One of the most interesting developments at the recent Teagasc Moorepark dairy open day was the launch of the new AgNav tool for estimating individual farm carbon footprints.

Until recently, when it came to greenhouse gases, the only statistics that were required were broad trends at national, regional and farm system level. However, given that farmers are now individually obliged to achieve carbon targets for their own farms, we have to have access to reliable and robust estimates of carbon for each individual farm.

Accuracy is a major challenge when compiling carbon footprint estimates at farm level. It’s highly likely that the individual farm estimates from the quality assurance audits and the Teagasc estimates from the SignPost farms will differ significantly.

Both sources have access to the AIMS data, so emissions associated with farm animals should be similar. It’s most unlikely, however, that data for fertiliser application, for example, and turnout dates will result in similar estimates.

The Bord Bia data is based on asking farmers to recall key management events, such as fertiliser purchases and so on. The Teagasc data is generated via a team of professional farm recorders that visit farms on a regular basis and who have access to evidential support for key farm purchases.

The “AgNav” initiative will, I’m sure, be addressing this accuracy issue, and it’s highly likely that with the National Fertiliser Database, the accuracy of the fertiliser data will be much better.

Broader issue

But there are broader issues involved in ensuring the acceptability of individual farm carbon estimates. These issues were highlighted at the recent ArcZero end of project conference and farm walk on John Gilliland’s farm in Derry. John was the prime mover in setting up a European Innovation Partnership (EIP) three-year project to measure the carbon footprint on a small sample of diverse farms in Northern Ireland.

The methodology used on the seven ArcZero farms differs at present from that used by Bord Bia and Teagasc in the south.

The big difference arises in that the ArcZero project estimates sequestration above and below ground, in addition to emissions, whereas the Bord Bia and Teagasc estimates, at this stage, only calculate emission data and do not report sequestration estimates.

The other main measurement difference concerns how the emission estimates are compiled. The Bord Bia and Teagasc methodologies strictly adhere to the IPCC approach.

Emissions are based on the gaseous impact of inputs – for example, fertilisers that are actually used on farms. This approach is in line with international agreements and national commitments.

The ArcZero adopts what’s called a lifecycle approach (LCA) and embeds the estimated carbon used to produce fertilisers, etc, and their transport onto farms.

It’s likely that the IPCC and LCA approaches will differ at individual farm level.

However, the standout feature of the ArcZero approach is their estimates of carbon sequestration at individual farm level. These estimates are very crude at this stage.

Sequestration is assumed based on theoretical potential and therefore isn’t actually measured. Measurement is still some way off. Farms will need to be tested for carbon every five years or so, and the annualised difference in the carbon stock would give a reasonable indication of the annual sequestration rate.

A big conundrum with the ArcZero approach is that while estimates are provided for sequestration on each farm, as well as emissions, which allow a net carbon estimate to be produced for each farm – under current rules, soil sequestration, or the amount potentially embedded in pasture and hedgerows, etc, is not officially recognised, given the absence of robust scientific measurements.

Storage

The driving philosophy of ArcZero is that farms are fundamentally different when it comes to carbon compared with any other sector. Farms do produce carbon, but farms also crucially store carbon in their soils and hedgerows, and can also replace fossil fuels through the production of biomass-based renewables. No other sector has this ability.

So, the ArcZero team is adamant that what needs to be measured at individual farm level is net carbon, namely, emissions, less sequestration.

This position is highly defensible, but does not at present accord with regulation or legislation. It’s a polemical position, as sequestration is not credited to agriculture at present and biomass-based renewables are credited to the energy sector.

The results from the ArcZero farms are encouraging. Over the three years, farms have achieved an annual reduction in emissions between 1% and 18%.

Considering that the national average reduction in the south has been just over 1%, this is a remarkable performance. Admittedly, a good deal of the reduction was aided by last year’s reduction in fertiliser use.

The results also illustrate that sequestration is potentially of enormous importance to farms. Two of the farms actually reported that estimated sequestration was in fact higher than emissions.

One farm reported sequestration at over 50% of emissions. And three of the farms report sequestration at about 30% of emissions.

While the sequestration data needs to be validated by measurement, there is little doubt that sequestration has to be part of the adjustment process on farms and that farms need to be encouraged, not only to reduce emissions, but also to enhance sequestration.