Abstract
Upgrading consists of a range of purification processes aimed at increasing the methane content of biogas to reach specifications similar to natural gas. In this perspective, an environmental assessment, based on the Life Cycle Assessment (LCA) method, of different upgrading technologies is helpful to identify the environmental characteristics of biomethane and the critical steps for improvement. The aim of this work is to conduct an LCA of biomethane production from waste feedstock, using the SimaPro software. The study focuses on the comparison of several upgrading technologies (namely, membrane separation, cryogenic separation, pressure swing adsorption, chemical scrubbing, high pressure water scrubbing) and the on-site cogeneration of electricity and heat, including the environmental benefits deriving from the substitution of fossil-based products. The results show a better environmental performance of the cogeneration option in most of the impact categories. The Fossil resource scarcity is the impact category which is mainly benefited by the avoided production of natural gas, with savings of about 0.5 kg oil eq/m3 of biogas for all the investigated technologies, with an average improvement of about 76% compared to conventional cogeneration. The results show that the membrane upgrading technology is slightly more environmentally convenient than the other upgrading technologies.
Highlights
In recent years, a growing interest has arisen in the generation and use of renewable energy (RE), to switch from fossil-based to more sustainable production and consumption patterns
The goal of the performed analysis is twofold: firstly, it is intended to identify the main contributors to the environmental impacts generated by the upgrading of biogas to bioCH4 in a life cycle perspective, in terms of physical flows, consumed resources and emissions to the environment, by quantifying the environmental benefits derived from the avoided production of natural gas
The impacts on Stratospheric ozone depletion, on Terrestrial acidification and on Freshwater eutrophication are very similar in all scenarios, whereas in the remaining impact categories the reference scenario shows the best environmental performance, generating smaller impacts than the upgrading scenarios
Summary
A growing interest has arisen in the generation and use of renewable energy (RE), to switch from fossil-based to more sustainable production and consumption patterns. RE plays a key role in minimizing several environmental and socio-economic concerns, the non-climate related environmental impacts generated from RE as compared to fossil-based energy are still rarely debated in the pertinent scientific literature [1,2]. Bioenergy from waste feedstock represents a valuable prospect that increasingly attracts the attention of populations and governments towards waste-based biorefinery processes. Energies 2019, 12, 718 for biogas production seems to be a viable way to simultaneously improve waste management while producing RE [3]. The main product of this bioconversion process is biogas, a mixture which mainly consists of methane (CH4 )
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