Lookup NU author(s): Dr Stephen MacKenzie,
Dr Ilkka Leinonen,
Professor Ilias Kyriazakis
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Purpose Several new “biophysical” co-product allocation methodologies have been developed for LCA13 studies of agricultural systems based on proposed physical or causal relationships between inputs and14 outputs (i.e. co-products). These methodologies are thus meant to be preferable to established allocation15 methodologies such as economic allocation under the ISO 14044 standard. The aim here was to examine16 whether these methodologies really represent underlying physical relationships between the material17 and energy flows and the co-products in such systems, and hence are of value.18 Methods Two key components of agricultural LCAs which involve co-product allocation, were used to19 provide examples of the methodological challenges which arise from adopting biophysical allocation20 in agricultural LCA: 1) The crop production chain and 2) The multiple co-products produced by21 animals. The actual “causal” relationships in these two systems were illustrated, the energy flows within22 them detailed and the existing “biophysical” allocation methods, as found in literature, were critically23 evaluated in the context of such relationships.24 Results & Discussion The premise of many biophysical allocation methodologies has been to define25 relationships which describe how the energy input to agricultural systems is partitioned between co26products. However, we described why none of the functional outputs from animal or crop production27 can be considered independently from the rest on the basis of the inputs to the system. Using the28 example of manure in livestock systems, we also showed why biophysical allocation methodologies are29 still sensitive to whether a system output has economic value or not. This sensitivity is a longstanding30 criticism of economic allocation which is not resolved by adopting a biophysical approach.31 Conclusions The biophysical allocation methodologies for various aspects of agricultural systems32 proposed to date have not adequately explained how the physical parameters chosen in each case33 represent causal physical mechanisms in these systems. Allocation methodologies which are based on34 shared (but not causal) physical properties between co-products are not preferable to allocation based35 on non-physical properties within the ISO hierarchy on allocation methodologies, and should not be36 presented as such.
Author(s): Mackenzie SG, Leinonen I, Kyriazakis I
Publication type: Article
Publication status: Published
Journal: The International Journal of Life Cycle Assessment
Print publication date: 01/02/2017
Online publication date: 14/07/2016
Acceptance date: 27/06/2016
ISSN (print): 0948-3349
ISSN (electronic): 1614-7502
Publisher: Springer Berlin Heidelberg
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