Environmental assessment of the integrated municipal solid waste management system in Porto (Portugal)

From the EMFA, it can be highlighted that the electricity generated in the energy recovery plant is the most important energy flow and that it largely exceeds the energy demands from the LIPOR system. According to the net EF results, the composting and energy recovery units were found as very beneficial in terms of resources savings. Despite the fact that the composting plant has the largest gross EF (0.28 ± 0.02 gm2 kg−1 in average for the period analyzed, where gm2 refers to global square meters), a significant counter footprint effect associated with the production of the compost was calculated (−1.51 ± 0.10 gm2 kg−1 of waste composted). The energy recovery plant shows the lower gross EF (0.05 ± 0.01 gm2 kg−1 of waste combusted), but also an important contribution to the counter footprint (−0.78 ± 0.01 gm2 kg−1 in average). These individual results are reported to 1 kg of waste treated at each facility. Meanwhile, the EF for the overall IWMS reaches −0.49 ± 0.12 gm2 kg−1, where this result is reported to the total wastes treated at LIPOR. The negative value means that, in terms of the EF, the global system is environmentally beneficial because of the recovery of resources such as the compost and electricity.