Integrated assessment of E-LCA and S-LCA based on a techno economic assessment of side stream valorization in the brewery industry

Today agricultural residues and side streams are often not valorised and still considered as a waste. A high potential to produce high value-added products lies in using residues and side-streams from beer production: in Europe, 34 billion litres of beer were produced in 2021 and each cubic metre of beer produces 0.2 ton of brewer’s spent grain and other substances as CO2, yeast, wastewater etc. Within the Horizon Europe Project “CHEERS”, the side streams of beer production are transformed with innovative biorefinery technologies into five bio-based products. One output of this biorefinery involves utilizing brewer's spent grain as feed for mealworms (Tenebrio molitor larvae) to produce protein flour. The other four products are created by microbiological processes using carbon dioxide and methane from the anaerobic digestion of wastewater. This research strives for a comprehensive life cycle sustainability assessment (LCSA) quantifying environmental, social, and economic impacts of the biorefinery established in a Spanish brewery in Europe. By taking a holistic perspective, LCSA aims to identify potential hotspots, trade-offs, and synergies across different life cycle stages and sustainability dimensions. The entire production system is examined in a screening based on the techno-economic assessment (TEA) for the environmental life cycle assessment (E-LCA) and the social life cycle assessment (S-LCA). For this purpose, the following methods are used: An E-LCA covers categories of the environmental footprint impact assessment method, such as greenhouse gas emissions, energy demand, biodiversity, water footprint, and resource depletion. A particular focus is on conducting a life cycle biodiversity impact assessment, which aims to measure the project's impacts on biodiversity in industrial sites and supply chains. The S-LCA evaluates socio-economic benefits following the "Guideline for Social Life Cycle Assessment of Products and Organizations 2020" (UNEP, 2020). It is conducted using the product social impact life cycle assessment (PSILCA) method. This assessment considers the social risks and opportunities and the positive impacts for five stakeholder groups along the entire life cycle of the products. The results demonstrate the integration of the independently conducted TEA, E-LCA, and S-LCA into a comprehensive framework. The combination is carried out using a qualitative approach, such as expert assessment and multi-criteria analysis. This approach still allows to see the strengths of each assessment method considering their individual perspectives, uncertainties, and limitations and showing the relevance of upstream processes like agricultural production, while recognizing the interconnections among the three sustainability dimensions. The other integration options like a) TEA with environmental externalities & social externalities and b) TEA as basis, social impacts based on (minimal) wellbeing, environmental impacts as limitations for the solution space are discussed. The greatest challenge for the evaluation is the integration of the results from the economic, social, and ecological dimensions, with particular attention to the high dependency of the results on the allocation decisions. The results are significantly influenced by the choice of the allocation method. It is crucial whether the cutoff approach or economic allocation is chosen. This initial assessment serves to identify the most relevant hotspots in the analyzed value chains and to explain the possibilities of extending the conclusions to valorization strategies in other foods productions.