In 2018 Drax received £321.5 million [John1] in subsidies for burning wood to generate electricity. The payments are the result of the UK Government’s CfD (Contract for Difference scheme) which seeks to encourage electricity producers to move toward low-carbon, renewable sources of power. Under the scheme Drax receives £100/MWh of electricity produced, exceeding the strike price for Hinkley Point C £92.5/MWh (2012 prices).
In 2018, the 2.6GW biomass units at Drax’s Yorkshire power station burnt 7.2 million tonnes of wood to produce 13.75TWh of electricity. To understand how much wood that we must know the typical yield per hectare of forest.
A fast-growing UK Sitka spruce forest yields 14 m3 ha−1 year−1. The dry weight of Sitka spruce wood is 425kg/m3 [John2] Meaning each hectare adds 5.95 tonnes [John3] of biomass per year. [John4] A typical spruce forest is harvested after 35 years, providing 208 tonnes of dry wood per hectare at harvest.
Therefore, an area of 34,600 hectares, 150 squre miles, the size of the Isle of Wight, is required to produce 7.2 million tonnes of wood.
However, the forest takes thirty-five years to grow back. Therefore, for the cutting to be sustainable Drax power station requires 1.2 million hectares of exclusive forest area, two thirds the size of Wales. However, that isn’t the end of the story.
Drax claims it doesn’t burn virgin forest or use high quality timber, only thinnings, residue and sawmill waste. The UK forestry commission estimates that UK forests yield two tonnes/year of biomass (derived from wood thinnings and residue). If Drax burns 7.2 million tonnes of wood annually, then every second Drax burns 2.0 tonnes of dry wood. That is the equivalent growth from one hectare of forest in a year. Therefore, to be sustainable, according to their own metrics, Drax requires a forest area of 7.2 million hectares. 72,000 square kilometres. A third of the entire United Kingdom.
This is for a single power station providing 4[John5] % of the UK’s energy. If the United Kingdom supplied 20% of its electricity from woodchip biomass it would need an exclusive forest the size of Germany.
If the world generated 20% of its electricity equivalent to 855TWh in similar woodchip burning biomass power stations then to be sustainable these operations would require a farmed forest half the size 1.3 times the size of Russia. Electricity production accounts for only 30% of energy used around the world.
As more biomass power stations come online slow growing native forest will be chopped down by unscrupulous governments and businesses and replaced by fast growing non-native species like Eucalyptus.
[John1]Page 126 CfD income
[John3]425kg x 14 cubic metres
[John5]13.725TWh / 333.9TWh *100
333.9TWh from pg9
pg 3. 0.75 x 18.3TWh = 13.725 of renewable generation from Drax biomass