Anaerobic Codigestion of Sludge and Food Waste for Enhanced Resource Recovery

Resource oriented management of organic waste streams, such as waste-activated sludge and food waste, presents an opportunity to recover energy and nutrients while mitigating climate change. The characteristics of sludge, including low nutrient and high solid contents, limit its treatment through anaerobic digestion. Anaerobic co-digestion of sludge with an abundant organic-rich substrate such as food waste can overcome the limitations of sludge mono-digestion. The sustainability of the codigestion approach is due to the ability to subsidise the energy demand of the entire wastewater treatment system with the bioenergy produced. Moreover, other resources, namely, struvite, liquid fertiliser, and compost, can be recovered. The present study reviews the anaerobic codigestion of sludge with food waste, focusing on the waste substrates produced in South Africa.