Abstract
A simplified and comprehensive model to evaluate energy flow and renewable resources was introduced into the region of our case study, Yasato-cho, Ibaraki. This model shows a picture of agricultural use of energy in individual agricultural domains. In the analysis of energy flow, the agricultural system of the region was divided into three subsystems, that is, the primary production, the secondary production and the soil subsystems. In the primary production subsystem, total annual energy production was estimated to be 5.79×102 TJ, of which 1.93×102 TJ was contained in agricultural products, 2.21×102 TJ in by-products, 2.38×10 TJ used for animal husbandry and 1.37×102 TJ recycled into the soil subsystem. Artificial energy input was 2.44×102 TJ. The efficiency of conversion of photosynthetically available radiation for total primary production was 0.52% and the output/input ratio was 0.79. In the secondary production subsystem, total annual energy production was estimated to be 5.18×102 TJ, of which 1.34×102 TJ contained in animal products and 3.84×102 TJ remaining in animal excreta. Artificial energy input was 3.49×10 TJ and feed energy from outside the system was estimated to be 1.03×103 TJ. The output/input ratio was 0.12.
