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Test Valley Devons & The Environment

You’ll have no doubt seen widely reported in the media that the cattle farming industry at large contributes unnecessarily to climate change, partly through the expulsion by cattle of methane, a greenhouse gas that over time converts into CO2, and partly because of carbon that goes into feed production, fencing and the fuel used to transport both feed and animals around the countryside. 


However what isn’t covered in the media is that farming is not ‘one size fits all’, and the style of farming and production methods have a significant impact on environmental sustainability.  To understand why, it’s important to understand firstly the natural process known as the biogenic carbon cycle and, secondly, the critical difference between intensive and extensive farming. 

What is the biogenic carbon cycle?

The biogenic carbon cycle centres on the ability of plants to absorb and sequester carbon. Through the process of photosynthesis, plants absorb CO2 from the atmosphere and deposit that carbon into plant leaves, roots, and stems, while oxygen is released back into the atmosphere. When plants perform photosynthesis, carbon is primarily converted to cellulose, a form of carbohydrate that is one of the main building blocks for growing plants. Cellulose content is particularly high in grasses and shrubs found on marginal lands, where grains and other human edible crops cannot grow.


Over 40% of all agricultural land in the UK is permanent grassland, full of cellulose dense grasses that are indigestible to humans – but not cattle. Cattle use the cellulose, for growth, milk production, and other metabolic processes. As a by-product of consuming cellulose, cattle belch out methane, thereby returning that carbon sequestered by plants back into the atmosphere. After about ten years, that methane is broken down and converted back to CO2.


Once converted to CO2, plants can again perform photosynthesis and fix that carbon back into cellulose. From here, cattle can eat the plants and the cycle begins once again. In essence, the methane belched from cattle is not, therefore, adding new carbon to the atmosphere. Rather it is part of the natural cycling of carbon through the biogenic carbon cycle

Keeping carbon inputs and outputs in balance

With intensive cattle farming common  in some parts of the world, for example, the USA, where cattle are housed in feed lots, or the area of grazing land is small compared to the large number of cattle, the quantity of CO2 absorbed by the land can never hope to balance out CO2 from methane expulsion, feed production and transport. 


By contrast, in extensive farming, where a smaller number of cattle graze a wide area, there is ample scope for CO2 sequestration from the soil, hedgerows, organic matter and woodland to offset the methane, as well any CO2 emitted through the use of fuel, or in the production of cattle feed.


When we understand the biogenic carbon cycle, it  is easy, therefore, to see how Test Valley Devons extensive farming methods of low input, conservation grazing, enables the organisation to achieve a  carbon balance calculation that is environmentally positive  – currently 8.52 tonnes per annum of CO2 emitted, countered by 10.93 tonnes of carbon absorbed through sequestration. Not only do a small number of animals graze a large expanse of land, but the grass fed nature of our farm means that apart from energy used during hay making for winter feed, the production of fencing supplies and diesel for the Landy, carbon emissions to run the farm are very low. 

With thanks to Stephen MacDonald and the The Farm Carbon Calculator for help producing this article.

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