Comparative Life Cycle Assessment of Industrial Multi-Product Processes

Smoking chimneys are a symbol for environmental impacts of industrial processes. Indeed, industrial processes are major contributors to environmental problems such as global warming. Beyond emission-related problems, industrial processes deplete limited resources because they require raw materials. Raw materials are directly linked to costs, emission-related impacts cause indirect expenditures, e.g., through the European emissions trading scheme (EU-ETS) for greenhouse gas emissions. Therefore, industrial enterprises seek to reduce costs by reducing environmental impacts of their processes. Two well-known strategies for reducing environmental impacts of industrial processes are process integration and recycling. Process integration establishes interconnections between formerly separate processes by utilizing co-products. Process integration thereby relies on unit processes with multiple products, so-called multi-product processes. Similarly, recycling uses waste as raw material for new products. But neither process integration for recycling guarantee reduced environmental impacts. E.g., recycling may cause more impacts than waste disposal. Decision makers thus need a holistic method for comparing environmental impacts from multi-product processes. This work investigates methods for comparisons of industrial multi-product processes. The environmental impacts of multi-product processes can be analyzed using life cycle assessment (LCA). LCA studies all environmental impacts of all processes involved in a procucts entire life cycle. Due to ist holistic approach, LCA identifies shifting of environmental problems between processes and between different types of environmental impacts. Results of LCA-studies can thus help avoiding such problem shifting.