• Energy Research

Canada is one of the world’s largest producers of oat (Avena sativa L.) grains and their derivatives, such as oat flakes. During oat flake production, considerable amounts of residue are generated, which constitutes a major issue for producers. We applied life cycle assessment (LCA): (1) to quantify the environmental impacts of oat flakes production in northeastern Canada and (2) to compare two agro-industrial symbiosis scenarios applied to agricultural residues (transformation of residues into feed for farm animals vs. composting). LCA results indicated that the environmental impacts of oat flake production are largely dominated by the production and use of synthetic fertilisers (contributing to at least 50% of the impact of each evaluated category). Regarding end-of-life scenarios, an environmental advantage is observed for the scenario of residue transformation into animal feed in the provinces of Quebec and Manitoba. However, this recommendation may change depending on the electricity mix used and the assumptions made for the avoided products. The choice of industrial symbiosis chains must take into consideration the economic characteristics of the region where they will be implemented and the methodological parameters that can influence the decision-making process.

Carbon fibers have been widely used in composite materials, such as carbon fiber-reinforced polymer (CFRP). Therefore, a considerable amount of CFRP waste has been generated. Different recycling technologies have been proposed to treat the CFRP waste and recover carbon fibers for reuse in other applications. This study aims to perform a life cycle assessment (LCA) to evaluate the environmental impacts of recycling carbon fibers from CFRP waste by steam thermolysis, which is a recycling process developed in France. The LCA is performed by comparing a scenario where the CFRP waste is recycled by steam-thermolysis with other where the CFRP waste is directly disposed in landfill and incineration. The functional unit set for this study is 2 kg of composite. The inventory analysis is established for the different phases of the two scenarios considered in the study, such as the manufacturing phase, the recycling phase, and the end-of-life phase. The input and output flows associated with each elementary process are standardized to the functional unit. The life cycle impact assessment (LCIA) is performed using the SimaPro software and the Ecoinvent 3 database by the implementation of the CML-IA baseline LCIA method and the ILCD 2011 midpoint LCIA method. Despite that the addition of recycling phase produces non-negligible environmental impacts, the impact assessment shows that, overall, the scenario with recycling is less impactful on the environment than the scenario without recycling. The recycling of CFRP waste reduces between 25 and 30% of the impacts and requires about 25% less energy. The two LCIA methods used, CML-IA baseline and ILCD 2011 midpoint, lead to similar results, allowing the verification of the robustness and reliability of the LCIA results. The recycling of composite materials with recovery of carbon fibers brings evident advantages from an environmental point of view. Although this study presents some limitations, the LCA conducted allows the evaluation of potential environmental impacts of steam thermolysis recycling process in comparison with a scenario where the composites are directly sent to final disposal. The proposed approach can be scaled up to be used in other life cycle assessments, such as in industrial scales, and furthermore to compare the steam thermolysis to other recycling processes.