Why mass allocation with representative allocation factor is preferential in LCA when using residual livestock products as organic fertilizers.

The production impact of agricultural residues are generally not accounted for in LCAs when they are given a second life as feedstocks for bio-fuels/plastics/fertilizers. Such is the case for the organic fertilizers manure and blood meal (stemming from livestock) used in organic cultivation. This raises questions on how realistic comparisons are between conventional cultivation systems and organic systems: the flows of resources and associated impacts are not represented equivalently in both systems.