How we calculate your carbon footprint:
our modelling methodology

Agrecalc: Footprinting methodologies

The Agrecalc team is committed to maintaining a consistent, defensible model of farm emissions based on the latest published reporting standards and scientific research. Our central model is based on greenhouse gas reporting guidelines published by the IPCC for national inventories. We also incorporate more specific national figures from the UK National Greenhouse Gas Inventory.

Our methods are certified by PAS 2050:2011, a standard for the robust quantification of product carbon footprints. In the interest of transparency, the following sections detail the methodologies we use to quantify farm greenhouse gas emissions.

Agrecalc combines higher IPCC Tier methods to develop own modelling methodology for carbon footprinting

The IPCC methods for greenhouse gas reporting are split into three tiers of increasing complexity and specificity. Tier I reporting standards use default figures published by the IPCC which provide a general estimate of greenhouse gas emissions, but likely miss important sources of variance. Tier II reporting standards are slightly more specific than Tier I, as they use national research to generate country-specific emission factors. Finally, Tier III reporting uses process-based models to predict emissions with the greatest accuracy and system-specificity. The IPCC published its original guidelines in 2006 and updated these guidelines in 2019. Our model reflects the latest published guidelines, and we aim to quickly assimilate new guidance to keep our model at the forefront of peer-reviewed published science.   

To balance model performance and data requirements, our model makes use of higher Tier methods for large emissions sources. Default methods are used where higher Tier methods would increase data requirements beyond what is generally available on a farm, for smaller emission sources, and for emission sources where more research is needed to improve the resolution of emission factors. 

Our modelling methodology for beef and dairy

Our beef and dairy models are based on IPCC Tier II guidelines. This Tier II calculation includes detailed modelling of the energy requirements of beef and dairy herds based on activity levels, growth rates, life stages, gender, and climate.

Enteric methane emissions and emissions from manure deposited on grazing lands are also calculated using IPCC Tier II methods published in the most recent guidance.

Our modelling methodology for sheep

Our sheep model is also based on the latest IPCC Tier II guidelines. This Tier II calculation includes detailed modelling of the energy requirements of sheep flocks based on activity levels, growth rates, life stages, gender, and climate.

Like our beef and dairy models, this model estimates emissions from enteric fermentation and manure deposited on grazing lands using IPCC Tier II methodology.

cute sheep in paddock

Our modelling methodology for pigs

Our pig model goes beyond IPCC reporting standards, incorporating a detailed energy balance model for pigs published by FAO.

This expansion upon standard methods allows us to use Tier II reporting standards for pigs, improving the detail of our pig model outputs beyond that provided by standard greenhouse gas reporting for pigs.

Poultry

Our poultry model also goes beyond IPCC reporting standards, incorporating a detailed energy balance model for poultry published by FAO. The outputs of this model are in line with IPCC Tier II methods.

This expansion upon standard methods allows us to estimate emissions at a similar level of detail to our beef and dairy models.

a wheelbarrow full of natural manure

Manure Management

Our manure management model estimates emissions related to storage and treatment of manures. We use Tier II methods to calculate methane emissions from manure, which uses the dietary characteristics of livestock to calculate methane emissions. 

For liquid storage systems, our model directly interacts with climate data to estimate methane emissions, in line with IPCC Tier II guidelines. We also calculate nitrous oxide emissions from manures using Tier II methods, which incorporate information about the nitrogen content of livestock diets.

Arable Enterprises and Improved Grassland

Our arable farming model is based on IPCC Tier I and Tier II factors for cropland management. This includes Tier II factors for direct nitrous oxide emissions from organic and inorganic fertilisers, derived from the UK National Inventory.

Tier I emission factors are utilised for indirect nitrous oxide emissions related to volatisation and leaching. Nitrous oxide emissions from crop residues are also calculated using IPCC Tier I methods.

soil being dug up in the field to admire the biodiversity richness

Soil Carbon Sequestration

Soil carbon is a recent addition to our model which has been built based on the updated 2019 IPCC Tier I guidance. The soil carbon model also considers sequestration from biochar application to soils in line with IPCC 2019 updates.

The IPCC soil carbon model is a stepwise model which makes decisions between emission factors based on farm management practices. To estimate grazing intensity, we currently employ a spatial grass growth model based on data from SoilGrids250 and RB209.

Our grass growth model also estimates nutrient inputs from nitrogen-fixing clover, based on RB209 figures. Total estimated grass growth is then compared to livestock energy demand to evaluate grazing intensity.

Hedges and Woodlands

Our woodland and hedge model currently reflects the latest climate-specific IPCC Tier I sequestration equations for different forest types.

We are currently working on expanding upon this groundwork to incorporate a greater diversity of agroforestry systems into our biomass sequestration model.

Embedded Resource Emissions

Our carbon footprint model draws on various external databases to estimate emissions from imported feed, fuel, electricity, and fertiliser inputs. For emissions related to energy use, we use figures published by DEFRA for UK energy use and figures published by the Greenhouse Gas Protocol (2012) for energy use in other countries.

For the embedded emissions of fertilisers, we draw on a study by Kool et al. (2012) which reported emissions related to different fertilisers in countries across the world. For emissions related to imported feed rations, we currently use the Dutch Feedprint database.

However, we are in the process of migrating to the GFLI database to allow our users to choose from a greater variety of feed ingredients.

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