Energy Consumption and Greenhouse Gas Emissions Associated with Rice Production in Rice Terraces

Abstract

The energy consumption and green house gas emissions associated with rice production in rice terraces were estimated by using the life cycle assessment (LCA) method. We conducted a survey on two farmers in Hoshino village, Fukuoka Prefecture, Japan. The energy consumptions for farmers A and B were 29,254 MJ/ha/Year and 29,637 MJ/ha/Year, respectively. The energy consumption due to fuel use accounted for the largest portion of the total energy consumption. We believe that the contributory factors are the inherent topographical disadvantages of rice terraces, which entail long hours of mowing in paddy levees and slopes and decrease the efficiency of machine operations. The surveyed farmer A has reduced his energy consumption by reducing fertilizer applications in accordance with the environmental conditions in mountainous areas. The carbon dioxide (CO₂) emissions for farmers A and B were 1,980 kg/ha/Year and 1,998 kg/ha/Year, respectively, which are approximately identical to that previously reported. The nitrogen fertilizer application amount was low for farmer A and led to a reduction in the nitrous oxide (N₂O) emission. The CO₂ equivalent emissions of greenhouse gas for farmers A and B were 6,533 kg CO₂/ha and 6,613 kg CO₂/ha, respectively, which are approximately identical to that previously reported. The percentage compositions of methane (CH₄), CO₂ and N₂O in the entire CO₂ equivalent emissions were approximately 68%, 30%, and 1~2%, respectively. Our results corroborate the conclusions of previous reports that reductions in methane emissions are important.