Current political objectives and requirements on both the national and EU level aim at raising significantly the share of renewable energy sources in energy supply. High expectations are mainly tied to the use of biomass for energy, in particular of biogenic residues and waste. The main focus here is on reducing the emissions of greenhouse gases. Against this background, a systems analysis was conducted by ITAS - funded by the German Federal Ministry of Food, Agriculture and Consumer Protection (BMVEL) - with the objective to analyze and assess the chances of the utilization of biogenic residues and waste for energy. Based on the results, recommendations for a modification of the given framework conditions and promotion strategies are developed. The study focuses on the following biogenic residues and the kinds of waste: liquid manure, straw, wood residues from forestry, industrial wood residues, demolition wood, kitchen and garden waste, sewage sludge, and municipal solid waste.

Initially, volumes and compositions of the biogenic residues and the kinds of waste that are available in Germany and suitable for energy production were estimated, supplemented by corresponding analyses of EU member states. Within the framework of the study, more than 50 logistics chains for the supply and preparation of biogenic residues and waste (collecting, conditioning, storage, and transport) are analyzed and assessed under technical, economic, and environmental aspects. Additionally, the supply of biogenic residues and waste was combined with about 40 bioenergy conversion technologies for heat and power production, including biogas/sewage gas production, combustion and gasification processes. The analyzed technical, economic, environmental, and socioeconomic parameters are compared in reference to energy technologies based on fossil fuels, like electricity generation in hard coal power plants and heat production by heating oil.

In Germany, the annual volume of biogenic residues and waste available for energy production amounts to about 75 million Mg of dry organic matter (dom), above all wood residues from forestry and industry, waste wood, cereal straw, and liquid manure. Furthermore, 5 to 15 million Mg dom from agriculture and industry could be made accessible. The amount of 75 and 90 million Mg dom corresponds to about 9 and 11 % of the present primary energy consumption, respectively, and is far from being marginal.

A comparison of the different technologies reveals that the present production costs of heat and electricity from biogenic residues and waste are not yet competitive with those of fossil alternatives. Apart from co-combustion and co-gasification in hard coal power plants, the large biogas and sewage gas plants may be the first to achieve competitiveness.

In comparison to other instruments of CO₂ reduction, the achievable CO₂ mitigation costs of the technologies considered in this study, such as biogas and sewage gas utilization as well as the combustion and gasification of biogenic residues and waste, are very interesting. Although the achievable employment effects are acknowledged as a positive spin-off, they cannot serve as a main motif for promoting the use of biogenic residues and waste for energy supply.

The work on the study was completed in July 2003 with the publication of the final report.

Bibliographic data:
Leible, L.; A. Arlt; B. Fürniß; S. Kälber; G. Kappler; S. Lange; E. Nieke; Ch. Rösch; D. Wintzer:
Energy from biogenic residues and waste. Research Centre Karlsruhe (Ed.), Scientific Report FZKA 6882, 278 pp. in German