Environmental assessment of energy and waste systems based on anaerobic digestion

The ever increasing growth in global energy consumption, the limited availability of fossil fuel resources, their increasing costs on world market as well as the related awareness about negative environmental impacts are major driving forces for a change of the existing global energy systems (IPCC, 2006; IEA, 2010). Even before efficiency measures or reduced energy consumption the use of renewable energy is dealt as the most promising instruments to confront those challenges in Germany. Therefore, the political goal in Germany is an increase of the percentage of renewable electricity generation from 16.8% in 2010 to 30% in 2020 and for heat generation from 9.8% to 14% (Memmler et al., 2009; Musiol, 2011). A well established method of using renewable energy is the production of biogas by anaerobic digestion of organic substances such as animal manures, sewage sludge, agricultural, industrial, residential residues or energy crops. Considering the current consumption of electricity in Germany it is possible to reach a total share of up to 6.5% from anaerobic digestion technology in 2030 (Ramesohl, 2006; Memmler et al., 2009). However, to reach these goals the current share of 1% for electricity and 0.3% for heat energy generation by biogas production needs to be increased significantly (Memmler et al., 2009).