Life cycle assessment of sub-units composing a MSW management system

This paper summarises the results of a number of life cycle evaluations that we have carried out in recent years about some of the sub-units (in particular, the recycling of the packaging materials, the treatment of the bio-waste, and the energy recovery from the residual waste) that compose a municipal solid waste management system (MSWMS) and about the MSWMS as a whole.The range of values estimated for cumulative energy demand (CED), global warming (GWP100), human toxicity, acidification, and photochemical ozone creation indicators according to the different analyses are presented in the paper for each sub-unit. The assumptions influencing the results have been identified, too. The proper aggregation of sub-units has allowed the estimation of the impacts associated with two integrated MSWMSs implemented in Italy and of the order of magnitude of those associated with a generic MSWMS, similar to those of the two case studies.The results show that the assumptions that most influence the environmental indicators are those about selection efficiencies and quality deterioration in the recycling of the packaging materials, about process emissions and avoided products in the composting, about the biogas yield and its way of utilisation in the anaerobic digestion, and about the efficiency of the plant and the kind of avoided energy in the energy recovery. All the indicators, except GWP100 under certain assumptions, are negative in sign, thus indicating a benefit for the environment thanks to the avoided impact associated with the production of material and energy during the waste management. The estimated order of magnitude of the CED and GWP100 indicators turns out to be respectively thousands of MJ eq. and tens of kg CO2 eq. per tonne of managed waste.