During the 19-century a global warming has been observed, which includes increases in global air and ocean temperatures, widespread melting of ice and snow, and rising global sea level. There is a clear connection between emissions of greenhouse gases caused by the human and the increase in temperature. Climatic changes caused by global warming can be stopped trough decreased emission of fossil fuels, for example by an increased use of biogas. Biogas is a renewable energy source which is produced through anaerobic (oxygen free) digestion of organic material. The gas is a mixture of methane (CH4) and carbon dioxide (CO2) and can be among others used as fuel in vehicles. Greengas is biogas produced from grains. The aim with this master’s thesis was to investigate a two-stage process for digestion of a rest by product from ethanol production, called drankvatten. Laboratory experiments were carried out with two process sets, each with two continues stirred tank reactors (CSTR). The process consisted of a thermophilic (55ºC) reactor as the first step in which the substrate was added. Afterwards there was a mesophilic (38ºC) second reactor in which the material from the first reactor was further degraded to produce more gas. The results were intended to be used for an assessment of whether a two-stage process is more efficient then a single-stage process in a full-scale production facility. One of the reasons to have a thermophilic first reactor is that the material has an average temperature around 80 ºC when it arrives to the facility today. It was proved that a two-stage process with this type of substrate generated a higher gas production but the improvements weren’t big enough to motivate a reconstruction of the facility into a two-stage process. The thermophilic process was stable with a retention time of 15 days and a loading rate of 6 g VS/(l•dygn). This retention time was the shortest which was achieved during that loading rate. During earlier mesophilic experiments a higher loading rate was achieved however the used retention time was longer. On the basis of this work no conclusions could be drawn whether a thermophilic process could withstand a higher loading rate then a mesophilic one. Longer adaptation times is probably needed to reach higher loading rates. In this work it also has been studied if it’s necessary to have continues mixing in the biogas reactors. The conclusion of this experiment is that continues mixing isn’t necessary, which results in less mixing and in that way less energy costs.

<p>During the 19-century a global warming has been observed, which includes increases in global air and ocean temperatures, widespread melting of ice and snow, and rising global sea level. There is a clear connection between emissions of greenhouse gases caused by the human and the increase in temperature. Climatic changes caused by global warming can be stopped trough decreased emission of fossil fuels, for example by an increased use of biogas. Biogas is a renewable energy source which is produced through anaerobic (oxygen free) digestion of organic material. The gas is a mixture of methane (CH4) and carbon dioxide (CO2) and can be among others used as fuel in vehicles. Greengas is biogas produced from grains.</p><p>The aim with this master’s thesis was to investigate a two-stage process for digestion of a rest by product from ethanol production, called drankvatten. Laboratory experiments were carried out with two process sets, each with two continues stirred tank reactors (CSTR). The process consisted of a thermophilic (55ºC) reactor as the first step in which the substrate was added. Afterwards there was a mesophilic (38ºC) second reactor in which the material from the first reactor was further degraded to produce more gas. The results were intended to be used for an assessment of whether a two-stage process is more efficient then a single-stage process in a full-scale production facility. One of the reasons to have a thermophilic first reactor is that the material has an average temperature around 80 ºC when it arrives to the facility today.</p><p>It was proved that a two-stage process with this type of substrate generated a higher gas production but the improvements weren’t big enough to motivate a reconstruction of the facility into a two-stage process. The thermophilic process was stable with a retention time of 15 days and a loading rate of 6 g VS/(l•dygn). This retention time was the shortest which was achieved during that loading rate. During earlier mesophilic experiments a higher loading rate was achieved however the used retention time was longer. On the basis of this work no conclusions could be drawn whether a thermophilic process could withstand a higher loading rate then a mesophilic one. Longer adaptation times is probably needed to reach higher loading rates. In this work it also has been studied if it’s necessary to have continues mixing in the biogas reactors. The conclusion of this experiment is that continues mixing isn’t necessary, which results in less mixing and in that way less energy costs.</p>

<p>Biogasprocessen är en komplex anaerob nedbrytningskedja där olika mikroorganismer är inblandade. Vanligast är att biogas produceras i mesofil rötning (cirka 38 ^oC), men även termofil rötning används (> 50 ^oC).</p><p>Svensk Biogas i Norrköping använder återstoden av etanoldestillationen hos en närliggande etanolproducent (drankvatten) som substrat. Substratets höga temperatur vid leverans motiverar termofilt rötningsförsök av drankvatten.</p><p>Försöket genomfördes i 55 ^oC med två kontinuerligt omrörda tankreaktorer (CSTR) och en termofil ymp. Biogasproduktion av drankvatten undersöktes. Sätt att hantera och motverka höga ammoniumhalter, samt effekter av näringslösningstillsats undersöktes. Det tog cirka 30 dagar för ympen att acceptera det nya substratet och då hade tillsats av processhjälpmedel KMB1 samt järnklorid använts. Reaktorerna kunde belastas med 3 g VS / (L • dygn) (VS, volatile solids, glödförlust). Den specifika gasproduktionen var 0,6 – 0,7 L / g VS och metanhalten ungefär 45 %. Höga ammoniumhalter motverkades genom förkortning av uppehållstiden. Under en period tillsattes nickelklorid i en av reaktorerna och under denna period hade reaktorn med nickelkloridtillsats något bättre specifik gasproduktion jämfört med reaktorn där ingen nickelklorid tillsattes.</p><p>Drankvatten kan rötas under termofila förhållanden. För att temperaturförändring vid biogasanläggningen i Norrköping ska var ekonomiskt försvarbart måste processen klara högre belastning.</p>

Biogasprocessen är en komplex anaerob nedbrytningskedja där olika mikroorganismer är inblandade. Vanligast är att biogas produceras i mesofil rötning (cirka 38 oC), men även termofil rötning används (&gt; 50 oC). Svensk Biogas i Norrköping använder återstoden av etanoldestillationen hos en närliggande etanolproducent (drankvatten) som substrat. Substratets höga temperatur vid leverans motiverar termofilt rötningsförsök av drankvatten. Försöket genomfördes i 55 oC med två kontinuerligt omrörda tankreaktorer (CSTR) och en termofil ymp. Biogasproduktion av drankvatten undersöktes. Sätt att hantera och motverka höga ammoniumhalter, samt effekter av näringslösningstillsats undersöktes. Det tog cirka 30 dagar för ympen att acceptera det nya substratet och då hade tillsats av processhjälpmedel KMB1 samt järnklorid använts. Reaktorerna kunde belastas med 3 g VS / (L • dygn) (VS, volatile solids, glödförlust). Den specifika gasproduktionen var 0,6 – 0,7 L / g VS och metanhalten ungefär 45 %. Höga ammoniumhalter motverkades genom förkortning av uppehållstiden. Under en period tillsattes nickelklorid i en av reaktorerna och under denna period hade reaktorn med nickelkloridtillsats något bättre specifik gasproduktion jämfört med reaktorn där ingen nickelklorid tillsattes. Drankvatten kan rötas under termofila förhållanden. För att temperaturförändring vid biogasanläggningen i Norrköping ska var ekonomiskt försvarbart måste processen klara högre belastning.