WO2012013235A1

WO2012013235A1 - Method and system for reducing greenhouse gas emission

Info

Publication number: WO2012013235A1
Application number: PCT/EP2010/061062
Authority: WO
Inventors: Alessandro Zampieri
Original assignee: Siemens Aktiengesellschaft
Priority date: 2010-07-29
Filing date: 2010-07-29
Publication date: 2012-02-02

Abstract

Method and system for reducing emission of a greenhouse gas from a stable, wherein the system comprise a first filter unit (15) adapted to be in gaseous communication with the stable (25) to receive a gas comprising air and methane, the first filter unit (15) configured to adsorb a first portion of methane from the gas, and an oxidation unit (20) in gaseous communication with the first filter unit (15) to receive the adsorbed first portion of methane, the oxidation unit (20) adapted to generate energy by using the adsorbed first portion of methane as a fuel.

Description

Method and system for reducing greenhouse gas emission The present invention relates to system and a method for re^¬ ducing greenhouse gas emissions from stables.

Methane is responsible for about 24% of the anthropogenic global warming. Ruminants are responsible for 26-28 % of the global methane emissions due to enteric fermentation. Enteric fermentation occurs when methane is produced in the rumen of the ruminants as microbial fermentation takes place. It is assumed that ruminants are directly responsible for about 6- 7 % of global warming. On a global basis, enteric fermenta- tion produces about 86 Mt of methane per year and animal ma^¬ nure accounts for 18 Mt of methane per year. Roughly, a rumi^¬ nant produces about 80 - 100 Kg of methane per year (110000- 140000 1/y or ca. 300 1/d) . This is equivalent to about 2- 2.5 t/year of carbon dioxide equivalent, given that the global warming potential of methane is ca. 25 for a 100 years time horizon.

Roughly, there are about 1.2 billion ruminants worldwide. On a global scale ruminants produce about 100-120 Mt/year of methane and 2.5-3 Gt/year of carbon dioxide equivalent (5-6 % of global carbon dioxide emission, which is about

45 Gt/year) .

It is an object of the embodiments of the invention to reduce the emission of a greenhouse gas from a stable.

The above object is achieved by a system according to claim 1 and a method according to claim 11. Methane is produced by ruminants housed in the stable. The methane produced gets mixed with the air available at the stable for ventilation. In the process of energy generation using the methane adsorbed at the first filter unit, the methane is converted to carbon dioxide. This results in po^¬ tential reduction in greenhouse gas emissions as carbon diox^¬ ide has a lower global warming potential as compared to meth^¬ ane .

According to an embodiment, the system further comprises a second filter unit adapted to be in gaseous communication with the stable to receive the gas, the second filter unit configured to adsorb a second portion of methane from the gas, the second filter unit adapted to receive the gas when the adsorbed first portion of methane is being provided to the oxidation unit, and the oxidation unit being in gaseous communication with the second filter unit to receive the ad^¬ sorbed second portion of methane, the oxidation unit adapted to generate energy using the adsorbed second portion of meth^¬ ane as the fuel.

The first filter unit and the second filter unit will alter^¬ natively be adsorbing and desorbing methane. This achieves in continuous adsorption of the methane produced at the stable and continuous supply of methane to the oxidation unit.

According to another embodiment, the first filter unit and the second filter unit comprises an adsorbent comprising one or more from the group consisting of zeolite, carbon, silica gel, and metal-organic frameworks.

According to yet another embodiment, the oxidation unit is one of the group consisting of a fuel cell, catalytic burner and an engine. The fuel cell can directly produce electrical power by electrochemical oxidiation of methane. The methane can be combusted in the catalytic burner unit to produce heat energy. The methane can be combusted in the engine to produce mechanical energy.

According to yet another embodiment, the system further comprises a prime mover operably coupled to the catalytic burner. The prime mover produces mechanical energy using the heat energy produced at the catalytic burner.

According to yet another embodiment, the system further com- prises a generator operably coupled to the prime mover or the engine. The generator is used for converting mechanical en^¬ ergy into electrical energy.

According to yet another embodiment, the system further com- prises a thermoelectric generator or a thermophotovoltaic generator operably coupled to the catalytic burner. This en^¬ ables conversion of heat energy into electrical power.

According to yet another embodiment, the system further com- prises a biogas plant in gaseous communication with the oxi^¬ dation unit, the biogas plant adapted to produce a biogas from manure generated at the stable. This enables in in^¬ creased energy generation. Additionally, the methane produced from the manure is also converted to carbon dioxide by the oxidation unit used for the methane contained in the gas ex^¬ iting the stable.

According to yet another embodiment, the system further comprises a heat exchanger adapted to extract heat from a flue gas exiting the oxidation unit. The extracted heat can be used to meet internal energy requirement of the stable.

According to yet another embodiment, the system further comprises a blower adapted to supply the air into the stable. The blower can be used for providing the air required for ventilation in the stable. Also, air can be blown into the stable for maintaining the concentration of methane below the self-ignition values and below an asphyxiation threshold. According to yet another embodiment, the system further comprises a temperature conditioner adapted to condition the temperature of the air being supplied into the stable. The air supplied into the stable can be heated or cooled as de- sired. In an aspect, the heat extracted by the heat exchanger from the flue gas exiting the oxidation unit can be provided to the temperature conditioner for conditioning. Embodiments of the present invention are further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1 illustrates a schematic block diagram of a system 10 for reducing a greenhouse gas emitted from a stable according to an embodiment herein,

FIG 2 illustrates the system 10 for reducing a green house gas emitted form a stable in detail according to an embodiment herein,

FIG 3 illustrates an oxidation unit according to an embodi^¬ ment,

FIG 4 illustrates an oxidation unit according to another embodiment,

FIG 5 illustrates an oxidation unit according to yet another embodiment,

FIG 6 illustrates a schematic block diagram of a system for reducing a green house gas emitted from a stable ac^¬ cording to another embodiment, and

FIG 7 is a flow diagram illustrating a method of reducing emission of a greenhouse gas from a stable according to an embodiment herein.

Various embodiments are described with reference to the draw^¬ ings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

FIG 1 illustrates a schematic block diagram of a system 10 for reducing a greenhouse gas emitted from a stable according to an embodiment herein. As illustrated, the system 10 com- prises a first filter unit 15 in gaseous communication with an oxidation unit 20. The first filter unit 15 is in gaseous communication with stable 25 to receive a gas comprising air and methane, exiting from the stable 25, designated using an arrow 30. The term stable is used herein to refer to a build^¬ ing in which livestock, such as ruminants are kept. The methane contained in the gas is emitted by ruminants housed in^¬ side the stable 25 due to enteric fermentation. The filter unit 15 comprises an adsorbent to adsorb a first portion of methane from the gas. The adsorbent may comprise zeolite, ac^¬ tivated carbon, silica gel, metal-organic frameworks (MOF) or any porous material capable for adsorbing methane. The ad^¬ sorbed first portion of methane is provided to the oxidation unit 20, illustrated by the arrow 35, where methane is used as a fuel to generate energy. The energy is generated by oxi^¬ dation of methane at the oxidation unit 20. The oxidation of methane is highly exothermic and is summarized in the reac^¬ tion provided below: CH₄ +20₂→C0₂ +2H₂0+89\Kj (1)

As equation (1) is an exothermic reaction, the enthalpy change (ΔΗ) is -891Kj, as heat is being released during the reaction .

Referring still to FIG 1, the energy generated at the oxida^¬ tion unit 20 can be heat and/or electrical power. For example, electrical power can be generated by oxidizing the meth^¬ ane electrochemically at the oxidizing unit 20. In an aspect, the system 10 can be implemented for generation of combined heat and power. During the energy generation process, methane is converted to carbon dioxide which exits as a flue gas, il^¬ lustrated by the arrow 37. Converting the methane emitted by ruminants into carbon dioxide, achieves in the reduction of release of methane into the atmosphere. As a molecule-for- molecule basis methane is about twenty five times stronger greenhouse gas than carbon dioxide, converting methane into carbon dioxide enables in the reduction of global warming. Methane when converted to carbon dioxide achieves in reduced emission of carbon dioxide due to the difference of the global warming potential of methane and carbon dioxide. FIG 2 illustrates the system 10 for reducing a green house gas emitted form a stable in detail according to an embodi^¬ ment herein. A valve 40 is provided in the pathway of the gas, illustrated by the arrow 30, being provided from the stable 25 to the filter unit 15. The valve 40 can be config- ured to cease the supply of the gas to the filter unit 15 when closed and supply the gas to the filter unit when open. For example, the supply of gas to the filter unit 15 can be stopped when the adsorbed first portion of methane is being provided to the oxidation unit 20. In an aspect, the valve 40 can be maintained in the open position till a certain degree of adsorption by the adsorbent. Thereafter, the valve 40 can be closed to stop the supply of gas to the filter unit 15.

Referring still to FIG 2, in an aspect, the oxidation unit 20 is maintained in gaseous communication with the filter unit 15 via a valve 45. The valve 45 can be opened for supplying the adsorbed first portion of methane from the filter unit 15 to the oxidation unit 20 and can be maintained in closed po^¬ sition while methane is being adsorbed at the filter unit 15. The methane adsorbed by the adsorbent at the filter unit 15 can be removed for supplying to the oxidation unit 20, for example, by applying a lower pressure or creating a tempera^¬ ture difference. Air contained in the gas can exit the filter unit 15, illustrated by the arrow 50, via the valve 55. The valve 55 can be maintained in a close position when the first portion of methane absorbed by the filter unit 15 is being provided to the oxidation unit 20 and can remain in an open position when methane is being adsorbed by the filter unit 15 to allow air to exit. Advantageously, the air exiting the filter unit 15 may be passed through a desulphurizer unit to remove sulphur prior to expelling of the air into the atmos^¬ phere . Referring still to FIG 2, in an aspect, the system further comprises a heat exchanger 60 downstream of the oxidation unit 20. The heat exchanger 60 can be used to recover heat from the flue gas exiting the oxidation unit 20, illustrated by the arrow 37. For example, the recovered heat can be used for meeting the internal energy requirement of the stable 25. In an aspect, air, as illustrated using the arrow 65, can be supplied into the stable 25 using a blower 70 for additional ventilation. Advantageously, the additional air can be sup- plied to maintain the concentration of methane in the gas ex^¬ iting the stable 25 below a self-ignition value and below an asphyxiation threshold. The concentration is selected such that the flammability of the gas is reduced and is below the asphyxiation threshold. For example, the concentration of methane in the gas can be maintained below five percent so that the concentration is below the explosion limits and asphyxiation threshold. The explosive limits for methane is up to a concentration of 5-14% in air. Concentration of methane above 14% in air displaces oxygen to a level below 18% in air, which can lead to asphyxiation. In an aspect, the blower 70 can advantageously be used to increase the capturing of methane by directing the gas to the exit of the stable 25 in gaseous communication with the filter unit 15. This enables in reducing the amount of gas flowing out of the stable 25. In another aspect, the capturing of methane can be increased by having a suction device at the exit of the stable 25 in gaseous communication with the filter unit 15. The suction device can increase the amount of gas provided to the filter unit 15 from the stable 25. In an implementation, the stable can be designed such that air is allowed to enter from one side and the gas comprising the methane and air is allowed to exit from the opposite side.

Referring still to FIG 2, a temperature conditioner 75 is po- sitioned downstream of the blower 70 for conditioning the air being blown into the stable 25. The air can be heated if the ambient temperature is cold or can be cooled if the ambient temperature is hot. As illustrated by the arrow 80, advanta- geously, the heat recovered by the heat exchanger 60 can be provided to the temperature conditioner 75. The recovered heat can be used by the temperature conditioner 75 to condi^¬ tion the air. This provides the advantage of conditioning the air without the use of external energy.

Referring still to FIG 2, in an aspect, the system 10 further comprises a biogas plant 90 in gaseous communication with the oxidation unit 20. Manure excreted by ruminants at the stable 25 can be provided to the biogas plant 90. The biogas plant

90 is adapted to produce a biogas comprising methane and car^¬ bon dioxide. The biogas produced is provided to the oxidation unit 20 where energy is generated using the methane of the biogas as fuel. Providing the biogas to the oxidation unit 20 can provide the advantage of combined energy production from the methane emitted by the ruminants in the form of gas and in the form of manure. The system 10 can be implemented to generate energy using only the methane exiting the stable in gaseous form or using both the methane exiting the stable in gaseous form and from the methane produced from the manure excreted by ruminants.

In an aspect, as illustrated in the example of FIG 3, the oxidation unit 20 can be a fuel cell 95 to produce electrical energy using the absorbed methane. Electrical energy can be produced at the fuel cell 95 by electrochemically oxidizing the fuel after on-cell or out-of-cell reforming. During oxi^¬ dation, electrical power is produced and the methane is con^¬ verted into carbon dioxide which exits the fuel cell 95, il- lustrated by the arrow 37. Air required for oxidation can be supplied externally into the fuel cell 95. In another aspect, as illustrated in the example of FIG 4, the oxidation unit 20 can be a catalytic burner 100. The catalytic burner 100 can be used to produce heat by combusting methane and in the process, convert the methane to carbon dioxide. The methane supplied into the catalytic burner 100 can be pre-mixed with air, as illustrated by the arrow 102. In an aspect, a prime mover 105 can be coupled to the catalytic burner 100 to pro- duce mechanical energy using the heat produced by the cata^¬ lytic burner 100. A generator 110 can be further operably coupled to the prime mover 105 to produce electrical energy. In certain implementations, thermoelectric generators or thermophotovoltaic generators can be coupled to the catalytic burnerlOO to produce electrical energy directly from a heat source. In another aspect, as illustrated in the example of FIG 5, the oxidation unit 20 can be an engine 115 at which the adsorbed methane can be combusted directly to produce me- chanical energy. A generator 110 can be further coupled to the engine 115 to produce electrical energy. The heat and electrical energy generated can be used internally at the stable. This would make the stable grid independent. Addi^¬ tionally, the electrical energy generated can be fed into the grid, and thus, generating additional revenue for the stable owner .

FIG 6 with reference to FIG 1 through FIG 5 illustrates a schematic block diagram of the system 10 for reducing a green house gas emitted from a stable according to another embodi^¬ ment. In the shown example of FIG 6, a second filter unit 130 comprising an adsorbent for adsorbing a second portion of methane is provided in gaseous communication with the stable 25. A valve 135 is provided in the pathway of the gas between the stable 25 and the first filter unit 15 and the second filter unit 130. The valve 135 is configured to supply the gas to either one of the filter units 15, 130. While the gas is being supplied to one of the filter units, supply of the gas to the other filter unit can be ceased. The value 135 can also be configured to cease the supply of the gas to both the filter units 15, 130. This arrangement enables in adsorbing methane at the filter units 15, 130 alternatively. For exam^¬ ple, when the first portion of methane absorbed by the filter unit 15 is being provided to the oxidation unit 20, the gas exiting the stable 25 can be provided to the second filter unit 130 for adsorption of a second portion of methane. Simi^¬ larly, when the second portion of methane adsorbed by the second filter 130 is being provided to the oxidation unit 20, the gas exiting the stable 25 can be provided to the first filter unit 15 for adsorption of the first portion of methane. The filter units 15, 130 alternatively adsorbing and de- sorbing methane enable in maintaining a continuous supply of methane to the oxidation unit 20 without stopping the supply as will be in the case on using a single filter unit.

Referring still to FIG 6, the methane adsorbed by the filter units 15, 130 is provided to the oxidation unit 20 via a valve 140. The valve 140 in configured to allow the supply of methane to the oxidation unit 20 from the filter units 15, 130. For example, when the adsorbed first portion of methane from the filter unit 15 is to be provided to the oxidation unit 20, the valve 140 can be configured to allow the flow of the first portion of methane from the filter unit 15 to the oxidation unit 20. The valve 55 is maintained in a closed po^¬ sition during the supply of the first portion of methane from the first filter unit 15 to the oxidation unit 20. During ad^¬ sorption of the first portion of methane at the first filter unit 15, the valve 55 is maintained in an open position to allow air to exit, as illustrated by the arrow 50. When the adsorbed second first portion of methane from the second fil^¬ ter unit 130 is to be provided to the oxidation unit 20, the valve 140 can be configured to allow the flow of second por- tion of methane from the filter unit 130 to the oxidation unit 20. During adsorption of the second portion of methane at the second filter unit 130, air from the filter unit 130 can exit via the valve 145, as illustrated by the arrow 150. Thus, during the alternative operation of adsorbing and de- sorbing of the filter units 15, 130 the valve 140 allows flow of methane from either of the filter units 15, 130 to the oxidation unit 20. As described in the example of FIG 2, in an aspect, methane produced using the biogas plant 90 can be provided to the oxidation unit 20 in combination with the methane provided by the filters 15, 130.

FIG 7, with reference to FIG 1 through FIG 6, is a flow dia^¬ gram illustrating a method of reducing emission of a green- house gas from a stable according to an embodiment herein. At block 155, a first filter unit 15 is provided in gaseous com^¬ munication with the stable 25 to receive a gas comprising air and methane, wherein the filter unit 15 is configured to ad- sorb a first portion of methane from the gas. Next at block 160, an oxidation unit 20 is provided in gaseous communica^¬ tion with the first filter unit 15 to receive the adsorbed first portion of methane, the oxidation unit 20 is adapted to generate energy by using the adsorbed first portion of meth- ane as a fuel, wherein the adsorbed first portion of methane is converted to carbon dioxide.

Example Based on the lower heating value (LHV) of methane, electrical power of about 140-170 W (1.2-1.5 MWh/year) can be generated from the methane emitted per animal. Assuming a stable with 100 cows produces about 1300-1600 1/hour of methane. Thus, electrical power of about 14-17 KW (120-150 MWh/year) can be generated.

Assuming that only 5% of the global ruminant population is housed at stables, which is about 60 M and that the average stable hosts 100 animals, the number of stables would total up to 600,000. From 600,000 stables, 8.4-10.2 MW of electri^¬ cal power can be generated.

The embodiments described herein enable in generating heat and electrical power using methane emitted by ruminants housed in a stable and reduce the greenhouse gas emission from the stable. Additionally, electrical power can be gener^¬ ated in remote areas having no grid connectivity for

autarchic/autonomous power generation. While this invention has been described in detail with refer^¬ ence to certain preferred embodiments, it should be appreci^¬ ated that the present invention is not limited to those pre^¬ cise embodiments. Rather, in view of the present disclosure which describes the current best mode for practicing the in^¬ vention, many modifications and variations would present themselves, to those of skill in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Claims

Patent Claims:

1. A system (10) for reducing emission of a greenhouse gas from a stable (25), comprising:

- a first filter unit (15) adapted to be in gaseous communi^¬ cation with the stable (25) to receive a gas comprising air and methane, the first filter unit (15) configured to ad^¬ sorb a first portion of methane from the gas, and

- an oxidation unit (20) in gaseous communication with the first filter unit (15) to receive the adsorbed first por^¬ tion of methane, the oxidation unit (20) adapted to generate energy by using the adsorbed first portion of methane as a fuel .

2. The system (10) according to claim 1, further comprising a second filter unit (130) adapted to be in gaseous communica^¬ tion with the stable (25) to receive the gas, the second fil^¬ ter unit (130) configured to adsorb a second portion of meth^¬ ane from the gas, the second filter unit (130) adapted to re- ceive the gas when the adsorbed first portion of methane is being provided to the oxidation unit (20), and the oxidation unit (20) being in gaseous communication with the second filter unit (130) to receive the adsorbed second portion of methane, the oxidation unit (20) adapted to generate energy using the adsorbed second portion of methane as the fuel.

3. The system (10) according to claim 1 or 2, wherein the first filter unit (15) and the second filter unit (130) com^¬ prises an adsorbent comprising one or more from the group consisting of zeolite, carbon, silica gel, and metal-organic frameworks .

4. The system (10) according to claim 1 or 2, wherein the oxidation unit (20) is one of the group consisting of a fuel cell (95), catalytic burner (100), and engine (115).

5. The system (10) according to claim 4, further comprising a prime mover (105) operably coupled to the catalytic burner (100) .

6. The system (10) according to claim 5, further comprising a generator (110) operably coupled to the prime mover (105) or the engine (115) .

7. The system (10) according to claim 3, further comprising a thermoelectric generator or a thermophotovoltaic generator operably coupled to the catalytic burner (100).

8. The system (10) according to any one of the claims 1 to 7, further comprising a biogas plant (90) in gaseous communica- tion with the oxidation unit (20), the biogas plant (90) adapted to produce a biogas from manure generated at the sta^¬ ble (25) .

9. The system (10) according to any one of the claims 1 to 8, further comprising a heat exchanger (60) adapted to extract heat from a flue gas exiting the oxidation unit (20) .

10. The system (10) according to any one of the claims 1 to

9, further comprising a blower (70) adapted to supply the air into the stable (25) .

11. The system (10) according to claim 10, further comprising a temperature conditioner (75) adapted to condition the tem^¬ perature of the air being supplied into the stable (25) .

12. A method of reducing emission of a greenhouse from a sta^¬ ble (25), the method comprising:

- providing a first filter unit (15) adapted to be in gaseous communication with the stable (25) to receive a gas com- prising air and methane, the first filter unit (15) being configured to adsorb a first portion of methane from the gas, and - providing an oxidation unit (20) in gaseous communication with the first filter unit (15) to receive the adsorbed first portion of methane, the oxidation unit (20) adapted to generate energy by using the adsorbed first portion of methane as a fuel, wherein the adsorbed first portion of methane is converted to carbon dioxide.

13. The method according to claim 12, further comprising:

- providing a second filter unit (130) adapted to be in gase- ous communication with the stable (25) to receive the gas, the second filter unit (130) configured to adsorb a second portion of methane from the gas, the second filter unit (130) receiving the gas when the adsorbed first portion of methane is being provided to the oxidation unit (20), and - providing the adsorbed second portion of methane to the oxidation unit (20), oxidation unit (20) adapted to gener^¬ ate energy using the adsorbed second portion of methane as the fuel, wherein the adsorbed second portion of methane is converted to carbon dioxide.

14. The method according to claim 12 or 13, wherein the first filter unit (15) and the second filter unit (130) comprises an adsorbent comprising one or more from the group consisting of zeolite, carbon, silica gel, and metal-organic frameworks.

15. The method according to any one of the claims 12 to 14, wherein the oxidation unit (20) is one of the group consist^¬ ing of a fuel cell (95), catalytic burner (100), and engine (115) .

16. The method according to any one of the claims 12 to 15, further comprising providing a biogas plant (90) in gaseous communication with the oxidation unit (20), the biogas plant (90) adapted to produce a biogas from manure generated at the stable (25) .