Inaintain said temperature of at least `
55C without the addition of external heat, said oxygenating gas being introduced at a rate sufficient to raise the dissolved oxygen level in said mixture to and maintain it above about 1.0 mg/l. after the temperature of said mixture has reached 55C. The temperature rise is thus created by the activity of thermoge~ic bacteria naturally occurring in the animal waste matter. Thus the process is self-initiating as it requires no heat input from external sources to raise the temperature to thermophilic digesting temperature. Thereafter, the ,, .

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1 waste matter is ayitated at a level and the oxygenating gas is 2 introduced at a rate effective to maintain the thermophilic 3 digestion temperatures for a period of at least four days. The 4 temperature of the diyesting material is maintained by the activity of the thermophilic, -thermogenic bacterla naturally occurring and

6 developing in the digesting material. By operating -the digestion

7 process in accordance with the present invention, no heat input is required even to maintain the thermophilic digestion conditions 9 for periods up to eight days or more. Moreover, no inoculation of the waste materials with a foreign microbe is necessary as the 11 naturally occurring bacteria in the waste materials are adequate 12 to produce these results. rrhe entire digested prodùct fro~ the 13 digester can then be directly refed to animals as a portion of 14 their nutritive diet.
A broader aspect of the present invention provides a 16 process for thermophilically di~.3esting an aqueous mixture of a 17 biochemically degradable organic material under aerobic conditions~
18 The aqueous mixture is introduced into a digesting zone that is 19 sufficiently insulated to prevent substantial heat loss from the digesting zone. To initiate the digestion process one of three 21 altern~tives are avilable. First, the a~ueous mixture can be 22 combined with at least a minor portion of animal waste matter.
23 '~he aqueous mixture~can then be introduced into a digesting zone 24 and aerated and agitated in a manner identical to that described above in relation to the digestion of the animal waste matter.
26 Alternativel~, the aqueous mixture can be inoculated with thermo-27 philic, thermogenic bacteria taken from the thermophilic digestion 28 process of animal waste matter as described above. As a further 29 alternative, the aqueous mixture of biodegradable material can be 30 introduced into a digesting zone containing animal waste matter -~ - 1(3~76'~ -1 ¦already digestlng ~t -thermophllic digestion temperatures in 2 ¦accordance with the process described above. When the aqueous 3 ¦mixture is introduced into the digesting zone along with animal 4 ¦waste matter or inoculum from thermophilically digesting animal 5 ¦waste matter, oxygenating gas is introduced into the mixture and 6 ¦the mixture is vigorously agitated while introducing the gas.
7 ¦The gas is introduced at a rate and the mixture lS agitated at a

8 ¦level effective to cause and promote the temperature of the ¦mixture to rise to thermophilic.digestion temperatures, if not 10 ¦already at such temperatures, without the addition of external 11 ¦heat to the mixture. Thereafter, the aqueous mixture is agitated 12 ¦at a level and the oxygenating gas is introduced into the mixture 13 ¦at a rate effective to maintain the thermophilic digestion tempera-14 ¦tures for a period of time sufficient to substantially digest the 15 ¦biodegradable matter or at least long enough to detoxify the 16 ¦ animal waste matter. Depending upon the initial biodegradable 17 ¦ material digested in accordance with the foregoing process, the 18 ¦ protein content of the digested products can be increased over 19 ¦ that of the material introduced into the digester. Moreover, the 20 ¦ available foodstuffs in the original material are broken down ~1 ¦ into a more usable form so that the digested product can be refed .
22 1 to animals as at least a portion of their normal nutritive diet.
23 ¦ In still another aspect, the present invention provides ~4 1 a process Eor microbiologically digesting materials containing lignocellulose complexes. Animal waste matter and a lignocellulosè . .
26 complex-containing material are combined in a digester to form a 27 digestion mixture. The temperature of the mixture is then raised 2~ to thermophilic digestion temperatures in accordance with the .
29 procedure used to raise the waste matter to thermophilic digestion 30 ~ tempera=u s as set forth above. When the mixture has been ,, . .' :
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l ¦raised to ~hcrmo~ ilic diges~irlg tempcratures, inkroductiorl of 2 ¦the oxygenatincJ c3as into the mixture is continued at a rate and 3 ¦the agitation of the mixture is continuecl at a level effective ~o 4 ¦maintclin the temp~rature oE t~le m:ixture ~t thermophilic digestion 5 ¦temperatures until the li~nocellulose complex-containing material 6 ¦is substantial]y diyested. In one form oE the invention, -the 7 ¦lignin is substantially digested or solubilized, leaving cellulosic 8 ¦cells and cell fragments in the digested product. By continuing

9 ¦the digesting process for a longer time, the cellulosic cells can

10 ¦also be microbiologically digested. The digested product contain-

11 ¦ing the freed cellulose celis can be fed to animals as a portion

12 ¦of-their nutritive diet. Thus the present invention provides a

13 ~method for direct and rapid conversion of lignocellulose material

14 ¦into single cell protein that can be used as a source of nutrients

15 ¦and energy for animals and that was heretofore unavailable.

16 ¦ Detailed Description

17 ¦ Microbiological digestion processes are those in which

18 ¦microbes, such as bacteria, digest waste matter and produce

19 ¦certain kinds of byproducts, depending upon the digestion environ-

20 ¦ment. Typical aerobic digestion processes of the prior art occur

21 ¦under conditicns where oxygen is available to at least a portion ,~J

22 ¦of the microbes in the digestion mixture. The bacteria operaking

23 ¦in a particular aerobic digestion process are classiEied as

24 ¦psychrophilic, mesophilic and thermophilic, dependent upon the

25 Itemperatures at which the particular organisms survive and metabo-

26 ¦lize. Tho~e of particular interest to the present invention are

27 ¦the thermophilic bacteria which generally digest organic matter

28 ¦at temperatures from 49C. up to 80C. and sometimes higher.

29 ¦ In one embodiment of the present invention, thermophilic

30 ¦bacteria that can digest animal waste matter under aerobic condi-

31 tions are employed to produce a proteinaceous digested product _g_ .~ . .

~0~ 6f~ _, . , .' 1 that c~n bc r~Eed to animals. s~sically, animal waste matter is 2 introduced in~o a digcstincJ zone, hereafter reEerred to as a 3 digester. The digester is sufficiently insulated to prevent any 4 substantial ~mount oE heat los5 through the walls and the bottom 5 o~ the diyester. In one embodiment, the top oE the digester can 6 be left open to the atmosphere, but is essentially insulated by 7 an aerated, foam-like layer of digesting material as will be 8 hereinafter described. After the waste material has been intro-9 duced into the digester, an oxygenating gas, such as air, is 10 introduced into the digester at a predetermined rate to create an 11 aerobic environment for the bacteria naturally occurring in the -lZ animal waste matter. At the same time the animal waste matter in 13 the digester is vigorously agitated so that all of the bacteria 14 in the digester have oxygen readily available for purposes of 15 metabolizing and digesting the organic matter present in the 16 digester. As will hereina~-ter be explained, the rate at which 17 the oxygenating gas is introduced into the digester and the level 18 of agitation of the waste material in the digester is critical.
19 That is, a substantial amount of air must be continuously intro-20 duced into the digester while the waste material is continuously 21 and vigorously agltated in order to achieve the results of the 22 present invention. The oxygenating gas is introduced into the 23 digester at a rate and the waste material is vigorously agitated 24 at a level efEective to cause the naturally occurring microorgan-25 isms in the digester to begin digesting the organic material 26 under aerobic conditions. Normally, the waste matter when placed 27 in the digester is at ambient temperatures, which are somewhat 28 below the thermophilic digestion temperature range. However, by 29 agitating the waste materials sufficiently and by introducing an 30 effective amount of oxygenating gas, the microorganisms begin to ' -10-:

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digest the waste materials with a thermogenic biochemical reaction.
Sincc the digester is sufficiently insulated to prevent any substant.ial heat loss rom the digesting materials, the heat generated by the biochemical reaction will be substantially retained within the digesting mass, causing the temperature of the digesting material to rise and ultimately achieve the thermo~
philic digestion temperatures. It has been found that under the - ;
conditions described below, the animal waste matter will reach `~
thermophilic digestion temperatures in from two to four days after the waste matter is introduced .into the digester under batch reaction conditions from an ambient temperature of from 0 *o 20C. :
~fter the waste matter has reached thermophilic digestion `~
temperatures in the digester, the oxygenating gas is still contin- ~:
uously introduced at a rate and the waste matter is still vigorously "
agitated at a level effective to maintain the temperature of the waste matter in the thermophilic digestion temperature range. `. -Again, the rate at which the oxygenating gas is introduced into ::
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the digester and the lavel at which.the waste matter is agitatecl ;. ~ .
is critical. If the rate at which the oxygenating gas is introduc~
ed into the digester drops below a certain critical rate~ the thermophilic microorganisms digesting the waste material will cease to be suficiently active to maintain the tempera~ure within the thermophilic digestion temperature ranges. However,.if the rate :.
of introduction of oxygenating gas is too high, the digesting mixture will tend to cool and drop below the thermophil.ic tempera-. ~, .
tures required by the present invention. It i5 believed that this cooling effect lS brought about by heat transfer from the digesting mixture to the gas being introducecl.and the subsequent 3Q . ~escape of the thus heated gas to the atmosphere. Likewise, if ~ ~`
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1 ¦th~ ~yltation l~vc:L clrol~s ~low Ll ccrt ~.lin k~v~!l., n,~mel~y bc~Low a 2 ¦lcvcl at which all parts of thc digestinc3 mass are in turbulent 3 ¦rnovement so that no part o~ the diyestincJ mass is unclergoing an 4 ¦aerobic di~estion, the same adverse results will occur, i.e., the 5 ¦thermophilic microorganisms will not be able to maintain the 6 temperature of the digesting waste material in the ther~ophilic 7 range.
8 The thermophilically digesting waste matter is continu-9 ously agitated and aerated to maintain the thermophilic digestion 10 temperatures for a period of at least about Eour days. After 11 this minimum digestion period, the protein level of the resulting 12 digested product has been increased on the order of from 2% up to 13 2s% by weight over that of the original waste material. It has 14 been found that waste material digested in accordance with the 15 foregoing process can be successfully fed to ruminant animals at 16 levels up to about 50~ by weight of their normal nutritive diet, 17 to swine at levels up to about 30% by wéight of their normal 18 nutritive diet, and to poultry at levels of up to about 15~ by 1~ weight of their normal nutritive intake, depending upon whether 20 the digested product is fed in a liquid form directly rom the 21 digester or whether it is first dried.
22 The oregoing process produces a proteinaceous material 23 that can be re~ed to animals from what, in general, i9 referred 24 to herein as "animal waste matter." By "animal waste matter" it is meant the fecal matter or manure produced as a byproduct of an 26 animal's digestion of ood. There is no limitation as to the 27 particular type of digestive system of the animal as the process 28 has been successfully operated utilizing cattle manure, hog 29 manure, sheep manure, horse manure, mink manure, chicken manure, ~0 or human waste as the starting material. It is to be understood ~ )8~76Z `---1 that the microorganisms naturally occurring in the animal was-te 2 ma~ter al^e those which are responsible for the microbial action 3 in the dicJestion process of the present invent,lon. No inoculation 4 from a cultured bacteria medium is necessary to effect the initial temperature rises in the process of the present invention or to 6 ¦ maintain the thermophilic digestion temperatures onc'e they are l~
7 ¦ reached. Preferably, the animal waste matter is in raw form and 8 1 has not been subjected to any pretreatment processes. It 9 ¦ is also preferable that the animal waste matter be reasonably 10 ¦ fresh, although it is possible ~o effect the presen-t invention 11 ¦ with animal waste matter that has been in storage for up to 12 ¦ thirty days or longer or which has received anerobic treatment, 13 1 such as activated human sludge.
14 ¦ To be economical, it is normally pre~erred that the dry 15 ¦ solids content oE the fecal matter in tjhe digester be at least ' 16 1 about 5~ by weight based on the total material in the digester. ~ ' 17 ¦ It has been found that i the dry soli~s pontent of the waste ', 1~ ¦ matter in the digester is ini'tlally below abou-t 5~ by weight that `19 1 the digestion process of the present invention cannot,be effected. ¦ , 20 ¦ That is, with any level of aeration and agitation it is difficult, 21 1 if not impossible, to promote the desired temperature rise from 22 ¦ambient condikions to thermophilic digestion temperatures by the 23 action o~ the naturally occurring thermogenic bacteria. Moreover, 24 even i~ it is possible to reach thermophilic digest.ion temperatures with solids content less than 5~ by weight during the initial 26 phases of the process, the thermophilic digestion temperatures 27 cannot be maintained for an adequate amount o~ time to digest the 28 waste materials. It is believed that this level of solids content 29 is necessary to provide a sufficient amount of digestable material 30 ~for the t rmophili_, thermogenic bacteria to continuously thrive , . , ..

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1 ¦~lnd to yeild ~I suf.ficicnt amount of ll~at -to ca~lsc the desired 2 ¦temperature rise ~nd temperature maintenance in the digesting 3 ¦material.
4 Sinc~ manure from dif.Ee.rent animclls will vary in its original water content when excreted, it may be necessary to add 6 water to the animal waste matter prior to being placed in the 7 digester or immediately after it is placed in the digester. The 8 addition of water will bring the viscosity of the waste matter i:
9 down to a reasonable level so that large amounts of energy are . .
not required -to agitate the waste matter. Under conditions in 11 many animal feed lo-ts, the fecal material from the feeding pens 12 is washed out with a water spray into troughs'and stored in tanks 13 for a short period of time. The aqueous fecal matter so stored 14 is normally adequate for direct placement into the digester. If the dry solids content of the animal waste ~fecal) material 16 placed in the digester is much greater than abou-t 20~ by weight, 17 ¦ the power requirements for agitating the digesting material rise 18 ¦ significantly because the viscosity of the material is relatively 19 ¦ high; thus it is preferred to maintain the dry solids content of 20 ¦ the fecal material below about 20~. It has been found that the ,:
21 ¦ most efficient and economical processing conditions from the ~.
22 1 agitation energy input standpo~nt dictate a dry solids content of 23 ¦ between about 5~ by weight and about l~ by weight oE the -total 24 ¦ aqueous mixture in the dic3ester when the process is initiated.
25 1 It is absolutely necessary in order to effect the 26 1 process of the present invention that the digester be insulated 27 ¦ to prevent. substantial heat loss through the walls and the floor 28 ¦ or bottom of thc digester. Normall~, digesters are constructed 29 ¦ from steel but can be constructed from fiberglass reinforced 30 ~polye~ter esins. Norm~lly a layer of ol~sed ceIl foam insulatioD

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~ 762 1 such as a polyuretllane Eoam having a thickness oE on the order of 2 l -to 3 inches is c~dequate -to insulate the sides and the bot-tom of 3 the digester to prevent substantial heat loss. If ambien-t condi-4 tions would normally cause a higher heat loss, such as high wind velocities or very low tempera-tures (below 0C.), additional 6 insulation may be required to adequately prevent heat loss so 7 that the process temperatures can be-initially raised to the 8 thermophilic range and thereafter maintained in the thermophilic 9 range for extended periods. The digester size is not critical, 10 but as will be seen later, the amount of agitation and rate of 11 aeration must be adjusted in accordance wi-th the volume of digest-12 ing material present in the digester. i~
13 A layer of foam is formed on the surface of the digesting 14 material by the aeration process, which layer serves to insulate the top of the digester to prevent heat loss in an upward direction.
16 As will be seen later, the preferred form o aeration causes the 17 air to be dispersed into relatively smalL bubbles in the digesting 18 material. This aeration procedure desirably produces a foam 19 layer comprising relatively small bubbles on the top o the liquid digesting material, which provides an excellent insulating . ~ :
21 layer to prevent substantial heat loss in an upward direction. i`

22 It is preferred that the thickness of the foam layer be maintained 23 at about 6 to 8 inches or less. IE it is not, the faam layer 24 will tend to grow beyond;that helght and possibly spill over the open top of the digester. The foam level is maintained at 6 to 8 26 inches or less by using a conventional foam breaker mounted on a 27 platform positioned across the top of the tank.

28 The pH of the starting materials need not be adjusted 29 as the slightly alkaline pH of relatively fresh fecal matter is adequate to support the desired mlcrobiological reaction. It is ~' ' -1~-. .

. -'` 1 ~ 7~Z `-1 ~reEerred however ~hat the ~ll oE the material b~ maintain~d 2 be-tween ~bout S.0 and about 8.5 with a most pre~erred pH of on 3 the order of from 5.9 to 7.5.
4 The thermophilic digestion temperatures -that are 5 considered to be operable within the purview of the present 6 invention are in the range of from 49C. to abou-t 80C. although 7 the best results in accordance with the present invention have 8 been obtained when the thermophilic digestion temperatures have 9 been maintained above 55C., and most preferably in the range of j 10 from 55C. to 75C. If the digested product is to be refed or 11 safely disposed of, it is most important -that the thermophilic 12 digestion temperatures be maintained above about 55C. for a 13 minimum period of about ten minutes to thirty minutes i`n order 14 that certain pathogens, such as salmonella bacteria, coliform 15 ¦ acteria and helminths are destroyed. Certain viruses and other 16 athogens present in the mixture may require a somewhat longer 17 esidence time for a complete kill at 55~. If the temperatures 18 re not maintained for a sufficient period of time, certain of 19 he pathogens may carry ov~er into the digested product and thus ontaminate it so that is cannot be safely refed to animals. If, 21 o~ever, the thermophilic digestion~mixture is maintained at a 22 temperature of above 65C. for on the order~of about.l4 minu-tes 23 r more, it has heen found that the pathogens, virus~s and worm 24 arvae will be killed~
The rate at which the digesting material is aerated is 26 ritical. If insufficient oxygenating gas, preferably air, is 27 upplied to the digesting tank, the thermophilic digestion 28 temperatures cannot be achieved or maintained, and thus the 29 igested product containing proteinaceous material capable of ., eing refed to animals will not be produced.

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1 During the initial start up phase~ of the digestion 2 process during which the ~emperature of the animal fecal material 3 is being raisecl to thermophilic digestion tempera-tures, the 4 digestlng material exhlbits a very high biological oxygen demand 5 (BOD) . During this initial period i-t is critical~that the BOD
6 requirements o~ the digesting material be me-t by supplying a l;
7 sufficient amo~lnt of oxygenating gas. If the BOD requirements 8 are not met, the proper succession of microorganisms will not 9 develop and thus the temperature of the digesting mixture will 10 not rise to the thermophilic range. Dissolved oxygen concentra-11 ions on the order of 0.~ mg/l. have been observed during initiatior 12 of the process while oxygenating air is supplied to the mixture. ;~
13 his low level of dissolved oxygen may remain ~or two to four 14 ays. However, when the temperature oE the digesting mixture pproaches and achieves the thermophilic digestion temperature 16 ange, the dissolved oxygen level will begin to rise~
17 Once thermophilic digqstion temperatures are achieved, 18 the dissolved oxygen level of the digesting mixture will rise to 19 about l.0 mg/l. or higher when the initial aeration rate is held onstant. If the initial aeration rate is continued as the 21 issolved oxygen level increases, the foam produced on top of the 22 igestiny mass will significantly increase. Thus it has been 23 Eound necessary in most cases to reduce the aeration rate once 2~ thermophilic digestion temperatures have been achieved to decrease he foam production to a level that can be managed by a conventional foam breaker. While decreasing the foam production, however, the 27 issolved oxygen level in the digesting mass mus-t be maintained 28 above about l.0 mg/l. once the dissolved oxygen level of l.0 . ,, 29 g/l. has been achieved when the fecal matter is digesting at i~
hermophilic digesting temFeratures. It is prererred that the , ' l ~

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1 oxygen level be maintained between about l my/l. and 4.5 mg/l., 2 although disso'Lved oxygen levels up to the oxygen saturation 3 point of the fecal matter are effective. The,preferred temperature 4 range of from 55C. to 75VC. is obtained when the dissolved oxygen level is maintained between about 2.0 rng/1. and about 3.0 6 mg/l. If the dissolved oxygen level drops below the 1.0 mg/l.
7 level while the thexmophilic digestion temperatures are being 8 maintained, the rate of protein production will be lowered as 9 well as, the nutritive quality of the digested end product. ' ,1, 10 Moreover, the proper succession of microorganisms necessary to 11 achieve the thermophilic digestion may not be developed if the 12 ¦ issolved oxygen level is allowed'to drop'below 1.0 mg/l. Also, ','~
13 1 as stated above, the rate at which oxygenating air is introduced 14 cannot be too high or the temperature of the digesting mixture 15 ¦ will drop below the thermophilic temperature range required by 16 the present invention. , 17 The preferred oxygenating gas i,s air, primarily because 18 f its ready availability and the generally low cost of compressing 19 atmospheric air, sufficiently to inject it into the digester.
~20 When air is introduced as the oxygenating gas into the bottom of 21 digester having a diameter of four feet and a li~uid depth of 22 bout four feet, it has been found that a rate of aeration of at 23 least about 0.02 volumes of air per minute per unit volume of 24 igesting material, that is the total aqueous mixture, is normally ,~
equired to initially raise the waste matter to thermophilic 26 digestion temperatures. If the rate of air introduction exceeds 27 about 0.02 volumes of air per minute per volume of digesting 28 material in -this size digester, foam production will b,e excessive 29 nd may cause foam to overflow from the digester. On the other , ;
and, aeration rates below 0.01 volumes of air per minute per ~.
'-18-~ , ' ,, ' . .1l ~ 76Z `~

1 ¦volumc o~ cl.icJostinc~ Inaterial will E~ro~oce an insuEicicnt amount 2 ¦of fo~m to illsulate the top of the dic3ester and to supply the 3 ¦microorganisms with sufficient oxygen to crea-te the thermogenic 4 ¦digestion required to raise the termperature of the digesting 5 ¦mass to the -thermophilic temperature range. ~fter -the thermophilic 6 ¦digestion temperatures have been reached in a digester of the 7 ¦ size just mentioned, the best digested product has been obtained 8 ¦ when air is introduced at rates of between O.Ol and 0.02 volumes j~ ;
9 ¦ of air per minute per volume of digesting material.
The exact quantity of oxygenating gas that must be 11 introduced into the digesting mass in accordance with the present 12 invention is critical in that if too much or too little is 13 introduced, either the requisite temperature rise to thermophilic 14 digesting temperatures will not be achieved, or the temperatures 15 cannot be maintained in the thermophili~c digesting range. The 16 exact amount of oxyyenating gas that must be introduced varies 17 with the quantity oE the digesting mass, the solids content of 18 the mass, the temperature at which the mass is digesting and the 19 efficiency with which oxygen is transferred from the oxygen gas 20 to a dissolved state in the digesting mass. In any event, the 21 critical parameter ls that a sufficient amount of oxygenating gas `~ ;
22 be introduced during the initial digestion phase so that the 23 thermogenic microbiological activity in the digesting material 24 will cause the temperature of the makerial to rise from ambient 25 to the themophillc range. Thereafter, it is critical that an 26 amount of air be supplied that is effective to maintain the 27 thermophilic digestion temperatures for a period of at least four 28 days.
29 Another descriptive parameter for the critical aeration 30 rate of the ~igestirg material is that each of the microbes in ~' ., , ' . ~

,:
' .
~, ., ' ,, . ' , , .
, ' ~8~t7~Z , 1 the dlc~esting waste matter MUSt be exposed to available oxygen at 2 least once every two and one-half minutes. This exposure rate is 3 accomplished not only by aerating at the rates set forth above 4 but also by vigorously agitating -the digesting waste matter at a level adequate to maintain thi.s exposure rate. During both the 6 initial start-up phase of the digestion reaction and while the 7 thermophilic digestion temperatures are being maintained, the 8 waste material must be sufficiently agitated so that every 9 portion of the digesting material is moving within the digester.
10 Moreover, the agitation must be at a sufficient level to cause 11 every portion of the surface of the digesting material to roll, 12 indicating that the digesting material is in a very turbulent 13 condition within the digester.
14 The foregoing contact rate between the microbes in the 15 digesting material and the dissolved oxygen in the digester was 16 empirically determined by observing the rate at which the bacteria 17 consume the available oxygen. That is, if aeration at the rates 18 set ~orth above is stopped, the bacteria wi.ll completely utilize 19 the available oxygen supply, i.e., the dissolved oxygen, in the digesting material in about two and one-half minutes or less.
21 For example, an aqueous mixture of fecal matter oontaining about ~;~
22 10% by weight of dry solids that is sàturated with oxygen and 23 that is digesting at 60C. in accordance with the present invention 24 will consume all of the available oxygen in the mixture in about two and one-hal~ minutes when the supply oE oxygenating gas to 26 he mixture is stopped but the agitation is continued. Thus the 27 aerobic bacteria present in the material being digested in accor~
28 ance with the present lnvention oxidizes organic matter at a 29 ery rapid rate, requiring rapid recontacting with available 30 xygen at least every two and one-half minutes. Even greater ;~
., -' . . ,~:, ~ -20-476~ ~

1 rates of agitation are required when t'he dissolved oxyyen levels 2 are less than saturation in the digesting mass.
3 Moreover, it has been found that it is necessary to 4 continuously cleanse the digesting material of carbon dioxide.
Removal of the carbon dioxide will allow a better contact rate 6 between the microorganisms in the digesting material and the 7 dissolved oxygen available in the digesting mixture. Carbon 8 dioxide is removed from the digesting material in accordance with 9 the present invention by the oxygenating gas passing through the mass of digesting material, which replaces the carbon dioxide and 11 drives the carbon dioxide to the surface of the digesting material.
12 The carbon dioxide can then escape from the digester through the ~'' 13 foam layer normally formed on the top of the digesting material.
14 In a most preferred form of aeration and agitation, the oxygenating air is introduced into a cylindrical digesting mass 16 via a sparger pipe adjacent the bottom o~ the cylindrical mass.
The sparyer pipe contains a check valvé to prevent digesting 18 material from entering the pipe. Air is supplied to the pipe by 19 an air compressor at the rates described above. A turbine blade mounted at the bottom of a rotatable'shaft oriented coaxially 21 with the cylindrical mass is positioned immediately above the 22 outlet of the pipe. The turbine blade is so oriented and configurec 23 as to'drive fluid upwardly from adjacent the boktom oE the digest-24 ing mass and force it up thraugh the central portion of the digesting mass, causing the liquid to roll on the surface of the 26 digesting mass. Thereafter, the liquid circulates down the sides 27 of the diges-ting mass and is recirculated by -the turbine. As 28 this occurs, the air introduced from the pipe is fed directly 29 through the turbine blade so that the shearing action of the turbine blades finely divides and disperses the oxygenating air, . .
~

~ -21- ' .
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. 1, ~ 76Z

1 thereby maintainin~ bett~r ancl more frequent contact between the 2 availablc air in the digesting mass and the microorganisms in the 3 m~ss. If desired the direction of rotat~on of the turbine can be 4 reversed to cause the Eluid to Elow in the opposi-te direction.
The fecal material mus-t be digested at thermophil1c 6 digesting temperatures for a period of at least four days. After ,~
7 about eight days at thermophilic digesting temperatures, it has 8 been found that the protein level in the digested product begins 9 to fall. Thus the optimum range for protein production requires 10 that the waste ma-terial be d}gested at thermophiIic temperatures 11 for a period of from four to eight days. It has also been fo~und 12 that after about five days at thermophilic digestion temperatures, 13 no significant increase in the protein level of the digested 14 product is obtained~ Therefore it is preferred that the fecal 15 matter be digested at thermophilic digestion temperatures for 16 only about four to about five days. When the process of the 17 present invention is conducted under batch conditions, that is, 18 when the digestion process is initially started at amblent tempera-19 tures below thermophilic digestion temperatures, it normally takes about three to four days for the waste ma~erial to rise 21 from ambient temperatures to the thermophilic range~ ThereaEter, 22 t has been found that a four to five day residence time in the 23 digester at thermophilic digestion temperatures produces the 24 optimum foodstu~ in the most economical manner~
Heretofore, the present invention has been described 26 only in relation to a batch process wherein the digestion reaction 27 is initiated on fecal matter that is at ambient temperatures.
28 The present invention is also applicable to continuous digestion 29 processes wherein a series of two or more digesters and preferably three a linked in a series rluid flow arrangemen-. The continuou~
~ ' ' ~

~ 6Z ~

1 rcaction :is ~ini ti~ltc~l :in a ~ st: d:i~Jocll:cr of ~ .scri.cs ~r~nycrllcnt2 in a manner idcntical to that described in conjunction with the 3 batch processes above. ~fter ~he fecal matter in the first 4 dic3ester has reached thermophilic digestion tempera-tures, a por-tion of it is transferrecl to a second digester where it is 6 allowed to digest for an additional period of time. At the same 7 time, additional fecal matter can be added to the first digester 8 without causing the temperature of the digesting mass in the 9 first digester to drop below thermophilic digestion temperatures.
The exact amount that can be continuously added to the first 11 diqester is of course dependent upon the particular thermophilic !~
12 digestion temperature at which the digester is operating as well ~i 13 as the relative volumes of fecal matter in the digester and fecal 14 matter being added. When the fecal material is digesting at temperatures above 55C., addi~ional quantities of fecal material 16 on the order of~S0~ by weight o~ the digesting material in a 17 given digester can be lntroduced into the first digester without 18 adversely affecting the digesting temperature. However, it is 19 important that if the temperature in the first digester is caused 20~ l to drop below the thermophilic digestion temperature ranges by 21 the introduction of too much additional fecal material, no more 22 fecal material be added until the temperature has again risen to 23 the thermophllic range. It has been found for a continuous 24 digestion process that a residence time of the digesting material in the two or more digesters be-maintained at from about four to 26 eight days. ~
27 The digested product of the present invention, which 28 largely comprises~a brownish liquid, can be directly fed to ;~ ~animals. For example, the digested product of the present ~ 30 invention ~as been direc.ly fed as a liquid ~o hoqs, cattle, n 2 3 ` ~

~ 62 1 sh~ep arld chick~ns. The p.r.otcin contcnt oE t.he dicJested product 2 is hic3her than that o~ the ini-tial ~ecal. material, indicating 3 that cellular, proteinaceous organisms have been produced. It is 4 believed that the protein present in the digested product is in the form of sing].e cell microorganisms and other protein sources, 6 which provide a very readily digestible energy and protein source 7 for animals. If desired, any precipitant in the liquid digested 8 product can be removed prior to refeeding the digested product to 9 animals. However, this has been found to be unnecessary as the inorganic materials in the digested product are present at 11 sufficiently low levels so as not to cause any harm to the 12 animals to which it is being refed. l~ :
13 Alternatively to feeding the digested product to 14 animals directly as a liquid, the liquid product can first be 15 filtered to remove the solid material ~n suspension. This solid ;
16 material can then be directly refed to animals. As a fur-ther .
17 alternative, this solid filtered material.can be dried and the.
18 dry product fed directly to animals. The product thermophilically 19 digested in accordance with the foregoing procedures has been filtered first through a 50-mesh screen and thereafter through a 21: 150-mesh screen. The solid material left on the screens can be 22 directly refed to animals. If desired, the solid material left ,.
23 on the screens can be dried by placing it on a drying platorm or ..
24 plate exposed to the air. The material can be air dried at ambient temperatures or can be heated to accelerate the rate at 26 which moisture is driven from the solid material. This dried 27 solid material can also be refed to animals. It has been found, 28 however, that the nutrient quality of the solid material after 29 the filtration process is not as high as the liquid digested product 30 ~ taken dire ly from th_ digester. Thi~ observation indlcates . . .
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~ 7~Z

1 that ~ subst~ntial po~tion ~E thc protcinaccous matcri~l produccd 2 by the digestion passes throuyh the 150~mesh screen with the 3 filtrate and is lost as a nutrient source when only the solid 4 aterial is refed. Thus, the preferred form of the invention 5 requlres refeeding oE the di~es-ted product in its whole liquid 6 orm. If -the diyested product is not fed in its whole liquid 7 form, the solid material cannot constitute as large a proportion 8 of the total nutritive diet for the animals as when the complete 9 liquid digested product is directly fed. An additional advantage 10 of drying the digested product is that it is stable and can be 11 stored for long periods of time, on the order of several months, 12 ith no loss in its nutritive valùe.
13 It is to be emphasized that the thermogenic bacteria 14 developed in accordance with the present invention are those that 15 naturally occur in animal Eecal matter and that are developed in 16 accoxdance with the procedures heretofore described. It is 17 believed that the genesis of the particular thermophilic bacteria 18 that digest the waste matter at the thermophilic temperatures is 19 a development through successive stages from the psychrophilic or 20 mesophilic and possibly dormant thermophllic bacteria present in 21 the fecal matter under ambient conditions. By properly aerating ~ ;
22 and agitating the animal fecal matter in accordance with the 23 fore~oing process, the bacteria developed through the successive 24 stages to the thermogenic thermophilic bacteria accomplish the 25 ends o~ the presenk invention. Atkempts have been made to 26 isolate and identify the particular thermophilic bacteria present 27 in the digesting mass at the thermophilic digestion temperatures;
28 however, no concrete identification oE the strain or strains has 29 been made at this point in time. It is to be further emphasized 30 that no external heat input to the digesting mass is required for ." . .

. . . . .. . ... .. .

~ 4~

1 purposes of tllC' inv~ntion a~ th~ bact~ria natu~lly occurring in 2 the fccal matter are thermoc3enic, th~t is khey are responsiblc 3 for the heat input to the diges-tiny material to raise the tempera-4 ture of tlle ~ic~esting matcrial from ambient to thermophilic 5 igestion temperatures and to maintain the material at those 6 temperatures. Although a small amount of energy is added to the 7 igesting mass via the mechanical action of the agitating mechanism 8 n the fluid, the amount of energy supplied to and dissipated in 9 the digesting mass as heat is small, and in fact, is insufficient 10 per se to raise the temperature of the digesting mass more than a E
11 few degrees and is certainly insufficient to raise the temperature 12 l f the digesting mass to the thermophilic digestion temperatures.
13 hus the thermogenesis responsible for the success of the present 14 l nvention is solely attributable to the metabolic activity of the 15 l acteria naturally occurring in the fecal matter.
16 Although the foregoing thermophilic aerobic digestion 17 l rocess is basic to the present invention, it has been found that 18 ¦the process has much broader application than only to the digestion 19 of animal fecal matter. The thermophilic thermogenic bacteria 20 present in thermophilically digesting animal fecal matter are 21 also capable o~ digesting other biologically degradable organic 22 materials. Included in the broad class of biodegradable organic 23 materials are the carbonaceous solid wastes such as human wastes 2~ including sewage sludges, carbonaceous domestic and industrial 25 wastes such as fruit and vegetable processing wastes, animal 26 packing plant wastes and fish cannery wastes. Other materials 27 such as biodgradable garbage wastes, for example fruit and vegetable 28 peels, chicken feathers and the like can be digested in accordance 29 with the present invention. These materials can be digested 30 utilizing the aforementioned thermophilic thermogenic bacteria into 31 a form suitable for feeding to animals as a nutrient source.

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- 1~)8~62 1 The proces~C3 ~or digestinc3 th~ organic biodegradable 2 materials mentioned above can be initiated in three ways. First, 3 the biodegradable materials can be digested in accordance with 4 this broad aspect of the present invention by comblning them wi-th 5 animal fecal matter and aerating and agitating within the critical 6 limits described above in relation -to digestion of animal fecal 7 matter alone. Alternatively, the biodegradable mat:erials can be 8 added to digesting fecal matter after the digestion process on 9 the fecal matter has been initiated and the temperature of the 10 digest1ng material has been raised to thermophilic digestion 11 temperatures in accordance with the present invention. As another 12 alternative, the`biodegradable materials can be combined with :~
13 water to form an aqueous slurry. Thereafter, an inoculum obtained 14 from thermophilically digesting animal fecal matter processed in 15 accordance with the invention can be introduced into the aqueous 16 slurry. ~gitation and aeration of the aqùeous biodegradable 17 slurry can then be initiated in accordance with the critical 18 parameters set forth above in relation to digestion of animal 19 feaal matter.
20 It is to be recognized that once the thermophilic -21 thermogenic bacteria of the present invention have been developed 22 by processing animal fecal matter in accordance with the present 23 invention, it is necessary only to add nutrients for the bacteria 7.4 to the digesting mass. Thus, once the thermophilic digestion 25 temperatures have been achieved utilizing animal fecal matter as 26 the starting material, other biodegradable materials such as 27 those mentioned above can be added on~a batch or continuous basis 28 to the digesting mass without the addition of more animal fecal 29 atter. The process can then be continued on a batch basis or on 30 a continuous basis for as long a period as desired. The biodegrad-31 able mate 1 is digesting at thermophi1ic temperatures in ~. : ' ~ ' ' " `

~ 76Z

1 ~Iccor~nce wi tll the invention, ~ddition~l biodegrad~ble material 2 to the digesting zone in amounts up to a quantity that will cause 3 a reduction in the temperature of the animal fecal matter below 4 the thermophilic cllgestion temperature range.
~hen the thermophilic aerobic diges~tion process of the 6 present invention is initiated by comblning animal fecal matter 7 and a biodegradable material at ambient temperatures, water must 8 normally be added to the mixture to form an aqueous slurry. To 9 initiate th~ thermophilic digestion process of the present invention from ambient tempera-tures, the dry solids content of 11 the fecal matter based on t~e entire aqueous slurry must be at ¦~
12 least about 5% by weight. The biodegradable material can be 13 present in the aqueous slurry in amounts up to 15~ to about 20~
14 by weight, although an excessive amount of solid material in the 15 aqueous slurry will greatly increase its viscosity and thus 16 increase the energy required for adequate agitation in accordance with the present invention. ~ter the aqueous slurry is introduced 18 into the digester, aeration and agitation are begun and are 19 maintained within the parameters described above in relation to the animal fecal matter digestion. The temperature of the aqueous 21 slurry will begin to rise and will achieve thermophilic digestion 22 temperatures. By continuing the agitation and aeration at the 23 prescribed critical rates, the thermophilic digestion temperatures 24 can be maintained. When an inoculum taken Erom thermophilically digesting animal fecal matter is employed to initiate the thermo-26 philic digestion of a biodegradable material, it is merely sub-27 stituted for the animal Eecal ma-tter as described in the immediatel~
28 preceding paragraph. Other than the change of the initiating 29 materials from undigested animal fecal matter to an inoculum from 30 digesting animal fecal matter, the procedures for initiating and 31 maintaining the thermophilic digestion process are the same.
-~8-~ z 1 ~s stated ahove, the thermophilically di~ested product 2 from biodegradable organic material in accordance with the 3 foregoing broader aspects of the present invention can be utilized 4 s animal feed. Some industrial processing wastes such as by-roducts from frui~ or vegetable processing plants, will contain 6 higher degree of nutrient than animal waste matter itself. ~he .
7 rocess o the present invention breaks down the biodegradable 8 aterial into a form that is readily digestible by animals.
9 ince the nutrient value o these materials exceeds that of nimal fecal matter, the digested product can be fed to animals 11 t higher levels than can the digested product derived from 12 nimal fecal matter alone. In alL cases however the nutrient 13 alue of the digested product must be analyz.~d and must be supple-14 nented to make up a full nutritive diet for a given animal or 15 ~nimals. ~
16 ~ Indiscriminate feeding of all digested biodegradable 17 ~aterials cannot be done since some of the biodegradable materials, 18 ¦for example sewage sludges, contain substances that may not be 19 ¦digestible by the thermophilic thermogenic bacteria and moreover 20 ~ay not be digestible by animals. Such substances included in 21 ¦sewaye sludges are glass, plastics and metals. If such substances :
22 ¦are present in the organic biodegradable materials at levels 23 ¦below that which would be toxic to animals, it may still be 24 ¦possible to :Eeed the digested product to animals.
25 ¦ . As in the thermophilic digestion of animal fecal matter 26 ¦ in accordance with the present invention, the digestion of 27 ¦ carbonaceous biodegradable materials will produce a protein 28 ¦ increase over that of the material introduced into the digesting 29 ¦zone. Again, the protein increase is believed to be caused by an ~ 30 ~increase in the microbial population during digestion, resulting -~ I -29-I . .
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~ 3~34t76:~

1 ¦.in an i.ncreasc in si.ngle cel.l pro~einaceous materi.al, that is, 2 ¦si.ngle cell protein derived from the microbial biomass present in 3 ¦the digested product. As with -the digestincJ animal wastes, ¦protein production is at its maximum aEter about four to eight days of diyesting at -the thermophil.ic digestion te~peratures.
6 ~fter about eight days of diyesting at the thermophilic digestion 7 temperatures, the protein content of the digested product begins 8 to decline. It is therefore preferred when the digested product 9 is to be fed to animals that the digestion process be operated at ..
10 thermophilic digestion temperatures only for period of from about 1.
11 four to about eight days.
12 It is recognized however that the thermophilic digestion 13 process of the present invention can be continued for periods 14 beyond eight days. I~ the thermophilic digestion process is 15 continued for a longer time, a significant reduction in the 16 biological oxygen demand tBOD) is achieved after about six days, 17 while the greatest BOD reduction is achieved after about seventeen 18 days of digesting at thermophillc digestion temperatures in 19 accordance with the invention. A reduction in the chemical j 20 oxygen demand (COD~ is also achieved while digesting biodegradable :21 material in accordance with the invention. A significant COD
22 reduction ha.s been achieved after about eleven days o digesting 23 at thermophilic digestion temperatures while a significant reduction 24 in COD has been obtained after about twenty-four days of digesting at thermophilic digestion temperatures. An unexplained rise in 26 COD has been observed within the period of from eleven days to 27 about twenty-four days. This rise in COD is thought to be 28 attributable to the increase in cellulose content as a percentage of total solids, as the solids other than cellulose are being -. 30 digested at a faster rate than the cellulose cells. After ~.

~ iq~8~76~

1 ¦twen~y-four days, however, both the BO~ and COD are reduced 2 ¦significantly and sufficiently so -that the digested product can 3 ¦be used as a fertilizer or can be disposed of relatively safely 4 ¦and economically. This digested product is especially useful as 5 1a fertilizer since the BOD and COD have been signiicantly 6 ¦reduced. Also, when sewage is used as the starting waste mat~rial, 7 1 the digested product will contain addi~cional amounts of plant 8 ¦ nutrients such as phosphorous and nitrogen;
9 1 ' If it is desired to completely stabilize a biodegradable 10 ¦ material such as a sewage sludge by the process of the present 11 ¦ inventionj relatively complete stabilization can be achieved by 12 1 continuing the thermophilic diges~ion process Qf the present 13 ¦ invention until the temperature of the digesting material drops 14 ¦ below the thermophilic digestion temperature range. When this 15 ¦ occurs, a compLetely stabilized digested product is obtained.
16 1 Time periods in excess of fourteen days and with heavy solids 17 ¦ concentrations may be required for complete stabiliz'ation.
18 ¦ Surprisingly, it has also been found in accordance with 19 1 a third aspect o~ the present invention that certain thermophilic 20 ¦ bacteria produced by d1gesting animal waste matter in accordance 21 ¦ with the present invention are effective to digest materials 22 ¦ containing lignocellulosic complexes. Such materials include the 23 ¦ woody'plants, such as trees, shrubs and wood reuse, and the 24 ¦ byproducts of wood processing industries. Heretofore, microbio-~5 ¦ logical digestion processes have not been able to digest ligno-26 ¦ cellulosic materials in any reasonable length of time. There are 27 1 of courqe certain Eungi that will digest the lignin present in ' 28 ¦ li~nocellulosic materials over a relatively long time, on the 29 ¦ order of l~0 years or more.
30 1 __ ~V~ 6'~

1 By ~dding lignocellulosic m~terials in coarsely divided 2 form to a dlgester containing animal ecal ma-tter digesting at 3 thermophilic temperatures in accordance with the foreyoing 4 described invention, .it has been found that in a matter of hours the lignocellulosic materials are partially digested and that in 6 four to five days, the lignocellulosic materials are substantially 7 digested. It is preferred that the lignocelluosic ma-terials be 8 coarsely comminuted by chipping or other convenient methods to 9 increase the sur~ace area of the lignocellulosic materials over 10 which the microorganisms can attack. The lignocellulosic material 11 can be added to digesting animal fecal matter in amounts up to ', 12 about 50~ by weight of the digesting mass. When amounts of 13 lignocellulosic material toward the upper end of this range are 14 added to the digesting fecal matter, the power requirements for agitation rise significantly. It is thereEore preferred that the 16 amount oE lignocellulosic material present in an aqueous digesting 17 edium be maintained below about 15~ by w,eight of the total 18 digesting mass.
19 It has also been found that lignocellulosic materials 20 can be combined with water and a relatively small amount of 21 animal ecal material in a digester. PreEerred proportions are 22 animal fecal material having a dry solids content on the order`of 23 3.5~ to S~, about ~ to about 8% o lignocellulosic material, and 24 rom 87~ to about 94.5~'water. When a mixture falling within the foregoing proportions is placed in a digester and the mixture is 26 aerated and agitated in accordance'with the procedures outlined 27 above in connection with the digestion of animal fecal matter the , 28 naturally occurring microorganisms in the animal fecal matter 29 will cause the temperature to rise in a manner very similar to ';
30 that when fecal material alone is present in the digester. By ~"
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, : ~ -32- ~' . I .

~ 762 -1 Icontinuing th~ vigorous agit~tion and aeration in uccordanc~ with 2 ¦ the ~bove procedurcs, thermoE)hilic digestion temper~tures are 3 1 achieved ln a matter of about four days. By maintaining -these 4 ¦ thermophilic digestion temperatures for a period of at least four 5 ¦ days up to twcnty-one days or more in accordance with the procedurec 6 ¦ outlined above, the lignocellulosic materials can be completely -7 ¦ digested.
¦ It is evident in such a process that the lignin is 9 ¦ being digested as a scum or layer o~ material first appears on 10 ¦ top of the digesting mixture containing the lignocellulose 11 ¦ materials. The material is ~ound to be cellulosic cells from 12 ¦ which the lignin has been substantially removed. These cellulosic 13 1 cells are in a form that can be digested by animals without 14 1 further digestion in accordance with the present invention. If 15 ¦ desired, the digestion process can be continued aEter substantially 16 ¦ all of the cellulosic cel}s are freed so that a portion or all of 17 ¦ the cellulosic cells are also digested to produce other nutrients 18`¦ for animals.
19 ¦ The process of the present invention wherein lignocel-20 ¦ lulosic materials are digested can also be operated either on a 21 ¦ batch basis or on a continuous basis. The same process parameters 22 lapply to the lignocellulosic digestion as to the digestion of 23 ¦animal Pecal matter alone and to the digesti.on oE other biodegrad-24 ¦able materiall especially the critical nature of the aeration and 25 ¦agitation.
26 ¦ It is believed that the genesis of the thermophilic 27 ¦bacteria that digests the lignocelIulosic materials is a successive 28 ¦development of a certain strain or strains of bacteria through 29 ¦thermophilic thermogenic aerobic digestion process of animal 30 ~fecal matt r as described abcve. A sample cultuFe taken frcm a ,'' . ' ~ '.
I .
~ :

thermophilically digestin~ mass, in which the starting material was animal fecal matter~ namely hog manure, and to which ligno- ~
cellulosic materials werc added after thermophilic digestion '' temperatures were reached, has been extracted from the digesting ;
mass. The culture has been deposited with the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Maryland '~
20852. The culture has been given Accession Number ATCC-31205 by the American Type Culture Collection. Access to the culture will ' be available during pendency of the patent application to one ;~
determined by the Co~nissioner to be entitled thereto under 37 C.F.R. 1.14 and 35 U.S.C. 122. Further, all restrictions on the availability to the public of the culture`so deposited will be ~' ;
irrevocably removed upon the granting of a patent hereon. The ' applicants hereof assure permanent availability o~ the'culture to ~ ;
the public through the American Type Culture Collection. The best description of the culture and taxonomy available at this time follows.
The thermophilically digesting liquid in which alder wood chips were being digested yielded'a mixed culture of thermo- ;~
philic organisms when cultured in the ollowing growth medium: ' Modified Trypticase Soy Agar. Modification'to the Agar included the addition o 0.~ gm/l. o yeast extract'and three additional ' grams o Agar Perl. 0:1 ml Perl. of concentrated ammonium hydro-xide were added after sterilization of the medium. The growth medium had a inal p~l of approximately 7.5. The culture time in this medium was 24 hours. The oganisms were separately cultured at both 55C. and 75C. on the medium or in its broth. Four organ-isms were observed.
The first organism was a gram negative rod having a length of from 0.7 to 1.7 microns and a diameter of 0.3 microns ' in the broth. The organism had spores, namely an endospore 1.4 - 3~

microns long and U.7 microns wide. The Eirst organism grew only at 55C. and dicl not grow at 75C. The organism was a vege~ative cell. Under phase contrast microscopy the organism showed definite~
darkJ granular-like bodies and had no motility. The colony of the first organism had a creamy white color and was opaque. The colony elevation was umbonate while the colony edge was between crenate and undulate.
The second organism was filamentous. The filaments were gram negative and contained gram positive granules. The organism was not a typical bacillus form but tended toward long filaments. The organism grew slowly at 75C. while excellent growth was obtained at 55C. The colony was light brown in color. The colony elevation was umbonate. The colony edge was lobate over its entire surface.
The third organism in the broth medium was observed to be gram negative bacillus-type rods. The rods were from 2.1 to 3.5 microns in length and 0.5 microns in width. The rods tended to bend in the center to form "U" or pretzel shapes. The rods ;
had a cytoplasmic spherical mass at the bend. The culture also conta m ed numerous large, ball-shaped bodies containing what appeared to be slnall rods shaped much like small rod-shaped bacilli.
On the solid media, the third organism was observed to be gram negative, highly filamentous rods. The rods were straight or curved. Some of the filaments were observed to form loops, some of which contained spherical shapes observed in the broth culture. The colony was cream colored and was opaque. The colony elevation was convex while the colony edge was entire.
The third organism grew at 75C. in both the broth and the solid media while very little growth was observed at 55~C. `
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~ 34~6Z

.
The fourth organism was a bacillus-type gram negative rod. 'rhe rod lcngth varied from 2.4 m:icrons to 35 microns with most rods being about 4.5 microns in length. The diameter of thc rods was a'bout 0.5 microns. A few filamen~s were observed up `~ '~
to 100 microns in length. The rods were generally s-traight. - '~, ;
Some of the rods tended to have poin~ed ends and some of the rods ,~
were slightly curved. The colony was light brown in color and ,',~', was opaque. The colony elevation was convex and the colony edge .
was entire.
Examples The following examples are intended to be illustrative `
o the present invention and are not intended in any way to be ,'~
delimitative of the broader concepts disclosed herein. The examples are further .intended to teach one cf ordinary skill how to make and use the invention and how to produce the results of the inventîon. '~
In all of the following Examples, a cylindrical digest~
ing tank having a diameter o~ 48 inches and a height of 5 feet was placed upright on a foundation. The'top of the tank was open to the atmosphere. A 1 inch thick layer of insulation surrounded '~
, the sides and the bottom oE the tank. The insulatLon was a ,' closed coll polyurethane foam material. A 0.5~inch diameter ~, aerating plpe was routed to the bottom~of'the tank and had its outlet positioned substantially along the axis Oe the tank about 6 inches above the bottom of the tank.' Oxygenating'air was fed through the pipe rom a compressed air source. A volume regulating valve was interposed between the air compressor and the outlet '-'~
from the aerating pipe. A four bladed impeller was mounted on a ~ ```;
rotatable shaft oriented coaxially with the tank. The four ;~
impeller blades were positioned 90 apart and had their longitudinal ~,~

, ~ 7~

1 imcn~ion or:icrll:.cd radially on th~ rotatab:Le sll~Et. 'l`hc blacle~
2 ere 3 inches long in radial dimension and 6 inches long in the 3 ~ransverse dimension. Tlle blacles were oriented at 30 to the 4 horizontal, i.e., to the boktom of the tank. A 2 H.P. electric otor was mounted on a platform resting on the upper edges of the 6 sides of the tank and coupled to drive the rotatable shaft at 860 7 rpm. The shaft was driven in a direction so that digesting 8 aterial in the digester would be driven upwardly from the bottom 9 of the tank, through the blades and on upwardly to the upper 10 surface level of the material in the tank. The bottom of the 11 impeller was positioned 2 inches ~bove the outlet from the aerating 12 ¦ ipe so that air issuing from the aerator pipe traveled upwardly 13 through the rotating impeller blades. The shearing action of the 1~ 1 lades on the airstream better dispersed the air throughout the 15 liquid to achieve a higher dissolved oxygen content in the liquid.
16 ¦ foam breaker was also mounted Oll the platform resting on the .
17 1 op edges of the side walls of the tank. The foam breaker consisted 18 ¦ f four blades positioned 90 degrees apart on a rotating sha~t 19 ¦ riven at 1725 rpm by a 1/4 H.P. electric motor. The blades were 6" long and were positioned at a level of 6" above the surface of 21 the digesting liquid. The foam breaker was offset from the ;
22 impeller shaft so as not to interfere wlth its operation.

~ .
24 Water was added to hog manure washed from hog feeding latforms and stored in a holding tank. The hog manure was about 26 10 days old when it was introduced into the digester. The manure 27 ad a dry solids content based on the total aqueous mixture 28 introduced into the tank oE about 10% by wcight. The ambie~nt 29 emperature was 10C. when the aqueous mixture was introduced into the digester. Immediately after the mixture was introduced .
'I

~ B4~762 `-1 linto thc di~ester, oxyg~na-tinc3 air wc~s pumped in-to the digest~r 2 ¦at the rate of 0.02 liters oE air per minute per liter of aqueous 3 ¦mixture in the digester. At the same time, the impeller was 4 ¦started. Aeration at this rate and agitation at this level were 5 ¦ continued throughout the run until immediately before the digested 6 ¦ produc-t was removed from the digester. Within 6 hours, the ¦ tempera-ture began to rise from the ambien-t and within 90 hours, 8 ¦ the temperature was at 55C. During the intial start-up phase 9 ¦ when the temperature was rising to the thermophilic digeqtion , 10 ¦ temperatures, foam was produced on the top of the aqueous mixture.
11 ¦ The foam breaker was adjusted so that the foam layer was maintained 12 ¦ at about 8 to 12 inches thick. The foam layer served as insulation 13 ¦ to prevent heat loss from the top of the tank.
14 ¦ The aqueous mixture was digested at thermophilic 15 ¦ temperatures for 6 days. During this 6~day period, the temperature 16 ¦ remained at thermophilic digestion temperatures in the range of 17 ¦ from 55C~ to about 65C. During this time the dissolved oxygen 18 ¦ levels were maintained within the range of from 1.5 mg/l. to 3 19 ¦ mg/l.
20 ¦ At the end of the 10 days after initiation of the 21 ¦ digestion process, the digested product was removed from the 2~ ¦ digester and soon ~thereafter fed to hogs as 10~ of their total 23 ¦nutritive diet with no adverse e~fects. ~he ba:Lance of the die~
24 ¦of the hogs was normal feed supplement and grains normally fed to 25 124 test hogs.
26 I The foregoing process was repeated over a period of 28 27 ¦days so as to produce a sufficient amount of liquid, digested 28 Iproduct to provide a constant supply of the material sufficient 29 Ito fPed to test hogs for 28 days. The liquid product was fed to 30 ¦the hogs on an ad libitum basis as the only source of liyuid, , I
I .. , ,,,,,' . I

~ ~84~GZ

1 ¦i.e. In thc plc~ce o wctcr, and consti.tucd about 30~ of -their 2 ¦daily protein requirements. After the 28 day period, the hog 3 Iweight g~in and feed conversion efficiency were substantially the 4 ¦same as an identical number of control hogs fed a tot~lly fresh 5 ¦diet of feed supplement and grain identlcal to that making up the 6 ¦ remainder of the nutritive diet of the test hogs. Feed conversion 7 ¦ efficiency is defined as the inverse ratio of the amount of feed 8 ¦ required to produce one pound of meat times 100%.
9 ¦ The digested product was analyzed and found to contain 10 ¦ single cell proteinaceous material. The amino acid profile of 11 ¦ the digested product was derived in accordance with common 12 ¦ laboratory procedures. The amino acid profile of the digested 13 ¦ aterial compared with the amino acid profile of the original hog 14 ¦ anure placed in the digester indicates that a significant 15 1 increase, on the order of 100~, in several of the amino acids is 16 1 achieved by digesting the hog manure in accordance with the 17 present invention~
18 Example II
19 The process of Example I was repeated with chicken 20 manure to which water was added to adjust the dry solids content 21 to about 12% by weight based on the total aqueous mixture. When 22 the digestion was begun, the ambient temperature was about 12C.
23 After the aeration and agitation were bègun, the temperature of 24 the dige~ting material rose to 55C. in about 72 hours. The temperature was maintained in the range of from 55C. to 8~C. by 26 1 continuous agitation and aeration for 12 days. The dissolved 27 oxygen levels in the digesting material were maintained in the 28 range of about 1 mg/l. to about 3 mg/l. After 12 days, the 29 digested product was removed from the diges-ter and fed to 340 30 ~est chickens as between 5% and 15% of their total nutritive -3g~
~,' 34 ~6Z

1 diet. No adverse eEfects were obsePved. The -test chickens' 2 weight gain ancl feed conversion efficiency were substantially the 3 same as the same number of con-trol chickens fecl a totally fresh 4 diet identical to that making up the remaining 85~ -to 95~ of the 5 diet of the test chickens.
6 Example III
7 The digestion process of Example I was repeated and 8 allowed to continu~ digesting for a period of three weeks, while 9 the aeration and agitation were continued. During that period 10 the temperature of the digesting material reached 74C. and then 11 dropped to 60C., indicating that the nutrient source ~or the i 12 microorganisms was being depleted. At the end of ths three week ~ ;
i3 period, 22 pounds of alder chips were added to the digesting ?
1~ ¦ mixture. The agitation and aeration was continued. The average 15 chip size was approximately 0.2 inches by 0.05 inches. Within 24 16 hours after the chips were added, the temperature of the digesting 17 mixture had risen to 64C. Thereafter 22 pounds of alder chips 18 were added to the digester every two to three days while agitation 19 ~nd aeration were continued. After approximately two weeks, ; ~ 20 digestion of the alder chips was noted. For appro~imately one 21 ¦ weeh thereafter, no new chips were added to the digester, during i 22 which period the yH of the digesting liquid rose from about 7.0 23 to about 8.8, accompanied by a strong ammonia smell from the 24 digester. 22 pounds of ald~r chips were added to the digester.
; Within 12 hours thereafter, the pH of the digesting liquid had 26 dropped to 7.0 and there was no further ammonia smell. The alder 27 chips were digested within 21 days after the initial batch was 28 introduced into the digester to an extent that no discrete chip 29 1 particles remained ln the d1gesting material. Thereafter, the 30 digested material was removed from the dlgesteF and fed ~to 15 ' I .' . ~ ~

, .. . , . : . ~ , ...

~3476Z

hogs with no adverse results as a portion of the total nutritive diet of the hogs. The cellulose cells, after being removed Erom the digester, are in a form that can be digested by animals, especially ruminants.
When following the procedure of the foregoing Example ~ ~
III, it will be noted ~hat when addition of alder chips at ~ ~ -regular intervals was stopped~ after about one week the pH of the digesting mass rose significantly into the`alkaline range.
In addition, an ammonia smell was observed indicating that ammonia was being generated in the digesting mass. These observa-tions indicate that nitrification wasitaking place in the digesting mass at temperatures of from 64C. to about 67C. Heretofore, it has been thoughtthat nitrification could not occur abové àbout 40C. The explanation for this nitrification is presently uncertain.
It is also to be observed that when additional lignocellulosic material is added to the digesting mass, the pH will very soon ~ ?
thereafter drop to about 7Ø This same phenomenon has been `
observed in extended digestion of animal fecal matter and other carbonaceous materials. That is, after the digesting mass is allowed to digest at thermophilic temperatures and is aerated and agitated in accordance with the invention, the pH will tend to ; ``, rise several days after the last carbonaccous matcr:ial was added.
Upon adding new carbonaceous material, a pH drop`has been observed.
Example IV
.. ~
The process o~ Example I was repeated, except that several pounds of fruit peels, chicken eathers, newspapers and other carbonaceous garbage were introduced into the digester after the temperature reached 60C; All of the garbage was .:~
digested at temperatures ranging from 55C. to 75C, The`digested - ~
product was fed to hogs as a portion of their nu~ritive diet with- ;
; . ~ ~;` ~ ` .
out adverse effects.

" . '',: ..

~ ~ 76Z`- ~
1 ¦ As ccln be obse~vecl by reading -the foregoing speci~ication, 2 ¦the objects se~ ~orth above have been achieved. The thermophilic 3 ¦aerobic dlgestion process of the present invention produces a 4 ¦ foodstuff that can be refed to animals as a portion of their 5 ¦ nutritive diet. When the critical levels of aeration and agitation 6 are maintained in accordance with the present invention, no 7 externaI heat need be added to the digesting ma~erial to raise 8 its temperature to the thermophilic temperature range or to 9 maintain the digesting ma-terial within that temperature range for lO a period of on the order of four days or more. Inoculation of 11 the fecal material to be digested is nqt required as microorganisms 12 naturally occurring in the animal fecal matter are adequate to 13 achieve the foregoin~ results. Moreover, the process of the 14 present invention produces single cell proteinaceous material and yields an end product having a protein content in the digested 16 product equal to or greater than that presen-t in the original 17 fecal materials introduced into the digester. Moreover the 18 equipment necessary to practice the present invention is relatively 19 simple and requires little capital investment to construct or .
: : 20 maintain, and little operating expense to conduct the digestion 21 process. ~ .
22 In a broader aspect of the invention, the thermophilic 23 digestion process of the present invention can be employed to 24. break down other organic biodegradable materials to either reduce them to a readily digestible form and to produce protein or to 26 stabilize the materials for disposal. The digested biodegradable 27 materials mentioned above can be fed to animals, thereby taking 28 adv~nt~ge of the nutrient value in waste products such as those 29 normally disposed of in animal processing plants and fruit and vegetable canneries. Moreover, other biodegradable wastes such :: ~42~

.. . - : .: . , :. . .
.

~ lO~
1 ~s sewage sludcses and the ].ike can be completely st~bilized by 2 conducting the thermophilic digestion process of the present 3 invention to a point where there is no longer sufficient nutrient 4 for the thermophilic thermogenic bacteria to digest. The resulting product thus digested is completely stabilized and can be disposed 6 of in a safe and economical manner. In all cases the dlgestion 7 process of the present invention does not require addition of external heat to the digesting zone. Instead, by proper aeration 9 and agitation in accordance with the present invention, ~he 10 thermogenic nature of the bacteria present in animal fecal matter ~:
11 is relied upon to both raise the temperature of the digesting ¦.
12 materials to the thermophilic range and to maintain the thermophilic :
13 digesting temperatures for periods o~ at least four days and 14 longer. .
An unexpected and perhaps more importan-t aspect oE the 16 present invention provides a process for microbiologically 17 digesting lignocellulosic materials under aerobic, thermophilic 18 conditions. Not only does the process of the present lnvention 19 digest.the lignocellulosic materials, but does so in a relatively short time, on the order of four to eight days. The digestion 21 process of the present inven-tion reduces the lignocellulosic 22 materials to a Eorm that is readily.digestible by animals. This 23 process provides a source o~ additional nutrient for animals 24 heretoEore unavailable, as prior chemical pulping processes for.
removing llgnin from a lignocellulosic material yield products 26 and byproducts that are not acceptable for feeding to animals.
27 Th~ signific~nt advantage oE the present process for dissolving .. .
28 the lignocellulosic materials is that the end product does not 29 contain the chemical contaminants normally yielded as a byproduct l:
of the rhe cal pulping processes.

. '-' .

. . , . ... ~ - . . .. , . ~ . ... - ., . . - . ....

1~)84~6Z

1 Tlle ~orcgoin~ invention has been described in rcl~tion 2 to preferred ernbodiments as well as deEininy the bro~d operational 3 p~rameters of the lnvention. One of ordinary skill, aEter reading 4 the foregoing specification, will be able -to eEfect various changes and substitutions of equivalents, and find additional 6 uses for the invention withou-t departing from the broad concepts 7 disclosed herein. For example, the dlgested product produced by 8 the present invention may be fit for human consumption. All 9 indications at this point in time are in that direction, for example, the digested product is nontoxic, is odorless, is taste-11 less, and has an increased protein content over that of the 1~ undigested material. It is therefore in-tended that the Letters 13 Patent granted hereon be limited only by the definitions contained 14 in the appended claims and the equivalents thereof.

16 What is claimed is:

26 '~

.
. , ,, ,,~
- . . .

~89~67~

SUPPLEM~NTARY DISCLOSURE
The thermophilic aerobic digestion process can also be operated, not only on fccal-based organic matter, but on other types of biodegradable organic material as well, without the presence of even a small quantity of animal waste matter or thermophilic bacterial culture extracted from the aforementioned fecal matter digestion process. ~
Accordingly, the present invention broadly includes the provision ~ ' of a process for biodegradable organic material such as animal waste products, sewage sludges, organic domestic and industrial wastes, and animal, vege~able and fruit processing plant wastes, under thermophilic and aerobic conditions to produce a proteinaceous foodstuff therefrom that can be refed to animals ~. ~
as part of the animal's nutritive diet. Additionally the present invention is a thermophilic, aerobic digestion process that requires the addition of no external heat to initiate and raise the digestion temperatùre to the thermophilic range; a thermophilic digestion process that can deoderize and pasteurize animal waste products and render them harmless to the environment;
a thermophilic aerobic digestion process that increases the protein content of -the digestion product over the protein content of the initial organic material ; being~digested; a thermophilic aerobic digestion process that kills all pathogens in organic material such as waste products, including coliform and ~
salmonella bacteria, virus, worms and larvae; a process for stabilizing sewage ;; ` , sludges and other biodegradable material so that they can be disposed of ~:;
economically and safely and an economical thermophilic aerobic digestion process that requires a minimum capital investment and which therefore can be installed on site at animal production sites.
In another aspect, the invention is directed at providing a thermophilic aerobic digestion process that is capable of digesting lignocellulosic material. Furthermore, the thermophilic aerobic digestion process can microbiologically digest lignocellulosic material in a very ;.
short time and provide a thermophilically digested product from lignocellulosic materials~that does not contain undesirable byproducts such as those yielded ~5-1~34~6Z

in chemical pulpi~g processes. ~lso, the lnventive process does not produce the undesirable odor and disposal problems normally associated with pulping processes.The ther~ophllic aerobic digcstion process when used for digesting lignocellulosic materials yields a new source of nutrients in digestible form for feeding to animals and fixes nitrogen from the air to produce a digestion product containing more usable protein than the original lignocellulosic starting material. The inventive process may also be used ~o produce enzymes ~hat will break down the cellulose in lignocellulosic materials.
In accordance with the present invention, there is provided a process for using thermophilic bacterial microorganisms for thermophilically digesting an aqueous mixture of a biochcmically degradable organic material under aerobic conditions comprising the steps of:
introducing said mixture into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, continuously introducing an oxygenating gas into said mixture and continuously, mechanically and vigorously agitating said mixture while introducing said oxygenating gas, said oxygenating gas being intro- -ducted at a rate and said mixture being agitated at a level effective to cause and promote the temperature of said mixture to rise from ambient temperatures, through mesophilic temperatures, to a temperature of at least 55C without the addition of external heat to said mixture until said material is digested, said mixture when digested forming a digested product, said oxygenating gas further being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the mixture, continuing to agitate said mixture at a level and to introduce said `
oxygenating gas at a rate effective to maintain said temperature of at least 55C without the addition of external heat, said oxygenating gas being ""~ j ~t~B~76;~

introduced at a rate suEficient to raise the dissolved oxygen level in said mixture to and maintain it above about 1.0 mg/l. after the temperature of said mixture has reached 55C. `
In further aspects of the present invention vitamin B12, amino acids such as lysine and methionine, and enzymes such as cellulose may be ;~
produced.
I~en the process is used to digest lignocellulosic material, such as woody plants, the lignin is first digested out of the material to leave free cellulosic cells that can be fed to and assimilated by animals.
Additionally, if the digestion of lignocellulosic material is allowed to continue for some tilne under the thermophilic conditions described above, a single cell protein that can be fed to animals as part of their nutritive diet is produced as the digestion product. Unexpectedly, the single cell ~`
protein produced by the thermophilic digestion o~ lignocellulosic material contains a significantly higher crude protein content than the original ~
lignocellulosic material introduced into the digester. Thus it is believed ; ~ `
that nitrogen from the air is fixed by the digestion process to produce the single cell protein. Additionally, the enzymes that assist in brea~ing down the lignocellulosic material can be extracted and utilized to aid wood ;~
degradation in other environments.
In accordance with another aspect of the present invention, biodegradable material to be digested can be seeded with organisms that are specially adapted to produce amino acids such as lysine and methionine.
The am:Lno acid producing organism can be introduced :Lnto the digesting mass while its temperature is in the mesophilic range or after the digesting mass - ~7 - ~
,:

.:

has achieved thermophilic temperatures. The amino acids can be extracted from the digested product ancl can be utilized as desired.
~ I'he thermophilic thermogenic bacteria produced by thermophilically digesting animal fecal matter are also produced by digesting other biological-ly degradable organic materials in accordance with the procedures and within the limitations just described with respect to the fecal mat~er digestion.
Included in the broad class of biodegradable organic materials that are digestible in accordance with the present invention are the carbonaceous solid wastes such as human wastes including sewage sludges, carbonaceous domestic and industrial wastes such as fruit and vegetable processing wastes, animal packing plant wastes, fish cannery wastes, and wood or woody materials.
Other materials such as biodegradable garbage wastes, for example, fruit and vegetable peels, chicken feathers and the like can also be digested in accordance with the present invention. All of these materials can be digested utilizing the aforementioned thermophilic thermogenic bacteria into single cell proteinaceous material suitable for feeding to animals as a nutrient source.
The process for digesting the organic biodegradable materials . .
mentioned above can be initiated in at least four ways. First, these biodegradable materiaIscan be digested in accordance with the present invention by merely placing them in a suitable digester and aerating and agitating and otherwise processing the materials within the conditions and bounds described above in relation to the digestion o:E fecal matter.
Secondly~ the biodegradable materials can be digested in accordance with this broad aspect oE~the present invention by combining them with animal fecal matter or other waste matter containing a microbial population of suficicnt composition to raise the temperature to and maintain the temperature of the mixture at thermophilic conditions and aerating and agitating within the critical limits described above in relation to digestion :`~; ``

~L~)8~

:

of animal ~ecal matter alone. Thir~ly, the biodegrada~le matericll~ can be a~ded to digesting fecal matter after the temperature of the digesting fecal ;`
matter has been raised to thermophilic ~igestion temperatures in accordance with the present invention. ~o~rth, the biodegradable materials can be combined with water to form an aqueous slurry. Therèafter, an inoculum ~ ;
obtained from an organic material that is thermophilically digesting in accordance with the invention can be introduced into the aqueous slurry.

Agitation and aeration of the aqueous biodegradable slurry can then be , ....
initiated in accordance with the critical parameters set forth above in - ~ ~
relation to digestion of animal fecal matter. ~ -As indicated above, the thermophilically digested product from biodegradable organic material can be utili7ed as animal feed. Some industrial processing wastes such as byproducts from fruit or vegetable ~`
processing plants, may contain a higher degree of carbonhydrate nutrient than animal waste matter. The process of the present invention breaks down `~ `~
the biodegradable material into a form that is readily digestible by animals. i ~
.~ ., The nutrient value o the digested product must be analyzed and must be `
supplemented to make up a complete nutritive diet for a given animal or animals.
Although lignocellulosic materials may be added, in a coarsely , divided form, to a digester containing animal fecal matter, it has been , surpris~ingly discovered that the presence o anlmal ecal matter or other biodegradable material is not essential for digestion. Tha~ is, ligno-cellulosic material can be combined with water to form an aqueous slurry.
Thereafter upon appropriate aeration and agitation, in accordance with the procedures outlined above~for animal waste matter and other biodegradable materlal, lignocellulose materials can be digested. Initial aeration and agitatlon produces thermogenic bacteria which raise the temperature from ambient temperatures~to the thermophilic temperature range on the order of ~ -55C or higher. Thereafter, the thermophilic thermogenic bacteria continue ~ ;~
to digest the lignocelluIose material. Similar to when the lignocellulose _ ~9 _ ,~,, ~ :
~'- .

material is added to already thermophilically digesting animal waste matter or other biodegradablc material, the lignocellulose material when digested in thc absencc oE other biodegradable material will also be partially digested within ~ to 5 days after the thermophillic digestion temperatures are reached.
It is preferred that the lignocellulosic materials be coarsely comminuted by chipping or other convenient methods to increase the surface area over which the microorganisms can attack. Coarsely comminuted materials include sawdust (having a mean particle size on the order of 1/32" in diameter or larger) or wood chips ~having an average particle size of on the order of 0.2 x 0.2 x O.Z inches~. It is not necessary, however, to ~inely divide or comminute the material to a dust or flour-like consistency in order for the present invention to be operable. The lignocellulosic material can be present in the digesting mass in amounts up to about 50% by weight of the digesting mass. When amounts of lignocellulosic material approaching 50% by woight are employed, however, the power requirements for agitation rise significantly. It is therefore preferred that the amount of lignocellulosic material present in an aqueous digesting medium be maintained below about 15% by weight of the total digesting mass to minimize agitation power requirements. ~ ;
It has also been ound that vitamin B12 can be extracted Erom the digested product formed from the fecal matter digested in accordance with the present invention. The vitamin B12 can be separated ~rom the cligestion product by various proceclures known in the art, including the methods out-lined in the "Association of Official Analytical Chemists"~llth Edition), Washington, D.C. Vitamin Bl2 oan also be extracted from the digested product of other biodegradable materials digested in accordance with the invention, such as food plant wastes, wood wastes and many biodegradable organic wastesJ
as vitamin B12 is produced as a function of the particular bacteria involved, and is not produced as a characteristic of the waste material.
Furthermore, amino acids can be produced. ~mino acids are produced ~ `

1~4~6;~ ~ ~

by seeding the digesting mixtur~ of any of the forcgoing biodegradable materials once thermophilic temperatures have been reached with organisms that havc a high natural content of amino acids such clS
lysine and methionine. The digestion process over a period of 3 to 4 days evolves into a mass containing high levels of lysine. Once the mass has been digested for a period of on the order of 4 days or moreJ
the digested product can be fed to animals to meet their requirements for lysine, methionine, and other selected amino acids. Similarly, organisms high in lysine or other amino acids can be seeded into the .
digesting mass as it is being brought through the mesophilic range from ambient temperatures. By the time thermophilic temperatures are reached, the microorganisms high in lysine or other selected amino acid would be the dominant species in the digesting mass. Of course, when purified, digested products containing amino acids would also be available for human consumption.
It is aLso within the purview of the invention to produce sugars and lignin from the breakdown of the lignocellulose bonds in wood products. The simple sugars thus produced can be used for commercial purposes, e.g., for fermentation to produce alcohol. The lignin fraction can be used in the feeding to ruminants as at least a portion of the fiber portion of their diet. The sugars so produced are also utilizable by ruminants and other animals.
Aspects of the present lnvention will now be further described in the following examples.
Example V
.
The procedure of Example 1 of the principal disclosure was repeated except that bovineanimal manure was employed as the biodegradable material. Once the digesting mass had reached thermophilic temperatures and digested at thermophilic temperatures for a period of four days, a salllple of 10 milliliters of the digestion product was taken. The sample was blended with 250 milliliters of a metabisulfite extraction buffer and .~, ...... . .

~4~6æ

diluted to one litcr with distilled water. The solution was thoroughly mixed and then autoclaved at 121C for a per:iod of lO minutes to extract the vitamin Bl2 from the sample. The experimental extraction procedure followed is the method outlined by the Association of Official Analytical Chemists ;
; (llth Edition), Washington, D.C. Vitamin ~12 was yielded in an amount of 0.3 mg/l. of the digested bovine animal manure.
Example VI
The procedure of Example V was repeated with poultry manure. The assay yielded 0.16 mg/l. of vitamin Bl2.
10Example VII
.
A mixture of water and alder chips was introduced into the digester.
Approximately 7 kilograms of alder chips were used; the alder chips con-stituted approximately 12.5 percent by weight of the total mass introduced into the digester. The alder chips were approximately 0.5 mm x 0.5 mm x 4 mm in size. The initial crude protein content of the alder chips was about 1.56% by weight before digestion. The ambient temperature was in the order of 8C., when the aqueous mixture was introduced into the digester. Immediately ater the mixture was introduced into the digester, oxygenating air was pumped into the digester at a rate of 0.02 liters of air per minute per liter of aqueous mixture in the digester. At the same time the impeller was started. Aeration at this rate and agitation at this level for a period of seventeen weeks. Within 12 hours after the impeller was started and aeration begun, the temperature of the mixture began to rise from ambient and within 13-1/2 days, the temperature had reaclled 74C. During the initial start-up phase when the temperature was rising to the thermophilic digestion temperatures, s~ome foam was produced on the top of the aqueous mixture. However, no oam :
breaker was necessary to reduce the thickness of the foam layer. ~ ~
,.
i F,xample VIII
.
The procedure of Example I was repeated with the exception that potato waste ~as employed instead of animal fecal matter. The potato waste ,comprised potato peels and adjacent potato material discarded by a potato : .

processing factory. The pOtcltO waste had a crude protein content of about 9% on a dry weight basis. The potato waste had been taken ~rom the raw potatoes from 0 to 7 days prior to its introduction into the digester.
Water was added to the digester to bring the total solids content in the digester up to about 8.3 percent on a dry weight basis. Thermophilic digestion temperatures of 50C were achieved within 64 hours after beginning the agitation and aeration in accordance with the present invention. ~ ~
Thermophilic digestion was continued for a period of about 16 days. At the ~`
end of the 16 day period, the digestion product was analyzed for crude `; 10 protein and was found to contain about 25 percent protein on a dry weight ~¦
basis. ~ ;~
Example IX ~- ;
~ The procedure of Example VII was repeated after the mass had ,1 ' : '' digested at thermophilic temperatures for a period of 20 days, a sample of '~ the digestion product was taken. The sample was found to contain certain enzymes that were capable of readily attacking and degrading the cellulose in the lignocellulosic material. These enzymes were isolated and identified I as cellulase in accordance~with the procedures outlined in Sumner and Somers, ~-'!- Laboratory Experimentation, Biological Chemistry, Academic Press, New York, p. 34.
I An aliquot of the digested material was taken from the digester and was centrifuged to separate the solid material. To one ~1) ml. of the remaining liquid was added one ~1) ml. of carboxymethylcellulose reagent.
; The resulting mixture was incubated at ~0C for one hour. Two ~2) ml. of dinitrosalicyclic acid were then added to the incubated mixture. The reduction rate of sugars was then measured. Six-tenths ~0.6) mg. of reduced sugars per minute per ml. of enzyme solution was obtained. It must be noted that the foregoing determination was conducted at the pH of the digested I material ~approximately pH 8). Since cellulase functions best at a pH on ... .
the order of 4.4, it is clear that the sugar reduction rate would have been higher had the determination been conducted at the lower pH.

_ 53 _ ..

In its broadest aspects the thermophilic digestion process of the present invention can be employed t~ break ~own organic biod~gradable materials to either reduce them to a readily digestible form and to produce protein or to stabilize the material for disposal. The digested product can be fed to animals, thereby taking advantage of the nutrient ~alue in waste products such as those normally disposed of in animal processing plants `~
and fruit and vegetable canneries. Moreover, biodegradable wastes such as sewage sludges and the like can be completely stabilized by conducting the thermophilic digestion process of the present invention to a point where there is no longer sufficient nutrient for the thermophilic thermogenic bacteria to digest. The resulting product thus digested is completely stabilized and can be disposed of in a safe and economical manner. In all -i: ., cases the digestion process of the present inventionJ the thermogenic nature of the working bacteria is relied upon to both raise the temperature of the digesting materials to the thermophilic range and to maintain the thermo-philic digesting temperaturesfor periods of at least four days and longer. ~
An unexpected and important aspect of the present invention provides `
a process for microbiologically digesting lignocellulosic materials under aerobic, thermophilic conditlons. Not only does the process of the present invention digest the lignocellulosic materials, but it does so in a ~ -. ~ : ~ . .
~ relatively short time, in the order of four to eight days. The digestion ;:, process of the present invention reduces the lignocellulosic materials to a form that is readily digestible by animals. This process provides a source of additional nutrient for animals heretofore unavailablo, as prior chemical pulping processes for removing lignin from a lignocellulosic material yield products and byproducts that are not acceptable for feeding to animals.
The significant advantage of the present process for dissolving the lignocellulosic materials is that the end product does not contain the chemical contaminants normally yielded as a byproduct of the chemical pulping processes. Other important aspects of the present invention include protein production utillzing atmospheric nitrogen and production of enzymes, ., ~ .

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and amino acids.
The Foregoing inventiotl has been described in relation to preferred embodiments as well as defining the broad operational parameters of tha invention. One of ordinary skill, a~ter reading the foregoing specification, will be able to effect various changes and substitutions of equivalents, and find additional uses for the invention without departing `
from the broad concepts disclosed herein. For example, the digested product produced by the present invention as disclosed is intended for animal consumption, the product may also be fit for human consumption. All indications at this point in time are in that direction; for example, the digested product is nontoxic, is odorless, is tasteless~ and has an increased protein content over that of the undigested material.

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Claims (60)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for using thermophilic bacterial microorganisms for thermophilically digesting an aqueous mixture of a biochemically degradable organic material under aerobic conditions comprising the steps of:
introducing said mixture into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, said mixture comprising at least about 5 percent by weight of animal fecal matter, based on the total mixture, continuously introducing an oxygenating gas into said mixture and continuously, mechanically and vigorously agitating said mixture while introducing said oxygenating gas, said oxygenating gas being introduced at a rate and said mixture being agitated at a level effective to cause and promote the temperature of said mixture to rise from ambient temperatures, through mesophilic temperatures, to a temperature of at least 55°C without the addition of external heat to said mixture to form a digested product, said oxygenating gas further being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the mixture, said mixture being agitated and said gas being introduced adjacent the bottom of said digester, continuing to agitate said mixture at a level and to introduce said oxygenating gas at a rate effective to maintain said temperature of at least 55°C without the addition of external heat, said oxygenating gas being introduced at a rate sufficient to raise the dissolved oxygen level in said mixture to and maintain it above about 1.0 mg/l. after the temperature of said mixture has reached 55°C.

2. The process of claim 1 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level in said mixture above about 0.2 mg/l. before the temperature of said mixture has reached 55°C.

3. The process of claim 1 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level in said mixture between about 1.0 mg/l. and the oxygen saturation point of said mixture after the temperature of said mixture has reached 55°C.

4. The process of claim 1 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level of said mixture between about 2.0 mg/l. and about 3.0 mg/l. after said mixture has reached 55°C.

5. The process of claim 1 further comprising the steps of:
adding a biodegradable carbonaceous material to said mixture after the temperature of the mixture has reached at least 55°C, to form a biodegradable mixture, continuing to agitate said biodegradable mixture at a level and to introduce said oxygenating gas at a rate effective to maintain the dissolved oxygen level in said mixture at at least about 1.0 mg/l. and to maintain the temperature of said mixture above about 55°C.

6. The process of claim 5 wherein said oxygenating gas is air and wherein said air is continuously introduced into said digester at a rate of at least about 0.01 liter of air per minute per liter of mixture.

7. The process of claim 6 wherein said mixture is agitated at a rate sufficient to permit the microorganisms in said mixture to contact oxygenating gas at least once every two and one-half minutes.

8. The process of claim 1 wherein additional organic material is introduced into said digester in the absence of additional fecal matter after said mixture has reached thermophilic digestion temperatures, the amount of said additional organic material being less than an amount that will cause the temperature of said mixture to drop below said thermophilic digestion temperatures while maintaining said introduction of oxygenating gas and said agitation.

9. The process of claim 8 wherein said additional organic material is added in an amount up to about 50 percent by weight of said total mixture.

10. The process of claim 8 wherein said agitation is maintained at a level and said oxygenating gas is introduced at a rate sufficient to maintain the temperature of said mixture at at least 55°C temperature after said additional organic material is added to the mixture.

11. The process of claim 8 wherein said mixture is maintained at a temperature of at least 55°C for a period of about four to about eight days.

12. The process of claim 1 wherein said temperature of at least 55°C
is maintained for a period of at least four days.

13. The process of claim 1 wherein said temperature of at least 55°C
is maintained for a period sufficiently long to detoxify said mixture.

14. The process of claim 1 wherein the dry solids content of said fecal matter in said mixture is between about 5% and about 10% by weight.

15. The process of claim 1 wherein said digester comprises a digesting tank having sides and a bottom and an open top and wherein said digesting tank is insulated by positioning a layer of insulating material on the sides and bottom of said digesting tank, said introduction of oxygenating gas being in an amount sufficient to produce a foam layer on the top of the mixture, where-by the top of said mixture is insulated by maintaining said layer of foam on said mixture.

16. The process of claim 15 wherein said oxygenating gas is introduced in an amount sufficient to maintain the dissolved oxygen level in the range of from about 1.0 mg/l. to about 4.5 mg/l. after the temperature of said mixture has reached 55°C.

17. The process of claim 16 wherein said oxygenating gas is introduced in an amount sufficient to maintain the dissolved oxygen level within the range of about 2.0 mg/l. to about 3.0 mg/l. after the temperature of said mixture has reached 55°C.

18. The process of claim 1 wherein said material in said mixture when digested forms a digested product, the process further comprising the steps of:
drying the digested product to obtain a solid feed.

19. The process of claim 15 wherein said mixture is agitated by placing a rotating turbine adjacent the bottom of said digesting tank, said oxygen-ating gas being introduced into said digesting tank adjacent the bottom of said turbine and below said turbine, said oxygenating gas thereby being dispersed into a moving fluid stream in said digesting tank.

20. A process for microbiologically digesting materials containing a lignocellulose material using thermophilic microorgranisms comprising:
combining a coarsely divided lignocellulose material, water and animal fecal matter to form a matter in a digester that is insulated to prevent substantial heat loss therefrom, said mixture initially having a dry solids content of said fecal matter of at least about 5% by weight based on the total mixture, and continuously introducing an oxygenating gas into said mixture and continuously, mechanically and vigorously agitating said mixture, said oxygenating gas being introduced at a rate and said mixture being agitated at a level effective to promote and raise the temperature of said mixture from ambient temperatures through mesophilic temperatures, to at least about 55°C and to maintain the temperature of said mixture at at least about 55°C
without the addition of external heat until said lignocellulose material is digested, to thereby form a digested product comprising single cell protein, said oxygenating gas being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the mixture before said temperature reaches 55°C and to maintain a dissolved oxygen level of at least 1.0 mg/l. after said temperature reaches 55°C, said mixture being agitated and said gas being introduced adjacent the bottom of said digester.

21. The process of claim 20 wherein said temperature of at least 55°C

is maintained for a period of at least four days.

22. The process of claim 20 wherein said temperature of at least 55°C
is maintained for a period of from four to eight days.

23. The process of claim 20 wherein said oxygenating gas is air and wherein said air is introduced at a rate of at least about 0.01 liters per minute per liter of mixture.

24. The process of claim 20 wherein said oxygenating gas is air and wherein said air is introduced at a rate sufficient to maintain the dissolved oxygen level in said mixture at at least 0.2 mg/l. before the temperature of said mixture reaches 55°C.

25. The process of claim 20 wherein said mixture is agitated sufficiently to allow the thermophilic microorganisms in said mixture to contact available oxygen in said mixture at least once every two and one-half minutes.

26. A process of thermophilically digesting materials containing a lignocellulose material comprising the steps of:
mixing a coarsely divided lignocellulose material with water to form a slurry having a dry solids content of at least about 5% by weight based on the total mixture, introducing said slurry into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, ineculating said slurry with a bacterial inoculant taken from a mixture containing animal fecal matter digesting at thermophilic temperatures, continuously introducing an oxygenating gas into said slurry and continuously, mechanically and vigorously agitating said slurry, said oxygenating gas being introduced at a rate and said slurry being agitated at a level effective to promote and raise the temperature of said mixture from ambient temperatures, through mesophilic temperatures, to at least about 55°C
and to maintain the temperature of said mixture at at least 55°C without the addition of external heat until said lignocellulose material is digested, to thereby form a digested product, said oxygenating gas being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of said mixture before the temperature of said mixture reaches 55°C and at a rate sufficient to maintain the dissolved oxygen level in said mixture above about 1.0 mg/l. after the temperature of said mixture reaches 55°C, said mixture being agitated and said gas being introduced adjacent the bottom of said digester.

27. A process for thermophilically digesting materials containing a lignocellulose material comprising the steps of:
mixing a coarsely divided lignocellulose material with water to form a slurry having a dry solids content of at least about 5% by weight based on the total mixture, introducing said slurry into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, inoculating said slurry with a bacterial inoculant consisting essentially of the same bacteria as contained in Culture Accession No. 31205 deposited at the American Type Culture Collection, continuously introducing an oxygenating gas into said slurry and vigorously agitating said slurry, said oxygenating gas being introduced at a rate and said slurry being agitated at a level effective to promote and raise the temperature of said mixture from ambient temperatures, through mesophilic temperatures to at least about 55°C, and to maintain the temperature of said mixture at at least 55°C without the addition of external heat until said lignocellulose material is digested, to thereby form a digested product, said oxygenating gas being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the digesting material before the temperature of said mixture reaches 55°C
and at a rate sufficient to maintain the dissolved oxygen level in said mixture above about 1.0 mg/l. after the temperature of said mixture reaches 55°C, said mixture being agitated and said gas being introduced adjacent the bottom of said digester.

28. A process for using thermophilic bacterial microorganisms for thermophilically digesting an aqueous mixture of a biochemically degradable organic material under aerobic conditions comprising the steps of:
introducing said mixture into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, said mixture comprising at least about 5% by weight of animal fecal matter based on the whole mixture, continuously introducing an oxygenating gas into said mixture and continuously, mechanically and vigorously agitating said mixture while introducing said oxygenating gas, said oxygenating gas being introduced at a rate and said mixture being agitated at a level effective to cause and promote the temperature of said mixture to rise from ambient temperatures, through mesophilic temperatures, to a temperature of at least 55°C without the addition of external heat to said mixture, said oxygenating gas being introduced at a rate sufficient to maintain the dissolved oxygen level above about 0.2 mg/l. before the mixture reaches 55°C, said mixture being agitated by placing a rotating impeller adjacent the bottom of said digester, said oxygenating gas being introduced into said digester adjacent the bottom of and below said impeller, said oxygenating gas thereby being dispersed into a moving fluid stream in said digester, continuing to agitate said mixture at a level and to introduce said oxygenating gas at a rate effective to maintain said temperature of at least 55°C without the addition of external heat for at least about four days, said oxygenating gas being introduced at a rate sufficient to raise the dissolved oxygen level in said mixture to and maintain it above about 1.0 mg/l. after the temperature of said mixture has reached 55°C.

CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE

29. A process for using thermophilic bacterial microorganisms for thermophilically digesting an aqueous mixture of a biochemically degradable organic material under aerobic conditions comprising the steps of:
introducing said mixture into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, continuously introducing an oxygenating gas into said mixture and con-tinuously, mechanically and vigorously agitating said mixture while intro-ducing said oxygenating gas, said oxygenating gas being introduced at a rate and said mixture being agitated at a level effective to cause and promote the temperature of said mixture to rise from ambient temperatures, through mesophilic temperatures, to a temperature of at least 55°C without the addition of external heat to said mixture until said material is digested, said mixture when digested forming a digested product, said oxygenating gas further being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the mixture, continuing to agitate said mixture at a level and to introduce said oxygenating gas at a rate effective to maintain said temperature of at least 55°C without the addition of external heat, said oxygenating gas being introduced at a rate sufficient to raise the dissolved oxygen level in said mixture to and maintain it above about 1.0 mg/l. after the temperature of said mixture has reached 55°C.

30. The process of claim 29 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level in said mixture above about 0.2 mg/l. before the temperature of said mixture has reached 55°C.

31. The process of claim 30 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level in said mixture between about 1.0 mg/l. and the oxygen saturation point of said mixture after the temperature of said mixture has reached 55°C.

32. The process of claim 31 wherein said oxygenating gas is introduced at a rate suficient to maintain the dissolved oxygen level of said mixture between about 1.0 mg/l. and about 4.5 mg/l.after said mixture has reached 55°C.

33. The process of claim 32 wherein said oxygenating gas is introduced at a rate sufficient to maintain the dissolved oxygen level of said mixture between about 2.0 mg/l. and about 3.0 mg/l. after said mixture has reached 55°C.

34. The process of claim 29 wherein said oxygenating gas is air and wherein said air is continuously introduced into said digesting zone at a rate of from about 0.01 liter to 0.02 liter of air per minute per liter of mixture.

35. The process of claim 29 wherein said mixture is agitated at a rate sufficient to permit the microorganisms in said mixture to contact oxygenating gas at least once every two and one-half minutes.

36. The process of claim 29 wherein said mixture is maintained at a temperature of at least 55°C for a period of at least 4 days.

37. The process of claim 29 wherein said mixture is agitated and said gas is introduced adjacent the bottom of said digester.

38. The process of claim 29 wherein said digesting zone comprises a digesting tank having sides and a bottom and an open top and wherein said digesting tank is insulated by placing a layer of insulating material on the sides and bottom of said digesting tank, said introduction of oxygenating gas being in an amount sufficient to produce a foam layer on the top of the mixture, whereby the top of said mixture is insulated by maintaining said layer of foam on said mixture.

39. The process of claim 29 wherein said mixture is agitated by placing a rotating turbine adjacent the bottom of said digesting tank, said oxygenating gas being introduced into said digesting tank adjacent the bottom of said turbine and below said turbine, said oxygenating gas thereby being dispersed into a moving fluid stream in said digesting tank.

40. The process of claim 29 further comprising the step of extracting vitamin B12 from said digested product.

41. The process of claim 29 further comprising the steps of:
after the temperature of the mixture has reached at least 55°C, adding a biodegradable organic material to said mixture to form a biodegradable mixture, continuing to agitate said biodegradable mixture at a level and to introduce said oxygenating gas at a rate effective to maintain the dissolved oxygen level in said mixture at at least about 1.0 mg/l. and to maintain the temperature of said mixture above about 55°C.

42. The process of claim 41 wherein the added organic material is lignocellulose material.

43. The process of claim 29 wherein said organic material is ligno-cellulosic material.

44, The process of claim 42 or 43 wherein the agitation and aeration is continued to produce a digested product comprising single cell protein from said lignocellulose material.

45. The process of claim 44 wherein said single cell protein contains a greater amount of fixed nitrogen in the form of crude protein than does the lignocellulose material introduced into said mixture.

46. The process of claim 44 wherein enzymes capable of degrading lignocellulose material comprise a portion of the digested product, the process further comprising the step of extracting said enzymes from said digested product.

47. The process of claim 29 wherein said organic material comprises fecal matter and lignocellulose material.

48. The process of claim 47 wherein said agitation and aeration is continued to produce a digested product comprising single cell protein from said lignocellulose material.

49. The process of claim 48 wherein said single cell protein contains a greater amount of fixed nitrogen in the form of crude protein than does the lignocellulose material introduced into said mixture.

50. The process of claim 48 wherein enzymes capable of degrading lignocellulose material comprise a portion of the digested product, the process further comprising the step of extracting said enzymes from said digested product.

51. The process of claim 29 further comprising the step of seeding the material with organisms adapted to produce substantial amounts of amino acids, and agitating and aerating so as to promote the growth of said organisms, thereby yielding a digested product comprising amino acids.

52. The process of claim 51 wherein said organisms are seeded in said material when the temperature thereof is in the mesophilic range.

53. The process of claim 51 wherein said organisms are seeded in said material after the temperature thereof has reached 55°C.

54. The process of claim 51 wherein said organisms are especially adapted to produce lysine.

55. The process of claim 51 wherein said organisms are especially adapted to produce methionine.

56. A process for thermophilically digesting materials containing a lignocellulose material comprising the steps of:
mixing a coarsely divided lignocellulose material with water to form a slurry having a dry solids content of at least about 5% by weight based on the total mixture, introducing said slurry into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, inoculating said slurry with a bacterial inoculant taken from a mixture containing animal fecal matter digesting at thermophilic temperatures, continuously introducing an oxygenating gas into said slurry and con-tinuously, mechanically and vigorously agitating said slurry, said oxygenating gas being introduced at a rate and said slurry being agitated at a level effective to promote and raise the temperature of said mixture from ambient temperatures, through mesophilic temperatures, to at least about 55°C and to maintain the temperature of said mixture at at least 55°C
without the addition of external heat until said lignocellulose material is substantially digested, to thereby form a digested product, said oxygenating gas being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the slurry before the temperature of said mixture reaches 55°C and at a rate sufficient to maintain the dissolved oxygen level in said mixture above about 1.0 mg/l. after the temperature of said mixture reaches 55°C.

57. The process of claim 56 wherein the agitation and aeration is continued to produce a digested product comprising single cell protein from said lignocellulose material.

58. The process of claim 57 wherein said single cell protein contains a greater amount of fixed nitrogen in the form of crude protein than does the lignocellulose material introduced into said mixture.

59. The process of claim 57 wherein enzymes capable of degrading lignocellulose material comprise a portion of the digested product, the process further comprising the step of extracting said enzymes from said digested product.

60. A process for thermophilically digesting materials containing a lignocellulose material comprising the steps of:
mixing a coarsely divided lignocellulose material with water to form a slurry having a dry solids content of at least about 5% by weight based on the total mixture, introducing said slurry into a digester that is sufficiently insulated to prevent substantial heat loss therefrom, inoculating said slurry with a bacterial inoculant consisting essentially of the same bacteria as that contained in Culture Accession No.
31205 deposited at the American Type Culture Collection, continuously introducing an oxygenating gas into said slurry and vigorously agitating said slurry, said oxygenating gas being introduced at a rate and said slurry being agitated at a level effective to promote and raise the temperature of said mixture from ambient temperatures, through mesophilic temperatures to at least about 55°C, and to maintain the temperature of said mixture at at least 55°C without the addition of external heat until said lignocellulose material is digested, to thereby form a digested product, said oxygenating gas being supplied at a rate sufficient to maintain a dissolved oxygen level in said mixture effective to supply the biological oxygen demand of the digesting material before the temperature of said mixture reaches 55°C and at a rate sufficient to main-tain the dissolved oxygen level in said mixture above about 1.0 mg/l. after the temperature of said mixture reaches 55°C.