<p>Despite big expansion of biogas plants in the world, does not have the levels in the Swedish market succeeded very good. Presently are not so many expanded biogas plants in Sweden. Especially biogas plants that are based on rest products from the industry. This study checks the possibility and takes up the profitability in producing biogas off spill products from rape oil production. The spill product that is interesting in this case is process water with high-energy contents that currently are given away to the local farmers for fertilization of farmland.</p><p> Results from the study show that the process water in itself is not appropriate substrate for digestion in a biogas plant. On the other hand if you use an involvement corresponding 20- 25% graft in the process water can the result become really good. But to use this biogas to heat power plant or upgrading to vehicle fuel can it be unsuitable on the basis of economic calculations. This entirely depends on that production of the process water is too little and that will give a result with smaller amount biogas production. This amount will not be neither enough to be sold to other companies for upgrading or other purposes.</p><p> This problem can be solved through cooperation with the municipality’s sewage treatment or local farmers that will supply their energy needs by themselves. If the cooperation takes in force can biogas plant becomes profitable irrespective of what the biogas will be used to.</p><p> Using biogas in heat power plant to force electricity and heat with minimum 200-kilowatt gas engine can investment be profitable, regardless of if the electricity will be sold on the market or it be used internal. It is also economic to upgrade biogas to vehicle fuel with a minimum prise of 7, 5 SEK/Nm³ biogas.   </p><p> Investment on biogas plant is depending on factors like interest rate, economic contribution, costs and political arrangements so. The results will be changed if the economic factors changed, for examples lower interest rate and higher economic contributions brings profitability in the investment. On the other hand higher raw materials or less economic contribution will make that the investment becomes uneconomical.</p>

Despite big expansion of biogas plants in the world, does not have the levels in the Swedish market succeeded very good. Presently are not so many expanded biogas plants in Sweden. Especially biogas plants that are based on rest products from the industry. This study checks the possibility and takes up the profitability in producing biogas off spill products from rape oil production. The spill product that is interesting in this case is process water with high-energy contents that currently are given away to the local farmers for fertilization of farmland.  Results from the study show that the process water in itself is not appropriate substrate for digestion in a biogas plant. On the other hand if you use an involvement corresponding 20- 25% graft in the process water can the result become really good. But to use this biogas to heat power plant or upgrading to vehicle fuel can it be unsuitable on the basis of economic calculations. This entirely depends on that production of the process water is too little and that will give a result with smaller amount biogas production. This amount will not be neither enough to be sold to other companies for upgrading or other purposes.  This problem can be solved through cooperation with the municipality’s sewage treatment or local farmers that will supply their energy needs by themselves. If the cooperation takes in force can biogas plant becomes profitable irrespective of what the biogas will be used to.  Using biogas in heat power plant to force electricity and heat with minimum 200-kilowatt gas engine can investment be profitable, regardless of if the electricity will be sold on the market or it be used internal. It is also economic to upgrade biogas to vehicle fuel with a minimum prise of 7, 5 SEK/Nm3 biogas.     Investment on biogas plant is depending on factors like interest rate, economic contribution, costs and political arrangements so. The results will be changed if the economic factors changed, for examples lower interest rate and higher economic contributions brings profitability in the investment. On the other hand higher raw materials or less economic contribution will make that the investment becomes uneconomical.

During this master thesis, the possibility of ammonia removal from digestate in combination with after hygienization has been investigated. The aim of the work was to see how much ammonia that could be removed but also the properties of other process parameters such as TS/VS content, pH and alkalinity of the digestate. It was also of interest to study the energy balances for a process that combines ammonia stripping with after hygienization. The purpose of hygienization in a biogas plant is to kill pathogens. To study ammonia stripping combined with after hygienization, a prototype of an ammonia stripper was built in a laboratory. The digestate was heated to the hygienization temperature of 70 °C and air was led through with the help of a peristaltic pump by the end of the system. Condensate was trapped in a bottle by cooling the tube and the gases were brought to another bottle containing 1 M sulfuric acid. Ammonia and sulfuric acid reacted and formed ammonium sulfate. The process was also tested with closed system using vacuum to decrease the boiling point and thereby create more condensate. The results from the experiments showed that with an air stripping process most of the ammonium was trapped in the sulfuric acid while with a vacuum process more ammonium was trapped in the condensate. The most important parameters to achieve a good ammonia removal were air flow and time. With the vacuum system, more condensate was removed. The removal of condensate could make it possible to recirculate process fluid from the stripping process and thereby save energy in the centrifugation part which is used to create a solid part of the bio digestate. It was concluded from the experiments that air stripping is more effective when it comes to ammonium recovery. The process could be improved by using higher air flow which could decrease the time to less than one hour, which is the desired hygienization time. However, it is desired to keep the pump flow as low as possible since it is energy consuming. A chemical increase of the pH would also be of interest to try since previous tests showed a strong correlation between high pH-value and good ammonia stripping. More tests overall are of interest to ensure a reliable result. Still, the combination of after-hygienization and ammonia stripping would contribute to a better environment and a sustainable agriculture with a natural and nutritious digestate.