Abstract
Life cycle analysis allows for the assessment of the qualitative and quantitative relationship between selected areas of human activity and the consequences for the environment. One of the important areas is the production of electricity and heat, for which the main raw material in Poland is hard coal. An alternative may be to use biogas as a fuel for energy purposes. This article presents the assessment of environmental hazards caused by the production of energy from biogas. The analysis took into account the change of the substrate from maize silage, commonly used in Polish biogas plants, to waste from the domestic agri-food industry. The evaluation covered the acquisition of substrates, their transport to a biogas plant, generation of electricity from biogas, and management of the generated by-products. The analysis was done in terms of both the impact and sensitivity categories. It was found that the emission of pollutants related to the acquisition of the substrate plays a key role and the use of waste for the production of biogas used for energy production brings environmental benefits. The analysis has shown that replacing coal with biogas, regardless of the raw materials used in its production, results in a positive environmental effect, especially in the areas of human health and resources categories. The positive environmental effect of the production of electricity from biogas can be enhanced by switching raw materials from purpose-grown crops to waste from the agri-food industry and agriculture. An important factor influencing the environmental impact is the degree of heat utilization (the greater the percentage of heat utilization, the greater the environmental benefits) and management of all by-products.