Towards a prototype of a modular biogas system
Abstract: As of today, large unused potential for biogas production exist within the Swedish agriculture sector. The biogas production within this sector is, however, associated with several problems such as poor energy efficiency and non-profitable systems. This is to some degree due to lack of standardized technical solutions. International Micro BioGas AB (IMB AB) has been aided by KTH since 2014. This project investigates several innovations from IMB AB in regards to biogas production: A mixing device A building capturing waste heat from the digesters (building concept) Insulation of the digester (cover concept) Small-scale and modular package systems The innovations listed above are evaluated from energy, economic and environmental perspectives by doing a case study on the dairy farm Ogestad close to Gamleby, Sweden. Two cases are considered. In Case 1, the raw biogas is burned in a combined heat and power-unit (CHP) in order to produce electricity. In Case 2, raw biogas is upgraded in a small-scale upgrading unit to vehicle gas standards which is sold to the market. The results show that the mixing device is promising in terms of energy use. It is therefore recommended to move on with testing of the equipment. The cover concept and the building concept show similar performance from energy and environmental standpoints. The building concept is concluded not to be economically viable. The cost reduction by applying a modular concept where one product can be used on different sized farms is significant. However, the needed investment from the company is large. The goal of achieving a modular system is therefore concluded desirable. The subsidy from the Swedish board of agriculture covering 40 % of the investment cost, has a major impact on the profitability of the systems. Without this subsidy, the systems are not viable in terms of economy. In Sweden, the small-scale vehicle gas production (Case 2) was concluded the most profitable as well as the best-performing from energy and environmental standpoints.
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