The National Trust has a target of producing 50% of its energy from renewable sources on its land by 2020. It’s a challenging target. The new biomass boiler which was installed at Ickworth Park near Bury St Edmunds in Suffolk and which was switched on in July 2015, is one of five pilot renewable energy projects that will address that goal. This is the story of how trees on the 1,800 acres estate are being turned into fuel.
The 199kw boiler is fuelled by wood chip produced from timber taken from the 600 acres of woodland on the estate and it will supply 100% of the fuel for heating the Rotunda and the West Wing. These are the main buildings in the centre of the park, and were the idea of the 4th Earl of Bristol, Frederick Augustus Hervey, who intended to use them as a place to display the treasures he gathered during his 30 years of travel in Europe. The Earl was seen more in Italy than in Suffolk.
Incidentally the Hervey family became more eccentric and more notorious right up to the 20th century; read more here. But ever since Ickworth was passed to the Trust in lieu of death duties following the death in 1951 of the 4th Marquess (and 8th Earl) , the buildings have been a nightmare to heat and the bills for the heating oil have been enormous.
Around 156 tonnes of wood chip fuel would be needed each year in addition to the 40 tonnes that was currently being supplied to the boiler at the Regional Office of the Trust at Westley Bottom a mile away. An independent assessment concluded that extracting this amount from the estate on rotation would be sustainable.
Removal of timber from the estate first started in autumn 2014 when ‘harvesting’ machines extracted non-native softwood trees like Western Red Cedar, Norway Spruce and Larch, from a small area of Lownde Wood in the south of the estate. The logs had to be stacked nearby as the wood chip store still had to be built. This was to be located next to the existing wood store in the north of the estate. In September last year, harvesting of softwood resumed in Lady Katherine’s Wood on the east side of the estate (photos 1 & 2). The harvester cuts the tree at its base, and as the trunk is lifted up, it is fed through rollers. Knives strip the branches off the trunk, and a chain saw cuts the trunk into 12′ lengths. This all seems to happen in just a few seconds and it is fascinating to watch.
These plantations of softwood were likely planted forty or fifty years ago but they had not been managed for a long time. Not all of the softwood is cleared, no more than 30% of the canopy in fact (photo 3). This is to keep some cover for wildlife until the wood is replanted with native broadleaf species that will improve biodiversity. It also serves to protect the wood from strong winds which could blow down thinly spread trees. Standing and fallen deadwood is left, again for the benefit of wildlife.
The land for the wood chip store had by this time been cleared so all the timber, including that from Lownde Wood, was taken up to wood store in the north of the estate (photos 4) where it was piled into five long stacks (photo 5), enough timber to last Ickworth’s needs for an estimated three and a half years. Ideally the timber needs to be stacked for 18 months to 2 years to dry out before it is chipped.