Avaliação do desempenho ambiental e energético da produção de hidrogênio a partir de resíduos sólidos urbanos (MSW-to-H2)

Abstract

The search for alternatives for the management of Municipal Solid Waste (MSW), given its continuous increase, coexists with ambitious goals for the supply and use of energy with better environmental performance. In the latter case, hydrogen (H2) stands out due to its high energy density and the various ways it can be produced and used. In this context, this work explores, through Life Cycle Assessment (LCA), the energy and environmental performance of four possible routes for hydrogen production from MSW (MSW-to-H2). The routes considered were: I) water electrolysis with electricity obtained from landfill biogas; II) steam reforming of biogas from landfill; III) electrolysis with electricity obtained from MSW incineration; and IV) gasification of RDF (Refuse-Derived Fuel) obtained from MSW. Conventional hydrogen production, by Steam Methane Reforming (SMR), was used as a baseline. The life cycle inventories, which covered from the transport and management of MSW to H₂ production, were adjusted for Brazilian conditions, assuming the MSW management of the Betim (Minas Gerais) landfill. Energy performance was estimated by the ratio between hydrogen production and the direct energy input throughout the life cycle. The environmental performance of the MSW-based routes considered the final disposal of MSW in a landfill as a counterfactual scenario. For this purpose, using the Recipe Midpoint (H) method, the following impact categories were considered for obtaining 1.0 kgH2: climate change, terrestrial acidification, particulate matter formation, photochemical oxidant formation, human toxicity, terrestrial ecotoxicity, and freshwater ecotoxicity. Route IV showed the highest energy efficiency (33.51%, 22.09 kgH₂/tMSW), standing out from the lowest efficiency presented by Route I (4.92%, 3.24 kgH₂/tMSW). In terms of environmental performance, none of the routes excelled in all the categories analyzed. The baseline route showed inferior performance in only two categories: climate change (11,60 kgCO2eq/kgH2, or 0,61%-2,19% higher than the MSW-based routes) and freshwater ecotoxicity (13,00 g1,4-DBeq/kgH2, or 0,21%-1,92% higher than the MSW-based routes). Even so, Route III was the best in the climate change category, with a result of -14.40 kgCO₂eq/kgH₂; the main contributor is the avoided emissions from the counterfactual scenario, which are mainly CH4 and, compared to CO2 emissions, have a higher characterization factor in this category.