Assessment of Energy Recovery Potential from Sewage Sludge and Organic Municipal Solid Waste: A Case Study of Mashhad, Iran

Background Municipal solid waste (MSW) and wastewater sludge are notable by-products of Iran's urbanization. Upwards of ۱,۹۰۰ tons of MSW from Mashhad is dumped every day at the Miami landfill, while the Al-Teymour wastewater treatment plant generates huge amounts of sludge. The waste streams have a high level of biodegradable organic matter but are not yet harnessed completely, thus emitting greenhouse gases and posing other environmental concerns. Harnessing their energy potential through anaerobic digestion may provide a sustainable and effective waste-to-energy approach. Methodologies This research formulated a deterministic mass-balance model coupled with the modified Gompertz model for the estimation of methane production from MSW, sludge, and co-digestion. Real composition data of Mashhad's MSW and real operating data of the AlTeymour WWTP were utilized as model inputs. Three scenario groups were modelled: (i) MSW-alone, (ii) sludge-alone, and (iii) co-digestion at different ratios (۸۵:۱۵, ۹۰:۱۰, ۸۰:۲۰, ۵۰:۵۰). Results The MSW-alone scenario had the greatest cumulative methane production (~۲.۱ × ۱۰⁵ m³ during ۴۵ days). Co-digestion at the ۹۰:۱۰ and ۸۵:۱۵ ratios generated earlier but lower-daily maxima (~۱۲,۵۰۰ m³/day), supporting limited-sludge-addition synergistic effects. The energy recovery potential amounted to ۷.۲ × ۱۰⁵ MWh after ۴۵ days, which would power tens of thousands of homes. As compared, the sole-digestion of the sludge produced little methane, whereas higher fractions of sludge (≥۵۰%) lowered the peak as well as cumulative yields. Conclusion Co-digestion of MSW and sludge is a more advantageous option than mono-digestion, especially for Mashhad. It can reduce landfilling, lower methane emissions, and support SDGs ۷, ۱۱, ۱۲, and ۱۳. Future studies should consider seasonal waste variations, inhibition factors, and economic assessments for broader adoption.

کلیدواژه ها:

Energy Recovery Potential ، Wastewater Sludge Co-digestion ، Modified Gompertz Model ، Sustainable Waste Management