In attributional life cycle assessment (ALCA), the goal is to map the environmental impact from the system under study in such a way that it reveals what share of the total global environmental impact that belongs to the product or service investigated. Any process performing multiple functions then gives rise to an allocation problem. It has been recommended that the partitioning in ALCA studies should be based on the drivers of the system. Wastewater collection and treatment facilities are increasingly exploited in different resource recovery attempts and therefore increasingly result in allocation problems. The drivers of present wastewater and sludge management systems is a mix of various ideas and concerns relating to environmental protection, resource recovery, economy, and other interests, that seem to vary among stakeholders, over time and across regions. We developed a two-stage Delphi procedure for finding partitioning factors for use in ALCA studies where multiple drivers and stakeholders are present in relation to multifunctional systems and tested it for a wastewater and sludge management system. The paper reports on the method, on the experiences from applying the method and implications for ALCA studies
