Biorefineries strive to maximise product mix and value while contributing to the bioeconomy. Circularity and waste valorisation are some important but often neglected concepts in this context. As such, biogas solutions in biorefineries could be a key technology to improve sustainability. This study has, through a literature review and investigation into three Swedish case studies, analysed this relationship between biogas solutions and biorefineries by assessing the added value and development potential to which biogas solutions may contribute. This analysis across agricultural, forest, and marine sectors indicates that biogas solutions contribute with several added values, including through making the biorefinery more sustainable and competitive. The study also shows that biogas solutions can be an enabler of biorefinery development through making the system more resilient and versatile, as well as through improving the value of the product portfolio.

Biorefineries are examples of industries striving towards a circular and bio-based economy through valorising natural raw materials to a spectrum of products. This is a resource-efficient process which also decreases overall environmental impact, as the products from a biorefinery can replace fossil-based products such as plastics or fuels. To become even more resource efficient, an optimisation of the by-product use can increase the performance. This study will evaluate different scenarios for the valorisation of stillage coming from a wheat-based biorefinery. The alternatives range from the direct use of the stillage for fodder, fertiliser or incineration to three different biogas production-based scenarios. The biogas scenarios are divided into the production of fuel at a local or distant plant and the alternative of creating heat and power at the local plant. The results show how locally produced biogas for vehicle fuel and fodder usage are the better alternatives regarding greenhouse gas emissions, the finances of the biorefinery, energy balance and nutrient recycling. The results also indicate that biorefineries with several high-value products may receive lower quality by-product flows, and to these, the biogas solutions become more relevant for valorising stillage while improving value and performance for the biorefinery. Graphical AbstractKeywords Biorefinery · Upcycling · Waste · Biogas · Fodder

Biomass is a valuable and limited resource that should be used efficiently. The potential of replacing fossil-based products with bio-based ones produced in biobased industrial systems is huge. One important aim of increasing the share of biobased products is to improve the sustainability of systems for production and consumption. Therefore, it is important to evaluate what solutions are available to improve the sustainability performance of bio-based industrial systems, and if they also bring negative impacts. The thesis focuses on assessing the role of biogas solutions in developing sustainable bio-based systems. Such assessments are often quite narrow in their scope and focus on quantitative environmental or economic aspects. This thesis aims at also including feasibility related aspects involving the contextual conditions that are assessed more qualitatively. Biogas solutions are identified as a versatile approach to treat organic materials which are generated in large volumes in bio-based industrial systems. The results show that biogas solutions in bio-based industrial systems (i) improve circular flows of energy and nutrients, (ii) are especially viable alternatives when the quality of the by-product streams become poorer, and (iii) may improve the profitability of the bio-based industrial system. To perform better assessments of these systems, it seems valuable to broaden the set of indicators assessed and include feasibility-related indicators, preferably through the involvement of relevant stakeholders as they contribute with different perspectives and can identify aspects that influence the sustainability in different areas. Future studies could benefit from applying those broader assessments on more cases to build on a more generalisable knowledge base.

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The transition toward a circular and biobased economy requires the biorefineries and bio-based industries to become more resource efficient with regards to their waste and by-product management. Organic by-products and waste streams can be an important source of value if used in feasible pathways that not only have a low environmental impact but also preserve or recover their energy, nutrients, and other potentially valuable components. Through development of a multi-criteria assessment framework and its application on a real case, this article provides methodological and practical insights on decision making for enhanced by-product management. Our framework includes 8 key areas and 18 well-defined indicators for assessing the environmental performance, feasibility, and long-term risk of each alternative. We studied six different management options for the stillage by-product of a Swedish wheat-based biorefinery and our results shows that the most suitable options for this biorefinery are to use the stillage either as animal fodder or as feedstock for local biogas production for vehicle fuel. This multi-criteria approach can be used by bio-based industrial actors to systematically investigate options for by-product management and valorisation for a circular and bio-based economy. Graphic Abstract