Open Access

Philip Nuss, Kevin H. Gardner, Stefan Bringezu

• 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 ofCarbon 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.…