Environmental burdens over the entire life cycle of a biomass CHP plant

To increase the use of biomass for energy production it is important to know the possible and significant environmental effects. A life cycle inventory (LCI) was made on a 1.3 MW,I biomass CHP plant located in Reuthe/Vorarlberg/Austria with the purpose of analysing the different environmental burdens over the entire life cycle. The plant is fired with coarse and small fuelwood (10,000 t/yr) from industrial waste and forest residues. The boiler for the steam process has a moving grate burner and a muffle burner. The annual production is 4700 MWh of electricity and 29,000 MWh of district heat. The methodology of the analysis is orientated on the ISO Comittee Draft of the Series 13,600. The analysis was carried out for the different sections of the biomass plant over their entire life cycle-construction (1 yr), operation (20 yrs) and dismantling (1 yr). The plant in Reuthe, which is the first cogeneration system of this kind in Austria, is a model for other similar projects. The results are shown as environmental burdens of one year and of the entire life cycle. Some results of the life cycle inventory, like the mass and energy balances, selected emissions to air, allocation results and effects on carbon storage pools are given. The results demonstrate that depending on the stage and the period of life, different environmental burdens become significant, i.e. CO2 emissions of fossil fuels during construction, NOx emission during operation, emissions to soil during dismantling. The different options for allocating the environmental burdens to electricity and heat show a wide range of possible results, depending on the choice of allocation parameters (energy, exergy, credits for heat or electricity, price) i.e. for the particles emissions: 161 mg/kWh(el) to minus 566 mg/kWh(el), 0 mg/kWh(th) to 118 mg/kWh(th). With the results of the analysis it is thus possible for future similar projects to know when and where significant environmental burdens might be further reduced, and what kind of reseach and developement work should be done for further improvements. The work for this paper has been part of the Austrian case study of the European Commission's ExternE project on external costs of power production. (C) 1998 Elsevier Science Ltd. All rights reserved.