Influence of scenario uncertainty in agricultural inputs on life cycle greenhouse gas emissions from agricultural production systems: the case of chemical fertilizers in Japan

Practical applications of life cycle assessment (LCA) to agricultural production systems require articulating uncertainties caused by scenario indeterminacy, because practitioners do not have sufficient knowledge about agricultural input production processes. However, current understanding about scenario uncertainties is still limited on account of insufficient knowledge. We propose a method to quantify scenario uncertainty in agricultural inputs and to assess the uncertainty in comparative LCA of agricultural production systems. We formulate uncertainty intervals due to scenario indeterminacy (a situation in which decision makers face decision problems without determining the details of the scenarios) and derive uncertainty intervals for conventional, environmentally friendly, and organic rice production systems in Japan, in addition to those for chemical fertilizer production and distribution. The result indicates that, although lack of information on transportation scenarios caused uncertainty, the ranking of global warming potential for conventional, environmentally friendly, and organic rice production systems remained unchanged. It implies that the result is stable with respect to scenario uncertainties due to location of fertilizer production. The proposed methodology for understanding the stability of results can be further developed as a technique to deal with uncertainty and instability in LCA of agricultural production systems.