Laurence Palmowski, Dr. Johannes Müller
Institute of Mechanical Process Engineering, Technical University of Braunschweig, Postfach 3329, D-38023 Braunschweig, Germany
The rate-limiting step in anaerobic digestion of organic solid waste is generally their hydrolysis. A size reduction of the particles and the resulting enlargement of the available specific surface can support the biological process in two ways. Firstly, in case of substrates with a high content of fibres and a low degradability, their comminution yields to an improved digester gas production. This leads to a decreased amount of residues to be disposed of and to an increased quantity of useful digester gas. The second effect of the particle size reduction observed with all the substrates but particularly with those of low degradability is a reduction of the technical digestion time. It enables a harmonization of the digestion of heterogeneous inputs and the possibility to reduce the digester volume without lost in the gas production. Furthermore, the particle size of organic waste has an influence on the dewaterability after codigestion with sewage sludge. The presence of organic waste residues improves the dewaterability measured as specific resistance to filtration but this positive effect is attenuated if the particle size of the solids is reduced.
L. Palmowski, J. Müller (1999). Influence of the size reduction of organic waste on their anaerobic digestion, Water Science and Technology, 41(2000)3, pp.155-162 and IAWQ II. International Symposium on anaerobic digestion of solid waste,15.-17. Juni 1999, Barcelona, Spain, Preprints Vol. 1, pp. 137-144