Slovak Society of Chemical Engineering Institute of Chemical and Environmental Engineering Slovak University of Technology in Bratislava PROCEEDINGS

Work was focused on possibilities of biogas production from a crude glycerol. This material is by-product of biodiesel production. In the work results of crude glycerol treatment in the laboratory mixed reactor and in the laboratory UASB reactors are described. Results from long-term co-digestion of maize silage and crude glycerol in full scale anaerobic reactor at biogas plant are also discussed. From this work resulted that the operation of mesophillic anaerobic degradation of crude glycerol as the only organic substrate is feasible; the process operation is very sensible to organic over-loading of reactor. The laboratory anaerobic mixed reactor achieved stable operation at the organic loading rate of 4 kg/m.d (COD) with ca 980 ml of biogas production per ml of dosed glycerol. The laboratory UASB reactor inoculated with granular sludge achieved stable operation at the organic loading rate of 6.5 kg/m.d with ca 840 ml of biogas production per ml of dosed glycerol. Inoculation of the UASB reactor with suspended biomass showed that this type sludge is not suitable for this purpose because of sludge flotation during reactor operation. Long term processing of crude glycerol in the full scale biogas plant for anaerobic treatment of maize silage showed that crude glycerol is suitable co-substrate. Evaluated specific production of biogas from crude glycerol was about 0.89 m per 1 kg of crude glycerol added. Dose of crude glycerol which represents only 5.2 % of overall dose to biogas plant produces almost 15 % of overall biogas production. Use of this co-substrate has significant influence on positive economical balance of biogas plant.