System Expansions to Handle Co-Products of Renewable Materials
The production of most renewable materials involves co-products. Traditionally, the environmental impacts have been allocated between the different co-products according to a more or less arbitrary allocation ratio. Following the new ISO requirements, and based on SETAC recommendations, allocation shall be avoided whenever possible. It has been the general belief that avoiding allocation through system expansion was not always possible for co-products from renewable material production, since the substitutions involved were believed to be too complex, difficult to determine, and sometimes involving endless regressions. However, these perceived problems can be solved by applying a stringent procedure for identifying the affected processes, earlier developed and presented by the author. This paper shows a number of case studies on renewable materials where allocations have been avoided through system expansion. Examples include the notoriously difficult problems of agricultural or industrial by-products applied as fodder (e.g. rapeseed cake, which substitutes soybean production, which again has oil as a by-product) or fertiliser (e.g. organic manure), the co-products from a cow (meat, milk, butter etc.), and the secondary functions of forestry and agriculture (e.g. maintaining rural income, amenity values such as maintenance of landscapes for recreation).