A METHOD OF PRODUCING BIOGAS AND AN ARRANGEMENT RELATED THERETO

FIELD OF THE INVENTION

The present invention relates to the field of renewable bioenergy. More specifical ly, the present invention relates to a method and an arrangement for producing bi ogas. Also, use of the arrangement for producing biogas is within the scope of the present invention.

BACKGROUND OF THE INVENTION

Biogas, e.g. methane and carbon dioxide, can be obtained by anaerobic fermenta tion of organic substrates which may come from agriculture, communes and indus try. As an example, FI patent 126680 discloses an arrangement and method for biogas production. The basic principle in the disclosure of said patent is to moisten the biomass in a bioreactor in phases thereby enhancing stabile biogas production using a single biomass reactor only.

However, there remains a significant unmet need for effective and low-cost meth ods and arrangements for producing biogas, specifically suitable for small farms and curtilages.

BRIEF DESCRIPTION OF THE INVENTION

There exists a need for an improved method for producing biogas by fermentation of the biomass, while substantially avoiding or at least reducing one or more of the problems of the prior art including but not limited to slow and inefficient production of biogas (e.g. unfermented biomass levels remain high), a difficult or inefficient recovery and use of biogas, and inappropriate size of the arrangement for produc ing biogas e.g. in small farms and curtilages.

The objects of the invention are achieved by utilizing a fluid distributor pipe for conducting the percolation fluid into the biomass, more specifically inside the bio mass (unit) of the biomass reactor. Such a solution enables efficient moistening of the biomass in a biomass reactor. It has now been found that with the method or arrangement of the present invention it is possible to convert solid or semisolid or- ganic substrates in small or large operating volumes into biogas. The present in vention enables surprisingly efficient or specifically even complete anaerobic fer mentation of biomass. Surprisingly, the biomass which can be used in the present invention does not need to be opened for effective digestion because the percola tion fluid comprising microbes is conducted with a fluid distributor pipe into the bi omass. Indeed, the present invention provides stabile and very effective biogas production with a very simple and inexpensive method or arrangement. And fur thermore, in the method or arrangement of the present invention biogas production can be enhanced simply by increasing circulation of the percolation fluid.

The method and arrangement of the present invention can be used e.g. as a small-scale solution for producing biogas, and the present invention is especially suitable for small farms, curtilages, households, communities, bakeries, restau rants, small food industry etc. Indeed, the present invention enables small-scale commercial products for biogas production.

The present invention relates to a method of producing biogas comprising

allowing biomass to contact with a percolation fluid in a biomass reactor of a container, and

recovering the biogas,

wherein the percolation fluid is conducted with a fluid distributor pipe into the bio mass in the biomass reactor.

Still, the present invention relates to an arrangement for producing biogas com prising:

a container comprising a biomass reactor,

a cover of the container comprising a biomass reactor or a cover of the bi omass rector, and

a fluid distributor pipe for conducting the percolation fluid into the biomass of the biomass reactor, wherein the fluid distributor pipe optionally compris es one or more perforations for allowing the percolation fluid to move from the pipe into the biomass of the biomass reactor.

Still furthermore, the present invention relates to use of the arrangement of the present invention for producing biogas. And still furthermore, the present invention relates to a device or container for re moving carbon dioxide from biogas, wherein said device or container comprises e.g. (e.g. crushed or powdered) concrete or limestone or any corresponding mate rial for removing carbon dioxide from biogas.

Also, the present invention relates to a method for increasing methane content of the biogas, wherein biogas is allowed to contact e.g. with (e.g. the crushed or powdered) concrete or limestone or any corresponding material, thereby removing carbon dioxide and/or hydrogen sulphide from biogas.

Other objects, details and advantages of the present invention will become appar ent from the following drawings, detailed description and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows schematically one embodiment of an arrangement or method for producing biogas. (1 ) biomass (e.g. in the bag, net, or basket) in the biomass reac tor, (2) biomass reactor (essentially gas tight and/or water tight) and a cover thereof, (3) optional support for ensuring circulation of the percolation fluid, (4) a fluid distributor pipe (optionally comprising one or more perforations) for conduct ing the percolation fluid into the biomass, (5) check valve, (6) a drainage pump or circulation pump, (7) filler material, (8) a percolation fluid container, (9) a moving cover as a gas storage, (10) a weight (e.g. liquid weight), (11 ) discharge pipe for the percolation fluid, controlling the level of the percolation fluid, (12) an optional (percolation) fluid collector, (13) a pipe for conducting biogas, conducting pro duced biogas from the biogas storage, (14) connecting pipe between the biomass reactor and the percolation fluid container, connecting the biomass reactor and the percolation fluid container with a pipe, (15) a pump for circulating percolation fluid, circulating percolation fluid with a pump, (16) anti-foaming, (17) a valve. An em bodiment of an arrangement or method of the present invention for producing bio gas may utilize one or more parts shown in Figure 1 or described above in this paragraph.

Figure 2 shows schematically one embodiment of an arrangement or method for producing or treating biogas. (21 ) biogas e.g. produced with the method or ar rangement of the present invention (e.g. see Figure 1 , (13)), (22) a device or con tainer, e.g. comprising (e.g. crushed or powdered) concrete or limestone, for in- creasing methane content of the biogas, increasing methane content of the bio gas, (23) means for drying biogas (e.g. a glycol storage), drying biogas, (24) means for compressing biogas, compressing biogas, (25) a vehicle such as a car. Methane content of biogas is increased (e.g. by conducting biogas to (22)), and thereafter the treated biogas is dried (e.g. by conducting the treated biogas to (23)) and compressed (e.g. by conducting the treated biogas from (23) to (24)). Biogas from (24) can be used in a vehicle (25). An embodiment of an arrangement or method of the present invention for producing biogas may utilize one or more parts shown in Figure 2 or described above in this paragraph.

Figure 3 shows schematically one embodiment of an arrangement or method for producing biogas. (31 a-31 c) biomass (e.g. in a baled form) in biomass reactors, (32) a percolation fluid container or collector, (33) a container (or reactor) compris ing fillers and percolation fluid, (34) a floating, moving or rotating cover. An embod iment of an arrangement or method of the present invention for producing biogas may utilize one or more parts shown in Figure 3 or described above in this para graph.

DETAILED DESCRIPTION OF THE INVENTION

Biogas is a mixture of different gases produced by the breakdown of organic mat ter in the absence of oxygen. It is a renewable energy source, and in many cases exerts a very small carbon footprint. Biogas as discussed here is produced by an aerobic fermentation of biodegradable materials. Biogas comprises primarily me thane (CH4) and carbon dioxide (CO2) and may have small amounts of other com ponents like hydrogen sulphide (H2S) and ammonium (NH3).

In economically feasible production the methane content of biogas is at least 40 v- %. Using the method and/or arrangement described herein it is possible to achieve very high-quality biogas having methane content of at least 40 v-%, at least 50 v- %, at least 60 v-%, at least 70 v-%, e.g. up to 50 v-%, 55 v-%, 60 v-%, 65 v-%, 70 v-%, 75 v-%, 80 v-%, or even more. In addition, in the present invention the gas production is continuous and furthermore, the gas production profile is very stable and optionally controllable.

In the present invention the biomass is allowed to contact with the percolation flu id. In this connection an expression“allowing the biomass to contact with a perco- lation fluid” covers an embodiment wherein the percolation fluid is conducted with a fluid distributor pipe into, inside or through the biomass and furthermore optional ly the percolation fluid is applied on the surface of the biomass or the biomass is surrounded by the percolation fluid. In one embodiment, the biomass is allowed to contact with the percolation fluid by conducting the percolation fluid with a fluid dis tributor pipe into, inside or through the biomass. In a further embodiment the bio mass reactor is filled with the percolation fluid by conducting said percolation fluid into, inside or through the biomass. In one embodiment when the percolation fluid contacts the outer surface of the biomass as well as the inner part of the biomass, it is possible to ferment the biomass more efficiently and in a specific embodiment even completely.

In one embodiment of the invention pH of the percolation fluid is from 7 to 9. This ensures that most of the living microbes remain in the container or biomass reac tor where pH and nutritional conditions are optimal. Said pH enhances efficient usage of the organic acids and thereby biogas production.

In one embodiment of the invention there are one or more biomass reactors in the container. In other words, the container comprises at least one biomass reactor, in a more specific embodiment more than one biomass reactor. In one specific em bodiment of the invention the container comprises 1 -10 biomass reactors, option ally e.g. 4 biomass reactors. The biomass reactors may be situated in the bottom of the container or anywhere above the bottom.

In addition to one or more biomass reactors, the container may comprise one or more percolation fluid containers. In one embodiment of the invention the level of the percolation fluid in the container comprising a biomass reactor, a percolation fluid container and/or biomass reactor(s), and/or circulation of the percolation fluid is controlled. Controlling may be carried out by any method known to a person skilled in the art, e.g. including introducing more percolation fluid to the container, a percolation fluid container or biomass reactor or reducing the amount percolation fluid. Controlling may also include any instruments known to a person skilled in the art including but not limited to one or more of the following: a pump, pipe, valve, gauge or sensor (e.g. for measuring the level of the percolation fluid).

In a specific embodiment the biomass reactor is a container (e.g. made of plastic). Biomass reactors can be made of any material suitable for biomass and percola- tion fluids including but not limited to a metal, steel, stainless steel, cast iron, cop per, plastic, composite, PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), rubber, or any combination thereof.

A fluid distributor pipe is used in the method or arrangement of the present inven tion for conducting the percolation fluid into or inside the biomass. In one embodi ment of the invention the fluid distributor pipe comprises one or more perforations for allowing the percolation fluid to move from the pipe into the biomass. The per colation fluid may move e.g. freely or by spraying from the perforation(s). Indeed, the perforation (s) may be open all the time or may be opened when needed. In one embodiment the perforation(s) has(have) a diameter from about 0.05 cm to about 5 cm, e.g. from about 1 cm to about 3 cm. However, said perforations may be selected from the group consisting of perforations having any shape and size suitable for the present invention. The fluid distributor pipe can be made of any material suitable for conducting percolation fluids including but not limited to a metal, steel, stainless steel, cast iron, copper, plastic, composite, PE (polyeth ylene), PP (polypropylene), PVC (polyvinyl chloride), rubber, or any combination thereof.

In one embodiment the percolation fluid is conducted with a fluid distributor pipe into or inside the biomass and furthermore the biomass is completely or partly in the percolation fluid. In a specific embodiment the biomass is completely in the percolation fluid in the biomass reactor. This embodiment allows further enhanced production of biogas, optionally within a shorter time period, compared to an em bodiment wherein the biomass is completely or partly in the percolation fluid with out a fluid distributor pipe for conducting the percolation fluid into or inside the bi omass. As used herein“enhanced production of biogas” or“increased production of biogas” refers to production of more biogas (e.g. measured by volume or Nm3 (normal cubic meter i.e. m ³ gas in normal pressure and 0°C or kg), optionally with in a shorter time period.

In one embodiment of the invention the distributor pipe(s) is(/are) placed through the biomass (e.g. horizontally or vertically) or the distributor pipe is placed so that the end of the distributor pipe or the perforation (s) of the distributor pipe are within or inside of the biomass. The distributor pipe allows the percolation fluid to contact with the inner part of the biomass (unit). In a specific embodiment only one distrib- utor pipe(s) is placed through or inside the biomass (unit or units) in one biomass reactor of the present invention.

In one embodiment of the invention, circulation of the percolation fluid (which is caused e.g. by a pump, e.g. in the percolation fluid container or percolation fluid collector, such as in the bottom of the percolation fluid container or collector, or e.g. outside of the percolation fluid collector) allows flow of the percolation fluid in the fluid distributor pipe and into the biomass in the biomass reactor. Indeed, in one embodiment of the invention only one or few electric means, e.g. a pump for circulating the percolation fluid, is used in the method and arrangement of the pre sent invention.

In one embodiment in addition to the fluid distributor pipe for conducting the perco lation fluid into or inside the biomass (the first fluid distributor pipe), the piping in the biomass reactor contains a second fluid distributor pipe for delivering the fluid on the biomass. In a further embodiment said second fluid distributor pipe com prises one or more perforations or contains means for controlled moistening of the biomass. Such means can be for example a pump or pumps, a valve or valves or a sprayer or sprayers, alone or in any combination.

In one embodiment of the present invention biomass is introduced to a biomass reactor of a container for biogas production. In one embodiment of the invention the biomass has been introduced to the biomass reactor optionally comprising the percolation fluid. Introducing the biomass to a biomass reactor can be arranged by any conventional means.

If the biomass introduced to the biomass reactor is dry, it may be useful to moisten it e.g. using water or percolation fluid from another reaction. This will speed up the release of the percolation fluid from the biomass and thereby starting of the biogas production.

In one embodiment of the invention, the biomass reactor is an integral tank, wherein circulation of the percolation fluid to and from the biomass reactor is con trolled. In one embodiment of the invention the percolation fluid is allowed to circu late between the percolation fluid container and the biomass reactor (e.g. percola tion fluid into the biomass reactor from the upper part of the container, and out of the biomass reactor from the lower part of the biomass reactor, e.g. from the wall and/or bottom of the biomass reactor) and/or between the percolation fluid con tainer and the biomass reactor (e.g. percolation fluid into the biomass reactor from the upper part of the container, and out of the biomass reactor from the lower part of the biomass reactor, e.g. from the wall and/or bottom of the biomass reactor). In a very specific embodiment, please see Figure 1 for conducting the percolation flu id from the percolation fluid collector to the biomass reactor and from the biomass reactor to the percolation fluid container.

Suitable biomasses for the biogas production include agricultural bio-waste (such as (dry) manure, plant material, green waste) and biomass such as grass; food waste, municipal waste, sewage, bio-waste and biomasses from forestry, domestic household, food and feed industry, fishing industry, forest industry and also peat and other natural biomasses. Examples of suitable biomass are grass, silage and straw. Biomass may also be a mixture of different kind of biomasses. In a specific embodiment of the method or arrangement of the present invention the biomass comprises or is bio-waste, manure, plant material, green waste, grass, hay, lawn, food waste, municipal waste, sewage, or bio-waste, or any combination thereof.

The biomass may be in any form, such as in a solid or semisolid, or fresh or dried form. In one embodiment the biomass is in the form of a bale (e.g. baled), or a pressed, dried or shaped unit, or any other form normally found in corresponding biomass. In one embodiment of the invention the biomass reactor is for biomass in the form of a bale, or a pressed, dried or shaped unit. In one embodiment the form of the biomass used in the present invention enables solving the problems of logis tics and storing of the biomass. Furthermore, in the present invention when the bi omass is in the form of a bale, or a pressed, dried or shaped unit, said biomass (e.g. a biomass unit or bale) does not need to be opened for effective digestion because the percolation fluid comprising microbes is conducted with a fluid distrib utor pipe into the biomass. The biomass used in the method or arrangement of the present invention may have been produced or treated by any conventional pro cesses known in the art.

In one embodiment the biomass (unit) is in a bag, net or basket, which allows penetration of the percolation fluid. A bag, net or basket enables easy handling of the biomass (unit) e.g. a bag, net or basket comprising biomass can be placed to the biomass reactor and a bag, net or basket comprising degraded biomass can be lifted from the biomass reactor and replaced with another bag, net or basket comprising new unfermented biomass.

In one embodiment of the present invention the method for producing biogas is an anaerobic batch fermentation method or the arrangement for producing biogas is for an anaerobic batch fermentation. Indeed, in one embodiment of the invention when the biomass has been fermented the fermented biomass (unit) is replaced with an unfermented biomass (unit) to be contacted with percolation fluid, and op tionally the method of the present invention is repeated once or several times. As used herein“a biomass unit” refers to a biomass unit such as a bale, or a pressed, dried or shaped unit optionally e.g. in a bag, net or basket. One or more biomass units are for one biomass reactor or in one biomass reactor.

Biogas production of the present invention can be controlled or optimized e.g. by utilizing only one or more biomass reactors of the container at the same time but e.g. not all biomass reactors present in the container. Maximal gas production may be obtained by using all the biomass reactors for biogas production at the same time. In one embodiment of the invention percolation fluid is not conducted to all biomass reactors of the container at the same time.

During the first days of the fermentation a lot of saccharides and amino acids and various small peptides are released from the biomass to the percolation fluid. Later the amount of organic acids is increased in the percolation fluid. According to one embodiment described herein the saccharides, amino acids or small peptides, or two or all of them, are recovered from the percolation fluid using conventional methods. The recovery may be performed using any separation method known within the art.

According to another embodiment the method comprises fermentation of the per colation fluid recovered from the percolation fluid container or collector, recovering the alcohol produced and returning the fluid recovered from the container or col lector to the biogas production. In one embodiment the amino acids and/or small peptides are used as a material in food, feed or pharmaceutical industry.

In one embodiment of the invention the arrangement for producing biogas com prises, or the method of producing biogas is carried out in an arrangement for pro ducing biogas comprising: a container comprising a biomass reactor,

a cover of the container comprising a biomass reactor or a cover of the biomass reactor (e.g. for recovering biogas), and

a fluid distributor pipe for conducting the percolation fluid into the biomass in the biomass reactor, wherein the fluid distributor pipe optionally comprises one or more perforations for allowing the percolation fluid to move from the pipe into the biomass of the biomass reactor.

In one embodiment of the invention the arrangement or container comprising a bi omass reactor further comprises a container comprising the percolation fluid (i.e. the percolation fluid container) and optionally a percolation fluid collector. Indeed, the percolation fluid container may be in the container of the present invention comprising a biomass reactor (e.g. the percolation fluid may surround the biomass reactors) or outside of said container of the present invention comprising a bio mass reactor.

In one further embodiment the arrangement for producing biogas comprises:

a container comprising a biomass reactor and a percolation fluid container (e.g. reactor),

a cover of the container comprising a biomass reactor, a cover of the biomass re actor and/or a cover of the percolation fluid container (e.g. for recovering biogas), and

a fluid distributor pipe for conducting the percolation fluid into the biomass in the biomass reactor, wherein the fluid distributor pipe optionally comprises one or more perforations for allowing the percolation fluid to move from the pipe into the biomass of the biomass reactor, and

optionally a fluid collector (e.g. for recovering and/or circulating percolation fluid); and

optionally a device (e.g. a pump) for circulating the percolation fluid to moisten the biomass.

Biogas production is not an exothermic reaction but requires temperature of about 34 to 45 °C, about 35 to 42 °C (mesophilic (anaerobic) digestion) or e.g. about 55 °C (thermophilic (anaerobic) digestion) in order to be efficient. The temperature of the container and/or biomass reactor(s) can be maintained by insulation layers around the container or reactors and/or heating the walls of the biomass reactor or heating the percolation fluid e.g. in the container using various equipment. Howev- er, the energy demand of these methods is reasonably high, the heating devices (such as heating elements inside or around the wall or immersed in the fluid) are expensive and the efficiency in transferring heat to the biomass and/or percolation fluid is poor. The present inventors have surprisingly found that efficient production of biogas can be achieved and maintained only by insulation. In one embodiment of the invention the container has been insulated, optionally with urethane. Any other insulation material suitable for insulating a container may alternatively be used in the present invention. The insulation prevents cooling of the container and therefore, warming of the container may be kept at a minimal level. In a very spe cific embodiment warming of the container and optionally of the biomass reactor is not needed at all. In a further embodiment, heating (e.g. heating the percolation fluid) can be used in addition to an insulation of the container.

In one embodiment the arrangement, container comprising a biomass reactor, bi omass reactor, percolation fluid container and/or percolation fluid collector is(are) essentially gas tight. In another or further embodiment heat, which exits the ar rangement, reactor, collector and/or container, is replaced, optionally with a heat exchanger.

In one embodiment the method of the present invention comprises heating the container, biomass and/or the percolation fluid (optionally before allowing the per colation fluid to contact with the biomass or before conducting the percolation fluid into the biomass), optionally using a heating device such as a heat exchanger. In one embodiment a heat exchanger is used for heating in the method or arrange ment of the present invention. Heating can take place at any location in a pipe used to deliver percolation fluid to the container or biomass reactor, in the contain er or biomass reactor, or even in the fluid distributor. In one embodiment the per colation fluid, biomass and/or the container is heated to temperature of about 34 to 45 °C, or about 35 to 42 °C, or about 55 °C, optionally before allowing the percola tion fluid to contact with the biomass or before conducting the percolation fluid into the biomass. One advantage of heating is the possibility to regulate the rate of bi ogas production. Typically, biogas production increases when the percolation fluid has been heated up to 45 °C.

In one embodiment of the invention the pH of the biomass is or reaches a value from 8 to 9. In such a case the biomass has been degraded essentially complete ly- According to the method or in the arrangement of the present invention the biogas production is very fast. As an example, when the method as described herein is used, gas production may begin in the container already within 1 to 12 hours from feeding the batch of biomass to the biomass reactor when suitable percolation flu id is used. Suitable percolation fluid can be e.g. a percolation fluid from an earlier biogas production method.

The container comprising a biomass reactor may have any shape suitable for fer- mentation of biomass and producing biogas, in one embodiment the container has a shape of a cylinder. In another embodiment the diameter of the container (e.g. cylinder) is approximately from 0.5 m to 10 m, more specifically from 1 m to 5 m, e.g. from 2 m to 4 m. The container comprising a biomass reactor can be made of any material suitable for percolation fluid and biomass reactors, e.g. including but not limited to a metal, steel, stainless steel, cast iron, copper, plastic, or composite, or any combination thereof. The container or arrangement of the present invention may be placed anywhere, but it is especially applicable for small farms and curtilages, because it is compact in size, inexpensive but still very effective. The container may be placed under ground and thus, it is quite invisible. Indeed, in one embodiment of the invention the container is completely or partly underground, and optionally the cover is above the ground.

In one embodiment of the present invention the method for producing biogas fur ther comprises introducing filler material to the container, optionally outside of the biomass reactor(s) (e.g. in the percolation fluid container), for immobilization of mi- crobes. Also, in one embodiment the container of the arrangement comprises filler material for immobilization of microbes outside of the biomass reactor(s) (e.g. in the percolation fluid container). As an example, the filler material can be intro duced to (the bottom of) the container comprising biomass reactors or to (the bot tom of) the percolation fluid container. In one embodiment filler material can be in- traduced between the biomass reactors when two or more biomass reactors are present in the container. A filler material for immobilization of microbes may be e.g. commercial filler material, plastic net or sections of drainpipe which provide adhesion surface to the microbes and thereby immobilize them. Aim of the filler is to enhance maintaining the microbes in the bottom of the container and/or be tween the biomass reactors. This ensures that the nutrition conditions are benefi cial for the microbes. Loss of living microbes would compromise the process.

In one embodiment the cover of the present invention is a cover of the container comprising the biomass reactor, thus also covering one or several biomass reac tors and/or optionally one or several percolation fluid containers and/or optionally one or several percolation fluid collectors. In another embodiment the cover of the present invention is a cover of a biomass reactor and/or a cover of the percolation fluid container. Indeed, one cover may be used over one biomass reactor only and/or over one percolation fluid container. The opportunity to cover either the container comprising a biomass reactor, single biomass reactor or the percolation fluid container or any combination thereof further increases the flexibility of the method allowing using the biomass reactors either simultaneously or e.g. sequen tially thereby optimizing the gas production profile.

In one embodiment of the invention a cover of the container comprising a biomass reactor or a cover of the biomass reactor prevents floating of the biomass in or on the percolation fluid.

In one embodiment the cover is capable of recovering biogas. The specific embod iment of the method or arrangement of the present invention i.e. a combination of the container for producing biogas and the cover for recovering biogas simplifies the gas production method and arrangement e.g. by reducing the number of sepa rate containers or other units of the arrangement.

In a specific embodiment the cover is capable of floating, moving (e.g. upward or downward) or rotating (e.g. suitable as a gas storage), and/or the cover is dome shaped (e.g. very suitable as a gas storage). The floating, moving or rotating cover results in gas tight properties of said cover. The pressure of the biogas under the cover can be controlled with said floating, moving or rotating cover.

In one embodiment of the invention the arrangement comprising a container (which comprises a biomass reactor), a cover and a fluid distributor pipe, or the ar rangement comprising a container (which comprises a biomass reactor), a cover, a fluid distributor pipe, optionally a percolation fluid container, and optionally a per colation fluid collector, further comprises one or more of the following:

a percolation pump or a pump for circulating the percolation fluid,

a heating device configured to heat the percolation fluid, biomass and/or the container,

a glycol storage (e.g. outside of the container comprising the biomass reac tor), and

a biogas storage (e.g. outside of the container comprising the biomass reac tor).

A pump or several pumps can be used in the container comprising a biomass re actor for circulating the percolation fluid e.g. in the percolation fluid container, per colation fluid collector and/or biomass reactor. Also, in some embodiment a pump is needed in order to ensure the percolation fluid flow from the percolation fluid col lector to the percolation fluid container and/or biomass reactor e.g. via a pipe.

Fluid balance of the percolation fluid container can be controlled with the fluid col lector and optionally a discharge pipe (see e.g. Figure 1 , (11 )) and/or a pipe con necting the lower parts of the percolation fluid container and the percolation fluid collector. Furthermore, fluid level of the biomass reactor can be controlled with the percolation fluid distributor pipe (see e.g. Figure 1 , (4)) and optionally the fluid col lector. A pipe connecting the lower parts of the biomass reactor and the percola tion fluid container can also be utilized.

Often pipes used in the present invention (including fluid distributor pipes) are equipped with a pump and optionally one or more valves. In one embodiment of the invention one or more of the pipes (pipings) are equipped with one or more valves.

In one embodiment the method or arrangement comprises also means or a heat ing device for heating the container, biomass and/or the percolation fluid. Said heating takes place optionally before allowing the percolation fluid to contact with the biomass or before conducting the percolation fluid into the biomass, optionally using a heating device such as a heat exchanger. In one embodiment said means is a heat-exchanger configured to heat the container, biomass and/or the percola tion fluid. The percolation fluid of the container may be recovered (e.g. using a fluid collec tor). In one embodiment the method or arrangement comprises a fluid collector for recovering or storing the percolation fluid (e.g. from the percolation fluid container). In one embodiment the fluid collector is placed outside of the container. This ar rangement enables emptying of the container and optionally the biomass reac tors). In one embodiment the fluid collector comprises a piping system for recov ering the percolation fluid from the container including but not limited to a pipe and a pump (or pipes and pumps).

In one embodiment of the invention biogas recovered by a biogas storage under the cover, which is optionally above the container comprising the biomass reactor, above the percolation fluid container above the percolation fluid collector and/or above the biomass reactor, may be further directed to another gas storage or for further processing of biogas e.g. via a pipe optionally equipped e.g. with a gas blower. In one embodiment of the invention a pressure increasing device is not needed for directing biogas to the biogas storage under the cover or for directing biogas for further processing. In a specific embodiment the cover of the container comprising a biomass reactor, a percolation fluid collector, a percolation fluid con tainer or a biomass reactor is capable of recovering or storing biogas. In one em bodiment there are one or more pipes connecting the biomass reactor and the percolation fluid container; the biomass reactor and the percolation fluid collector; the biomass reactor, the percolation fluid container and the percolation fluid collec tor; and/or the percolation fluid container and the percolation fluid collector; for conducting biogas.

In one embodiment the method or arrangement comprises a device or system for recovering the biogas from the biogas storage. The device for recovering the bio gas can be any device known within the field. Biogas obtained by the method of the present invention may be recovered and processed further using methods known within the field. Possible further processes include but are not limited to separation of gases and compression. In a very specific embodiment the gas stor age is connected to means for further processing the gas e.g. by compression, or to means for introducing the gas to a device outside of the gas storage. In one embodiment there is a device or means for compressing the gas and/or separation of the biogas components from each other at least partially in the arrangement of the present invention. In one embodiment of the invention, carbon dioxide and/or hydrogen sulphide is removed from the produced biogas e.g. with (e.g. crushed or powdered) concrete or limestone or any corresponding material capable of removing carbon dioxide and/or hydrogen sulphide from biogas. In one embodiment of the invention me thane content of the produced biogas is increased by allowing the biogas to con tact one or several times with (e.g. crushed or powdered) concrete or limestone or any corresponding material, thereby removing carbon dioxide and/or hydrogen sulphide from the produced biogas. In a further or alternative embodiment the bio gas is dried and/or compressed. In a very specific embodiment methane content of the produced biogas is increased by allowing the biogas to contact with (e.g. crushed or powdered) concrete or limestone or any corresponding material, there by removing carbon dioxide and/or hydrogen sulphide from the produced biogas and furthermore, the biogas is dried and/or compressed. Indeed, biogas produced by the present invention may be utilized as fuel in vehicles such as cars (see e.g. Figure 2).

In one embodiment of the invention the arrangement of the present invention comprises an arrangement (e.g. for processing or treating biogas) comprising one or more devices or containers comprising (e.g. crushed or powdered) concrete, limestone or any corresponding material for removing carbon dioxide and/or hy drogen sulphide from biogas. In one embodiment said arrangement further com prises means for drying and/or compressing biogas and optionally means for con ducting (e.g. with a tube) said biogas to a vehicle (see e.g. Figure 2). In a further embodiment said arrangement is utilized in the method or with the arrangement of the present invention.

In one embodiment of the invention the arrangement comprises a glycol storage (as means for drying biogas). Biogas usually contains a large amount of water and the purpose of a glycol storage is to store glycol for removing water from biogas by absorption. In one embodiment of the invention the method for producing biogas comprises removing water from biogas with glycol. The glycol may be selected e.g. from the group consisting of triethylene glycol (TEG), diethylene glycol (DEG), ethylene glycol (MEG), and tetraethylene glycol (TREG).

The present invention also relates to an arrangement (e.g. for processing or treat ing biogas) comprising a device or container comprising (e.g. crushed or pow dered) concrete or limestone or any corresponding material for increasing me- thane content of the biogas. In one embodiment said (crushed or powdered) con crete or limestone or any corresponding material is for removing carbon dioxide and/or hydrogen sulphide from biogas. In a specific embodiment of the invention said arrangement further comprises means for drying and/or compressing biogas and optionally means (e.g. a tube) for conducting said biogas to a vehicle. In one embodiment of the invention said arrangement is utilized in the method for produc ing biogas or with the arrangement of the present invention.

Furthermore, the present invention relates to a method for increasing methane content of the biogas, wherein biogas is allowed to contact with (e.g. crushed or powdered) concrete or limestone or any corresponding material, thereby removing carbon dioxide and/or hydrogen sulphide from biogas. In a further embodiment the biogas is dried and/or compressed and optionally said biogas is conducted (e.g. with a tube) to a vehicle such as a car.

Biogas produced by the present invention may be utilized as fuel in vehicles such as cars.

In one embodiment the arrangement of the present invention is a small-scale ar rangement for producing biogas or the method of the present invention is a small- scale method for producing biogas. As used herein“small-scale arrangement or method” refers to an arrangement or method, which is suitable for small farms, curtilages, households, communities, bakeries, restaurants or small food industry.

Description of an embodiment with references to drawings

In a very specific embodiment of the invention the arrangement of Figure 1 is uti lized for producing biogas from biomass, which is in the form of a bale. The bale is placed in a net bag and introduced into a biomass reactor (see Figure 1 , (1 ) or Figure 3, (31 a-31 c)) of the container for producing biogas.

After introducing the biomass into the biomass reactor (see Figure 1 , (1 ) and (2)) said biomass reactor is filled with the percolation fluid through a fluid distributor pipe (see Figure 1 , (4)) optionally comprising one or more perforations for allowing the percolation fluid to move from the pipe into the biomass. Pumping of the perco lation fluid to the biomass reactor is continued (e.g. from a fluid container (12) in Figure 1 ) and sugar and organic acids start to flow with the fluid from a percolation fluid collector (e.g. from (12) in Figure 1 ) to a filler container (a percolation fluid container comprising fillers) in a pipe connecting the lower parts or bottom of the percolation fluid collector and the filler container (see Figure 1 , (7), or Figure 3, (33)).

A pump for circulating the percolation fluid is located in the percolation fluid collec tor (e.g. Figure 1 , (12)). Performance of the biomass reactor is controlled by ad justing amount of pumpings. Valves ((17) in Figure 1 ) are used for leading the fluid from the fluid collector to the biomass reactor (Figure 1 , (1 ) and (2)) and/or to the percolation container comprising fillers (Figure 1 , (8), (7)). The foam produced in the percolation container comprising fillers (Figure 1 , (7), (8)) is removed with the fluid of the fluid container ((12) in Figure 1 ) by utilizing a nozzle ((16) in Figure 1 ).

At first production of biogas starts in the percolation container comprising fillers and later during anaerobic fermentation in the biomass reactor. A connecting pipe (Figure 1 (14)) is used for conducting the produced biogas from the biomass reac tor to the gas storage in the percolation fluid container comprising fillers. The pro duced biogas is compressed to the desired (operating) pressure of about 30 mbar by a moving cover (Figure 1 (9)). The pressure is controlled by one or more weights on the cover (Figure 1 (10)).

Fluid balance is controlled with the fluid collector (Figure 1 , (12)), and discharge pipe (Figure 1 , (11 )) controls the fluid level of the percolation fluid container com prising fillers.

Before removing the biomass from the biomass reactor, the percolation fluid is re moved from said biomass reactor with a pump (Figure 1 , (6)).

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described below but may vary within the scope of the claims.

The present invention also concerns the following items: Item 22. An arrangement comprising a device or container comprising (e.g. crushed or powdered) concrete or limestone or any corresponding material for in creasing methane content of the biogas.

Item 23. The arrangement of item 22, wherein (e.g. crushed or powdered) con crete or limestone is for removing carbon dioxide and/or hydrogen sulphide from biogas.

Item 24. The arrangement of item 22 or 23, wherein said arrangement further comprises means for drying and/or compressing biogas.

Item 25. The arrangement of any of items 22-24, wherein said arrangement is uti lized in the method or with the arrangement of the present disclosure.

Item 26. A method for increasing methane content of biogas, wherein biogas is al lowed to contact with (e.g. crushed or powdered) concrete or limestone or any cor responding material, thereby removing carbon dioxide and/or hydrogen sulphide from the biogas.

EXAMPLES

The arrangement of Figure 1 was utilized for producing biogas. In one example the biomass was in the form of a bale. It was placed in a net bag and introduced into a biomass reactor (see Figure 1 , (1 ) or Figure 3, (31 a-31 c)) e.g. in an arrangement for producing biogas.

After introducing the biomass into the biomass reactor (see Figure 1 , (1 ) and (2)) said biomass reactor was filled with the percolation fluid through a fluid distributor pipe (see Figure 1 , (4)) optionally comprising one or more perforations for allowing the percolation fluid to move from the pipe into the biomass. Pumping of the perco lation fluid to the biomass reactor was continued (e.g. from a fluid container (12) in Figure 1 ) and sugar and organic acids started to flow with the fluid from a fluid col lector (e.g. from (12) in Figure 1 ) to a filler container in a pipe connecting the lower parts or bottom of the fluid collector and the filler container (see Figure 1 , (7), or Figure 3, (33)). A pump for circulating the percolation fluid was located in the fluid collector (e.g. Figure 1 , (12)). Performance of the biomass reactor was controlled by adjusting amount of pumpings. Valves ((17) in Figure 1 ) were used for leading the fluid from the fluid collector to the biomass reactor (Figure 1 , (1 ) and (2)) and/or to the perco lation container comprising fillers (Figure 1 , (8), (7)). The foam produced in the percolation container comprising fillers (Figure 1 , (7), (8)) was removed with the fluid of the fluid container ((12) in Figure 1 ) by utilizing a nozzle ((16) in Figure 1 ).

At first production of biogas started in the percolation container comprising fillers and later during anaerobic fermentation in the biomass reactor. A connecting pipe (Figure 1 (14)) was used for conducting the produced biogas from the biomass re actor to the gas storage in the percolation fluid container comprising fillers. The produced biogas was compressed to the desired (operating) pressure of about 30 mbar by a moving cover (Figure 1 (9)). The pressure was controlled by one or more weights on the cover (Figure 1 (10)).

Fluid balance was controlled with the fluid collector (Figure 1 , (12)), and discharge pipe (Figure 1 , (11 )) standardizes the fluid level of the percolation fluid container comprising fillers.

Before removing the biomass from the biomass reactor, the percolation fluid was removed from said biomass reactor with a pump (Figure 1 , (6)).

With the method and arrangement of the above example anaerobic fermentation took place by conducting the percolation fluid with a distributor pipe into the bio mass. The anaerobic fermentation was surprisingly excellent when the biomass was completely in the percolation fluid or under the level of the percolation fluid in the biomass reactor and the percolation fluid was conducted with a distributor pipe into the biomass. In this case a time-lag was at least 1 ,5 months.

The method and arrangement described in this example was carried out with a bale of straws of oat (total solids 75%). Anaerobic fermentation of one bale pro duced 148 m ³ biogas having the energy content of about 890 kWh. When a typical load is 8 bales the total energy content reaches about 7 MWh or more.

The method and arrangement described in this example was carried out with a bale of clover hay (total solids 30%). Anaerobic fermentation of one bale produced 66 m ³ biogas (anaerobic fermentation was not completed) having the energy con tent of about 390 kWh. When a typical load is 8 bales the total energy content reaches about 3 MWh or more. The energy content produced with bales of hay can be increased by baling drier hay.

The method and arrangement described above in this example can also be used for any other biomass, e.g. dry manure (e.g. of horses) (optionally in a net bag).

Energy consumption of one detached house is 20 MWh on average. Therefore, said energy content can be obtained with about 23 bales of oat straw or with about 50 bales of ensilage.