Let trees grow

In his letter of 10 January on the use of wood pellets as fuel, Drax CEO Andy Koss claims the company has delivered carbon savings of 80 per cent.

Figures from Drax in 2013 showed it emitted 13 per cent more Co2/unit of energy than from coal. Mr Ross also claims that Drax wood pellets sourced from the US are only made from tree tops, branches, sawmill residues, sawdust etc – not pulpwood.

An investigation by the EU and the US Forest and Paper Association concluded that tops and branches are poorly suited for industrial wood pellets; that mill residues form an insignificant part of pellet feedstock, virtually all sawdust is used for particle boards and pellets are actually 75 per cent from pulpwood, ie whole trees.

Pine trees can live 150 years and continue growth throughout, fixing CO2 into trunk, needles and roots. When death intervenes, decay and CO2 release is slow and minerals are recycled. When 40-year old immature trees are cut down to make pellets, the trunk and needle minerals are lost, depleting the soil.

The root system (one third of the tree mass) decays, no longer increasing fixed carbon. Incineration leads to immediate increases in atmospheric CO2.

There is also evidence that natural forests have been cleared to be replaced by more profitable monoculture pine with evident depletion of biodiversity. The best result for climate change and conservation is to leave trees in the ground, not burn them. (PROF) ANTHONY TREWAVAS

FRS FRSE Alliance Scotland North St David Street

Edinburgh