chapter  11
18 Pages

Biogas

ByK. B. Zwart, J. W. A. Langeveld

Although biogas production had been known for over 100 years, widespread attention to large-scale biogas (methane and carbon dioxide) production from organic materials started only after the first energy crisis in the 1970s. The initial attention faded when this crisis ended rather quickly, many of the early installations suffering from problems such as low productivity and corrosion caused by high sulphur contents. Small household-scale biogas production has been applied for a long period in China and India, using cattle, pig manure and human excreta as organic feed, small-scale biodigesters being introduced more recently in Africa (Kamfor, 2002). Attention was regained around 1990, when material quality had

improved and demand for renewable energy increased. Biogas now was considered as an alternative to reduce CO2 emissions or reduce dependency on oil imports. These drivers, combined with substantial public financial support, renewed attention to biogas production and stimulated the construction of new installations, especially in NW Europe. Biogas production includes the following steps: (i) feedstock (crops,

crop residues, manure, industrial residues) production, collection, transport and storage; (ii) digestion and biogas production; (iii) gas cleaning and upgrading; and (iv) digestate storage and application. Biomass production involves crop cultivation (soil management, fertilization, crop protection, harvesting). Transport of crops and manure generally is limited to relatively short distances (no more than 10-50km). Industrial residues might come from longer distances, especially if a high-energy content is combined with a low-cost price. Most products must be stored at the biogas production site, especially crops and crop residues that are available during a limited period of the year. Industrial residues are often available year round. The next section of this chapter describes the principles of large-scale

(0.1MWe and above) anaerobic digestion, feedstock that may be used are described in the third section, and products that are generated are described in the fourth. In addition, this chapter discusses biogas applications in the

fifth section, and the role of biogas in a biobased economy (sixth section). The chapter ends with some conclusions (seventh section).