PRODUCTION OF BIOGAS AS A RENEWABLE ENERGY RESOURCE FROM SOLID SLAUGHTERHOUSE WASTES IN IRELAND

The slaughtering industry produces high energy organic waste streams and as such it is an attractive material to treat through biogas transformation. However there are many potential problems associated with the biogas transformation of slaughterhouse waste streams, including the practical handling according to the Animal By Products Regulation (ABPR 1069/2009/EC) and the high protein and fat content resulting in high ammonia, VFA and LCFA formation rates. This work reports Biochemical Methane Potential (BMP) analysis to identify the possible energy recovery from individual waste streams from slaughterhouses in Ireland. The possible uses of this potential energy are also examined through a technical energy balance. The methane potential of slaughterhouse waste streams from a cattle slaughtering facility were investigated in batch reactor experiments under mesophilic conditions. The methane potential determined through batch assays were 504.96, 227.30, 49.41 m(3)CH(4)/tVS for offal, paunch and wastewater sludge respectively. Biogas transformation, upgrading the biogas to biomethane, and distributing as a transport fuel is the optimum energy pathway for the recovered energy from the slaughterhouse waste streams. Through this pathway one Compressed Natural Gas (CNG) bus could be fuelled for a year by 156.6t of offal with only 15.5% loss of the gross energy produced. Energy losses through Combined Heat and Power (CHP) utilisation presented as 62.3% of gross energy produced due to the lack of an accessible thermal market in Ireland.