Challenges in Quantifying Greenhouse Gas Impacts of Waste-Based Biofuels in EU and US Biofuel Policies: Case Study of Butanol and Ethanol Production from Municipal Solid Waste

Conversion of wastes to biofuels is a promising route to provide renewable low-carbon fuels, based on a low- or negative-cost feedstock, whose use can avoid negative environmental impacts of conventional waste treatment. However, current policies that employ LCA as a quantitative measure are not adequate for assessing this type of fuel, given their cross-sector interactions and multiple potential product/service streams (energy, fuels, materials, waste treatment service). We employ a case study of butanol and ethanol production from mixed municipal solid waste to demonstrate the challenges in using life cycle assessment to appropriately inform decision-makers. Greenhouse gas emissions results vary from −566 gCO2 eq/MJbiofuel (under US policies that employ system expansion approach) to +86 gCO2 eq/MJbiofuel and +23 gCO2 eq/MJbiofuel (under initial and current EU policies that employ energy-based allocation), relative to gasoline emissions of +94 gCO2 eq. LCA methods used in existing policies thus provide contradictory information to decision-makers regarding the potential for waste-based biofuels. A key factor differentiating life cycle assessment methodologies is the inclusion of avoided impacts of conventional waste treatment in US policies and their exclusion in EU policies. Present EU rules risk discouraging the valorisation of wastes to biofuels thus forcing waste toward lower-value treatment processes and products

Environmental and financial implications of ethanol as a bioethylene feedstock versus as a transportation fuel

Bulk chemicals production from biomass may compete with biofuels for low-cost and sustainable biomass sources. Understanding how alternative uses of biomass compare in terms of financial and environmental parameters is therefore necessary to help ensure that efficient uses of resources are encouraged by policy and undertaken by industry. In this paper, we compare the environmental and financial performance of using ethanol as a feedstock for bioethylene production or as a transport fuel in the US life cycle-based models are developed to isolate the relative impacts of these two ethanol uses and generate results that are applicable irrespective of ethanol production pathway. Ethanol use as a feedstock for bioethylene production or as a transport fuel leads to comparable greenhouse gas (GHG) emissions and fossil energy consumption reductions relative to their counterparts produced from fossil sources. By displacing gasoline use in vehicles, use of ethanol as a transport fuel is six times more effective in reducing petroleum energy use on a life cycle basis. In contrast, bioethylene predominately avoids consumption of natural gas. Considering 2013 US ethanol and ethylene market prices, our analysis shows that bioethylene is financially viable only if significant price premiums are realized over conventional ethylene, from 35% to 65% depending on the scale of bioethylene production considered (80 000 t yr−1 to 240 000 t yr−1). Ethanol use as a transportation fuel is therefore the preferred pathway considering financial,GHGemissions, and petroleum energy use metrics, although bioethylene production could have strategic value if demand-side limitations of ethanol transport fuel markets are reached

Study of pyrolysis for biochar production from biomass feedstocks using a simplified Aspen Plus model

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Steam-treated wood pellets: Environmental and financial implications relative to fossil fuels and conventional pellets for electricity generation

© 2016 Elsevier Ltd Steam-treated pellets can help to address technical barriers that limit the uptake of pellets as a fuel for electricity generation, but there is limited understanding of the cost and environmental impacts of their production and use. This study investigates life cycle environmental (greenhouse gas (GHG) and air pollutant emissions) and financial implications of electricity generation from steam-treated pellets, including fuel cycle activities (biomass supply, pellet production, and combustion) and retrofit infrastructure to enable 100% pellet firing at a generating station that previously used coal. Models are informed by operating experience of pellet manufacturers and generating stations utilising coal, steam-treated and conventional pellets. Results are compared with conventional pellets and fossil fuels in a case study of electricity generation in northwestern Ontario, Canada. Steam-treated pellet production has similar GHG impacts to conventional pellets as their higher biomass feedstock requirement is balanced by reduced process electricity consumption. GHG reductions of more than 90% relative to coal and ∼85% relative to natural gas (excluding retrofit infrastructure) could be obtained with both pellet options. Pellets can also reduce fuel cycle air pollutant emissions relative to coal by 30% (NOx), 97% (SOx), and 75% (PM10). Lesser retrofit requirements for steam-treated pellets more than compensate for marginally higher pellet production costs, resulting in lower electricity production cost compared to conventional pellets ($0.14/kWh vs.$0.16/kWh). Impacts of retrofit infrastructure become increasingly significant at lower generating station capacity factors, further favouring steam-treated pellets for both environmental and financial metrics

Comparative LCA of different graphene production routes

This study is an LCA of three graphene production routes: electrochemical exfoliation of graphite rods, chemical oxidation and subsequent chemical or thermal reduction and chemical vapour deposition (CVD). Different processes for each route are analysed and their cradle-to-gate LCA is presented. A comparative LCA of the least impacting processes for each route is also presented showing that the chemical oxidation process followed by thermal reduction is the least impacting to produce large quantities of graphene when lab equipment is used to its full potential.A prospective LCA on a likely commercial scale of the least impacting processes is also presented and shows that almost all processes benefit from a scale-up activity and that the least impacting material route remains the chemical oxidation followed by thermal reduction. An optimistic scenario in which all electricity comes from renewable sources is also presented. While this last scenario promotes the more energy intensive processes, the least impacting technology to produce large quantities of graphene remains the chemical oxidation followed by thermal reduction

An assessment of financial viability of recycled carbon fibre in automotive applications

Carbon fibre (CF) recycling has been demonstrated to achieve reductions in environmental impacts compared to virgin CF production, but there is limited understanding of the financial viability of recycling and reutilisation of recycled CF (rCF). In this work, cost analysis and identification of market opportunities for rCF are performed by evaluating the cost of recycling, composite manufacture, and applications in automotive industry. Cost impacts of using rCF as a substitute for conventional materials and competitor lightweight materials are assessed over the full life cycle, including in-use implications. Recovery of CF can be achieved at $5/kg and less across a wide range of process parameters, approximately 15% of the cost of producing virgin carbon fibre. The life cycle cost results show that rCF composites, especially aligned rCF composites, give substantial cost reductions relative to virgin CF composites and even steel and aluminium

Biowaste to biochar: hydrothermal carbonisation & high temperature torrefaction of food waste anaerobic digestate

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Application of ZnO nanoparticles in a self-cleaning coating on a metal panel: an assessment of environmental benefits

This article is focused on assessing environmental benefits of a self-cleaning coating (SCCs) containing nanoparticles (NPs) applied on metal panels. ZnO NPs are incorporated in the coating to enhance the level of hydrophobicity, which enables a dramatic reduction in the need for surface maintenance. The key question evaluated in this paper is whether the overall environmental performance of a nanobased SCC is better than the environmental performance of a coating without NPs. Much of the paper is dedicated to a comparison of advanced polyvinylidene fluoride (PVDF) protective coating with an alternative coating in which part of the PVDF is replaced by ZnO NPs. An integral part of the paper represents a detailed environmental assessment of the key ingredient of the nanoenhanced coating, ZnO NPs produced by large-scale supercritical hydrothermal synthesis developed within the Sustainable Hydrothermal Manufacturing of Nanomaterials (SHYMAN) project. LCA results show that the coating with NPs performs better than the coating without NPs in all assessed impact categories. This is due to the elimination of environmental impacts during the use stage where no maintenance is needed in the case of the coating with NPs. This reduction clearly outweighs the small additional environmental impacts of the production stage associated with the ZnO NPs

Comparative techno-economic and life cycle analyses of synthetic “drop-in” fuel production from UK wet biomass

Renewable synthetic hydrocarbon “drop-in” fuels can help mitigate greenhouse gas emissions from transport, particularly in hard-to-abate sectors like freight and aviation. However, no study has extensively addressed the concerns over biomass availability, cost viability, and CO2 reduction feasibility that are associated with diverse production configurations and feedstocks. Here, we report detailed techno-economics and life cycle greenhouse gas emission assessments of drop-in fuel productions via hydrothermal liquefaction to assess their economic viabilities, CO2 mitigation potentials, and prospects for scale-up specifically within the UK context. Our approach integrates key production factors which include regional availability of main feedstocks (digestates, food waste, biodegradable municipal waste, and sewage sludge), plant configurations (centralised vs decentralised) and hydrogen sources (grey, blue, green). We demonstrated the economic trade-off between economy-of-scale and feedstock transport distances in the centralised/decentralised configurations, and also the economic and emissions trade-offs associated with the use of different hydrogen sources. We find that co-processing of different waste feedstocks is an important strategy to minimise fuel selling price by enabling better economy of scale and feedstock transport, resulting in a fuel selling price of £14.76 – 20.30 per GJ. The corresponding greenhouse gas emissions from the co-processing case vary from 11.4 to 24.9 kg CO2eq per GJ for 2021, based on the consequential life cycle assessment approach. Furthermore, we estimated that the utilisation of key UK wet feedstocks could only provide 4.5 % of current fuel consumptions and reduce emissions by 4.5 – 5.4 Mt CO2eq/year, which translates to 3.4 – 4.0 % reduction in the UK’s 2021 transport emissions

Impacts of pre-treatment technologies and co-products on greenhouse gas emissions and energy use of lignocellulosic ethanol production

Life cycle environmental performance of lignocellulosic ethanol produced through different production pathways and having different co-products has rarely been reported in the literature, with most studies focusing on a single pre-treatment and single co-product (electricity). The aim of this paper is to understand the life cycle energy use and greenhouse gas (GHG) emissions implications of alternative pre-treatment technologies (dilute acid hydrolysis, ammonia fiber expansion and autohydrolysis) and co-products (electricity, pellet, protein and xylitol) through developing a consistent life cycle framework for ethanol production from corn stover. Results show that the choices of pre-treatment technology and co-product(s) can impact ethanol yield, life cycle energy use and GHG emissions. Dilute acid pathways generally exhibit higher ethanol yields (20 to 25%) and lower net total energy use (15 to 25%) than the autohydrolysis and ammonia fiber expansion pathways. Similar GHG emissions are found for the pre-treatment technologies when producing the same co-product. Xylitol co-production diverts xylose from ethanol production and results in the lowest ethanol yield (200 litres per dry t of stover). Compared to producing only electricity as a co-product, the co-production of pellets and xylitol decreases life cycle GHG emissions associated with the ethanol, while protein production increases emissions. The life cycle GHG emissions of blended ethanol fuel (85% denatured ethanol by volume) range from -38.5 to 37.2 g CO2eq/MJ of fuel produced, reducing emissions by 61% to 141% relative to gasoline. All ethanol pathways result in major reductions of fossil and petroleum energy use relative to gasoline, at least 47% and 67%, respectively. Pathways with electricity as the sole co-product use the least fossil energy All ethanol pathways studied meet the USA Energy Information and Security Act requirement of a 60% reduction in GHG emissions compared to gasoline for classification as a cellulosic biofuel; however, greater reductions are achievable through strategic selection of co-products