Growth of fungi on alternative substrates and fungal pre-treatment for biogas production

Abstract

This report starts with a literature review on the topic. From literature it is known that fungi can selectively digest lignin, thereby releasing other components which may subsequently be easily converted into biogas during anaerobic digestion of normally recalcitrant compounds. In addition, several authors have found that commercial fungi can be grown on alternative substrates such as digestates. Four substrates (flax shives, solid fractions of ACRRES digestate, Greendal digestate and cow manure) were incubated with 10 fungi species (Coprinus comatus, Ceriporiopsis subvermispora, Pleurotus ostreatus, Pleurotus eryngii, Lentinula edodes, Hypholoma frowardii, Clitocyba dusenii, Bjerkandera adusta, Hypholoma fasciculare, Gymnopilus sapineus and Kuehneromyces mutabilis). Most combinations of substrates and fungi resulted in growth/colonization, except for all combinations with Greendal digestate, probably due to fungicidal compounds. The most successful combinations were those with P. eryngii, P. ostreatusand G. lucidumon ACRRES digestate, flax shives and cow manure, based on visual signs of fungal colonisation (air mycelium). In general, (average) biogas productions from the different substrates with or without fungal pre-treatmentdid not vary to a large extent and were relatively low (35-73 nm3biogas per ton product). Although in some graphs a slight positive effect on biogas treatment seemed to be taking place, statistical analysis showed that treatment of cow manure with P. ostreatus,P. eryngiiand G. lucidumdid not significantlyincrease the amount of biogas that could be collected. Fungal pretreatment of flax shives also did not lead to increased biogas production with P. eryngiiand G. lucidumand even to a significantly lower biogas production with P. ostreatus.