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Waste-related greenhouse gas (GHG) emissions have been recognized as one of the prominent contributors to global warming. Current urban waste regulations, however, face increasing challenges from stakeholders' trade-offs and hierarchic management. A combined method, i.e., life cycle inventories and scenario analysis, was employed to investigate waste-related GHG emissions during 1995–2015 and to project future scenarios of waste-driven carbon emissions by 2050 in a pilot low carbon city, Xiamen, China. The process-based carbon analysis of waste generation (prevention and separation), transportation (collection and transfer) and disposal (treatment and recycling) shows that the main contributors of carbon emissions are associated with waste disposal processes, solid waste, the municipal sector and Xiamen Mainland. Significant spatial differences of waste-related CO 2e emissions were observed between Xiamen Island and Xiamen Mainland using the carbon intensity and density indexes. An uptrend of waste-related CO 2e emissions from 2015 to 2050 is identified in the business as usual, waste disposal optimization, waste reduction and the integrated scenario, with mean annual growth rates of 8.86%, 8.42%, 6.90% and 6.61%, respectively. The scenario and sensitivity analysis imply that effective waste-related carbon reduction requires trade-offs among alternative strategies, actions and stakeholders in a feasible plan, and emphasize a priority of waste prevention and collection in Xiamen. Our results could benefit to the future modeling of urban multiple wastes and life-cycle carbon control in similar cities within and beyond China. [ABSTRACT FROM AUTHOR]

The performance, microbial enzymatic activities and the microbial community of sequencing batch reactors (SBRs) were evaluated under the single and combined nickel (Ni2+) at 20 mg/L and cadmium (Cd2+) at 10 mg/L. The single and combined Ni2+ and Cd2+ had no adverse impacts on the COD removal, whereas the NH 4 +-N removal efficiency declined sharply from about 99% to 34.42% and 42.67% under the single Ni2+ and combined Ni2+ and Cd2+. Compared with the absence of Ni2+ or Cd2+, the specific oxygen uptake rate (SOUR), ammonia-oxidizing rate (SAOR), nitrite-oxidizing rate (SNOR), nitrite-reducing rate (SNIRR) and nitrate-reducing rate (SNRR) declined by 24.09%, 56.63%, 51.50%, 58.01% and 52.09% under the combined Ni2+ and Cd2+, which were slower than the sum of those under single Ni2+ and Cd2+. The dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrate reductase and nitrite reductase activities showed the similar varying trends to the SOUR, SAOR, SNOR, SNIRR and SNRR, suggesting that the combined Ni2+ and Cd2+ displayed antagonistic inhibition on the nitrogen removal rates and microbial enzyme activities. The combined Ni2+ and Cd2+ declined the microbial diversity and richness less than the sum of those under single Ni2+ and Cd2+. The relative abundance of Nitrosomonas , Nitrospira and identified denitrifying bacteria displayed some changes under single and combined Ni2+ and Cd2+. These findings would contribute to better understand the combined impacts of multiple heavy metals on biological wastewater treatment systems. Unlabelled Image • Combined Ni2+ and Cd2+ showed less inhibition on nitrogen removal than Ni2+ and Cd2+. • Combined Ni2+ and Cd2+ inhibited the nitrogen removal rate less than Ni2+ and Cd2+. • Combined Ni2+ and Cd2+ displayed antagonistic inhibition on the enzymatic activity. • Combined Ni2+ and Cd2+ showed less inhibition on microbial diversity and richness. [ABSTRACT FROM AUTHOR]