Analysis of the potential to recover energy and nutrient resources from cattle slaughterhouses in Australia by employing anaerobic digestion

Cattle slaughterhouses contain high strength waste and wastewater streams and are therefore strong candidates for treatment processes that recover energy and nutrients. Analysis of 6 Australian slaughterhouses showed the potential for renewable energy production from a production facility was up to 400 GJ or 40 MWh per day while the potential for recovery of renewable fertilizer was over 1 ton per day as struvite. The composition of individual wastewater streams varied depending on the source within the slaughterhouses. Biochemical methane potential varied from 250 to 300 L kg−1 VS for cattle yard and paunch wastewater to 500 L kg−1 VS for slaughter floor wastewater and over 1000 L kg−1 VS for rendering wastewater. Different anaerobic biodegradability and degradation rates between streams within a slaughterhouse suggests that conventional treatment processes such as anaerobic lagoons are not an optimized treatment strategy. Therefore separate and specialized treatment of red waste (rendering and slaughter floor) and green waste (paunch and offal waste) is recommended. Rendering and paunch wastewater were concentrated resource streams that contribute up to 75% of the methane potential, phosphorus and potassium loads, in only 20% of the volumetric flow. These concentrated streams provide opportunities to enhance the recovery of nutrients using crystallization technologies.