Assessment of Gaseous Emissions from Cattle Abattoir Wastes in Cameroon

Abstract

Abattoirs are potentially a significant source of greenhouse gas (GHG) methane (CH4) and nitrous oxide (N2 O) emissions. Measurements were conducted in a beef cattle abattoir located in Bamenda, Cameroon, to characterise waste production and quantify GHG emissions. A male and female cattle were randomly selected on each day for waste measurement over a period of two weeks. Waste from each cattle was quantified by collecting all the intestinal/stomach contents after slaughtering and determining the mass of dry matter (DM) and volatile solids (VS). Emissions from the outdoor solid waste storage heap was measured using flux chambers. The average cattle weight was 420 kg and the average intestinal/stomach waste was 37 ± 6 kg cattle−1, half of which was dumped outdoor in a heap, while the rest was discarded with wastewater into a stream. The DM produced was 4.19 ± 0.85 kg cattle−1, representing 11% of the wastes, and the VS produced was 3.42 ± 0.82 kg cattle−1. The average ratio of waste DM to cattle weight was 1.0%, while the ratio of waste VS to cattle weight was 0.8%. Modelled CH4 emissions from the total waste was estimated at 37.84 ± 8 g CH4 cattle−1 with a range of 27.57–56.03 g CH4 cattle−1. Measured GHG emission from the outdoor heap was 5.89 ± 4.78 mg CH4 m−2 min−1, 0.137 ± 0.151 mg N2 O m−2 min−1, and 95 ± 83 mg CO2 m−2 min−1. The total GHG (CH4 + N2 O) emission rate was 229 mg CO2 e m−2 min−1, indicating that CH4 contributes 82% of the total GHG. Improved waste management strategies, such as anaerobic digestion for biogas production or using covers over waste heaps, would help abattoirs mitigate GHG emissions.