Farm Carbon Toolkit – Carbon Calculator
As part of the CHCx3 project, Farm Carbon Toolkit has collaborated with AFBI, Crops for Energy and Calvium to investigate how transitioning to biomass crops can influence a farm’s carbon footprint.
While many farmers who use carbon calculators will want to run their own numbers, Farm Carbon Toolkit has developed a series of example scenarios that clearly highlight the carbon-saving potential of biomass crops—making them a compelling choice for farmers looking to lower their environmental impact.
Developing Tools to Measure Farmland Carbon Stocks
Farm Carbon Toolkit is enhancing its existing Farm Carbon Calculator to help farmers and growers more accurately estimate changes in their farmland carbon stocks, particularly when cultivating high carbon capture crops. As part of this project, we are also carrying out carbon baselining at trial sites. For our project partners, we have established a soil sampling protocol and are compiling all relevant carbon data.
Expanding the Carbon Calculator to Include Biomass Crops
In October 2024, we updated the calculator to incorporate biomass crops, improving assessments for biofuels, biomaterials, and biomass production. The newly included crops—short rotation coppice (such as willow and poplar), miscanthus, switchgrass, and hemp—enable farmers to comprehensively account for emissions across their systems. This is particularly important in the biofuels and biomaterials sectors, where environmental claims are subject to increasing scrutiny. Further updates to the calculator will be introduced throughout the project, using research and findings on both above-ground and below-ground carbon storage from routine soil analysis.
Understanding Emissions from Biomass Crops
Previously, biomass crops were excluded due to the challenges of calculating emissions from plant residue decomposition. When residues such as straw, leaf litter, or roots break down, they release nitrogen, which can convert into nitrous oxide (N₂O), a potent greenhouse gas. The level of N₂O emissions depends on factors such as the nitrogen content of the plant material, the proportion left in the field post-harvest, and how much of the above-ground and below-ground material decomposes annually. While some of this data is available in the UK’s annual greenhouse gas inventory, working with industry professionals and FCT advisors has been crucial in filling knowledge gaps and establishing emissions factors for biomass crops.
Addressing Challenges of Perennial Crops
Perennial crops like miscanthus present additional complexities when estimating emissions. Each year, miscanthus grows 3–4 metres of above-ground material, with leftover litter decomposing annually. However, its root system remains active for over 20 years, meaning that minimal decomposition occurs annually, as most nitrogen remains locked within the living roots. To calculate emissions, we estimate the proportion of below-ground material that decomposes each year versus what remains active. We also consider the plant’s full productive lifespan, as the entire root system will eventually decompose, contributing to long-term emissions.
Delivering Reliable Emissions Data
With input from industry experts, farmers, and agricultural advisors, we have developed robust emissions factors for biomass crops suited to UK farming conditions. These improvements ensure farmers can effectively measure and manage emissions from biomass-based systems. By enhancing the Carbon Calculator, we are helping farmers implement sustainable practices and contribute to a more environmentally responsible future.
Read the full Study Here
Access the Carbon Calculator here
