<p>This thesis is made by Carl Persson and Alejandro Saavedra for Gryaab. Gryaab is Gothenburg’s water processing plant and produces about 60 GWh biogas annually with a flow around 1150 Nm3/h. Gryaab wants to research their possibilities to become independent with electrical energy and the possibilities to enrich, upgrade biogas. The use of methane rich gases like biogas and natural gas is today low in Sweden compared to major parts of the world. Natural gas is one of the most established energy sources in the world, it contributes to about a quarter of the world energy supply. In Sweden natural gas only contributes about 2 % of the energy supply. The natural gas in Sweden is being imported from Denmark and the gas net goes from Malmo to Gothenburg. Usage of gas in that region is about 20 % of total energy usage. There are a total of 26 municipalities along the south- and west coast. Biogas is climate neutral and all infrastructures being used today with natural gas can potentially be used with biogas. The purpose of this thesis is to examine old and new technology intended to harvest energy in biogas and compare these technologies in a decision matrix. We have chosen two areas, combined heat and power (CHP) and upgrading biogas. In this report there are short reviews of heat engines, gas turbines, fuel cells, PSA, scrubbers, cryogenics, internal methane enrichment, ecologic lung, sulphide- and water removal. Interesting and appropriate technologies for Gryaab might be high temperature fuel cells, like molten carbonate fuel cells, or big gas engines in MW range, like Jenbacher J624 GS, in combined heat and power. These CHP systems are flexible in fuel quality, the biogas only need simpler purification, and they have a high electrical efficiency. To upgrade biogas to vehicle gas quality are water scrubbers, PSA and cryogenics all good choices. Cryogenically treated biogas gives liquid or combusted methane and liquid carbon dioxide as a byproduct.</p><p>Det här examensarbetet är gjort av Alejandro Saavedra och Carl Persson åt Gryaab. Gryaab är reningsverket i Göteborg vilka producerar cirka 60 GWh biogas årligen med ett flöde runt 1150 Nm3/h. Gryaab vill undersöka deras möjligheter att bli självförsörjande av elenergi och möjligheter att förädla, uppgradera biogasen. Användning av metanhaltiga gaser som biogas och naturgas är idag i Sverige låg jämfört stora delar av världen. Naturgas är en av världens mest etablerade energikällor, den står för cirka en fjärdedel av världens energiförsörjning. I Sverige står naturgasanvändningen för bara 2 %. Naturgasen i Sverige importeras från Danmark och stamnätet sträcker sig från Malmö till Göteborg. Användningen i den regionen uppgår till cirka 20 % av total energiförbrukning. Det är totalt 26 kommuner längst syd- och västkusten. Biogas är CO2-neutral och all infrastruktur som idag används för naturgas är potentiellt användbar för biogas. Syftet med examensarbetet är att undersöka ny och gammal teknik för att nyttja biogas på samt att utvärdera och jämföra teknikerna i en utvärderingsmatris. Vi har riktat in oss på två områden, el- och värmegenerering samt förädling av biogas. I det här arbetet står det kortfattade summeringar om värmemotorer, gasturbiner, bränsleceller, PSA, scrubbers, kryoteknik, processintern metananrikning, ekologisk lunga, svavelväte- och vattenavskiljning. Intressanta och lämpliga tekniker för Gryaab kan vara högtempererade bränsleceller, som smältkarbonat-bränsleceller, eller stora gasmotorer i MW- skala, som Jenbacher J624 GS i el- och värmegenerering. Dessa kraftvärmesystem är mycket flexibla när det gäller bränslekvalité, biogasen kräver endast enklare rening och dessutom har de hög elverkningsgrad. För att förädla biogasen till fordonsgaskvalité är vattenscrubber, PSA och kryoteknik alla bra val. Kryoteknisk uppgradering av biogas kan ge flytande eller gasformig metan samt flytande koldioxid som biprodukt.</p>

This thesis is made by Carl Persson and Alejandro Saavedra for Gryaab. Gryaab is Gothenburg’s water processing plant and produces about 60 GWh biogas annually with a flow around 1150 Nm3/h. Gryaab wants to research their possibilities to become independent with electrical energy and the possibilities to enrich, upgrade biogas. The use of methane rich gases like biogas and natural gas is today low in Sweden compared to major parts of the world. Natural gas is one of the most established energy sources in the world, it contributes to about a quarter of the world energy supply. In Sweden natural gas only contributes about 2 % of the energy supply. The natural gas in Sweden is being imported from Denmark and the gas net goes from Malmo to Gothenburg. Usage of gas in that region is about 20 % of total energy usage. There are a total of 26 municipalities along the south- and west coast. Biogas is climate neutral and all infrastructures being used today with natural gas can potentially be used with biogas. The purpose of this thesis is to examine old and new technology intended to harvest energy in biogas and compare these technologies in a decision matrix. We have chosen two areas, combined heat and power (CHP) and upgrading biogas. In this report there are short reviews of heat engines, gas turbines, fuel cells, PSA, scrubbers, cryogenics, internal methane enrichment, ecologic lung, sulphide- and water removal. Interesting and appropriate technologies for Gryaab might be high temperature fuel cells, like molten carbonate fuel cells, or big gas engines in MW range, like Jenbacher J624 GS, in combined heat and power. These CHP systems are flexible in fuel quality, the biogas only need simpler purification, and they have a high electrical efficiency. To upgrade biogas to vehicle gas quality are water scrubbers, PSA and cryogenics all good choices. Cryogenically treated biogas gives liquid or combusted methane and liquid carbon dioxide as a byproduct. Det här examensarbetet är gjort av Alejandro Saavedra och Carl Persson åt Gryaab. Gryaab är reningsverket i Göteborg vilka producerar cirka 60 GWh biogas årligen med ett flöde runt 1150 Nm3/h. Gryaab vill undersöka deras möjligheter att bli självförsörjande av elenergi och möjligheter att förädla, uppgradera biogasen. Användning av metanhaltiga gaser som biogas och naturgas är idag i Sverige låg jämfört stora delar av världen. Naturgas är en av världens mest etablerade energikällor, den står för cirka en fjärdedel av världens energiförsörjning. I Sverige står naturgasanvändningen för bara 2 %. Naturgasen i Sverige importeras från Danmark och stamnätet sträcker sig från Malmö till Göteborg. Användningen i den regionen uppgår till cirka 20 % av total energiförbrukning. Det är totalt 26 kommuner längst syd- och västkusten. Biogas är CO2-neutral och all infrastruktur som idag används för naturgas är potentiellt användbar för biogas. Syftet med examensarbetet är att undersöka ny och gammal teknik för att nyttja biogas på samt att utvärdera och jämföra teknikerna i en utvärderingsmatris. Vi har riktat in oss på två områden, el- och värmegenerering samt förädling av biogas. I det här arbetet står det kortfattade summeringar om värmemotorer, gasturbiner, bränsleceller, PSA, scrubbers, kryoteknik, processintern metananrikning, ekologisk lunga, svavelväte- och vattenavskiljning. Intressanta och lämpliga tekniker för Gryaab kan vara högtempererade bränsleceller, som smältkarbonat-bränsleceller, eller stora gasmotorer i MW- skala, som Jenbacher J624 GS i el- och värmegenerering. Dessa kraftvärmesystem är mycket flexibla när det gäller bränslekvalité, biogasen kräver endast enklare rening och dessutom har de hög elverkningsgrad. För att förädla biogasen till fordonsgaskvalité är vattenscrubber, PSA och kryoteknik alla bra val. Kryoteknisk uppgradering av biogas kan ge flytande eller gasformig metan samt flytande koldioxid som biprodukt.

<p>Biogas is a renewable energy source that is produced by anaerobic digestion of organic mate-rial. In Sweden, biogas predominately comes from sewage water sludge and landfills or from organic waste of households and industries. Small scale digestion plants at farms are espe-cially expected to contribute to increased biogas production in the future. Biogas can be ob-tained directly in it’s raw form and used as fuel in a combustion chamber. However, gas en-gines require biogas purification from hydrogen sulphide and drying from water to avoid cor-rosion. In order to increase the calorific value, carbon dioxide is separated and the Swedish Standard Type A requires the methane content to be 97 % for vehicle gas.</p><p>In the gas treatment process from biogas to vehicle gas, the upgrading step when carbon diox-ide is separated represents the highest cost since conventional upgrading techniques require high investments. This makes the upgrading costs for smaller biogas plants relatively high. In this master thesis, six upgrading methods have been evaluated and four of them are expected to be commercialized within two years. The following upgrading methods are of interest for Sweden:</p><p>- In situ methane enrichment; air desorbs carbon dioxide from the sludge in a</p><p>desorption column. The method is intended for digestion of sewage water sludge and the total upgrading cost is approximately 0,13 kr/kWh by a raw biogas flow 62,5 Nm3/h.</p><p>- Small scale water scrubber; carbon dioxide is absorbed in water under enhanced pressure. The upgrading process is very similar to the conventional water scrub-bing technique and the total upgrading cost is approximately 0,42 kr/kWh by a raw biogas flow of 12 Nm3/h.</p><p>- Cryogenic upgrading; the biogas is chilled to under -85 °C under a pressure of at least 5,2 barg and carbon dioxide can be separated in the liquid phase. The total upgrading cost is approximately 0,12 kr/kWh by a raw biogas flow of 150 Nm3/h. The total upgrading cost can be reduced if the recovered liquid carbon dioxide can be sold.</p><p>- Membrane technique; biogas is upgraded with polymeric membranes that are per-meable for carbon dioxide but not for methane molecules. The method is expected to be adaptable for both smaller and bigger biogas plants and the total upgrading cost is approximately 0,14 kr/kWh by a raw biogas flow of 180 Nm3/h.</p><p>All above mentioned upgrading techniques have methane losses less than two percent and all methods except for the in situ methane enrichment are expected to upgrade biogas to vehicle gas according to the Swedish Standard. In situ methane is expected to upgrade biogas up to 95 % methane content.</p><p>By combustion of unpurified landfill gas in a gas engine, corrosive combustion products and white deposits are formed. Purification of landfill gas can decrease maintenance costs for gas engines. Two landfill gas purification methods have been evaluated and with the first method, contaminants are trapped in ice crystals when the gas is chilled to -25 °C. The second method purifies landfill gas with condensed carbon dioxide.</p><p>An important result of the master thesis is that the in situ methane enrichment has a chance to become an interesting alternative for smaller sewage treatment plants but the method requires additional upgrading to reach 97 % methane content. The most important conclusion is that cryogenic upgrading and membrane technique are expected to satisfy the Swedish Standard. The methods have relatively low upgrading costs and the methane losses are less than two percent. This gives them a good chance to establish in Sweden.</p>

Biogas is a renewable energy source that is produced by anaerobic digestion of organic mate-rial. In Sweden, biogas predominately comes from sewage water sludge and landfills or from organic waste of households and industries. Small scale digestion plants at farms are espe-cially expected to contribute to increased biogas production in the future. Biogas can be ob-tained directly in it’s raw form and used as fuel in a combustion chamber. However, gas en-gines require biogas purification from hydrogen sulphide and drying from water to avoid cor-rosion. In order to increase the calorific value, carbon dioxide is separated and the Swedish Standard Type A requires the methane content to be 97 % for vehicle gas. In the gas treatment process from biogas to vehicle gas, the upgrading step when carbon diox-ide is separated represents the highest cost since conventional upgrading techniques require high investments. This makes the upgrading costs for smaller biogas plants relatively high. In this master thesis, six upgrading methods have been evaluated and four of them are expected to be commercialized within two years. The following upgrading methods are of interest for Sweden: - In situ methane enrichment; air desorbs carbon dioxide from the sludge in a desorption column. The method is intended for digestion of sewage water sludge and the total upgrading cost is approximately 0,13 kr/kWh by a raw biogas flow 62,5 Nm3/h. - Small scale water scrubber; carbon dioxide is absorbed in water under enhanced pressure. The upgrading process is very similar to the conventional water scrub-bing technique and the total upgrading cost is approximately 0,42 kr/kWh by a raw biogas flow of 12 Nm3/h. - Cryogenic upgrading; the biogas is chilled to under -85 °C under a pressure of at least 5,2 barg and carbon dioxide can be separated in the liquid phase. The total upgrading cost is approximately 0,12 kr/kWh by a raw biogas flow of 150 Nm3/h. The total upgrading cost can be reduced if the recovered liquid carbon dioxide can be sold. - Membrane technique; biogas is upgraded with polymeric membranes that are per-meable for carbon dioxide but not for methane molecules. The method is expected to be adaptable for both smaller and bigger biogas plants and the total upgrading cost is approximately 0,14 kr/kWh by a raw biogas flow of 180 Nm3/h. All above mentioned upgrading techniques have methane losses less than two percent and all methods except for the in situ methane enrichment are expected to upgrade biogas to vehicle gas according to the Swedish Standard. In situ methane is expected to upgrade biogas up to 95 % methane content. By combustion of unpurified landfill gas in a gas engine, corrosive combustion products and white deposits are formed. Purification of landfill gas can decrease maintenance costs for gas engines. Two landfill gas purification methods have been evaluated and with the first method, contaminants are trapped in ice crystals when the gas is chilled to -25 °C. The second method purifies landfill gas with condensed carbon dioxide. An important result of the master thesis is that the in situ methane enrichment has a chance to become an interesting alternative for smaller sewage treatment plants but the method requires additional upgrading to reach 97 % methane content. The most important conclusion is that cryogenic upgrading and membrane technique are expected to satisfy the Swedish Standard. The methods have relatively low upgrading costs and the methane losses are less than two percent. This gives them a good chance to establish in Sweden.