Role of Microbial Communities in the Low-Cost, Sustainable Treatment of Pig Effluent Waste

Effluent waste treatment ponds are a major source of methane emission in piggeries. Anaerobic digestion (AD) is an efficient and sustainable technology that converts waste into bioenergy and fertilisers. This is often too expensive to implement on farms without government subsidies. One simple, sustainable and affordable option, that harnesses microbial activities involved in AD, is to cover these effluent ponds with geosynthetic materials to create covered anaerobic pond (CAP)digesters that both treat the waste and generate bioenergy. Here, piggery waste is anaerobically degraded by a series of microbial-mediated biochemical pathways producing biogas. The remaining nutrient-rich digestate can be further developed into a fertiliser or compost. The biogas can then be used either directly as a fuel or converted to electricity. Therefore, CAP systems offer multiple benefits including waste stabilisation, greenhouse gas mitigation, renewable energy generation, production of soil improvers and improved community amenity via odour control. There is limited knowledge about the microbial processes governing the bioconversion of waste into biogas and how these microbial communities can be manipulated to increase productivity and reduce emissions. This information is needed to increase the environmental sustainability of CAPs using best management practices and monitoring tools leading to improved pond stability and biogas yields whilst highlighting conditions that induce system failure.