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• LCA and LCC were conducted for bioethanol production from MSW. • MSW-derived ethanol can reduce greenhouse gas emissions versus gasoline. • S. cerevisiae and Z. mobilis can achieve higher cumulative net present value. • Better environmental benefit but less economic competitiveness are observed. • Key process improvements must be achieved to improve the financial viability. Globally, 2.01 billion tonnes of municipal solid waste (MSW) were generated in 2016, about 37% of which was disposed of into landfills. This study evaluates the environmental and financial viability of producing ethanol from autoclaved MSW via fermentation. Experimental screening of four different microorganisms (i.e., S. cerevisiae , Z. mobilis , E. coli , and S. pombe) and process modelling indicate that MSW-derived ethanol can significantly reduce greenhouse gas emissions relative to gasoline (84% reduction following EU Renewable Energy Directive accounting methodology, and by 156–231% reduction following the US Energy Independence and Security Act methodology). Utilisation of wastes for biofuel production in the UK benefits from policy support and financial support for renewable fuels (Renewable Transport Fuel Certificates). Financial analysis highlights that microorganisms achieving higher ethanol yield and productivity (S. cerevisiae and Z. mobilis) can achieve financial viability with higher cumulative net present value than E. coli , S. pombe. However, the positive net present value can be achieved primarily due to the benefit of gate fees received by diverting wastes to autoclave and ethanol production (64% of total revenues), rather than from revenues from ethanol sales (7% of total revenues). Key process improvements must be achieved to improve the financial viability of ethanol production from MSW and deliver a clear advantage over waste incineration, specifically improving hydrolysis yield, reducing enzyme loading rate and, to a lesser extent, increasing solid loading rate. The results provide significant insights into the role of policy and technology development to achieve viable waste-to-biofuel systems. [ABSTRACT FROM AUTHOR]

Abstract: The potential of biofuels contributing to the UK emission reduction targets in the formulated UK Low Carbon Transition Plan (LCTP) and the UK’s obligation in the wider EU emissions reduction targets are assessed using four scenarios. The scenarios were evaluated using hybrid lifecycle assessment developed in a multi-regional input–output (MRIO) framework. In the hybrid MRIO LCA framework, technology-specific processes in the biofuels and fossil fuels LCA systems are integrated into a generalised 2-region (UK and Rest of the World) environmental-economic input–output framework in order to account for economy-wide indirect GHG emissions in the biofuels and fossil fuels LCA systems in addition to other indirect impacts such as indirect land use change. The lifecycle greenhouse gas emissions of biodiesel (soybean, palm, rape, waste cooking oil) and bio-ethanol (sugarcane, sugarbeet, corn) were assessed and compared to fossil fuel (diesel and petrol) baseline. From one of the scenarios, biodiesel production from waste cooking oil and bioethanol from sugarbeet offer the biggest potential for emissions savings relative to fossil fuel equivalent and offering a maximum emission savings of 4.1% observed with a biofuel market share of 10% reached in 2020. It was also established that under current biofuel feedstock mix, to achieve the 6% emissions saving primarily from biofuels as proposed in the LCTP, 23.8% of the transport fuels market would be required to be held by biofuels by 2020. [Copyright &y& Elsevier]

Background: Salt marshes are major natural repositories of sequestered organic carbon with high burial rates of organic matter, produced by highly productive native flora. Accumulated carbon predominantly exists as lignocellulose which is metabolised by communities of functionally diverse microbes. However, the organisms that orchestrate this process and the enzymatic mechanisms employed that regulate the accumulation, composition and permanence of this carbon stock are not yet known. We applied meta-exo-proteome proteomics and 16S rRNA gene profiling to study lignocellulose decomposition in situ within the surface level sediments of a natural established UK salt marsh., Results: Our studies revealed a community dominated by Gammaproteobacteria, Bacteroidetes and Deltaproteobacteria that drive lignocellulose degradation in the salt marsh. We identify 42 families of lignocellulolytic bacteria of which the most active secretors of carbohydrate-active enzymes were observed to be Prolixibacteracea, Flavobacteriaceae, Cellvibrionaceae, Saccharospirillaceae, Alteromonadaceae, Vibrionaceae and Cytophagaceae. These families secreted lignocellulose-active glycoside hydrolase (GH) family enzymes GH3, GH5, GH6, GH9, GH10, GH11, GH13 and GH43 that were associated with degrading Spartina biomass. While fungi were present, we did not detect a lignocellulolytic contribution from fungi which are major contributors to terrestrial lignocellulose deconstruction. Oxidative enzymes such as laccases, peroxidases and lytic polysaccharide monooxygenases that are important for lignocellulose degradation in the terrestrial environment were present but not abundant, while a notable abundance of putative esterases (such as carbohydrate esterase family 1) associated with decoupling lignin from polysaccharides in lignocellulose was observed., Conclusions: Here, we identify a diverse cohort of previously undefined bacteria that drive lignocellulose degradation in the surface sediments of the salt marsh environment and describe the enzymatic mechanisms they employ to facilitate this process. Our results increase the understanding of the microbial and molecular mechanisms that underpin carbon sequestration from lignocellulose within salt marsh surface sediments in situ and provide insights into the potential enzymatic mechanisms regulating the enrichment of polyphenolics in salt marsh sediments. Video Abstract.