Abstract
An inventory analysis method was carried out to estimate the direct and indirect energy consumption of mechanized rice production system using the database of inter-industry relations table. The specific energy consumption of the rice production process was calculated by taking into account the life span and operating time of agricultural machineries. The total direct and indirect energy consumption of 22,621 MJ/ha and 62.8% of total direct energy, respectively for Utsunomiya University farm (area: 7.2 ha, yield: 4,650 kg/ha, 2001) was calculated as the standard example of inventory analysis for rice production system. The application of chemical fertilizer and agricultural machinery operation also resulted in large indirect energy consumption during the production process. The possibility of reducing energy use for agricultural machineries, material in production process, and low-input rice farming in the university farm while sustaining rice yields were analyzed by comparing the data from other paddy fields with conventional cultivation practices, and from previous published data. Adoption of rice production technology that reduces operating time for cultivation, paddling, planting, harvesting, drying, as well as reducing chemical fertilizer application by using organic fertilizer, are the primary factors in increasing the energy efficiency (output/input) of rice production. Furthermore, the importance of utilizing heat from burning of rice, chaff, and straw produced by rice cropping system was emphasized because of the lower output/input energy ratio (1.47 or less ) of ethanol fuel-based rice production system compared to other energy utilization of biomass.
