Methane production from briquettes of birch sawdust

Renewable energy sources have the potential to reduce emissions of GHG when compared to the combustion of fossil fuels and thereby to mitigate climate change. Bioenergy systems can contribute to climate change mitigation if they replace traditional fossil fuel use (IPCC, 2012). Latvia is also striving to achieve neutral emissions by 2030. Therefore, the use of renewable energy is supported. Wood waste maybe an important resource for biogas production. The biodegradability is however limited because of the recalcitrant nature of the biofibres (lignocellulosic biomass) it contains. More and more biogas plants used the pellets or briquettes from various residues as a raw material. Their advantage is not only cheaper transport over longer distances, but also they absorb moisture well and do not form a floating layer. Hydraulic retention time working with such raw materials as birch sawdust and briquettes is relatively long and requires large volumes of bioreactors. Variety of additives can be used to improve the anaerobic digestion process. This article shows the results, where the enzymes alpha amylase, xylanase and biocatalyst Metaferm are used for the digestion process of birch briquette improvement. Birch briquettes were digested in 0.75 l bioreactors at temperature 38 °C in a batch mode process. Two bioreactors were for control purposes and contained inoculums only. Other 14 bioreactors contained biomass substrates without or with added enzymes or biocatalyst. Average specific biogas or methane yield from anaerobic fermentation of birch briquettes was 0.427 L·gE−1 DOM or 0.178 L·gE−1 DOM respectively. Addition of enzymes and biocatalyst (1ml) in bioreactors with birch briquettes increases the average methane yield.