Degradation of digestion residues by lignolytic fungi

In different European countries new legislative regulations and laws demand the reduction of the amount of wastes. In nature, the reduction steps of o rganic compounds in waste material are managed by symbiotic organisms, wher e a combination of aerobic and anaerobic degradation sequences leads to a n ear mineralization of organic material. Modeled on this principle, the proc ess presented here combines a two-stage digestion with a following aerobic mineralization step. To gain a maximum amount of methane which is a regener ative energy carrier, the process reducing organic waste-in this case kitch en refuse- was begun by a run through a digestion cascade. The residues fro m the anaerobic step, containing mainly lignocellulosic substances that are recalcitrant to anaerobic degradation, were concentrated and then treated aerobically by white-rot and soft-rot fungi. In this article, it is demonst rated that many fungi species can use digestion residues as a substrate. Th e soft-rot fungus Chaetomium cellulolyticum could aerobically degrade the d igestion residues, measured as volatile solid reduction of 39%. Within the process, lignin was reduced by almost 45%. Exposed again to the digestion, these residues of the aerobic treatment were degraded anaerobically with a rate of 42%. Therefore, a three-stage process combining anaerobic, aerobic and anaerobic degradation lends to organic matter reduction of more than 96 % of the original amount. It can be concluded at least that organic waste material can almost complet ely be mineralized by biotechnological treatment. (C) 2000 Elsevier Science Ltd. All rights reserved.