WO2024068556A1

WO2024068556A1 - A method for processing fines

Info

Publication number: WO2024068556A1
Application number: PCT/EP2023/076411
Authority: WO
Inventors: Lisa ROSGAARD; Anna GRANLY HANSEN
Original assignee: Renescience A/S
Priority date: 2022-09-26
Filing date: 2023-09-25
Publication date: 2024-04-04

Abstract

The present invention relates to a method of processing fines and a method for producing a bioliquid suitable as a methane substrate. The use of fines from waste for producing a bioliquid suitable as a biogas, e.g., methane substrate, as well as a method of producing methane. In particular, the present invention relates to a method for processing fines and producing a bioliquid suitable as a methane substrate from fines of waste, such as municipal solid waste (MSW).

Description

A Method for processing fines

Technical field of the invention

The present invention relates to a method for processing fines, use of fines from waste for producing a bioliquid, as well as a method of producing bioliquid and biogas, such as methane and other green energy products. In particular, the present invention relates to a method for processing fines and producing a bioliquid, which is suitable as a methane substrate from fines of waste, such as municipal solid waste (MSW).

Background of the invention

There is an increasingly need to exploit the resources and energy stored within waste comprising organic material. Agricultural material/waste, household waste and municipal waste are examples of sources containing a high content of dry matter and organic material, where it is of particular interest to effectively utilize the resources and the stored energy within the organic material instead of disposing or incineration of the waste, which less effectively utilizes the stored energy. Considerable interest has arisen in development of efficient and environmentally friendly methods of processing waste, to maximize recovery of their inherent energy potential and, also, to recover recyclable materials.

The commonly used methods for treatment and subsequent disposal of waste such as household, agricultural or municipal waste include among others incineration, landfill, mechanical and biological treatment, where the method of choice often depends on e.g., the content of organic material compared to the content of non- organic material. However, none of these methods can effectively process the fines fraction of waste and thereby utilize the energy potential of this fraction.

The fines fraction of waste or the fines resulting from treating waste are problematic for incineration plants due to small size, sticky nature of the fines and for the AD plants when used directly since they cause extensive sedimentation. Also, facilities such as mechanical biological treatment (MBT) produces fines as output products, which are currently mainly processed without utilization of energy by composting (without energy recovery and without using compost as fertilizer) or treated in AD plants where extensive sedimentation causes operation expenses. Yet the fines fraction comprises a significant energy potential, which is currently not exploited in full.

The present inventors have found that fines from waste, e.g., household waste, such as MSW, can be processed according to a method based on enzymatic hydrolysis and/or microbial fermentation, such method have shown suitable for processing waste e.g., unsorted waste such as MSW wherein the waste, comprising organic matter, is subject to enzymatic treatment and/or microbial fermentation to produce a bioliquid and recyclable and non-recyclable solids. Examples of such processes are disclosed in W02006056838, W02007036795, WO2011032557, WO2013185778, WO2014198274, W02016030480, W02016030472,

W02016050893, WO2017174093, WO2017076421 and WO2019158477, which is hereby expressly incorporated by reference in their entirety. Applying a method of enzymatic hydrolysis and/or microbial fermentation to the fines effectively utilize the energy potential in the fraction. This is surprising as this fraction up to now have not been considered suitable for effective conversion to energy. Processing fines according to the method of the invention provides, improved energy recovery and operation comparing to current treatment methods, as well as reduced mechanical problems in e.g., AD plants in comparison to when fines are treated directly in AD plant.

The Fines fraction may be an intermediate fraction or an end product of processing of e.g., waste in a Mechanical Biological Waste Treatment (MBT) facility, which combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion. A fines fraction may also be produced from Materials Recycling Facilities (MRF) and Refuse- Derived Fuel (RDF) production. Fines may also be produced by other means of treating waste, such as household waste by e.g., liquefaction of the waste, optionally subsequent solid-liquid separation, followed by e.g., filtering or sieving the liquified waste. Alternatively, a fines fraction may be produced directly from the waste by sorting and e.g., sieving to a particle size below approximately 150 mm.

In particular, the present invention provides a method for efficient energy recovery from the fines fraction without extensive mechanical problems in e.g., an AD plant. The invention further provides a bioliquid obtained by treating fines from waste, such as MSW or from a MBT like facility, using the method of the present invention which give rise to a significant methane potential and in some embodiments even an improved methane potential compared to the methane potential obtained using MSW. Thus, the inventors have surprisingly found the fines can be effectively processed and the energy potential released and in addition, that the fines have significant biogas potential when processed according to the method of the present invention. Further, the bioliquid from fines may even have a higher biogas e.g., methane potential, biofuel or chemical production potential, than bioliquid from waste, such as MSW.

These findings are advantageous since, as described above, the fines fraction is in general considered a problematic intermediate product, or final processed product, or end-product of most waste processing facilities and thus a product suitable only for biodrying, landfill or restoration i.e., without exploiting the energy potential of the fraction. By isolation or retrieving the fines fraction a very potent bioliquid with high energy potential can be retrieved and processed to provide green energy products, such as biogas.

Thus, the method of the invention provides an improved, compared to current treatment methods used in the industry, energy recovery from fines e.g., originated from waste, preferably MSW. The method of processing fines using enzymatic hydrolysis and/or microbial fermentation provides a bioliquid with a surprisingly high methane potential.

Summary of the invention

One aspect relates to a method for processing fines from waste, such as MSW comprising the steps of:

(i) providing fines from waste, wherein the fines are obtained by separation of the waste using a separator, preferably a sieve or ballistic separator, having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages; (ii) enzymatic hydrolysis and/or microbial fermentation of the biodegradable organic material of the fines resulting in liquefaction of organic material of the fines; optionally followed by

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines and microbial metabolites.

Non-biodegradable solids may be further treated with purpose of recovery of resources and/or energy recovery.

A second aspect of the present invention relates to a method of producing methane comprising the steps of

(i) providing fines from waste, wherein the fines are obtained by separation of the waste using a separator, preferably a sieve or ballistic separator, having a screen size of between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

(ii) enzymatic hydrolysis and/or microbial fermentation of the biodegradable parts of the fines resulting in liquefaction of biodegradable parts of the fines, preferably wherein microbial fermentation is performed concurrently with the enzymatic hydrolysis and, more preferably, is accomplished by inoculation using lactic acid bacteria, or bacteria naturally present in the waste; optionally followed by

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines comprising microbial metabolites;

(iv) transferring the bioliquid into an anaerobic digestion system;

(v) conducting anaerobic digestion of the bioliquid to produce methane, wherein the anaerobic digestion is conducted at a pH between 6.0 and 9.0, preferably between 6.5 and 8.5, most preferred 8.0.

A third aspect of the present invention relates to the use of fines from waste, such as municipal solid waste (MSW), for producing a bioliquid suitable as a methane substrate comprising the steps of: (i) providing fines from waste, wherein the fines are obtained by separation using a separator, preferably a sieve or ballistic separator, having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines comprising microbial metabolites.

A fourth aspect of the present invention relates to a bioliquid suitable as a methane substrate obtained from fines of waste, such as municipal solid waste (MSW), obtained by the process of:

(i) providing fines from waste, wherein the fines are obtained by separation using a separator, preferably a sieve or ballistic separator, having a screen size between 30 mm to 100 mm, preferably screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

Description of drawings

Figure 1 illustrates an exemplary reactor. The exemplary reactor is a low stationary large diameter tanks upright standing equipped with various agitation equipment, such as: (a) a bottom scraper that can extract heavy sedimented particles as sand, metal, glass etc. after short retention/processing time such as 1 hour or from 10 min to 5 hours, or

(b) a top skimmer that can extract the floating layer as plastic bottles, polystyrene, wood and other low density after short retention/processing time such as 1 hour or from 10 min to 5 hours, or

(c) a submerged agitator/mixer system that can secure good mixing between liquid, enzymes and fines.

Detailed description of the invention

The present invention provides a method for processing of fines and utilising the energy potential of this fraction. The inventors have found that the bioliquid from fines e.g., from waste have significant energy potential. The energy potential of the fines is utilized by processing fines from waste e.g., municipal solid waste or (partly) processed waste from e.g., a Mechanical Biological Waste Treatment (MBT) facility, in combination with the enzymatic hydrolysis and/or microbial fermentation, which provides a bioliquid with a surprisingly high energy potential, such as methane potential when used as a methane substrate.

Thus, the present inventors have found that fines from waste, such as municipal solid waste (MSW) or other types of waste comprising fines, can be processed effectively according to the method of the invention and provides surprising energy potential e.g., measured as methane potential when treated according to the method of the present invention.

In particular, the bioliquid obtained by treating fines from MSW using the method of the present invention gives rise to a significantly improved methane potential as compared to the methane potential of bioliquid obtained using MSW or compared to the methane potential of other methods of treating waste.

The fines fraction may be derived directly from waste e.g., after sorting of fines may be the intermediate fraction or a product of processing of waste e.g., in a MBT facility, which combines a sorting facility with a form of biological treatment, such as composting or anaerobic digestion. MBT plants are designed to process mixed household waste as well as commercial and industrial wastes, thus the fines may derive from any of these types of waste. A bioliquid with high energy potential results from treatment of fines in an enzymatic hydrolysis and/or microorganism process as described in the present invention, such as an enzymatic hydrolysis and/or microorganism process, wherein the fines are derived from the mainly biodegradable component of waste, which have been treated in a MBT plant.

The high energy potential of the bioliquid from fines renders the method of the invention and resulting bioliquid more beneficial to the environment by increasing the energy output as compared to other methods of treating waste or treatment of other waste fractions and provides at the same time a better overall process economy rendering the final product e.g., bioethanol or biogas such as methane more competitive in terms of lower costs to the end user.

The higher energy potential or density of the bioliquid from fines provides for a higher output of methane per ton bioliquid as compared to other waste or waste fractions when fines are treated according to the method of the present invention.

In one embodiment the bioliquid result from treatment of fines in an enzymatic hydrolysis and/or microorganism fermentation, wherein the fines are derived from the mainly biodegradable component of waste which have been treated in a MBT plant, where such treatment is usually composting or anaerobe digestion.

One aspect relates to a method for processing fines from waste, wherein the fines are derived from the mainly biodegradable component of waste, which may have been treated in a MBT or similar plant, comprising the steps of:

(i) providing fines from waste, wherein the fines are obtained by separation of waste using a separator, preferably a sieve or ballistic separator, having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

(ii) enzymatic hydrolysis and/or microbial fermentation of the biodegradable organic material of the fines resulting in liquefaction of organic material of the fines; optionally followed by

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines. As mentioned above the bioliquid obtained by treating fines from MSW using the method of the present invention gives rise to a significantly improved methane potential as compared to the methane potential of bioliquid obtained using MSW.

One aspect relates to a method for processing fines from waste, such as municipal solid waste (MSW), comprising the steps of:

Non-biodegradable solids may be further treated with purpose of recovery of resources and/or energy.

In one embodiment, the fines are obtained by separation of waste or any fraction hereof, using a separator, preferably a sieve or ballistic separator, having screen size between 20 mm to 150 mm, between 30 mm to 150 mm, between 50 mm to 150 mm, between 30 mm to 100 mm, between 50 mm to 100 mm, between 70 mm to 150 mm, between 70 mm to 100 mm, preferably between 40 mm to 70 mm, more preferably screen size between 40 mm to 50 mm, most preferably about 50 mm or below.

In another embodiment, the fines are obtained by separation of waste or any fraction hereof, using a separator, preferably a sieve or ballistic separator, having screen size about 20 mm, a screen size of about 30 mm, a screen size of about 40 mm, a screen size of about 50 mm, a screen size of about 60 mm, a screen size of about 70 mm, a screen size of about 80 mm, a screen size of about 90 mm, a screen size of about 100 mm, a screen size of about 110 mm, a screen size of about 120 mm, a screen size of about 130 mm, a screen size of about 130 mm, a screen size of about 140 mm or a screen size of about 150 mm.

In another embodiment, the fines are obtained by sieving the waste through a sieve having screen size of 150 mm or below, 100 mm or below, preferably screen size of 70 mm or below, more preferably screen size of 50 mm or below.

The separation can take place in one stage or multiple stages, e.g., by decreasing the screen size.

An alternative aspect relates to a method for processing fines from waste, comprising the steps of:

(i) providing fines from waste, such as municipal solid waste (MSW), wherein at least 50%, such as at least 60%, preferably at least 75%, more preferably at least 90%, most preferably 100% by weight of the fines have a particle size in the range of 0 to 100 mm, preferably 0.01 to 100 mm, more preferably 0.01 to 70 mm, most preferably 0.01 to 50 mm or can pass through a screen size of 30 mm to 100 mm, such as 40 mm to 70 mm or 40 mm to 50 mm;

In one embodiment of the present invention, the fines have a major part of material with particle size of 50 mm or below, such as at least 60%. In one embodiment the fines comprise 15-100%, such as 35-100%, such as 50-100%, preferably 60- 100%, more preferably 75-100%, most preferably 90-100% by weight of fines having a particle size in the range of 0 to 150 mm, such as 0.01 to 100 mm, such as 0.01 to 90 mm, such as 0.01 to 80 mm, such as 0 to 70 mm, such as 0 to 50 mm, such as 0.01 to 70 mm, such as 0.01 to 50 mm, such as 0.1 to 50 mm or preferably 0.01 to 70 mm. In another embodiment, a major part such as 50-100%, preferably 60-100%, more preferably 75-100%, most preferably 80-100% by weight of the fines have a particle size of 100 mm or below, 70 mm or below, such as 50 mm or below, preferably in the range of 0.01 to 50 mm, such as 0.01 to below 50 mm, such as 0.01 to 49.9 mm or preferably 0.01 to 49 mm.

In an additional embodiment of the present invention, the fines have a particle size in the range of 0 to 100 mm, such as 0 to 70 mm, such as 0.01 to 100 mm, such as 0.01 to 70 mm, such as 0.1 to 50 mm or preferably 0.01 to 70 mm. In a further embodiment, the fines have a particle size below 50 mm, preferably a particle size in the range of 0.01 to below 50 mm, such as 0.01 to 49.9 mm or preferably 0.01 to 49 mm.

In one embodiment the fines can pass through a screen size of 20 mm to 150 mm, such as a screen size of 30 mm to 150 mm, such as 40 to 150 mm, such as 50 to 150 mm, such as 30 mm to 100 mm, such as 40 mm to 100 mm, such as 50 mm to 100 mm, such as 70 mm to 100 mm, such as 40 mm to 70 mm or such as 40 mm to 50 mm.

In one embodiment, a major part such as 50-100%, preferably 60-100%, more preferably 75-100%, most preferably 80-100% by weight of the fines can pass through a screen size of 20 mm to 150 mm, such as a screen size of 30 mm to 150 mm, such as 40 to 150 mm, such as 50 to 150 mm, such as 30 mm to 100 mm, such as 40 mm to 100 mm, such as 50 mm to 100 mm, such as 70 mm to 100 mm, such as 40 mm to 70 mm or such as 40 mm to 50 mm.

In one embodiment the fines can pass through a screen size of about 20 mm, a screen size of about 30 mm, a screen size of about 40 mm, a screen size of about 50 mm, a screen size of about 60 mm, a screen size of about 70 mm, a screen size of about 80 mm, a screen size of about 90 mm, a screen size of about 100 mm, a screen size of about 110 mm, a screen size of about 120 mm, a screen size of about 130 mm, a screen size of about 130 mm, a screen size of about 140 mm or a screen size of about 150 mm.

As mentioned above, the energy potential of the fines expressed as the methane potential has been effectively utilized by the method of the present invention. In one embodiment of the present invention, the bioliquid from fines has a methane potential in the range of 20 to 200 Nm3/ ton fines, 30 to 200 Nm³/ton fines, 40 to 200 Nm³/ton fines, 50 to 200 Nm3/ ton fines, 60 to 200 Nm³/ton fines, 70 to 200 Nm³/ton fines, 80 to 200 Nm3/ ton fines, 90 to 200 Nm3/ ton fines, 20 to 150 Nm3/ ton fines, 50 to 150 Nm3/ ton fines, 70 to 150 Nm3/ ton fines, 90 to 150 Nm3/ ton fines, 20 to 100 Nm3/ ton fines, 30 to 100 Nm3/ ton fines, 40 to 100 Nm3/ ton fines, 50 to 100 Nm3/ ton fines, preferably 20 to 200 Nm³/ton fines, 30 to 200 Nm³/ton fines, 40 to 200 Nm³/ton fines, 50 to 200 Nm³/ton fines, preferably 60 to 150 Nm³/ton fines, more preferably 65 to 100 Nm³/ton fines, most preferably 70 to 100 Nm³/ton finesNm³/ton fines at STP 0 °C and 1 atm.

In one embodiment, the fines have a methane potential ratio compared to MSW of 1.1: 1 - 2: 1, preferably 1.2:1 - 2: 1, more preferably 1.3:1 - 2: 1, most preferably 1.4: 1 - 2: 1.

In another embodiment of the present invention, the fines obtained in step (i) is mixed with liquid in an amount of 100 to 10.000 L/ton fines, 500 to 5000 L/ton fines or preferably 1000 - 3000 L/ton fines, before enzymatic hydrolysis and/or microbial fermentation in step (ii).

The liquid may be any of, water e.g., brown water, rainwater, towns water or water from any other source such as lakes, sea etc. The liquid may further be recycled water from the process by which the fines are liquified. In one embodiment the liquid is bioliquid. In another embodiment of the present invention, the liquid is provided by recycling wash waters or process solutions used to recover residual organic material from non-degradable solids.

In another embodiment of the present invention, inoculation with microorganisms is provided by recycled water from the process by which the fines are liquified, bioliquid, or wash waters or process solutions used to recover residual organic material from non-degradable solids.

In one embodiment of the present invention, the non-water or dry matter content of the fines is between 10 and 100%, between 10 and 80%, between 10 and 70%, between 20 and 70%, between 30 and 65%, between 40 and 65% between 45 and 65%, preferably between 50 and 65%, more preferably between 50 and 65% by weight of fines.

In another embodiment of the present invention, microorganism inoculation and/or enzyme hydrolysis of fines is provided at least partly by recycling wash waters (or liquids used for washing) or liquid process solutions (process water or process liquid). The liquid added in step (ii) is used for liquefaction of fines as well as to recover residual organic material from non-degradable solids.

It can be advantageous to adjust the temperature in the method of the invention prior to initiation of enzymatic hydrolysis and/or microbial fermentation in step (ii). In a preferred embodiment of the invention, at least one enzyme used in the hydrolysis of fines comprises cellulase activity. As is well known in the art, cellulases and other enzymes typically exhibit an optimal activity within temperature range 30°C - 75°C. The objective of heating may simply be to render the majority of e.g., cellulosic fines from waste and a substantial fraction of the fines from waste in a condition optimal for enzymatic hydrolysis and/or microbial fermentation. To be in a condition optimal for enzymatic hydrolysis and/or microbial fermentation, fines should ideally have a temperature and water content appropriate for the enzyme activities used for enzymatic hydrolysis. Thus, one embodiment of the present invention, the liquid e.g., water is preheated to a temperature in the range of 30- 75 °C, preferably 45-56 °C, more preferably around 50 °C, such as 49-51°C. In one further embodiment the temperature of the method of the invention is in the range 30°C - 75°C, and preferably the liquid (e.g., water) to fines ratio within the range of 100 to 10.000 L/ton fines, 500 to 5000 L/ton fines or preferably 1000 - 3000 L/ton fines, before enzymatic hydrolysis and/or microbial fermentation in step (ii).

It can be advantageous to agitate during heating to achieve evenly heated fines from waste. Agitation further achieves the introduction of mechanical energy to create shear forces in the fines. Agitation can comprise free-fall mixing, such as mixing in a reactor, which may have a chamber that rotates along a substantially horizontal axis or in a mixer having a rotary axis lifting the slurry of fines or in a mixer having horizontal shafts or paddles lifting slurry of fines. Agitation can comprise one or more of shaking, stirring or conveyance through a transport screw conveyor. The agitation may continue after the slurry of fines has been heated to the desired temperature.

The method of the invention may be performed in a long horizontal and rotating tank or reactor, sometimes termed a bioreactor, wherein step (ii) enzymatic hydrolysis and/or microbial fermentation is performed. Such reactors are often big, complicated, and expensive. When processing fines according to the method of the invention another type of reactor design may be applied that may have some additional benefits.

An example of such reactor is shown in Figure 1

The reactor is a low stationary large diameter tanks upright standing equipped with various agitation equipment, such as:

(a) a bottom scraper that can extract heavy sedimented particles such as sand, metal, glass etc. after short retention/processing time such as 1 hour or from 10 min to 5 hours, or

(b) a top skimmer that can extract the floating layer such as plastic bottles, polystyrene, wood and other low-density elements after short retention/processing time such as 1 hour or from 10 min to 5 hours, or

Such reactor has many similarities to e.g., clarifiers used in the mining industry or separation tanks (sedimentation tanks, settling tanks) used in waste-water treatment systems. Furthermore, several reactors can easily be arranged in a system that allows for optimal separation and transport of the various content of the fines fraction and allowing these fractions for optimal recycling, retention time, temperature, pH, flocculation media, enzyme composition and enzyme concentration.

The reactors can be placed in a way that allows for easy hydraulic transport/flow from one reactor to the next and/or for easy transporting of fractions in/out of the area. In one particular embodiment of the invention step (ii) enzymatic hydrolysis and/or microbial fermentation of fines is performed in a reactor, e.g., a reactor as shown in Figure 1, wherein agitation equipment such as

In a further embodiment of the present invention, if inoculation with microorganisms is performed, the inoculation with microorganisms may be made before or concurrently with the addition of enzymatic activities or with the addition of microorganisms that exhibit extra-cellular cellulase activity. In one preferred embodiment the fermentation of the fines in step (ii) is made by microorganisms already present in waste or the fines from waste. In one embodiment of the present invention, microbial fermentation of step (ii) is accomplished by inoculation using e.g., lactic acid bacteria, or with bacteria naturally present in the waste. Preferably, microbial fermentation in step (ii) is performed concurrently with the enzymatic hydrolysis.

The enzymes of the enzymatic activities used in the method according to the present invention may comprise cellulase(s) and/or hemicellulase(s) as defined herein, such as one or more of exoglucanases, endoglucanases, endoxylanases, xylosidases, acetyl xylan esterases and beta glucosidases, including any combination thereof.

The enzymatic activities may be added in an amount of 0.01-2%, such as in an amount of 0.01-1.5%, such as in an amount of 0.1-1.0%, preferably 0.1-0.9%, more preferably 0.125-0.9% by weight of the fines. The enzyme, such as cellulase activity may be added to step (ii) (a) by inoculation with a selected microorganism that exhibits extra -cellular enzyme such as cellulase activity and/or (b) as an isolated enzyme e.g., cellulase preparation.

In an additional embodiment of the present invention, the microbial fermentation if this is accomplished by inoculation use one or more species of lactic acid bacteria.

In one embodiment of the present invention, the enzymatic hydrolysis and/or microbial fermentation are conducted within the temperature range of 30-75 °C, preferably 45-56 °C, more preferably around 50 °C, as described above. The enzymatic hydrolysis and/or microbial fermentation may be performed for a period of 1-48 hours, preferably 5-30 hours, preferably 10-48 hours, preferably 5-24 hours, preferably 15-30 hours, more preferably 15-24 hours, most preferably 18- 24 hours.

In another embodiment of the present invention, the enzymatic hydrolysis and/or microbial fermentation are conducted at a pH between 4.0 and 8.5, between 4.0 and 6.0, preferably between 4.5 and 5.5.

Step iii) is an optional separation, where the bioliquid is separated from the non- degradable solids. The separation in step iii) may be performed by any means known in art, such as in a mechanical filter, sieves, ballistic separator, washing drums, hydraulic presses, etc.

Step iii) can be conducted in one separation operation or in a combination of at least two different separations operations.

Fines can be processed effectively according to the method of the invention and provides surprising energy potential e.g., measured as methane potential when treated according to the method of the present invention.

(i) providing fines from waste, wherein the fines are obtained by separation of waste using a separator, preferably a sieve or ballistic separator having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

(ii) enzymatic hydrolysis and microbial fermentation of the biodegradable parts of the fines resulting in liquefaction of biodegradable parts of the fines, preferably wherein microbial fermentation is performed concurrently with the enzymatic hydrolysis and, more preferably, is accomplished by inoculation using lactic acid bacteria, or bacteria naturally present in the waste; optionally followed by

(iv) transferring the bioliquid into an anaerobic digestion system;

An alternative aspect of the present invention relates to a method of producing methane comprising the steps of

(i) providing fines from waste, such as MSW, wherein at least 50%, such as at least 60%, preferably at least 75%, more preferably at least 90%, most preferably 100% by weight of the fines have a particle size in the range of 0 to 100 mm, preferably 0.01 to 100 mm, more preferably 0.01 to 70 mm, most preferably 0.01 to 50 mm or can pass through a screen size of 30 mm to 100 mm, such as 40 mm to 70 mm or 40 mm to 50 mm;

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines comprising microbial metabolites; (iv) transferring the bioliquid into an anaerobic digestion system;

(v) conducting anaerobic digestion of the bioliquid to produce methane.

Anaerobic digestion (AD) is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products is methane, which can be combusted to generate electricity, heat and/or can be processed into renewable natural gas and/or transportation fuels. A range of anaerobic digestion technologies exists in the state of the art for converting waste, such as municipal solid waste, municipal waste-water solids, food waste, high strength industrial waste water and residuals, fats, oils and grease, and various other organic waste streams into biogas. Many different anaerobic digester systems are commercially available, and the skilled person will be familiar with how to apply and optimize the anaerobic digestions process. The metabolic dynamics of microbial communities engaged in anaerobic digestion are complex. In typical anaerobic digestion for production of methane biogas, biological processes mediated by microorganisms achieve four primary steps - hydrolysis of biological macromolecules into constituent monomers, polymers and/or oligomers or other metabolites; acidogenesis, whereby short chain hydrocarbon acids and alcohols are produced; acetogenesis, whereby available nutrients are catabolized to acetic acid, hydrogen and carbon dioxide; and methanogenesis, whereby acetic acid and hydrogen are catabolized by specialized archaea to methane and carbon dioxide.

The anaerobic digestion may comprise one or more reactors operated under controlled aeration conditions, eliminating or minimizing the available oxygen, in which methane gas is produced in each of the reactors comprising the system. The AD reactor(s) can, but need not, be part of the same waste or fines processing plant as the bioreactor applied in step ii) in the methods of the invention, and can, but need not, be connected to the bioreactor in step ii). Moreover, the AD process may be in the form of a fixed filter system. A fixed filter anaerobic digestion system is a system in which an anaerobic digestion consortium is immobilized, optionally within a biofilm, on a physical support matrix.

In order for the AD process to work efficiently, the pH should generally remain between 6.0 and 9.0, preferably between 6.5 and 8.3. This can be largely affected by the carbon dioxide produced within the methane. The process itself produces the pH buffer (alkalinity concentration) by the production/release of HCCh' and NH4⁺. Stability may be increased by maintaining high alkalinity concentrations. Decreases in pH may be due to accumulation of organic acid intermediates, often due to the presence of waste elements that reduce the ability of methanogens to turn the waste into biogas, because of the inhibition of the methanogenic conversion of previous process products into biogas. Ammonia is passively released as proteins are broken down. Bicarbonates are the primary buffer for balancing alkalinity with pH. Bicarbonate is produced in the same process as methane. Ammonia ions can be released into the liquid from protein breakdown. Ammonia is always as an equilibrium of ammonia to ammonium-ion in a liquid. When temperature increases, more is available as free ammonia, which can act as a methanogene inhibitor at the right concentration.

To ensure proper pH maintenance, e.g., in laboratory batch digesters, alkaline agent(s) can be added at the beginning of the digestion batch. Common alkaline additives include sodium bicarbonate, potassium bicarbonate, potassium carbonate, sodium nitrate, and anhydrous ammonia. The AD digestate released from the AD process is accordingly alkaline, typically with a pH around 8.

Thus, in one embodiment of the present invention, the anaerobic digestion is conducted at a pH between 6.0 and 9.0, preferably between 6.5 and 8.5, most preferably 8.0.

In another embodiment, the anaerobic digestion is conducted within the temperature range of 30-55 °C, preferably 37-52 °C, most preferably 40-45 °C. The anaerobic digestion may be performed for a period of 5 - 30 days, preferably 10-20 days, most preferably 10-15 days.

In a further embodiment, methane is produced from fines in the range of 50 to 200 Nm³/ton fines, preferably 60 to 150 Nm³/ton fines, more preferably 65 to 100 Nm³/ton fines, most preferably 70 to 100 Nm³/ton fines.

In another embodiment, ethane is produced from fines in a ratio compared to MSW of 1.1:1 - 2: 1, preferably 1.2: 1 - 2: 1, more preferably 1.3: 1 - 2: 1, most preferably 1.4: 1 - 2: 1 by weight. A third aspect of the present invention relates to the use of fines from waste, such as municipal solid waste (MSW), for producing a bioliquid suitable as a methane substrate comprising the steps of:

An alternative aspect of the present invention relates to the use of fines from waste, for producing a bioliquid suitable as a methane substrate comprising the steps of:

(ii) enzymatic hydrolysis and/or microbial fermentation of the biodegradable parts of the fines resulting in liquefaction of biodegradable parts of the fines, preferably wherein microbial fermentation is performed concurrently with the enzymatic hydrolysis and, more preferably, is accomplished by inoculation using lactic acid bacteria, or bacteria naturally present in the waste; optionally followed by (iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines comprising microbial metabolites, suitable as substrate for biogas e.g., methane production.

A fourth aspect of the present invention relates to a bioliquid suitable as a methane substrate obtained from fines of waste, such as municipal solid waste (MSW), obtained by the method of:

(i) providing fines from waste, wherein the fines are obtained by separation of waste using a separator, preferably a sieve or a ballistic separator having a screen size between 30 mm to 100 mm, preferably a screen size between 50 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages; (ii) enzymatic hydrolysis and/or microbial fermentation of the biodegradable parts of the fines resulting in liquefaction of biodegradable parts of the fines, preferably wherein microbial fermentation is performed concurrently with the enzymatic hydrolysis and, more preferably, is accomplished by inoculation using lactic acid bacteria, or bacteria naturally present in the waste; optionally followed by

An alternative aspect of the present invention relates to a bioliquid suitable as a methane substrate obtained from fines of waste, such as municipal solid waste (MSW), obtained by the method of:

(iii) separation of non-biodegradable solids and biodegradable parts to produce a bioliquid of the liquefied, biodegradable parts of the fines comprising microbial metabolites, suitable as substrate for methane production.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Definitions

"%" In the context of the present invention, unless indicated otherwise, "%" indicates % weight/weight (w/w).

"Aerobic" means in the presence of free oxygen. The aerobic microbial populations proliferating in the bioliquid is accordingly able to live, being active and occur under conditions where free oxygen is present. Aerobic microorganisms have different levels of sensitivity to absence of oxygen. In the context of the present invention, aerobic microbial populations refer to microbial populations that are not capable of growth and of producing bioliquid subject to conditions absent to free oxygen.

"Anaerobic" means, in the context of the present invention, absence of free oxygen. The anaerobic microbial populations providing the hydrogen gas is accordingly able to live, being active and occur under conditions where free oxygen is absent. Anaerobic microorganisms have different levels of sensitivity oxygen. In the context of the present invention, anaerobic microbial populations refers to microbial populations that are not capable of growth and of producing hydrogen gas subject to conditions where free oxygen is present.

"Anaerobic digestion system" or "AD system" refers to a fermentation system comprising one or more reactors operated under anaerobic conditions in which methane gas is produced in each of the reactors. Methane gas is produced to the extent that the concentration of dissolved methane in the aqueous phase of the fermentation mixture within the "AD system" is saturated at the conditions used and methane gas is emitted from the system. The "AD system" may be a fixed filter system. A "fixed filter AD system" refers to a system in which an anaerobic digestion microbial consortium is immobilized, optionally within a biofilm, on a physical support matrix.

"Biodegradables" refers to the components in a fraction, which can be degraded biologically using enzymes and/or microorganisms.

"Bioliquid" is the liquefied and/or saccharified degradable components obtained by enzymatic treatment of fines from e.g., waste comprising organic matter. Bioliquid also refers to the liquid fraction obtained by enzymatic treatment of waste comprising organic matter once separated from non-fermentable solids. Bioliquid comprises water and organic substrates such as protein, fat, galactose, mannose, glucose, xylose, arabinose, lactate, acetate, ethanol and/or other components, depending on the composition of the waste (the components such as protein and fat can be in a soluble and/or insoluble form). Bioliquid comprises also fibres, ashes and inert impurities. The resulting bioliquid comprising a high percentage of solubles provides a substrate for gas production, a substrate suitable for anaerobic digestion e.g., for the production of biogas.

"Cellulase(s)" according to the present invention is meant to comprise one or more enzymes capable of degrading cellulose and/or related compounds. Cellulase can also be used for any mixture or complex of various such enzymes, that act serially or synergistically to decompose cellulosic material. Cellulases break down the cellulose molecule into monosaccharides ("simple sugars") such as glucose, and/or shorter polysaccharides and oligosaccharides. Specific reactions may comprise hydrolysis of the 1,4-beta-D-glycosidic linkages in cellulose, hemicellulose, lichenin, and cereal beta-D-glucans. Several different kinds of cellulases are known, which differ structurally and mechanistically. Synonyms, derivatives, and/or specific enzymes associated with the name "cellulase" comprise endo-l,4-beta-D-glucanase (beta-1, 4-glucanase, beta-1, 4-endoglucan hydrolase, endoglucanase D, 1,4- (l,3,l,4)-beta-D-glucan 4-glucanohydrolase), carboxymethyl cellulase (CMCase), avicelase, celludextrinase, cellulase A, cellulosin AP, alkali cellulase, cellulase A 3, 9.5 cellulase, and pancellase SS.

Cellulases according to the present invention can also be classified based on the type of reaction catalysed, where endocellulases (EC 3.2.1.4) randomly cleave internal bonds at amorphous sites that create new chain ends, exocellulases or cellobiohydrolases (EC 3.2.1.91) cleave two to four units from the ends of the exposed chains produced by endocellulase, resulting in tetra-, tri-or disaccharides, such as cellobiose. Exocellulases are further classified into type I - that work processively from the reducing end of the cellulose chain, and type II - that work processively from the nonreducing end. Cellobiases (EC 3.2.1.21) or betaglucosidases hydrolyse the exocellulase product into individual monosaccharides. Oxidative cellulases depolymerize cellulose by radical reactions, as for instance cellobiose dehydrogenase (acceptor). Cellulose phosphorylases depolymerize cellulose using phosphates instead of water. The prevalent understanding of the cellulolytic system divides the cellulases into three classes; endo-l,4-[beta]-D- glucanases (EG) (EC 3.2.1.4), which hydrolyse internal p-l,4-glucosidic bonds randomly in the cellulose chain, exo-l,4-[beta]-D-glucanases or cellobiohydrolases (CBH) (EC 3.2.1.91), which cleave off cellobiose units from the ends of cellulose chains; ; l,4-[beta]-D-glucosidase (EC 3.2.1.21), which hydrolyses cellobiose to glucose and also cleaves off glucose units from cellooligosaccharides.

A commercially available cellulase preparation optimized for biomass conversion can be used, such as one that is e.g., provided by GENENCOR™ (now DuPont), DSM or NOVOZYMES™.

Usually, such compositions comprise cellulase(s) and/or hemicellulase(s), such as one or more of exoglucanases, endoglucanases, endoxylanases, xylosidases, acetyl xylan esterases and beta glucosidases, including any combination thereof.

Such enzymes can e.g. be isolated from fermentations of genetically modified Trichoderma reesei, such as, for example, the commercial cellulase preparation sold under the trademark ACCELLERASE TRIO™ from DuPont (and/or GENENCOR). A commercially available cellulase preparation optimized for biomass conversion that can be used is provided by NOVOZYMES™ and comprises exoglucanases, endoglucanases, endoxylanases, xylosidases, acetyl xylan esterases and beta glucosidases, such as, for example, the commercial cellulase preparations sold under either of the trademarks Cellic® CTec2 or Cellic® CTec3 from NOVOZYMES™.

"Chemical Oxygen Demand" or "COD" quantifies the amount of oxygen required for the total oxidation of organic material. The test does not differentiate between biologically biodegradable and non-degradable organic matter; hence, it gives an overestimate of the biogas potential of a given sample.

"Concurrent microbial fermentation and enzymatic treatment" degradation of biopolymers into readily usable substrates and, further metabolic conversion of primary substrates to short chain carboxylic acids such as glucose, xylose, arabinose, lactate, mannose, galactose, acetate and/or ethanol occurring simultaneously in the bioreactor. Protein and/or fat is also at least partly degraded.

"Dry matter," also appearing as "DM", refers to total solids, both soluble and insoluble, and effectively means "non-water content." Dry matter content is measured by drying at approximately between 60 to 105°C until constant weight is achieved. In a preferred embodiment, dry matter content is measured by drying at approximately 105 °C. The lower temperature range is used when the analysis substrate contains volatile compounds which may escape when boiling water and decrease the analysis result accuracy.

"Fermenting microorganism" refers to any microorganism, including bacterial and fungal organisms, suitable for use in a desired fermentation process to produce a fermentation product. The fermenting organism can be hexose and/or pentose fermenting organisms, or a combination thereof. Both hexose and pentose fermenting organisms are well known in the art. Suitable fermenting microorganisms are able to ferment, i.e., convert, sugars, such as glucose, xylose, xylulose, arabinose, maltose, mannose, galactose, and/or oligosaccharides, directly or indirectly into the desired fermentation product. The fermenting microorganism can e.g. produce glucose based chemicals, such as lactic acid, 3-hydroxypropionic acid (3-HPA), 1,4-butanediol (BDO), butanedioic acid (succinic acid), ethane-1,2- diol (ethylene glycol), butanol and/or 1,2-propanediol (propylene glycol). In a specific embodiment the fermenting microorganism can produce ethanol. Examples of fermenting yeast include strains of Candida, Kluyveromyces, and Saccharomyces, such as Candida sp., e.g. Candida sonorensis, Kluyveromyces sp., e.g. Kluyveromyces marxianus, and Saccharomyces sp., e.g. Saccharomyces cerevisiae.

Examples of fermenting organisms that can ferment pentose sugars in their native state include bacterial and fungal organisms, such as some yeast. Xylose fermenting yeast include strains of Candida, preferably C. sheatae or C. sonorensis; and strains of Pichia, e.g., P. stipitis, such as P. stipitis CBS 5773. Pentose fermenting yeast include strains of Pachysoien, preferably P. tannophiius. Organisms not capable of fermenting pentose sugars, such as xylose and arabinose, may be genetically modified to do so by methods known in the art.

Examples of bacteria that can efficiently ferment hexose and pentose to ethanol include, for example, Bacillus sp., e.g. Bacillus coagulans, Clostridium sp., e.g. Clostridium acetobutylicum, Clostridium thermocellum, Clostridium phytofermentans, Geobacillus sp., Thermoanaerobacter sp., e.g. Thermoanaerobacter saccharolyticum, and Zymomonas sp., e.g. Zymomonas mobilis (Philippidis, G. P., 1996, Cellulose bioconversion technology, in Handbook on Bioethanol: Production and Utilization, Wyman, C. E., ed., Taylor & Francis, Washington, DC, 179-212).

"Fines" refers to a fraction of waste e.g., MSW. Fines is a subtraction of waste defined by separation by size with for example a screen with a defined screen size. A waste fraction will typically be denoted "fines" when extracted from separation screen size of 150 mm and below. Fines may be separated from full waste e.g., MSW fraction using a sieve, such as a trommel screens, drum sieve/screen e.g., with 150 mm, 100 mm, 70 mm, or 50 mm screen size. The fraction of fines corresponds e.g., to approx. 15-70% of MSW by wet weight when using MSW as a waste source. Fines may be a product such as an intermediate or an end-product of processing of e.g., waste in a MBT facility, MSF or RDF facility. Such fines may be used as is in a method of the invention i.e., without separation as described above. The fraction may be a product of waste separated through a sieve having a screen size of 150 mm or below or by sieving bioliquid resulting from liquefaction of waste through a sieve having a screen size of 150 mm or below. Separating fines from waste may be performed by one stage or multistage separation. In any of the preceding embodiments the waste may be shredded before processing and subsequent separation by size.

"Green products and green energy products" are products produced be methods not requiring use of fossil sources. Such products are often denoted with the prefix "bio", which may include biofeedstocks, biofuels, such as biogas, e.g., methane, CO2, H2, ethanol, sugars such as simple carbohydrates, glucose, sucrose, or galactose, lactic acid and ammonium.

"Hydrolysis" is the splitting of chemical bond with the participation of water as cosubstrate. The term is applied when municipal solid waste material is treated with an enzyme composition to break down cellulose and/or hemicellulose and other substrates to fermentable sugars, such as glucose, cellobiose, xylose, xylulose, arabinose, mannose, galactose, and/or soluble oligosaccharides (also known as saccharification). The enzymatic treatment is performed enzymatically by one or more enzyme compositions in one or more stages. In the present disclosure, the terms "hydrolyzation", "liquefaction", "saccharification" and "solubilization" may be used interchangeably.

"Inoculum" the incoming MSW stream may simply be inoculated with an inoculum of microorganisms naturally occurring in the waste, and optionally "raised" on local waste or components of local waste as a food source in fermentation conditions of temperature within the range 37 to 55°C, or 40 to 55°C, or 45 to 50°C, and at a pH within the range 4.2 and 6.0.

"Lactic acid producing bacteria" comprises lactic acid bacteria (LAB) where the currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) - an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature of Bacteria. The phylogeny of the order is based on 16S rRNA-based LTP release 106 by 'The All-Species Living Tree' Project. In addition to bacteria belonging to the LAB order, the term "lactic acid producing bacteria" used herein also comprises bacteria that do not belong to the LAB order, but that are nevertheless capable of producing lactic acid. "Liquid fraction", means the mainly liquid slurry obtained after the waste to be processed has been subjected to a combined enzymatic and microbial treatment and thereafter has been subjected to one or more separation step(s), separating the treated waste into a liquid, i.e. a slurry, and a solid or semi-solid fraction.

"Methane Potential test" refers to a biological test providing a fast indication of the methane production that can be achieved by anaerobic digestion. It is expressed e.g. in rr -CF /ton-MSW/Fines or mL-CH4/g-VS.

"Microbial consortium" refers to a consortium comprising one or more of any bacteria and/or yeasts capable of providing microbial fermentation.

"Microbial metabolites" refers to metabolites produced during enzymatic hydrolysis or fermentation and comprises short chain carboxylic acids/fatty acids, such as formate, acetate, butyrate, proprionate, or lactate, and glucose, xylose, arabinose, lactate, mannose, galactose or ethanol.

"Municipal solid waste" (MSW) refers to waste fractions which are typically available in a city, but that need not come from any municipality per se, i.e., MSW refers to every solid waste from any municipality but not necessarily being the typical household waste - could be waste from airports, universities, campus, canteens, general food waste, among others. The terms municipal solid waste and household waste may be used interchangeably in this application. MSW may be any combination of one or more of cellulosic, plant, animal, plastic, metal, or glass waste including, but not limited to, any one or more of the following: Garbage collected in normal municipal collections systems, optionally processed in a central sorting, shredding or pulping device, such as e.g., a Dewaster® ora reCulture®; solid waste sorted from households, including both organic fractions and paper rich fractions; Generally, municipal solid waste in the Western part of the world normally comprise one or more of: animal food waste, vegetable food waste, newsprints, magazines, advertisements, books, office paper, other clean paper, paper and carton containers, other cardboard, milk cartons and alike, juice cartons and other carton with alu-foil, kitchen tissues, other dirty paper, other dirty cardboard, soft plastic, plastic bottles, other hard plastic, non-recyclable plastic, yard waste, flowers etc., animals and excrements, diapers and tampons, cotton sticks etc., other cotton etc., wood, textiles, shoes, leather, rubber etc., office articles, empty chemical bottles, plastic products, cigarette buts, other combustibles, vacuum cleaner bags, clear glass, green glass, brown glass, other glass, aluminium containers, alu-trays, alu- foil (including tealight candle foil), metal containers (-AI), metal foil (-AI), other sorts of metal, soil, rocks, stones and gravel, ceramics, cat litter, batteries (button cells, alkali, thermometers etc.), other non-combustibles and fines.

"Non-biodegradable solids" refers to solids comprised in the fines, which is not degradable by enzymatic hydrolysis and/or fermentation according to a method of the invention. The non-biodegradable solids include materials, such as plastic, rubber, metal, or glass, but also larger organic solids, which has not been sufficiently degraded during the enzymatic hydrolysis and/or fermentation, such as wood, cardboard, carton and paper.

The term "Particle" is used in the context of the present invention for an object of any shape and dimension. Thus, the object maybe circular, squared, flat etc. and includes any 2D and 3D objects. The term "Particle size" is used in the context of the present invention to describe the size of fines measured by the shortest dimension of the fines object (length, width, height etc.). Thus, fines having a particle size of 50 mm or below, means that at least one cross section of the fines particle is 50 mm or below.

"Process water" is water of lower quality than drinking water such as in terms of e.g. any one of organic and/or inorganic salt(s), microbial organisms / plate counts, suspended solids, DM, and/or pH, including any combination thereof. Process water may comprise water that is recycled from an industrial process, such as a process according to the present invention including wash water, reject water and bioliquid. Process water may be adjusted in terms of mineral/salt content, pH and the like. The Reject water is renamed "Process water" when entering the waste treatment plant, such as a Renescience plant. It is thus only at the production place we discern between Reject water and Process water. "Sorted", refers to a process in which waste, such as MSW, is substantially fractionated into separate fractions such that organic material is substantially separated from plastic and/or other non-biodegradable material.

"Sorted waste" (or "sorted MSW") as used herein refers to waste in which approximately less than 30%, preferably less than 20% and most preferably less than 15% by weight of the dry weight is not biodegradable material.

"Total Solids" or "TS" is a measure of the material remaining after removal of water at 60°C or 100°C. The lower temperature ensures that volatile organic compounds are not lost and accounted for as water. The higher temperature is used for some fractions where loss of volatiles is not considered an issue.

"Unsorted" refers to that the waste or the MSW is not substantially fractionated into separate fractions such that organic material is not substantially separated from plastic and/or other inorganic material, notwithstanding removal of some large objects or metal objects and notwithstanding some separation of plastic and/or other inorganic material may have taken place. The terms "unsorted waste" (or "unsorted MSW"), as used herein, refers to waste comprising a mixture of biodegradable and non-biodegradable material in which 15% by weight or greater of the dry weight is non-biodegradable material. Waste that has been briefly sorted yet still produce a waste (or MSW) fraction that is unsorted. Typically, unsorted MSW may comprise organic waste, including one or more of food and kitchen waste; paper- and/or cardboard-containing materials; recyclable materials, including glass, bottles, cans, metals, and certain plastics; burnable materials; and inert materials, including ceramics, rocks, and debris. The recyclable material might be before or after source sorting.

"Volatile Solids" or "VS" is the amount of total solids that is lost by combustion. VS is therefore a measure of material that can potentially be converted to biogas in an AD process as well as plastic and other non-convertible organics. The weight difference between the sample after the measurement of TS and ash reflects the VS content of the sample. "Waste" comprises, sorted and unsorted, municipal solid waste (MSW), food waste, agriculture waste, hospital waste, industrial waste, e.g., waste fractions derived from industry such as restaurant industry, food processing industry, general industry; waste fractions from paper industry; waste fractions from recycling facilities; waste fractions from food or feed industry; waste fraction from the medicinal or pharmaceutical industry; waste fractions from hospitals and clinics, waste fractions derived from agriculture or farming related sectors; waste fractions from processing of sugar or starch rich products; contaminated or in other ways spoiled agriculture products such as grain, potatoes and beets not exploitable for food or feed purposes; or garden refuse.

"Waste fractions derived from agriculture or farming related sectors" comprises waste fractions from processes including sugar or starch rich products such as potatoes and beet; contaminated or in other ways spoiled agriculture products such as grain, potatoes and beet not exploitable for food or feed purposes; garden refuse; manure, or manure derived products.

"Waste fractions derived from households" comprises unsorted municipal solid waste (MSW); MSW processed in some central sorting, shredding or pulping device such as e.g. Dewaster® or reCulture®; Solid waste sorted from households, including both organic fractions and paper rich fractions; RDF (Refuse-Derived- Fuel); fraction derived by post treatment as e.g. inerts, organic fractions, metals, glass, and plastic fractions. In a preferred embodiment a 2D and 3D fraction is prepared. The 2D fraction can be further separated into recyclables and/or residuals such as SRF (Solid Recovered Fuel), RDF (Refused Derived Fuel) and/or inerts. The 3D fraction can also be further separated into recyclables and/or residuals such as metals, 3D plastic and/or RDF.

"Waste fractions derived from the industry" comprises general industry waste fractions containing paper or other organic fractions now being treated as household waste; waste fraction from paper industry, e.g. from recycling facilities; waste fractions from food and feed industry; waste fractions from the medicinal industry, hospital and clinic waste, airport waste, other public and private services derived waste. "Yeasts" refer to any type of yeast including yeast that can ferment pentose and/or hexose and/or xylose. Yeasts refer e.g. to strains of Candida, Kluyveromyces, and Saccharomyces, e.g., Candida sonorensis, Kluyveromyces marxianus, and Saccharomyces cerevisiae; fermenting organisms that can ferment pentose sugars in their native state; xylose fermenting yeasts such as strains of Candida, including C. sheatae or C. sonorensis; and strains of Pichia, e.g., P. stipitis, such as P. stipitis CBS 5773; pentose fermenting yeasts such as strains of Pachysolen, including P. tannophilus.

All patent and non-patent references cited in the present application, are hereby incorporated by reference in their entirety.

The invention will now be described in further details in the following non-limiting examples.

Examples

Materials and Methods

Waste (MSW and Fines)

Waste mostly collected from household areas, although with a limited amount originating from commercial waste producers (hotels and restaurants). Fines was sorted from the waste. The size sorting was performed in a rotating drum sieve equipped with blades to cut open bags. The Fines fraction, which in this experiment were particles 50 mm or below i.e., <50 mm, was collected.

In total, 60 tons of MSW and 40 tons of fines were prepared.

Enzymes

The enzyme solution Cellic® CTec3 from Novozymes was used during the whole test. The enzyme was received in pallet tanks from which it was pumped into the process in an amount of 0.9% per weight of Fines. The enzyme was stored at room temperature and not exposed to direct sunlight according to the manufacturer's instructions.

Sampling

During both the MSW and Fines trials, two types of sampling were performed:

1. Large samples of the ingoing MSW and Fines were retrieved for analyses Samples of the ingoing Fines were sampled for analysis of total solids (TS), and volatile solids (VS).

2. Liquid samples were taken at high frequency, every 4 hours, to support the continuous monitoring of the process. The analysis performed on these samples included pH, total solids (TS), volatile solids (VS) and chemical oxygen demand (COD).

Sampling procedure of high frequency samples

During the entire test, samples of the bioliquid was taken routinely 6 times per day, for measurement of COD, TS, VS and pH. Immediately after sampling, the liquid samples were placed at 5°C until time of analysis, performed no more than 3 days after sampling. Details of the sampling are listed in Table 1.

Table 1. Samples were retrieved every 4 hours.

Sample point _ Sampling frequency _ Measurement bioliquid _ 6/dav _ pH, TS, VS, COD

After completing the analysis, all samples were stored at -20°C.

TS and VS

Using approximately 30 g of sample in pre-conditioned crucibles (550°C), TS was determined after 2 days heated to 60°C. The dried samples were burned at 550°C for 16 hours, for determination of ash and calculation of VS. For both determination of TS and VS, crucibles were cooled in desiccator prior to weighing.

PH

For the analysis a Yokogawa PH71 pH-meter equipped with the Yokogawa PH72SN-11-AA electrode was used. Once a day, calibration was executed using buffer pH 4 and 7. Cleaning of the electrode between measurements was executed using ultra-pure water. COD

COD analyses were carried out with Merck Millipore Spectroquant instruments (thermoreactor and spectrophotometer Nova 60) and cell tests (COD Cell Test Hg- free cat. no. 1.09773). Before analyses, bioliquid samples were diluted approximately 180 times with ultrapure water, while LB01 samples were diluted 50 times. LB01 was tank heated recycled, semi cleaned water from the wash water of the downstream process and fed to the reactor with the waste. LB01 samples were thus sample of the ingoing water.

Measurement of the Methane Potential

Methane Potential (MP) of the samples were measured with an Automated Methane Potential System (AMPTS) from BioProcess Control. The system consists of fifteen 0.5 L closed bottles, mounted with a mechanical mixer. The gas production is purified from the CO2 by a soda trap and eventually quantified in a gas flow-meter. The bottles and the flow-meter are kept at constant temperature. The 15 reactors used for the test are inoculated one week before the actual test, to exhaust the inoculum from remaining substrate. By doing so, it was also checked that the system works properly for the 15 bottles and check the homogeneity of the inoculum. The test was carried out with fresh effluent from the reactor which has been producing bioliquid for several months.

Four different samples can be tested in parallel, each of them in triplicate; three other reactors are used to measure the endogenous methane production. The substrate is added to the reactors with a VS ratio inoculum:substrate of 2, in order to have a large excess of inoculum to avoid any inhibition from the substrate. As opposed to the standard test protocol, the set-up used here differs by being performed without addition of micro-nutrients, as the bioliquid usually contains enough.

The test is finished when the gas production is negligible. Due to the preacclimation period, the actual test usually only takes 5 to 10 days.

Measurement of the methane yield in a continuous reactor

The Methane Potential (MP) method offers a reasonably fast response and is a common way to characterise the feedstock for any industrial Biogas plant. However, a continuous system, as the one used at industrial scale, will usually exhibit lower yields because in a continuously stirred tank reactor, a part of the feedstock does not have the time to totally react before being washed-out. As explained below, the difference between the MP and the actual methane yield of a continuous reactor will depend on the ratio between the Retention Time applied to the reactor and the kinetic of degradation.

Moreover, the anaerobic digestion is a biological process sensitive to several sources of inhibitions, caused either by compounds from the substrate (ammonia, salts, antibiotics) or by the imbalance between reactions causing the accumulation of intermediate compounds (Volatile Fatty Acids); as the MP test is designed to lower the effect of these inhibitions, they might have a stronger effect on the continuous system.

To quantify the methane production from the bioliquid, 60 L of bioliquid have been collected and fed to a continuous anaerobic fixed film reactor, already acclimated to the bioliquid. The reactor reached stable operation after five days; after four more days at the nominal retention time, a stable methane yield was quantified for the MSW bioliquid, and then the feedstock was changed to Fines for two more days in order to quantify the methane yield of the bioliquid derived from Fines. After one day on bioliquid from Fines, stable performance was achieved and the methane production from the Fines was determined over 9 hours of stable operation.

Composition of the delivered fines

The fines were separated from MSW. The overall solids content of the Fines was determined. The total solids (TS) content of the ingoing Fines was 56±3% and the volatile solids (VS) fraction was 24±1% of the total weight. The volatile solids (VS) value of the fines includes biodegradable material but also measures smaller pieces of plastics as the VS content is determined by burning the sample at 550 °C.

The Fines are primarily small rest, kitchen waste, paper and cardboard.

Process

Shortly after the first truckload of MSW was delivered to the waste plant, the test was initiated. In the following two weeks, the plant operated for a total of 311 hours, first using MSW as feedstock and secondly with Fines. The operating times and main process parameters are presented in Table 2.

Table 2. Overview of tested parameters at the Renescience plant. Unit MSW Fines

Dmation houis 213

Load kg horn 250 250

Watei:MSW kg. kg

Enzyme load % of waste 0.9 0.9

Retention time h

pH adjustment - None None

* indicates 50 °C in the in-going water, 50 °C in the buffer tank and 70 °C in the water heater.

The mass balance provides insight into whether all the ingoing streams are accounted for in the outgoing fractions, and thus if the data were adequate.

The bioliquid

The main output is the bioliquid, which contains the majority of the biodegradables captured from the MSW and Fines. The methane production from the pure bioliquid was evaluated.

Methane production

Bioliquid from both the MSW and Fines trials were collected for determination of the methane yield. A continuous assay, using a lab-scale fixed bed anaerobic digester, was used to estimate the methane production in a full scale AD plant.

Table 3. The methane production from bioliquid produced during the MSW and Fines trials of the test. In addition, the predicted production from a mixture of 83% MSW and 17% Fines (MSW+Fines) was calculated as a linear combination of MSW and Fines.

MSW Fines MSW+Fines

Sp. Methane Yield (L-CH4/kg-VS) 381 ±19 368 ±11 379±16 bioliquid VS capture rate (kg-vs/ton-MSW or Fines) 154 ±13 203 ±28 162±15

Methane production (Nm3-CH4/ton-MSW or Fines) 59 ±6 75 ±11 61 ±6

From the MSW trial, the bioliquid, which was produced yielded 59±6 Nm³ methane per ton of MSW. From the Fines trial, the bioliquid yielded 75±11 Nm³/tonFines methane per ton of Fines in the continuous reactor. Thus, the yield of methane from the Fines bioliquid was significantly higher than from the MSW bioliquid. When the MSW and Fines were mixed in the 83% NSW and 17% Fines ratio, the production of methane was increased compared to MSW alone. Thus, the bioliquid yielded 61±6 Nm³ methane per ton of MSW + Fines.

Batch process

In another example, a sample of 150 kg Fines was used in a batch process whereas the previous example describes continuous process.

In the batch process test, a seven-chamber closed reactor was used to process 8 kg Fines in each chamber. The reactor was a horizontally mixing drum reactor with the inner space divided into 7 separate compartments. The Fines were mixed by free-fall mixing as the fines were lifted by internal, stationary horizontally placed paddles during reactor rotation.

To each chamber containing Fines was added water (2: 1 ratio by weight of Fines), acetic acid and Cellic CTec3 in the range 0 - 0.9 % by weight of Fines. The reaction conditions were 50 °C and 18 hours hydrolysis time.

After hydrolysis, the reactor chambers were emptied and passed through a press to collect the solid material and liquid fraction (bioliquid) separately. The solid material was transferred back to the reactor and washed by addition of water at a 1 : 1 ratio by weight of Fines and the resulting wash water was collected separately. The solid samples were dried for prolonged time 60 °C to determine total solids content. The bioliquid was analysed using the methods described in the previous example to determine the TS, VS, COD and methane potential by AMPTS.

The methane potential of the bioliquid was up to 68 L methane per kg Fines when enzyme was added whereas no addition of enzyme resulted in 64 L methane per kg Fines.

The example thus demonstrate that batch processing of Fines will return a bioliquid with significant methane potential.

List of reference symbols used:

1 Feed Well

2 Scrapper Blade

3 Rake Arm 4 Energy Dissipating Inlet

5 Effluent Trough

6 Scum Trough

7 Walkway

8 Drive Unit 9 Influent

10 Sludge Discharge

11 Skimmer

12 Scum Baffle

13 Effluent Launder 14 Support Column

Claims

1. A method for processing fines from waste, such as municipal solid waste (MSW), comprising the steps of:

2. The method of any of the preceding claims, wherein the dry matter content of the fines is between 20 and 70%, preferably between 40 and 65%, more preferably between 50 and 65% by weight of fines.

3. The method of any of the preceding claims, wherein the bioliquid obtained in step (iii) have a methane potential in the range of 50 to 200 Nm³/ton fines, preferably 60 to 150 Nm³/ton fines, more preferably 65 to 100 Nm³/ton fines, most preferably 70 to 100 l\lm³/ton fines.

4. The method of any of the preceding claims, wherein the bioliquid obtained in step (iii) have a methane potential ratio compared to bioliquid from MSW of 1.1: 1 - 2: 1, preferably 1.2: 1 - 2:1, more preferably 1.3: 1 - 2: 1, most preferably 1.4: 1 - 2:1.

5. The method of any of the preceding claims, wherein the fines obtained in step (i) is mixed with liquid in an amount of 100 to 10.000 L/ton fines, such as 500 to 5000 L/ton fines, preferably 1000 - 3000 Lyton fines, more preferably 1500 - 3000 L/ton fines or most preferably in the range 1500 to 2500 L/ton fines, before enzymatic hydrolysis and/or microbial fermentation in step (ii).

6. The method of claim 5, wherein the liquid is preheated to a temperature in the range of 30-75 °C, preferably 45-55 °C.

7. The method of any of the preceding claims, wherein the fines in step (i) are obtained by sieving the waste through a sieve having screen size of 100 mm or below, more preferably screen size of 70 mm or below, most preferably 50 mm or below.

8. The method of any of the preceding claims, wherein enzymatic hydrolysis and/or microbial fermentation are conducted within the temperature range of 30-75 °C, preferably 45-55°C, preferably wherein enzymatic hydrolysis and/or microbial fermentation is conducted concurrently, and/or wherein enzymatic hydrolysis and/or microbial fermentation are conducted at a pH between 4.0 and 6.0, preferably between 4.5 and 5.5.

9. The method of any of the preceding claims, wherein the enzymatic hydrolysis and/or microbial fermentation may be performed for a period of 10-48 hours, preferably 15-30 hours, more preferably 15-24 hours, most preferably 18-24 hours.

10. A method of producing methane comprising the steps of

(i) providing fines from waste, wherein the fines are obtained by separation the waste using a separator, preferably a sieve or ballistic separator, having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably about 50 mm or below, the separation can take place in one stage or multiple stages;

(v) conducting anaerobic digestion of the bioliquid to produce methane, preferably wherein the anaerobic digestion is conducted at a pH between 6.0 and 9.0, preferably between 6.5 and 8.5, most preferred 8.0.

11. The method of claim 10, wherein methane is produced from fines in the range of 50 to 200 Nm³/ton fines, preferably 60 to 150 Nm³/ton fines, more preferably 65 to 100 Nm³/ton fines, most preferably 70 to 100 Nm³/ton fines.

12. The method of claim 10 or 11, wherein the methane produced from fines is in a ratio compared to MSW of 1.1:1 - 2: 1, preferably 1.2:1 - 2:1, more preferably 1.3: 1 - 2: 1, most preferably 1.4: 1 - 2: 1.

13. Use of fines from waste, such as municipal solid waste (MSW), for producing a bioliquid suitable as a methane substrate comprising the steps of:

(i) providing fines from waste, wherein the fines are obtained by separation the waste through for example a sieve or ballistic separator having a screen size between 30 mm to about 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably 50 mm or below, the separation can take place in one stage or multiple stages;

14. A bioliquid suitable as a methane substrate obtained from fines of waste, such as municipal solid waste (MSW), obtained by the process of:

(i) providing fines from waste, wherein the fines are obtained by separation the waste through a sieve having a screen size between 30 mm to 100 mm, preferably a screen size between 40 mm to 70 mm, more preferably a screen size between 40 mm to 50 mm, most preferably 50 mm or below, the separation can take place in one stage or multiple stages;