This report presents the key outcomes of a collaborative research study between NSW Department of Primary Industries (DPI) and Cotton Research and Development Corporation (CRDC). The study used the science-based method of Life Cycle Assessment (LCA) and aimed to:

(1) produce a clear picture of the greenhouse gas (GHG) emissions profile for a representative cotton production system in North West NSW;

(2) identify the most plausible set of emission reduction opportunities;

(3) create a platform in SimaPro (an LCA tool), through the North West NSW LCA, from which industry can routinely test emission mitigation options or the consequences of new productivity-based technologies in an ongoing way; and,

(4) undertake sensitivity analysis to check whether the case study region is representative of other regions.

We followed the LCA principals, as defined by ISO 14040:2006 Standard [1] and ISO 14044:2006 Standard [2]. The functional unit of the assessment was 1 t (1000 kg) of cotton lint at port, produced between 2011- 2014 by a continuous (back-to-back) cotton production system. A mixture of irrigated and rainfed cotton was modelled, in which irrigated cotton predominated. The system boundaries of the assessment included all processes involved in pre-farm, on-farm, and post-farm stages. The foreground data included that from questionnaires sent to some ginning plants, interviews conducted with some cotton farmers, gross margin data, industry surveys and case study research. Data were also validated by obtaining expert opinion from industry representatives. The background data (e.g. fertiliser production) were accessed from the different sources mainly from the Australian life-cycle inventory (AusLCI).

To assign the calculated CC impact between cotton lint and cotton seed, we followed the relevant hierarchy recommended by ISO 14044:2006. We initially applied the system expansion approach in which the total CC impact of the cotton system is assigned to cotton lint but it is credited for the avoided CC impacts of the products displaced by cotton seed (i.e. animal feed and oilseeds). Through this approach, we calculated the CC impact of the functional unit to range from 1254 kg CO2e to 1307 kg CO2e for four investigated scenarios. As other scenarios are also possible, these results should be treated as subjective. Given this uncertainty, we finally applied the economic allocation approach in which we allocated around 86% of the total CC impact to cotton lint and around 14% of the impacts to cotton seed, in proportion to their revenue.