Background: There are large amounts of manure and crop residues that could be used for
the generation of renewable energy. Anaerobic digestion [AD] converts the easily degraded part of
these materials into bio-methane and other gases. Bio-methane can be used for the generation of heat
and electricity. Only combinations of manure slurries and crop residues are economic substrates for
AD. Crop residues are lignocellulosic materials that need to be macerated for efficient conversion into
Results: Methane yields for different straw lengths and energy requirements for maceration were
compiled. The need for sufficient bioavailable micronutrients was established and methane yields for
combinations of manure slurries and straw are given. Harvesting methods for crop residues are discussed
and a model is developed for the effective organic matter in the effluent of the AD plant.
Conclusion: AD of straw and manures is, with the present subsidies, economic only where AD is
done in cooperatives with the members delivering straw and manure and taking back the effluent.
The large scale of AD of manures and crop residues requires reductions in the costs of harvesting
transport and storage of crop residues and a solution to the phosphate surplus in the regions with a
large concentration of animals.