Zero carbon farm

Dr Adrian Williams

It is important to reduce emissions from nitrous oxide which is produced from the manufacturing and use of nitrogen fertilisers, crop residue incorporation, also reducing CO2 from fossil fuel in cultivations, crop drying and crop storage. There are a range of technologies that can reduce greenhouse gas emissions (GHGE) from these areas, however some produce emissions themselves. Fine tuning all fertiliser use by better soil sensing incurs much smaller GHGE overheads. Life Cycle Assessment (LCA), considers the net effects of delivering a product or service.

Another aspect of net zero for arable agriculture is the radical reduction of GHGE from fertiliser manufacture and tillage itself. Reducing these GHGE is possible but depends on having a decarbonised energy system. Nitrogen fertiliser is normally made from methane in natural gas, which creates collateral emissions. If it were made from green hydrogen, the manufacturing impacts would be much reduced. The next step in delivering fertiliser, which must be by green electric power directly through batteries or via green hydrogen fuel cells. A much bigger term, especially for crops like potatoes or sugar beet is tillage and harvesting energy. These are currently almost all based on diesel, however they could be replaced by green fuelled electric traction in time. The big challenge is addressing the need to decarbonise electricity in a range of areas, such as, current electricity needs, heating, transport, manufacturing and indeed novel and innovative food production.

What are the limiting factors?

Professor Andrew Barnes

• The FAO estimates that around a third of the world's soils are already degraded, so actions such as these will take longer and have different effects to soil which have been converted to organic. It depends on the crop that is grown on that land and the management practices. For example, land given over to legumes provides some fixing of nitrogen and would be more beneficial than mono cropping of wheat.

• It would require significant upscaling of ecological approaches which, at least in the short term, would lead to a fall in supply of food as the land may be exhausted and currently reliant on non-organic inputs.

• It relies on an available source of organic matter. One aspect of this is using livestock to provide organic material and create a more circular system. Hence some redistribution may have to occur of animals to ensure levels of organic fertilisation are attained, meaning significant changes to our current farming system.

• In the global North there are few incentives for the whole farming population to adopt these methods due to the need and requirements for cheaper food.

• In the private sector there are pockets of initiatives, e.g. the LEAF marque. However, there are issues of transparency in the supply chain. Adopting a suite of measures to improve soil carbon is more difficult due to problems in measurement and the long time frame in improving soils. However, in Austria the scheme ‘Healthy Soil for Healthy Food’ was a private scheme funded by SPAR and WWF. There is work on a Soil Carbon Code (much like the Woodland Carbon Code) which may create some transparency in the supply chain.

• Until farmers get to know how to manage their systems then there has to be some long-term support from Government to keep these farmers afloat. An alternative is seen in France where, by law, supermarkets must pay farmers for at least the cost of producing the goods. Also, if SOC is a long-term investment, an agreement with the landowner is required as incomes may dip in the short-term and methods will change on the farm.

• We could also include knowledge and capacity for support, which exists in the UK and most high income countries, but in less developed countries there is limited capacity to support healthy soil management.

Professor Mads Fischer-Moller

Who pays? Is the taxpayer to pay through subsidies? Can we create markets for the 'ecosystem services' for big emitters to buy as carbon offsetting? Or can we create new markets where food consumers are willing to pay extra for food that has a low GHG impact – and what do we need to bring these changes about?

Dr Adrian Williams

• Most of the methods are inefficient for crops like potatoes where soil disturbance caused by tillage intensity is very high at both planting and harvesting.

• At times, min-till (direct drilling) will fail if weed build up is too high and weeds are resistant to current herbicides. In that case, the only weed control available is by more tillage, which will tend to reverse the beneficial process.