Miljö- och samhällsekonomisk analys av behandling av biologiskt avfall

Abstract

Biogas is a renewable fuel that can be extracted from anaerobic digestion of many different substrates, for example biological household waste. An alternative handling of the waste is to mix it with other wastes and incinerate it in a combined heat and power (CHP) plant. This study uses life cycle assessment to investigate which type of waste handling that is better from an environmental point of view, anaerobic digestion with biogas production or incineration. The results are based on a case study of a biogas production plant owned by the company Ragn-Sells in Vänersborg. The alternative is incineration at a CHP plant in Gothenburg. Three different weighting methods were used, which produced different results on the detailed level. Overall however, the alternative with digestion and biogas production had significantly lower potential environmental impact than incineration according to all three methods. An economic valuation of the biogas production potential showed that the biggest societal savings would result from using all the produced biogas in heavy vehicles or to replace fuel oil for heating. However, since biogas is a high quality fuel it should be used as transportation fuel rather than for heating. By digestion and biogas production many potential services are gained from the organic waste. Waste volumes are reduced, emissions from the transport sector are reduced, local air quality is improved and valuable nutrients are returned to farmland through the organic fertilizer produced. The infrastructure and knowledge built up around the biogas system is also very valuable as a bridge to future gas based transport systems.