The production of chemicals from renewable feedstocks is becoming an attractive area of investment for industries in the framework of a more sustainable economy. From a technical point of view, a large fraction of industrial chemicals and materials from fossil resources can be replaced by their bio‐based counterparts. Nevertheless, fossil‐based chemistry is still dominant because of optimized production processes and lower costs. The best approach to maximize the valorization of biomass is the processing of biological feedstocks in integrated biorefineries where both bio‐based chemicals and energy carriers can be produced, similar to a traditional petroleum refinery. The challenge is to prove, together with the technical and economic feasibility, an environmental feasibility, in terms of lower impact over the entire production chain. In this review, potential renewable substrates, conversion pathways, and target molecules are carefully investigated with reference to the most recent technological advancements. Potential environmental impacts and benefits over the life cycle of products are also reviewed. While an economic and technical feasibility can be, and sometimes has been already, reached, the same is not true yet for environmental feasibility, where several issues still need to be explored and the risk for burden shift is not negligible. The aim of this review is to provide an overview of the opportunities and constraints related to the transition from petroleum to biomass chemistry and to draw a roadmap of the most sustainable technologies and promising biomass value chains, screening in parallel their environmental implications, toward a market implementation of bio‐based chemistry. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

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SummaryArsenic resistance is commonly clustered in ars operons in bacteria; main ars operon components encode an arsenate reductase, a membrane extrusion protein, and an As‐sensitive transcription factor. In the As‐resistant thermophile Thermus thermophilus HB27, genes encoding homologues of these proteins are interspersed in the chromosome. In this article, we show that two adjacent genes, TtsmtB, encoding an ArsR/SmtB transcriptional repressor and, TTC0354, encoding a Zn2+/Cd2+‐dependent membrane ATPase are involved in As resistance; differently from characterized ars operons, the two genes are transcribed from dedicated promoters upstream of their respective genes, whose expression is differentially regulated at transcriptional level. Mutants defective in TtsmtB or TTC0354 are more sensitive to As than the wild type, proving their role in arsenic resistance. Recombinant dimeric TtSmtB binds in vitro to both promoters, but its binding capability decreases upon interaction with arsenate and, less efficiently, with arsenite. In vivo and in vitro experiments also demonstrate that the arsenate reductase (TtArsC) is subjected to regulation by TtSmtB. We propose a model for the regulation of As resistance in T. thermophilus in which TtSmtB is the arsenate sensor responsible for the induction of TtArsC which generates arsenite exported by TTC0354 efflux protein to detoxify cells.

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.

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