Reducing the amount of fossil fuels, reducing excess N fertiliser, and increasing woody vegetation all reduce the total emissions released on a cotton farm. This is good news for you if the corporations you sell cotton to want to reduce their emissions or are required by legislation to report GHGs in their value chain. But it’s also good news for you because using inputs like energy and N as efficiently as possible will increase your margins and will most likely involve soil health practices that improve the resilience of your farm to seasonal extremes, such as storing more rainfall, and being less susceptible to erosion.

GHG accounting is fairly new, but there are just a handful of concepts to understand.

Firstly, GHG emissions are measured in carbon dioxide equivalent (CO₂e) to standardise the impact of different on the earth’s climate. For example, one tonne of N₂O is equivalent to 273 tonnes of CO₂, so it is referred to as 273t CO₂e. This is referred to as the 100-year Global Warming Potential (GWP100) of a GHG and it should be noted that the GWP100of a GHG is determined by things that can vary over time such as the GHG’s atmospheric concentration, so these values are re-calculated and change over time.

Secondly, GHG emissions are divided into three categories:

• Scope 1:On-farm emissions from your direct actions, like N₂O from the denitrification of nitrogen fertiliser in your soil and CO₂ from diesel combusted in machine you use to produce cotton
• Scope 2:On-farm use of purchased fossil-fuel-generated electricity in cotton production (eg for pumping irrigation water)
• Scope 3:Emissions from third-party activities associated with growing your cotton, such as GHGs emitted by the manufacture of fertiliser and the transport of inputs to farm.

And finally, GHG emissions are estimated by calculators that use equations and emissions factors (EF). The most robust calculators use equations and EF that are consistent with those Australia uses to calculate its GHG emissions for reporting to international climate change frameworks. These calculators require farm management data such as fertiliser type and use, diesel use, electricity use and crop yield to estimate GHG emissions associated with cotton production. Therefore, to estimate your GHG emissions, you need to enter data like yield, fertiliser rates and diesel use into a cotton-specific emissions calculator, and the calculator tells you your scope 1, 2 and 3 emissions in CO₂e.