Heather (Calluna vulgaris) is one of the dominant plant species of heath and moor – particularly in upland areas. In such areas, land managers may burn back areas of heather (in a selective fashion) to create better feeding for sheep or grouse. Left to grow, heather can form a ‘blanket’ that makes for poor grazing in a nutritional sense (more woody material – lignin, that is essentially indigestible) and can give rise to intense fires in dry, hot summers. The selective burning / rotational burning of heather moors has been questioned in recent times as the underlying peat, and also water quality, may degrade.
Present burning practices are estimated to release energy - some 821 PJ/yr *. However, if the U.K.’s heather was to be harvested as a biofuel or bioenergy crop** then it could yield as much energy as 1.7 million tonnes of coal per year. This would represent some 15% of the U.K.’s 2020 biomass target and it could be achieved without the loss of highly productive farm land.
Heather generally grows in ‘unproductive’ areas of heath and moorland. Professor F Worrall (Durham University) has calculated this potential energy yield from heather by :
- Determining the energy released from (dried) heather samples to calculate the energy value per M2 of heather (energy content can be calculated using calorimeters).
- Using the results of the Countryside Survey to work out the area of heather coverage throughout the U.K.
- Estimating the energy costs involved in harvesting heather and transporting it to suitable incinerators.
Clearly, there would be problems in using heather – not the least of which being the 'ingrained' tradition of land use,but here would also be problems with cutting / harvesting / baling, without damage to the ecology and stability of these special ecosystems.
(Note : Some heather is currently harvested and baled as a seed source, for using in re-establishing heather on old conifer plantation sites).
* PJ = Petajoule: unit of energy measurement equal to1015 joules