Biomass & Bioenergy, Vol.9, No.1-5, 127-140, 1995
Mechanisation of short rotation forestry
This paper is split into two distinct parts since it addresses two very different crops grown in North America and Europe. In North America short rotation forestry is being developed principally to generate a feedstock for the wood pulping industry and is typically single stem hardwood plantations grown for 6 -10 years before harvest. In Europe by contrast, coppiced willow plantations are being grown as an energy crop and harvested on a 3-4 year cycle. In North America, the industry is being driven by the large pulp producing companies; plantations are designed to fit the local conditions and specialist mechanisation is generally not being used. Rather, the companies are using standard agricultural or forestry practices for planting and husbandry and using the crews which already exist to harvest the crop. This paper describes the type of plantations which are being used and the mechanisation which is being applied. In Europe, the coppice crops are grown commercially in Sweden and will shortly be planted on a commercial scale in the UK. In Sweden, the resulting wood fuel is fed into the many wood fired district heating plants and combined heat and power plants. In the UK, the majority of new planting will be used to fire power generation plants working on the gasification principle. Three plants have been given contracts to generate electricity under a premium price scheme and this could result in the planting of 8,000 ha of coppice. Sweden has lead the development of mechanisation for the crop and two harvesters are now considered to be commercial; they are based on existing machines for harvesting forage and sugar cane. Planters are also at the commercial stage of development and machines for weed control have been tested. This paper covers the machinery developments and discusses issues relevant to the mechanisation of the crop such as : whether to harvest as chips or as whole shoots (sticks), the impact of soil compaction, weed control and plantation layout.