Short-rotation forestry

Chemical iajections iato piae trees have been reported to have stimulatory effects on the natural production of resias and terpenes and may result ia high yields of these valuable chemicals. Combiaed oleoresin—timber production ia mixed stands of piae and timber trees is under development, and it appears that when short-rotation forestry is used, the yields of energy products and timber can be substantially higher than the yields from separate operations. 

Considering the full production cycle, methanol from biomass emits less carbon dioxide than ethanol from biomass. This is because short rotation forestry, the feedstocks of methanol, requires the use of less fertilizer... 

Woody biomass. As mentioned earlier, wood is the oldest biofuel. Conventionally, wood would be harvested from forests by simple logging. This conventional method does not replenish the harvested wood and is therefore not sustainable. The current paradigm is to grow wood specifically for purposes of harvesting by means of short-rotation forestry. 

Short Rotation Forestry has relative good potential to be used in non arable land and provides a sustainable approach to energy (22), however, since the land has to be blocked for about 15-20 years, fanners in the EU are reluctant to implement SRF schemes. The only exceptions are Sweden, where there is a long tradition for SRF mostly for pulp and paper and the UK where recently successful schemes have been introduced to the farming community (23). The USA (24) has also an ambitious programme for the development of SRF while Canada also has carried out significant work and is examining various SRF implementation schemes. Brazil has successfully established eucalyptus plantations (23). On the other hand, very few tests have been carried out with SRF feedstocks and the industry is a somewhat uncertain about the properties of SRF fuels. A sensitive area is that of heavy metals some of which are easily up taken by the plants (e.g. cadmium). 

The supply of the coppice will be undertaken by Yorkshire Environmental Ltd., which will try to maximise the utilisation of biomass fuels supplied by short rotation forestry. Slurry of domestic treated sewage sludge supplied by Yorkshire Wafer Services Ltd. will be applied to the coppice plantations as organic fertiliser to increase crop yield. The sludge will be low in heavy metal, pathogens and odour. Waste ash from both the gasifier and the catalytic cracker will be recycled to the coppice plantations as a soil conditioner and source of base cations and micronutrients to improve soil fertility. 

Leadership in short rotation forestry lies in the sub-tropics. Table 5.6 represents a typical regime for Firms taeda in Brazil, i.e. all trees are pruned in the first lift and potential final erop trees only in the second lift. Improved genetics and management have raised average productivity of pine plantations from 18 to 23 to 33 m /ha/yr in the sueeessive deeades, in the 1970s, 80s and 90s respectively. Whether eorewood quality issues have been addressed remains to be seen. 

If there is an explieit message it would be the neeessity of seeing one s loeal plantation timbers in eontext, to understand the enormous variability within and between speeies, and to appreeiate the opportunities offered by diversity. Short rotation forestry favours hardwoods, but the ease has to be argued step by step. 

Producing methanol from biomass or coal costs about twice as much as producing it from natural gas. This encourages the use of nonrenewable petrochemical sources over biomass or coal. Considering the full production cycle, methanol from biomass emits less carbon dioxide than ethanol from biomass. This is because short rotation forestry, the feedstocks of methanol, requires the use of less fertilizer and diesel tractor fuel than the agricultural starch and sugar crops which are the feedstocks of ethanol. 

A further possibility for wood fuel production is for intensive short-rotation forestry when small trees might be harvested every five or ten years with a mobile mower/chipper laid out similarly to a grain combine. Such a machine might be expected to cover one acre per hour for a throughput of about 20... 

Nine hardwood species were investigated as fuelwood in short-rotation forestry with the astonishing result that the observed differences in the caloric values of woods were just 4 % (mean 20.0 kJ/g) and that only bark (with less importance as fuel due to its small contribution to biomass) showed larger variations of up to 13 % (mean 20.08 kJ/g) [56]. Highest energy contents were found in leaves (21.13 kJ/g ovendry). Thus, biomass yield and ecological tolerance will have more influence on the specific harvest than the caloric values. 

---