Anaerobic treatment of rapeseed meal

Rapeseed meal is a solid by-product obtained from rapeseed after oil extraction. This contribution summarises experiences from batch experiments as well as the long-term processing of this substrate in a laboratory stirred anaerobic reactor (continuous stirred-tank reactor). On the basis of the batch tests of hydrolysis, acidogenesis, and methanogenic activity, it was concluded that the anaerobic degradation of rapeseed meal can be performed using a one-step system and it is not necessary to include a hydrolytic-acidogenic step prior to the methanogenic step. Although the methanogenic potential of rapeseed meal appears to be very promising, the long-term processing as a single substrate led to serious problems arising from the inhibitory effects. It was, therefore, co-fermented with crude glycerol from biodiesel production. From the long-term operation of the laboratory model, it may be stated that, due to the co-fermentation of by-products from biodiesel production, the individual inhibition effects can be suppressed to a large extent and biogas production can be stabilised. The maximum organic loading rate in the continuous stirred reactor achieved 2.42 kg m(-3) d(-1) of volatile solids (15 g of rapeseed meal and 20 mL of gas-phase), which was 3.13 kg m(-3) d(-1) of chemical oxygen demand.