Greenhouse Gas Emissions-Based Development and Characterization of Optimal Scenarios for Municipal Solid and Sewage Sludge Waste Management in Astana City

Landfilling is the most applied solid waste management method in developing countries, which leads to a large amount of greenhouse gas (GHG) emissions. It is thus imperative to develop strategies for evaluating different economically viable waste management scenarios to mitigate GHG emissions. According to the Paris Agreement, Kazakhstan planned to decrease GHG emissions by 25% by 2050 as compared to 1990 levels, while reaching carbon neutrality by 2060. In this context, we herein propose four different scenarios for municipal solid waste (MSW) treatment and three scenarios for sewage sludge (SS) treatment with the aim of evaluating the GHG potential for Astana, the capital city of Kazakhstan, using the (solid waste management) SWM-GHG calculator developed by the Institute for Energy and Environmental Research. The MSW treatment scenarios include: (A) 15% recycling of secondary materials and 85% landfilling of remaining MSW; (B) 30% recycling of secondary materials; 70% sanitary landfilling with biogas collection; (C) 30% recycling and 70% biological stabilization and landfilling without biogas collection; and (D) 30% recycling, 20% composting, and 50% (waste-to-energy) WtE incineration. The sewage sludge management scenarios include (1) 100% landfilling; (2) 100% WtE incineration; and (3) co-incineration of sewage sludge and coal. The results reveal that more complex scenarios lead to extensive ecological benefits; however, there are economic constraints. Based on the analysis of the proposed scenarios, we recommend the optimal strategy for MSW treatment to be 30% recycling with biological stabilization that has a total cost of EUR 16.7 million/year and overall GHG emissions of -120 kt of CO2 eq/year. In terms of sewage sludge management, the addition of coal to sewage sludge simplifies the combustion process due to the higher heat capacity. Considering lower cost and higher energy recovery, it is recommended as a favorable process.