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Carbon recycling, in which organic waste is recycled into chemical feedstock for material production, may provide benefits in resource efficiency and a more cyclical economy - but may also create "trade-offs" in increased impacts elsewhere. We investigate the system-wide environmental burdens and cost associated with carbon recycling routes capable of converting municipal solid waste (MSW) by gasification and Fischer-Tropsch synthesis into ethylene. Results are compared to business-as-usual (BAU) cases in which ethylene is derived from fossil resources and waste is either landfilled with methane and energy recovery (BAU#1) or incinerated (BAU#2) with energy recovery. Monte Carlo and sensitivity analysis is used to assess uncertainties of the results. Results indicate that carbon recycling may lead to a reduction in cumulative energy demand (CED), total material requirement (TMR), and acidification, when compared to BAU#1. Global warming potential is found to be similar or slightly lower than BAU#1 and BAU#2. In comparison to BAU#2, carbon recycling results in higher CED, TMR, acidification, and smog potential, mainly as a result of larger (fossil-based) energy offsets from energy recovery. However, if a renewable power mix (envisioned for the future) is assumed to be offset, BAU#2 impacts may be similar or higher than carbon recycling routes. Production cost per kilogram (kg) MSW-derived ethylene range between US$1.85 and US$2.06 (Jan 2011 US$). This compares to US$1.17 per kg for fossil-based ethylene. Waste-derived ethylene breaks even with its fossil-based counterpart at a tipping fee of roughly US$42 per metric ton of waste feedstock.
This article presents the accounts of China's Total Material Requirement (TMR) during 1995–2008, which were compiled under the guidelines of Eurostat (2009) and with the Hidden Flow (HF) coefficients developed by the Wuppertal Institute. Subsequently, comparisons with previous studies are conducted. Using decomposition, we finally examine the influential factors that have changed the TMR of China. The main findings are the following: (1) During 1995–2008 China's TMR increased from 32.7 Gt to 57.0 Gt. Domestic extraction dominated China’s TMR, but a continuous decrease of its shares can be observed. In terms of material types, excavation constituted the biggest component of China's TMR, and a shift from biomass to metallic minerals is apparent; (2) Compared with two previous studies on China's TMR, the amounts of TMR in this study are similar to the others, whereas the amounts of the used part of TMR (Direct Material Input, DMI) are quite different as a result of following different guidelines; (3) Compared with developed countries, China's TMR per capita was much lower, but a continuous increase of this indicator can be observed; (4) Factors of Affluence (A) and Material Intensity (T), respectively, contributed the most to the increase and decrease of TMR, but the overall decrease effect is limited.