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<em>A </em>social life cycle assessment is proposed for the evaluation of the social potential impact in regard to the production and use of biomethane derived from biomass (algae and manure) in Latvia. The Multi-Criteria Analysis (MCA) is used to evaluate the social performances, which have been selected based on literature, statistics and legislation data. Seven alternatives are evaluated by experts and the best alternative is figured out.

Economic and environmental considerations of fossil fuel use, such as its shortage and impact on the air quality, as well as contribution to the climate change process, has lead to the necessity to develop biomass-based energy supply systems. Biomass is a renewable resource, which is an alternative for the fossil fuel. However, use of solid biomass is limited by the applicable technologies – it is not possible to use it in gas turbines or internal combustion engines, which are applied for the efficient combined heat and power generation. Therefore, biomass gasification is considered as a means of perspective energy conversion. In gasification, the intrinsic chemical energy of solid biomass is converted into the energy of combustible gas that can be used in gas-consuming engines. Tar is a by-product of gasification; it mainly consists of organic substances heavier than benzene and leads to clogging of pipes and downstream equipment because of its condensation on the inner surfaces. Determination of tar mass concentration and composition depending on the gasifier operational mode is the first step for process optimization aiming to get the maximal yield of useful syngas. An industrial experiment is examined in the paper, the gasifier model is compared with the results of practical measurements, and the method for tar determination is tested? on a real object. The predicted tar value in the model was 58 g/mn3, practical measurements showed that gravimetric tar mass concentration is in the range of 0.54…5.64 g/mn3.