Greenhouse gas emissions and final compost properties from co-composting bovine specified risk material and mortalities with manure

The increased disposal costs of cattle specified risk materials (SRM) have reduced the competitiveness of the Canadian beef industry. The SRM materials include the skull, brain, trigeminal ganglia, eyes, palatine tonsils, spinal cord and dorsal root ganglia. This study investigates greenhouse gas (GHG) emissions and final compost properties from open windrow co-composting of manure with bovine SRM and mortalities. There were two compost treatments with four replications: SRMC consisting of SRM, cattle manure and barley straw and COWC consisting of cattle mortalities, cattle manure and barley straw. Average windrow temperature was higher (P < 0.05) for SRMC (47.1°C) than for COWC (44.1°C) over the first 139 days. The final compost coliform count, moisture, pH and TC contents were not significantly different between treatments while TN and available N (NH4+ + NO3- + NO2-) were lower for SRMC than for COWC. The average surface GHG flux from SRMC were 24.3 g C day-1 m -2 and 0.17 g N day-1 m-2 for CO2 and N2O, respectively, and were not significantly different from those from COWC (31.6 g C day-1 m-2 and 0.17 g N day -1 m-2 for CO2 and N2O, respectively), but CH4 emissions from SRMC (0.47 g C day-1 m-2) were lower than from COWC (1.57 g C day-1 m -2). While a few large bones were left in the cattle mortality treatment, composting decomposed all SRM suggesting that it may be a viable alternative to rendering for SRM disposal. © 2008 Springer Science+Business Media B.V.