The National Trust is two-thirds of the way through a major carbon footprint project on its 13,500-acre Wallington Estate in Northumberland.

The project, which is running across a range of land types, aims to work out the carbon content of the soil and match farming practices to it.

Annual carbon output on the estate has been estimated at 785,000 tonnes – equivalent to a city the size of Sheffield, Peter Nixon, director of conservation for the National Trust, told the Central Association of Agricultural Valuers’ AGM last week.

Through good management practices, results so far indicated that the estate was already “sinking” a net 400t of carbon a year, he said. “However, if we reduced our electricity and heating oil, putting in biomass boilers, changing our pasture management and planting more woodland, we believe we could raise that to 2500t.

“We could be sequesting an additional 5,50t a year over the next 20 years,” he added.

The project, run in conjunction with Durham University, is expected to be completed in 2010 and will produce comprehensive recommendations for carbon management.