Effectiveness evaluation of energy crops production as a biofuel sources
Abstract
Energy crops are grown for energy purposes. Traditionally energy crops are corn and sugarcane which are grown for industrial scale ethanol, rapeseed for producing biodiesel, annual and perennial grasses, for example cane, miscanthus, cereal straw, as well as fast-growing tree crops for biomass production. The most interesting for the temperate climate zone of Europe are the fast-growing willow species. The interest in growing energy crops, which can be used as a renewable energy source, in European countries arose in the 1970s, which was related with rising prices for traditional energy sources. The growth of energy crops has been fueled by political decisions at the international level, in particular by documents such as the Renewable Energy Development Plan for Europe and the Kyoto Protocol. After some recession, landing areas for energy crops in the EU and North America have been stabilized. The fastest growing willow occupies the largest area in Europe. The average yield of willow wood in our experiments was about 50 tons per hectare at a moisture content of 45%, with a three-year biomass harvest cycle or 9.2 tons per year and dry matter from 9 to 15 tons per year per dry biomass, in depending on the conditions of cultivation, soil, clone. The weighted average cost of one ton of willow wood with a moisture content of 10% at an area of 100 hectares of plantation for its lifetime (22 years) will be $ 30.5. The cost of growing willow, transporting and shredding timber at a plantation area of 30 hectares is about $ 510 per hectare. About half of all biofuel production costs are depreciation deductions for the operation of special planting and harvesting equipment. The expansion of the plantation area 3–4 times compared to the base variant (30 hectares) allows to increase the profitability of energy production by 30–50%. The return on initial costs required to organize a willow plantation depends on the use of biomass. When replacing wood with traditional energy sources (natural gas), according to our calculations, the simple payback period is 3.8 years and the discounted time is 4.7 years, which corresponds to the time of harvesting the first biomass crop. With the direct sale of biomass on the market in the payback period increases to 6–11 years, which corresponds to the second or third harvesting period (with a three-year cycle). The unit cost of energy derived from willow wood is lower relatively to other energy crops, but 1.5 times and 1.8 times higher than that of natural marsh vegetation and straw, respectively. However, the additional interest in planting willow is due to their conservation value. The main indicators for calculating cost-effectiveness have been taken experimentally. The higher combustion heat of the above-ground part of the willow tree stand averaged 18500 kJ/kg. This is in line with the results obtained by other researchers for willow wood. The maximum specific heat of combustion of willow wood according to the results of experiments carried out in Sweden ranged from 18.3 to 19.7 MJ/kg, depending on the harvesting time and the willow clones. Therefore, we can confidently say that to grow energy willow is expediently and cost-effectively.
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