How to remove carbon from the atmosphere and put it back in the ground? Although the Government might like its big-ticket solutions such as unproven carbon capture and storage (CCS) technologies for coal-fired power plants, a more effective answer may lie right beneath our feet.
Soil is the third-largest carbon sink in the world (after the oceans and fossil fuels themselves), and a change in the way we farm could offset a quarter of global carbon dioxide emissions annually, a new report reveals. Land use accounts for more than 30 per cent of the world’s greenhouse gas emissions.
Mitigating Climate Change Through Food and Land Use, a report by the Worldwatch Institute and Ecoagriculture Partners, identifies five ways in which changes in agricultural practices could reduce and sequester carbon emissions.
The measures include enriching soil carbon through minimising tillage, using less fertiliser and adding biochar to increase its carbon-storage capacity; farming with perennials; adopting a more climate-friendly approach to livestock production, including a reduction in numbers and rotational grazing; protecting natural habitats by minimising the effects of forest and grass fires, and limiting deforestation and land clearances; and restoring degraded watersheds and rangelands.
The findings of the report are consistent with a shift away from harmful industrial practices towards the adoption of a more organic approach.
‘Organic farming plays a key role in soil carbon sequestration in comparison to conventional farming, which instead of returning carbon to the soil relies on chemicals,’ says Clio Turton of the Soil Association. ‘Organic farming has more grassland and organic red meat production is a grass-fed system, and therefore maintains huge carbon stores in permanent grassland. Organic techniques such as crop rotations and adding organic matter to the soil also play key roles in sequestering carbon.’
The Department for Environment, Food and Rural Affairs (Defra) acknowledges that industrial agriculture has a net negative impact on the environment. A spokesperson said the department was working to raise awareness of the issue, promoting emerging technologies such as anaerobic digestion, and conducting a research programme on other ways to reduce the impact of farming, such as emissions trading and incentives to increase greener land management.
‘Farming is on the front line of tackling climate change,’ said a spokesperson. ‘Through our Agriculture and Climate Change Project, we are aiming to equip the agricultural sector with the tools, expertise and support that will enable it make a strong contribution to cutting greenhouse gas emissions and adapting to the impacts of the changing climate – as well as making the most of the business opportunities that are presented by the emerging green industries.’
An International Trade Centre (ITC) report carried out in 2007 by the Research Institute of Organic Agriculture (FiBL) found that organic agriculture techniques can contribute significantly to the carbon sequestration capabilities of soil. Under northern European conditions, converting to organic practices such as the use of animal manure, green composting techniques and rotational grazing would result in an increase of soil organic matter of 100kg to 400kg per hectare annually during the first 50 years. A steady state of organic matter would be reached in 100 years, the report found.
UK agriculture currently accounts for seven per cent of total UK greenhouse gas emissions, half of which occurs as a result of nitrous oxide emissions from tillage.
The National Farmers Union (NFU) was prickly towards the report.
‘The production of nitrous oxide is a side-effect of food production,’ said Jonathan Scurlock, the NFU’s chief adviser on renewable energy and climate change. ‘At the moment it’s not technically possible drastically to reduce these emissions.
‘In terms of actually mitigating greenhouse gas emissions there are a lot of embedded renewable energy options that are much easier to implement, from anaerobic digestion and the optimal management of slurries to wind turbines in fields and solar photovoltaics on farm buildings. We need policy measures that encourage the uptake of renewable energy and low-carbon opportunities within the agricultural sector.
‘Perennial crops have many advantages and the theory behind biochar is sound as a means of locking carbon into the soil, but I don’t agree that reducing livestock numbers is the answer. Farmers will follow consumer preferences, but most of the world is seeing an increase in meat production. We can reduce emissions through a variety of measures but there’s no magic bullet – it will be gradual and progressive. What is important is to transfer the best available technologies to emerging markets in developing counties.’
A report from the United Nations Environment Programme (UNEP) also supports a more natural approach to reducing emissions. Its authors claim trees and soil could sequester as much as 50 gigatonnes of carbon over a few decades – and do so far more effectively and cheaply than CCS.
According to the report, The Natural Fix? The Role of Ecosystems in Climate Mitigation, less intensively grown crops and a reduction in grazing rates would lead to an increase in the carbon-storage capacity of soil. It estimates the measures would cost as little as £6 per tonne of avoided carbon dioxide emissions. CCS – capturing carbon dioxide from coal-fired power plants at source and pumping it underground – could cost anything from £12 to £170 per tonne.
‘Tens of billions of dollars are being earmarked for carbon capture and storage at power stations, with the CO2 to be buried underground or under the sea,’ said UNEP executive director Achim Steiner. ‘The Earth’s living systems might be capable of sequestering more than 50 gigatonnes [billion tonnes] of carbon over the coming decades with the right market signals.’
Cost aside, with greenhouse gas emissions increasing at a rate of three per cent a year, the speed at which carbon-capture technologies must be developed and built may make CCS unviable. As Greenpeace’s False Hope report made clear last year: ‘The IEA estimates that for CCS to deliver any meaningful climate mitigation effects by 2050, 6,000 projects each injecting a million tonnes of CO2 per year into the ground would be required. […] Currently, only three such storage projects exist worldwide.’
Eifion Rees is a freelance journalist