L. Kabaivanova, I. Simeonov, D. Denchev, V. Hubenov, S. Mihaylova, E. Chorukova and E.
Stephan Angel off Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria;
Biotechnological exploitation of lignocellulosic wastes is considered promising for sustainable and environmentally-friendly energy provision because of the abundant availability of these renewable sources. The aim was development of an effective technology for anaerobic digestion of lignocellulosic wastes for methane production. Substrate constituents are highly resistant to biochemical conversion, so chemical pretreatment with NaOH, NH4OH in combination with amphyphylic substance Polyethylene glycol-4000 and biological pretreatment with fungal strains were applied. Experiments were carried out at different experimental conditions in laboratory bioreactors, as well as on a pilot scale. Wheat straw and cattle manure were involved in a ratio 65:35% and different organic loads. Pre-treatment lead to breakage in hemicelluloses and cellulose structure, reduction of crystallinity and increase of porosity that can significantly improve accessibility of enzymes. Cellulose quantity before and after treatment and the ratio between cellulose and the amount of volatile solids was changed. Infra red spectroscopy revealed lower peaks for the bonds, characteristic for lignin after treatment. As a result, an increased methane yield was realized for a shorter period by application of pretreatment techniques (highest after biological pretreatment) compared to the processes with untreated wheat straw.