photo by Paul Shelley
What is carbon farming, how it could increase farmers’ incomes and why it makes tastier food
Did you know that farmers are going to save our bacon in the 21st Century? This is because there is already so much CO2 in the atmosphere that reaching net zero CO2 emissions alone won’t stop climate change – we will also need ways to draw down the existing CO2. The great news is that farming done in the right way can absorb CO2 and bury it in the soil. This process is called carbon sequestration. A bi-product of sequestration is more fertile soil, which in turn produces more nutritious and tasty crops.
How does it work?
Soil is made up of air, water, rock dust (sand and clay) and organic matter. Organic matter is the living part of the soil, essentially compost made from rotted down plants and animals, and it is around 50% carbon.
The organic matter content is usually between 1% and 10% of soil. The higher the level, the more carbon the soil contains and the more fertile and nutritious it is. If the level of organic matter goes up from one year to the next it means the soil is absorbing CO2 from the atmosphere. Conversely if it goes down the soil is emitting CO2. Even a small increase in organic matter of 0.1% per year absorbs a huge amount of CO2 per hectare.
What makes soil absorb CO2?
Plants absorb CO2 and bury it in the soil. Some do it faster than others, for example trees, tall grasses, bamboo and clover. Once in the soil the CO2 needs to be trapped there by making it into stable compost, which is done by worms, microbes and fungi. So to get the fastest sequestration you need the right kinds of plants and treatment of the soil – which nature does well in the wild.
Many of today’s farming practices emit CO2. For example deep ploughing exposes soil carbon to oxygen in the air and produces CO2. Nitrate fertilisers produce nitrous oxide, a greenhouse gas which is 300 times more powerful than CO2. And slurry pits cause anaerobic decomposition of animal manure, creating up to 50 times more greenhouse gases than the aerobic decomposition of traditional farm-yard manure mixed with straw.
The transition to carbon farming means more of practices like adding natural compost and manure to the soil, shallow ploughing and no-dig methods, use of green manures like clover and rye in between cropping periods, and making sure compost and manure can breath while it is rotting. These are assisted by wider field margins, larger hedgerows, lower animal densities and planting trees in areas not suitable for crops and grazing. Whilst this can produce lower yields for some crops, if done correctly, yields for many types of produce can even be increased.
Generating income for farmers
Farmers who work the land in this way are providing a service of CO2 sequestration, which has considerable economic value. Sequestered carbon can be sold on carbon trading markets to high emitters like aviation and energy companies, and current rates are around £30/tonne. This can earn farmers extra revenue in addition to their crops.
A case study is Devon organic food producers, Chagfood, who tested samples of their soil and recorded a 6% rise in soil organic matter over the last 7 years, representing a phenomenal 76 tonnes of CO2 sequestered per hectare per year. At £30/ tonne this represents around £2,000 of potential income per hectare per year – almost ten times more than current UK farm subsidies.
The IPCC (Intergovernmental Panel on Climate Change) states that if global agriculture could increase soil organic matter by just 0.1% per year it could sequester 1/3 of current global CO2 emissions. If we reduce emissions from other human activity to zero this would draw down CO2 from the atmosphere. But Chagfood is increasing soil organic matter by 0.8% which if replicated globally would absorb 12x current total CO2 emissions. This has exciting potential for both farmers and the planet.
Organic matter is also where most of the nutrition including vitamins and minerals is stored, and the more organic matter there is in the soil, the more nutrition gets absorbed by the crops. Therefore carbon farming produces food that is more nutritious, and this leads to better health and more flavour. So what’s good for the atmosphere is also good for farmers and our health and well-being. It’s a win-win-win.
Kinder to nature
We have lost half of Britain’s birds in the last 50 years, and this is partly due to the use of pesticides and herbicides to kill insects and weeds. Experts say the loss of insects risks future crops and the resulting loss of birdlife spoils our enjoyment of the natural world. Organic agriculture enables birds, bees and butterflies to flourish in our hedgerows, making it good for wildlife as well as saving CO2.