Green Electricity from Biomass, Part II: Environmental Impacts Considering Avoided Burdens from Replacing the Conventional Provision of Additional Functions

Abstract

Environmental impacts of the introduction of electricity generation from biomass are investigated on the basis of data from plants operated in Austria. Different conversion technologies (anaerobic digestion, combustion, gasification) are considered and environmental impacts are analyzed according to ISO 14040 for Life Cycle Assessment. For the impact assessment the CML 2001 base line approach covering 11 impact categories is used. The paper presents the calculation of the avoided environmental burdens from replacing the conventional provision of functions by the additional functions of the biomass system. These additional functions are the provision of heat, nutrients and waste disposal. The conventional provision of heat and the disposal of manure and organic residues show the highest influence on total results. After the consideration of avoided burdens emission-savings are calculated in the impact categories GWP, ADP, ODP, AP and EP, while emissions remain in the impact categories POCP, LUC, HTP, TAETP, FAETP and MAETP for most of the plant types. In comparison with the UCTE-electricity-production-mix total emissions are lower for almost all plant types and impact categories. A ranking of the total results based on the unweighed aggregation of all impact category results is lead by anaerobic digestion of mainly organic residues followed by gasification of wood chips, the anaerobic digestion in small plants and combustion of wood chips. These results show that it is essential to consider both direct and indirect environmental impacts.