From Raymond Gray
In his article on energy from biomass, Colin Barras says that the problem with it is that felled trees have an energy density of only 7 gigajoules per tonne (11 October, p 39). True, newly felled trees contain 50 per cent moisture or more. Chipping wood in this condition and then transporting it in bulk to a power plant many miles away to generate electricity is senseless.
Cutting wet wood into small logs and air-drying will bring the moisture content down to less than 20 per cent and increase the energy content to over 14 gigajoules per tonne. Admittedly this demands time and space, but doubling energy output surely has to be worthwhile.
Minsterley, Shropshire, UK
