Carbon footprint associated with two organic waste management: tunnel composting system versus landfill

Abstract

This study assesses the environmental impact of a tunnel composting system, quantifying greenhouse gas emissions and carbon sinks of compost throughout its life cycle and comparing outcomes to an alternative sanitary landfll scenario. The research applies a carbon footprint method incorporating the burden of waste input biomass, a key innovation particularly important in the circular economy thinking where organic waste is seen as a valuable resource. The functional unit was one ton of unpackaged compost. The greenhouse gas emissions were quantifed using SimaPro software and the Ecoinvent database, supplementing with literature data for processes not covered in the database. Uncertainty analysis, supported by Monte Carlo simulations, was conducted on various parameters, while uncertainties related to biological processes, such as composting and soil emissions and sinks, were specifcally addressed through sensitivity analysis. One ton of compost resulted in 453±18 kg of carbon dioxide equivalents, excluding soil carbon sinks (−8%). Monte Carlo simulations indicated a coefficient of variation of 4.08%, while sensitivity analysis pinpointed nitrous oxides emissions post-compost application as the key infuencing factor (±14%) of the carbon footprint. Environmental sustainability of composting becomes appar ent when compared to landflling; each ton of biomass waste composted instead of landflled reduces approximately 110 kg of carbon dioxide equivalents. The study concludes that composting is environmentally advantageous over landflling, underscoring the need to include environmental burden of waste input biomass, particularly food waste, in compost carbon footprint evaluations