What is woody biomass?
Woody biomass comes from trees and woody plants growing in forests, woodlands and rangeland environments. As a fuel it is not new, seeing as the use of wood as fuel for heating purposes is likely older than civilization itself. During Industrial Revolution fossil fuels became the ideal energy source and took over the world’s wood-fueled economy. The energy crisis and growing concern about CO2 level has resurged interest in woody biomass, as large volumes are obtained in the process of thinning forests to remove diseased trees and prevent wildfires. Woody biomass also comes from trees damaged or destroyed by natural disasters, by-products from the timber industry, agriculture or crop residues as well as from yard trash. Most of this material either reaches landfill sites or is burned or left to decay. This woody biomass can become raw material to produce energy in the form of heat, fuel and electricity without the cost of cultivation.
Energy crops are another source of woody biomass. Fast growing plants or trees and other herbaceous biomass are harvested for energy production. Willow and poplar trees are high yield varieties of woody biomass. Species are selected depending on climate and soil conditions. These energy crops are used as feedstock to produce advanced biofuels such as cellulosic ethanol and as heating fuels. They can also be used as solid fuel either alone or in combination with other fuels in electric power generating stations. Short-rotation woody crops are fast growing hardwood tress that can be planted on marginal lands which are not suitable for food crops. Harvesting takes place in a 2-5 year cycle, and only small portions of branches and leaves are removed leaving established root system which helps in conservation of nutrients in roots and stumps for vigorous growth of new shoots. A plantation can be harvested for up to thirty years before being replanted.
Woody Biomass is most alluring in its potential to be used as liquid transportation fuel. Cellulosic ethanol from woody biomass can help resolve food vs. fuel controversy as most of the ethanol used as biofuel today comes from corn, sugarcane and other food crops. New gasification and fermentation technologies are being developed for the successful commercial production of cellulosic ethanol.
Sustainable woody biomass utilization is an option to mitigate negative climate change effects, and it has the potential to increase the share of renewable energy in the world energy mix.