An agricultural credit in our case, from our credits at Bank Farm, is a combination of carbon captured from increased growth above ground, and carbon sequestered below ground through various approaches. Crucially, as explained by Doug Wanstall and Pete Wain in the video, the additional carbon is measured so that it’s not wishful thinking.
Above ground natural capital is measured through photogrammetry plugged in to Pete’s systems and network for evaluation. Below ground carbon sequestration is measured by taking and testing cores of soil using a sampling pattern at structured random locations and different depths.
There are numerous initiatives in progress to sequester the carbon below ground at Bank Farm. Soils around the farm have various levels of degradation from historic farming practices, and therefore different capacities to add and store carbon. Many of the approaches provide multiple soil benefits such as water retention and soil stability gains. To be able to provide credits, the farm first has to demonstrate it is Carbon Net Zero in operation using the Farm Carbon Toolkit, so the credits are genuinely additional to what may have been regulated in the future.
Some of the key techniques I was shown in the flesh (and in the rain!):
- Agroforestry – the deliberate integration of trees, shrubs and wildflower in strips within the fields providing above and below ground benefits including acting as wildlife corridors
- No tilling for crop planting in harness with planting of cover crops – avoids emissions from release of CO2 when soils are ploughed, with cover crops storing more carbon in the soil. Ecosystems are complex and lots of research is being done to assess what works best for the long term. Variables include duration of cover crops, carbon capture and release at different depths with and without tilling, and the effects of herbicides.
- Mob grazing – moving livestock round the pasture in tighter herds to graze an area hard, return the organic consequences (dung!), and then leave the area to regrow. Apparently the cows aren’t too clever at self managing this given the whole place to roam as they please.
- Compost “tea” spreading – capturing the microbes in compost and spreading them over wider areas when the conditions are right from them to colonise.
There is a considerable element of experimentation with all of the above. That’s why the periodic measure of the soil carbon content is so important. To make the experiments on what works for soil sequestration scientific, they have partnered with the University of Kent to optimise progression.
The next post In this series will conder the thorny (excuse the pun) issue of the permanence of the carbon offset.