科研之友
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摘要
Lack of energy for powering irrigation pumps limits off-season production of rice in Malawi. This paper reviews a 10-year historical rice production data from rice farms in Karonga district in Malawi to assess the impact on rice yields and availability of straws and husks for on-site bioenergy production in small scale gasifiers, to power irrigation pumping during off season over a projected period of 15 years. Annual production of rice straw and husks has been estimated using residues to product ratio while taking into account collectable amounts and allocations to competing uses. The heating values obtained from literature and validated by analytical Gross Calorific Values of straws and husks have been used to estimate the bioenergy potential. Irrigation pump capacity and pumping rate calculated from daily water demand, and carbon emissions savings determined from the differences between emissions generated by fossil diesel and bioenergy powered irrigation have been used for calculating environmental benefits. The sales of excess rice provided estimates for financial gains. In the base year, generation of straws and husks of about 44117 and 6703 t and collectable portions of 40% and 65%, respectively, are estimated, providing a total bioenergy potential of 16.64 GWh. With onsite-generated bioenergy, irrigated land can increase from 2367 to 13362 ha while rice and bioenergy production increases from 34703 to 59970 t and 15.34-87.72 GWh, respectively, by the 10th cycle. Cumulative revenue of US $354.60 million from sales of excess rice and net carbon emissions saving of 285.33 kilotonnes can be achieved by using electricity generated for irrigation pumping. Investment costs in electricity generation can breakeven by 8th year if sold at US0.166/kWh. Therefore, on-site generated bioenergy targeting irrigation pumping for off-season rice production is an enabler for promoting positive and sustainable fuel/food nexus in rice farming communities through intensive farming.
- 出版日期2017-8
