Prediction of Greenhouse Gas Emissions from Wastewater Treatment and Biogas Production in Tunisia

Tunisia, a country located in North Africa, is one of the MENA region countries suffering from several problems due to climate change, such as water stress, need for electricity, and waste and wastewater management. Wastewater treatment with biogas and electricity production represents a promising energy option for Tunisia, especially with the important quantities of sludge extracted from wastewater and disposed of in landfills. It is important, though, to know the number and sources of emissions that can be generated with biogas in order to ensure a good implementation of it. This study quantifies the emissions from different processes in a wastewater treatment plant with biogas production using adequate estimation methods for this case. Results showed that total annual emissions from wastewater treatment and biogas production on a national level could reach 515.25 kt CO2eq. Methane emissions from anaerobic digestion were the highest source of emissions. Carbon dioxide emissions from activated sludge were also significant. The other sources of emissions were nitrous oxides from the whole plant, electricity consumption, cogeneration, and carbon dioxide emissions from anaerobic digestion. This work represents a first attempt to picture the future wastewater treatment scenario that considers emissions when installing biogas production technologies in Tunisia, which can support emission management and, therefore, reduce the resulting environmental impact.