Emergy Accounting of a Specialized Danish Pig Production – Potential Allocation of Resource Use

Three different Danish pig production systems were evaluated using emergy assessment aiming at comparing their efficiency in transforming natural and societal resources into pigs sold. The systems differed in their production strategy by selling different groups of pigs either piglets, weaners, finishers or sows, gilts & boars. Both organic and conventional production was considered. We compared resource use efficiency as indicated by UEVs for the different weigh groups as well as for the complete production. We applied three different methodologies for allocating emergy flows to the different groups based on either 1) live weight according to emergy algebra from splits, 2) time spent on the farm within a year or 3) price of the sold pigs. The ranking of systems and groups with respect to UEV differed depending on the allocation method. Allocation by weight resulted in equal UEVs for all groups varying among the systems as 0.99, 1.20 and 1.25 E+10 seJ/g. With allocation by time, the corresponding values for finishers in the three systems were 0.99, 1.05 and 0.62 E+10 seJ/g. For weaners and finishers the two allocation methods by time and by price gave approximately the same results within system. The overall results showed that a system producing only finishers is more resource efficient than a system producing also piglets and weaners. A sensitivity analysis showed a reduction of 8 to 19% in UEV when assuming that straw was a co-product of the grain used for feed. In conclusion, despite that the emergy algebra rules prescribe split allocation by available energy (or mass), the allocation by time seems to reflect the resource use the best for the individual groups.