WO2008067524A2

WO2008067524A2 - Sewage-sludge-derived fertilizer and method of making

Info

Publication number: WO2008067524A2
Application number: PCT/US2007/086052
Authority: WO
Inventors: V. Joyce James
Original assignee: James V Joyce
Priority date: 2006-11-30
Filing date: 2007-11-30
Publication date: 2008-06-05

Abstract

A method of making fertilizer from wastewater sludge includes drying sludge to 70%/30% water/solids, mixing 2.5% potash per ton of solids, and 5% anhydrous ammonia. Additionally, a method of making fertilizer can include obtaining farm animal waste, adding ammonia, and adding nitrogen, the nitrogen in embodiments being in the form of urea.

Description

SEWAGE-SLUDGE-DERIVED FERTILIZER AND METHOD OF MAKING

BACKGROUND AND SUMMARY

[0001] It has been common practice to replace nutrients removed from the soil by farming using fertilizers. Nitrogen and water are the most limiting factor in crop output

worldwide. The most widely used nitrogen fertilizers today are produced from chemicals, are very concentrated, and are expensive. Nitrogen for such commercial chemical fertilizers

comes from ammonia derived from fossil fuels. The price of the nitrogen additives thus fluctuate with the price of fossil fuels, depending on the world markets. There is a need for

a fertilizer that is less dependent on fossil fuels for its additives to stabilize and reduce costs.

[0002] In an attempt to meet this need while finding a practical use for the output

of wastewater treatment plants, municipal sludge is presently being used for agricultural purposes in many locations. Such use of sludge reduces contributions to the millions of tons

of sludge that are placed in landfills each year, which can undesirably concentrate chemical substances that can invade groundwater. By some estimates, between 40-50% of the sludge

being generated is being applied on agricultural land. A typical analysis of the direct application of macronutrients and micronutrients follows.

TABLE 1

TYPICAL COMPOSITION OF RAW AND ANAEROBICALLY DIGESTED PRIMARY SLUDGES

TABLE 2 TYPICAL ANALYSIS OF SLUDGE MICRO NUTRIENTS

[0003] As can be seen, municipal sludge contains significant quantities of desirable compounds and elements for agriculture. However, sludge that is currently applied suffers several drawbacks, such as odor, undesirably high or active pathogen populations, and nutrients that are not in a form usable by the plants the fertilizer is intended to feed. Thus, there is a need for an improved form of municipal sludge that can be applied to agricultural fields without the odor, pathogen, and nutrient problems. [0004] Embodiments disclosed herein comprise a fertilizer produced at modest costs that can decrease operating costs for farmers, particularly in the United States and Latin America. The fertilizer of embodiments will use sewage sludge as its base, which already contains an average of 3.3% nitrogen. The end product of embodiments is a fertilizer that, having stabilized the sludge and added nitrates, phosphates, and potash, is an equivalent to commercial fertilizers, such as 2-2-2 or 5-5-5 type fertilizers.

[0005] Due to the nature of the sludge base, pathogen population must be knocked down or eliminated before the fertilizer can be used. Embodiments use additives, such as lime and phosphoric pentoxide, to raise the pH of the sludge to from about 12.0 to about 13.5. At these levels of pH, pathogens such as bacteria, viruses, protozoa, and Helminth worms are destroyed.

[0006] Additionally, before plants can use elements of the fertilizer, mineralization, the decomposition of organic molecules to release inorganic ions, must occur. Sewage with an average composition of approximately 3.3% nitrogen, 2.3% phosphorous, and 0.3% potassium is used in embodiments as a base for this product fertilizer/conditioner. The chemicals will be added to make up 2-2-2 fertilizer. The ratio of nitrate to phosphate to potash can be adjusted for each crop for maximum growth. In addition, the organic matter would help maintain the humus in the soil, and acts as a soil conditioner.

[0007] Since only municipal waste streams are used in embodiments, the product is by nature low in quantity of heavy metals. Each municipality effectively regulates the sludge heavy metal content since it must test for heavy metals in its waste stream, and municipal analytical records can be used to screen for sludge use in embodiments. [0008] The fertilizer of embodiments used on crops in field trials has produced

higher yields than conventional commercial fertilizer. One possible reason for this, in addition to the superior delivery of nutrients, is that the sludge fertilizer provides moisture

around the root system of the plants due to the action of deliquesce, a property of absorbing water from moisture in the air. This action tends to keep plant nutrients and

water near the roots, reduces leaching, and minimizes erosion. By some estimates, embodiments can produce 30% increased crop yields when used in place of commercial

fertilizer. Additional benefits can include an increase in soil aeration, improved soil workability, and an improved drought tolerance. Embodiments further avoid the use of

prills and formaldehyde, instead employing anhydrous ammonia as a source of nitrogen.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 is a schematic flow diagram of a method according to embodiments.

[0010] FIG. 2 is a schematic flow diagram of a variant of a method according to embodiments.

DESCRIPTION [0011] Embodiments begin by obtaining municipal or wastewater treatment plant sewage sludge. Most plants produce both digested and undigested sludge, both of which can

be used according to embodiments. While the analyses of the plants can be used as a guide, embodiments preferably include testing the sludge obtained for heavy metal organic

compounds and pathogens. Such testing preferably includes guidelines such as those shown in Table 3, below, for heavy metal organic and pathogen content. If stockpiling is necessary, sludge can be placed in a protected area to prevent contamination of the surroundings and of the sludge.

TABLE 3

CHEMICAL GUIDELINES FOR SLUDGE

[0012] Depending on the water content of the sludge, embodiments contemplate drying the sludge. Sludge must have the appropriate water/ solids before proceeding. In embodiments, a preferred water/ solids ratio is 70% water to 30% solids, such as humic solids.

[0013] The sludge can be processed in a large mixing chamber or the like.

Embodiments contemplate loading the chamber with a conveyor belt on which the sludge can be deposited, but other methods and containers can be used. Once the sludge is in a suitable container, embodiments proceed by adding micro- and macronutrients as appropriate to achieve a desired grade of fertilizer, such as 2-2-2, 4-4-4, 5-5-5, or even 10- 10-10 fertilizer. Preferably, potash, phosphate, liquid ammonia, and urea are added. The liquid ammonia employed is preferably 32% anhydrous liquid ammonia, though other formulations could be used with modifications. Mixing of the sludge with the additives commences in the chamber until a thorough mixture is achieved, the mixture representing a finished fertilizer product that can be bagged or otherwise contained and shipped. [0014] Biological sewage sludge contains sufficient levels of pathogens to pose a public health and environmental concern. EPA Regulation Part 305 requires sewage sludge to be treated by a Class A pathogen treatment process or a Class B process with site restrictions. Some of the factors that influence the survival of pathogens include pH, heat, competition from other microorganisms, sunlight, contact with host organisms, proper nutrients and moisture level. Embodiments treat for parasites while disallowing the reinfestation of the fertilizer through protozoan cysts or helminth ova.

[0015] Fecal coliform bacteria are abundant in human feces and therefore are always present in untreated sludge. When processing sludge according to embodiments, studies of aerobic or anaerobic digestion of sludge have shown the reduction of these pathogens will be significant and sufficient. With the additives of embodiments, there is no significant regrowth of pathogen populations and it is believed that high pH, along with the use of liquid ammonia, inactivates some pathogens, such as Cryptosporidium oocytes.

[0016] With regard to particular pathogens in Class A Biosolids, regulations require that populations be reduced below particular limits, as can be seen in Table 4 below.

TABLE 4 PATHOGEN REQUIREMENTS

[0017] The method of embodiments reduces pathogen population in sludge by elevating the pH of the sludge to about 12 or more and maintaining this pH for more than 72 hours. It is not necessary to keep any particular pH save that the pH remains at or above about 12. [0018] Preferably, applying biosolids occurs during the elevated pH period to reduce odor. Alternate odor management practices in the field can be employed, such as injecting, incorporating, or top dressing the biosolids with additional lime. Such lime stabilization can reduce bacteria and viral pathogens by 99% or more.

[0019] As disclosed above, embodiments produce a multinutrient fertilizer containing several additives, including sludge, hydrated lime, liquid ammonia, phosphate (P₂O₅), and potash (K₂O). Embodiments particularly aim to provide fertilizers that are equivalent to currently available chemical fertilizers. Thus, embodiments contemplate producing a 2-2-2 fertilizer, a 4-4-4 fertilizer, a 5-5-5 fertilizer, and/or a 10-10-10 fertilizer, though the method could be employed to make fertilizers with other weight portions. To obtain 4-4-4 fertilizer according to embodiments, the appropriate ratios are obtained using a formula as illustrated in Table 5, below. Specific quantities of nitrogen, phosphate, and potash are included to make eighty pounds (80 lbs.) of each nutrient available in approximately 2000 pounds of fertilizer. As Table 5 indicates, a fertilizer unit is 20 lbs. of the respective nutrient. Thus, 80 pounds of nutrient represents 4 units, and when each of nitrogen, phosphorous, and potash are at 4 units, the fertilizer is a 4-4-4 fertilizer. Table 5 also illustrates how the lime component is used as pH adjustment to reach a pH of from about 12 to about 13.5 to destroy pathogens.

TABLE 5 ORGANIC FERTILIZER COMPOSITION OF 4-4-4

[0020] To obtain 5-5-5 fertilizer according to embodiments, the appropriate ratios are obtained using a formula as illustrated in Table 6, below. Specific quantifies of nitrogen, phosphate, and potash are included to make one hundred pounds (100 lbs.) of each nutrient available in approximately 2000 pounds of fertilizer. As Table 6 indicates, a fertilizer unit is 20 lbs. of the respective nutrient. Thus, 100 pounds of nutrient represents 5 units, and when each of nitrogen, phosphorous, and potash are at 5 units, the fertilizer is a 5-5-5 fertilizer.. Table 6 also illustrates how the lime component is used as pH adjustment to reach a pH of from about 12 to about 13.5 to destroy pathogens.

TABLE 6

ORGANIC FERTILIZER COMPOSITION OF 5-5-5

100 Ib. Limestone CaO (1 .5% Mg) for a pH adjustment

Equations: 1 ) 4P + 5O₂ = 2P₂O₅ % P in P₂O₅ 62P/ = 44%

124 + 160 = 284 142 P₂O₅

2) 4K + O₂ = 2 K₂O % K in K₂O 39.1 K/ = 42%

156 + 32 = 188 94 K₂O

[0021] To obtain 10-10-10 fertilizer according to embodiments, the appropriate

ratios can be obtained, for example, using a formula as illustrated in Table 7, below. Specific quantities of nitrogen, phosphate, and potash are included to make two hundred pounds

(200 lbs.) of each nutrient available in approximately 2000 pounds of fertilizer. As Table 7 indicates, a fertilizer unit is 20 lbs. of the respective nutrient. Thus, 200 pounds of nutrient

represents 10 units, and when each of nitrogen, phosphorous, and potash are at 10 units, the fertilizer is a 10-10-10 fertilizer. Table 7 also illustrates how the lime component is used

as pH adjustment to reach a pH of from about 12 to about 13.5 to destroy pathogens. TABLE 7 ORGANIC FERTILIZER COMPOSITION OF 10-10-10

100 Ib. Limestone CaO (1.5% Mg) for a pH adjustment

Equations: 1 ) 4P + 5O₂ = 2P₂O₅ % P in P₂O₅ 62P/ = 44%

124 + 160 = 284 142 P₂O₅

2) 4K + O₂ = 2 K₂O % K in K₂O 39.1 K/ = 42%

156 + 32 = 188 94 K₂O

[0022] Other ways of approaching these formulations include starting with a ton of

sewage and adding the additional components to achieve the desired number of units of each nutrient. The final weight is thus 2000 pounds of sewage plus the weight of the additional components, which will vary depending on the particular number of units

desired.

[0023] It should be noted that only approximately 47-48 percent of the urea activates as usable nitrogen, necessitating a higher weight of urea in the mix than is the case

for P₂O₅ and K₂O to achieve the desired ratios.

[0024] Embodiments thus use uncontaminated municipal sludge in combination

with additives that are not commonly used in commercial fertilizer to produce a viable fertilizer from municipal sludge. While commercial fertilizers are made up of a source of phosphorus, potassium and nitrogen in the form of nitrate in urea, and other ingredients, the main ingredient of the new fertilizer is municipal sludge, with added phosphate and potash. Other additives, such as liquid ammonia, can be used for odor control, nitrogen source, and pathogen control. Phenol can also be used for pathogen control.

[0025] Additionally, embodiments contemplate the use of farm animal waste as the sewage sludge base for the fertilizer. For example, chicken waste can be employed, which comprises about 4% nitrogen, 2% potassium, and 3% phosphorous. To this, embodiments add ammonia and nitrogen, the ammonia sanitizing the chicken waste and adding to the nitrogen level. An additional source of nitrogen in this and other embodiments can be urea.

[0026] It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will also be appreciated that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

WHAT IS CLAIMED IS:

Claims

1. A method of producing a wastewater sludge-based fertilizer comprising: obtaining wastewater sludge; testing the sludge obtained for heavy metal organic compounds and pathogens; drying the sludge to a predetermined water to solids ratio; and mixing the sludge with micro- and macronutrients to achieve an equivalent to a desired grade of fertilizer.

2. The method of claim 1 wherein the sludge is digested.

3. The method of claim 1 wherein the sludge is undigested.

4. The method of claim 1 wherein drying the sludge comprises drying to a water/solids ratio of 70% water to 30% solids.

5. The method of claim 1 wherein mixing the sludge comprises loading the sludge into a mixing chamber with a conveyor belt.

6. The method of claim 1 wherein the desired grade is 4-4-4 fertilizer.

7. The method of claim 1 wherein the desired grade is 5-5-5 fertilizer.

8. The method of claim 1 wherein mixing comprises adding potash, phosphate, and liquid ammonia.

9. The method of claim 8 wherein adding liquid ammonia comprises adding 32% anhydrous liquid ammonia.

10. The method of claim 8 wherein adding comprises adding 2.5% potash per ton of solids and adding 5% total volume of liquid ammonia.

11. The method of claim 8 wherein mixing further comprises adding 8 ounces per ton of LYSOL®.

12. A fertilizer composition consisting of sludge of 70% water and 30% solids, 2.5% per ton potash, and 5% volume of 32% anhydrous ammonia.

13. A method of making a farm animal waste fertilizer comprising obtaining farm animal waste, adding ammonia, and adding nitrogen.

14. The method of claim 13 wherein adding nitrogen comprises adding urea.