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• Can carbon fiber composites have a lower environmental impact than fiberglass?. • The use of CFRP is likely to have a lower environmental impact than GFRP. • The most promising route is the recycling of the composites. • The impact of CFRP can decrease by using bio-based materials and microwave heating. Carbon fiber composites are increasingly used to decrease fuel consumption in the use phase of vehicles. However, due to the energy intensive production, the reduced fuel consumption may not lead to life cycle environmental savings as much as for other lightweighting materials, for example fiberglass. This study uses life cycle assessment methodology to assess how different future development routes including using bio-based raw materials, microwave technology, and recycling of composites with the recovery of fibers influence the environmental impact of both carbon fiber composites and fiberglass in vehicles. Results show that combining different development routes could lead to carbon fiber composites with a lower environmental impact than fiberglass composites in the future and that recycling of composites with recovery of fibers is the route that alone shows the greatest potential. [ABSTRACT FROM AUTHOR]

Screening the life cycle assessment literature for information and recalculating extracted results was proven useful for identifying environmental challenges and opportunities in new, but related, contexts at early stages of technology development. The method was applied to carbon fiber reinforced polymers, a material of growing importance in industrial applications where a strong and/or light material is needed, such as in aircrafts and road vehicles. Many technology development efforts with the purpose of further improving such composite materials are on-going, in particular regarding the origin of carbon fibers. Using lignin as a bio-based feedstock and various recycling techniques have been suggested. However, these technologies do not yet exist at a scale that would enable a meaningful life cycle inventory, while the need for environmental guidance is urgent in order to ensure that only the more promising development paths are pursued before lock-in occurs. With a specific focus on the shift to lignin as a feedstock for carbon fibers and on recycled carbon fibers in composites, this article not only illustrates the type of information that can be obtained from mining and refining information from earlier life cycle assessment studies, but it also provides direct guidance on environmental opportunities and challenges specific for carbon fiber reinforced polymers. Thereby, it informs both technology development efforts and environmental assessment efforts. Amongst other things, the analysis reveals that an important factor behind the environmental impact of composites is the energy demand in carbonization of the carbon fibers and that both the shift to lignin-based and to recycled carbon fibers can potentially reduce this environmental impact. However, assessments of both lignin (as an output from a multifunctional process) and recycled carbon fibers (as an output from end-of-life activities) are connected to challenges related to the allocation of environmental impacts in an environmental assessment. Extracting and refining information from the literature proved useful for the specific task but remains to be tested in other fields of emerging technologies. • Replacing materials with CFRP decreased energy use in less than half of the cases. • The use of lignin as a raw material can decrease the impact of carbon fibers. • Recycling carbon fibers was shown to decrease energy use significantly. • Using recycled carbon fibers was more beneficial than using lignin as a raw material. [ABSTRACT FROM AUTHOR]

In this paper, the potential impacts in the techno-environmental performance of a municipal wastewater treatment plant with integrated mixed-microbial-culture polyhydroxyalkanoate (PHA) production are presented for the first time. A life cycle assessment was conducted based on mass and energy balances. The techno-environmental performance was evaluated for five wastewater treatment configurations: a reference case and four alternative processes producing PHA-rich biomass using influent municipal wastewater as the only organic carbon source. The integration of PHA-rich biomass production into a municipal wastewater treatment plant with sludge digestion sustains the overall conversion yield for total products of biogas and PHA-rich biomass (around 0.26 gCOD products per influent gCOD treated). PHA production integration has the potential to improve the overall environmental performance with respect to the reference case. Even when no benefits were accounted for substitutions related to the biogas and PHA-rich biomass, similar or improved environmental performances were estimated for all four alternatives for global warming potential, acidification potential, terrestrial eutrophication potential, and photo-oxidant formation potential. When benefits were accounted from substitutions of electricity and heat co-generated from biogas and of PHA-rich biomass by pure-culture PHA-rich biomass from sugar fermentation, gains were even higher due to the diversion of carbon from biogas to PHA-rich biomass. Freshwater and marine eutrophication potentials were dependent on effluent specifications. Case-by-case process configurations influence the mass and energy balance and trade-offs of process integration. The production and export of PHA-rich biomass decreased the aeration requirements for COD and nitrogen removal; however, increased demands for heat, power and chemicals were incurred for the generation of volatile fatty acids from primary solids fermentation. The choice of nitrogen-removal approach (nitrification-denitrification vs. anammox) also impacted energy consumption. Using influent wastewater as the sole carbon supply, the energy balance and PHA production were sensitive to the efficiency of primary treatment and available flux of volatile fatty acids into PHA production. Other regional inputs of organic residuals may improve carbon recovery in the treatment facility. The improved environmental performance of the treatment configurations motivates the idea that individual municipal wastewater treatment plants may become suppliers of renewable raw materials of higher value than that of biogas and/or energy and heat today. [ABSTRACT FROM AUTHOR]

In Life Cycle Assessments (LCAs) of biorefinery products, a common challenge is the choice of method for allocating environmental burdens of multifunctional processes (feedstock cultivation and biorefinery processes), a choice which can substantially influence LCA results and hence decision-making. The aim of this paper is to explore how this choice influences results and in which decision contexts the choice is particularly important. To do this, we tested six allocation methods in a case study of a biorefinery using pulpwood as feedstock. Tested methods included: main product bears all burden, substitution, traditional partitioning methods (based on economic value and exergy), a hybrid method combining elements of substitution and partitioning, and an alternative hybrid method developed by us, which allocates less environmental burden to co-products with a high potential to mitigate environmental burdens. The methods were tested in relation to decision contexts and LCA questions of relevance for biorefineries. The results indicate that the choice of allocation method deserves careful attention, particularly in consequential studies and in studies focussed on co-products representing relatively small flows. Furthermore, the alternative hybrid allocation method is based on a logical rationale – favouring products with higher substitution potential – and has some other potential benefits. However, in cases where the scales of co-product flows are of different orders of magnitude, the method yields extreme results that could be difficult to interpret. Results also show that it can be important with consistent allocation for both cultivation and biorefinery processes, particularly when substitution is applied. [ABSTRACT FROM AUTHOR]