Typically, Methane (CH4) emissions from the solid waste disposal are the largest source of greenhouse gas emissions in the waste sector. However, the methane emissions from the wastewater treatment and disposal may also be important. The CH4 from landfills and wastewater accounted for about 90% of waste sector emissions which is representing about 18% of global anthropogenic methane emissions in2008. The rapid increases in population, income, and industrialization in MENA-Region will increase the municipal solids waste (MSW) generation and sewage sludge as well. Most of MENA-region countries will divert more MSW into sanitary landfills which may cause significant increases in the methane emissions. The Non-CO2 greenhouse gas emissions growth, including CH4 emissions, are predicted to be greatest from 1990–2020 in the Middle East by about 197 percent. Significant GHG generation can be avoided in the waste sector in MENA-region countries by reducing waste generation, exploitation of energy from waste (landfill gas, anaerobic digester biogas) and recycle which will produce an indirect reduction of GHG emissions through the conservation of raw materials, improved energy and resource efficiency, and fossil fuel avoidance. The treatment and disposal of sewage sludge is an expensive and environmentally sensitive problem especially in the MENA-region countries. It is also a growing problem in Egypt, which is the biggest country in this region, since the sludge production is continuously increasing due to the current rapid increase in population and wastewater treatment facilities construction. The main objectives of this study are to evaluate the environmental consequences of the application of anaerobic digestion and controlled composting process in sewage sludge management in Egypt as example from MENA-region. The Life Cycle Assessment (LCA) approach is used to estimate the direct and indirect environmental impacts resulting from these processes. The results are shown the application of anaerobic digestion process with energy production was shown to be a promising option for sludge stabilization processes. The biogas production has a mitigation effect on environmental impacts due to fossil fuel substitution. While the aerobic digestion process requires approximately 1350 kWh/dry ton of digested sludge, the anaerobic digestion with biogas production and a subsequent electricity generation produces approximately 730 kWh/dry ton of digested sludge. The application of anaerobic digestion and composting processes showed a positive enhancement in all tested environmental impact categories. While the global warming potentials (GWP) for the life cycle of aerobic digestion was 1009 kg-CO2/ton dry solids, the anaerobic digestion and composting reduce the GWP by -480 and -300 kg-CO2/ton respectively.
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