A review of greenhouse gas emission factors for fertiliser production.

6. SummaryThis report collates published greenhouse gas (GHG) emission factors associated withthe production of a range of nitrogen, phosphate and multi-nutrient fertilisers, for usein agricultural and forestry Life Cycle Assessments. Overall, there were fewpublished studies that present GHG emission factors for fertiliser production and, withthe exception of one study from the US, all were based on fertiliser manufacture inWestern Europe. Emission factors for the intermediate products Ammonia and NitricAcid were more widely available, but these are less useful in an agricultural LCAcontext.The major GHG emissions associated with nitrogen-containing fertiliser productionare carbon dioxide (CO 2 ) emitted when natural gas is combusted as part of ammoniasynthesis, and nitrous oxide (N 2 O) emitted during nitric acid production. ForPhosphate Fertilisers, GHG emissions were primarily CO 2 emitted during theconsumption of fossil fuels used in the various production processes. Transport of rawmaterials was an important contributor to phosphate fertiliser GHG emissions.For each fertiliser product, emissions factors varied markedly between studies. Thisvariation is due to differences in plant design and efficiency, emissions controlmechanisms and raw material inputs. Differences may also be attributed toassumptions made by the analysts during the calculation of the emission factors,particularly in relation to the interpretation of energy and emissions credits andtransport considerations. An understanding of these factors is required to make aninformed decision as to which emissions factor is most applicable for the particularfertiliser product being considered for a specific study.18