Can British farmers transform themselves into carbon-cutting heroes? Arable farmer, Duncan Farrington has worked hard to reduce the carbon emissions from his farm. He's replanted hedges and trees and cut down on diesel-powered machinery. He's even persuaded some of his staff to cycle to work. But Duncan's farm isn't just zero carbon, it's actually sucking in and locking up vast quantities of carbon dioxide from the atmosphere.
Duncan explains to Tom how he's transformed the management of his soil and proven to doubters that commercial British arable farms can play their part in cutting the planet's carbon emissions.
Listen now on BBC Radio 4
What our experts say
We asked Society Fellows Dr Adrian Williams from Cranfield University and Professor Andrew Barnes, Professor Bob Rees and Professor Mads Fischer-Moller from Scotland’s Rural College to offer some observations on the potential of maximising the carbon-carrying capacity of arable farms in reducing carbon emissions. Their points take some of the themes of the programme a step further.
Professor Andrew Barnes
Supplemental data of Global Carbon Budget 2020 (Version 1.0) estimates that globally we emitted (after sequestration) 36.44 billion tonnes of carbon in 2019. Therefore, if all arable land were immediately converted to these (maximising carbon-carrying capacity) methods it could sequester around 8% of global carbon emissions but only over a time period of 10 to 20 years when soil organic carbon (SOC) has time to build up. This has high error bars around given the management of soil and the baseline, i.e. how much carbon is in that soil already. The Food and Agriculture Organization of the United Nations (FAO) provide detailed values by global arable area, however some of these, such as treenuts and citrus fruits, may be effectively unmanaged and would carry their own sequestering potential.
Professor Bob Rees
Agriculture is an important source of UK greenhouse gas emissions and is responsible for 41 Mt CO2e (million metric tonnes of carbon dioxide equivalents) each year or 9% of overall emissions.
The agriculture sector is different to many sectors of the economy that contribute to greenhouse gas emissions in that these emissions are from biological sources and are mostly in the form of nitrous oxide and methane rather than carbon dioxide. There is a misconception that zero-carbon farming is mostly about removing carbon from the atmosphere. While this has an important role to play in our pathway to net zero, it is probably more important in UK farming to focus on the reduction of the non-CO2 greenhouse gases.
It has been estimated that we could remove as much as 0.7 Gt CO2e per year by locking up carbon in soil organic matter, however in the UK:
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UK soils are already rich in soil carbon so getting more into them is not easy.
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Techniques such as minimum or reduced tillage tend to increase the concentration of carbon near the soil surface, and it was assumed that this resulted in more carbon storage overall. But a more detailed analysis has shown that very often, tillage simply redistributes the carbon, leaving less carbon deeper down and no additional carbon storage. One possible approach to this problem is to convert some of our crop residues into biochar – a charcoal like product which could be incorporated into soils and stay there for a long time.
Another way of reducing the emissions from arable soils is to focus on nitrogen, in particular nitrous oxide.
Biochar (Image: Oregon Department of Forestry/Flickr, CC BY 2.0)
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
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
Wheat harvest (Image: TheOtherKev/Pixabay)
What are the co-benefits?
Professor Andrew Barnes
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Improved soil fertility: increased biodiversity may be a consequence of this. Silvoarable systems put arable crops with trees, promoting greater biodiversity.
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Wider health benefits may come about through reduction in applications of agrochemicals in our food (however this may come at a higher financial price).
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There may be benefits for long-term resilience in terms of reducing reliance on imported inputs.
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There should be less susceptibility of pests and diseases, if we are also promoting intercropping and diverse rotations.
Professor Bob Rees
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Increasing soil carbon offers multiple co-benefits, including: increased soil quality, increased soil resilience, reduced erosion and improved crop productivity.
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Improving nitrogen use efficiency also has many co-benefits, including: cleaner air, water and soils, as well as reduced input costs to farmers.
Professor Mads Fischer-Moller
Changing farming practice will also entail changing what is being produced on the farm. More legumes (pulses, beans) in the rotation will not only increase soil quality but also potentially be a beneficial contribution to UK diets that are currently too heavy in meat and too light in fibre.
Neighbouring countries to the UK are looking at low or zero carbon farming as key to market access in the future. Consumers are already demanding lower GHG foods and big funders, such as the Danish Sovereign Investment Fund, are solely funding projects that are contributing to solving the climate crises.
Dr Adrian Williams
A co-benefit would be a major reduction in diesel use. This is about 50% for direct drilling and around 10 to 20% for reduced tillage.
Potential negative impacts of this idea?
Professor Andrew Barnes
Recently some US economists claimed that the European Farm to Fork initiative, which embeds uptake of these organic and ecological practices, would increase food prices and global food insecurity.
Increasing demands for organic matter: human waste may be used on land but at a cost of reprocessing that material which would push the carbon emitted upstream.
Dr Adrian Williams
Herbicide use will increase, leading to more toxic materials being applied to the land. There is a relatively small carbon footprint from producing these.
Further reading
About the series
39 ways to save the planet is a new radio series by BBC Radio 4 developed in partnership with the Society and broadcast in 2021. It showcases 39 ideas to relieve the stress that climate change is placing on the Earth. In each 15 minute episode Tom Heap and Dr Tamsin Edwards meet the people behind a fresh and fascinating idea to cut the carbon.
Programme website
Over the course of 2021, the Society will be producing events and digital content to accompany the series.