The objectives of this study are to clarify the fuel procurement range of woody biomass power plants and the shape of the fuel, and to determine whether the fuel is actually sufficient or not. To realize the above objectives, a questionnaire survey was conducted for power plants using wood-based fuels, excluding the ones using only general waste. The results show that some plants of which the rated outputs are less than 10 MW can procure from only the located prefecture, whereas the plants having higher outputs can procure from overseas. The result shows that when the rated output becomes 1 MW or more, cases of fuel procurement extending beyond the prefecture will increase. The rated output of 5 MW is the minimum scale to ensure power generation efficiency and may require fuel procurement outside the prefecture. Therefore, if such plants operate in each prefecture, fuel procurement may become competitive and difficult. In addition, the solid fuel mostly comes in the form of chips, and the amount of unutilized wood procurement is smaller than planned. With these facts, it is predicted that the price of unutilized wood chips will increase, and from our results such a trend might be seen; however, no such trend could be found from published statistical data.

The profitability of a biomass power station is low because its installation cost and fuel cost are high and its power generation efficiency, around 25%, is lower than the efficiency of an LNG power station, about 50%. On the other hand, the profitability of a combined heat and power (CHP) could be higher since it sells both electricity and heat. To prove the profitability of a CHP plant, we developed a tool for assessing profitability on a steam turbine CHP system using wood biomass. Then we assumed four plant sizes, i.e. maximum power output 1,200, 1,600, 1,999, and 5,700 kW, and simulated the internal rate of return and other factors, under the following three scenarios: 1) stand-alone (without heat supply), 2) CHP with steam supply and 3) CHP with hot water supply. We decided two heat prices, 7.7 and 5.2 yen/kWh, referring to the heavy oil price. We found the following results: a) The profitability of CHP became higher than that of the stand-alone case. b) In the case of the 1,200 kW plant, the CHP project could not make a profit under the lower heat price because of its lower power generation efficiency. c) The profitability of CHP with hot water supply became higher than that of CHP with steam supply because the decrease of power output by steam extraction was smaller. d) Larger heat demand is necessary to make the profitability of CHP higher.

This paper examines potential for three wood biomass power generation plants operating in Hokkaido, especially in terms of unused wood, which is called D rank wood, in an artificial conifer forest. We considered transportation cost and chipping cost by a forestry organization in Hokkaido, and the maximum purchase price of unused wood that would maintain the power generation plant's 8% internal rate of return. We used the business simulator for woody biomass power generation and cogeneration to estimate the maximum purchase price. In conclusion, the price was estimated to be about ¥6,200-¥12,500/m³. We conclude that even though every power generation plant could maintain their 8% IRR with D rank wood sourced from nearly 50 km away, thus giving an annual supply potential of 12,000-88,000 m³, this which would fall short of the required demand volume when the plants were approved.

I investigated the supply of woody biomass to power plants in central and northern Miyazaki Prefecture, where the demand is high, to identify important considerations in establishing a stable supply. Interviews with power plant companies, collectors, suppliers, and supporters informed this study. Power plants and collectors have taken steps to secure a stable supply of woody biomass. They have established, maintained, and strengthened a collection network; have provided increased benefit to suppliers by raising log prices and reducing handling charges; have made it easier for suppliers to provide woody biomass by collecting it at wood yards in the mountains; accept unsorted logs; produce woody biomass; and purchase lumber remnants such as treetops, branches, and twigs. The prefecture office and forestry industry bodies have provided support for information sharing among power plants, collectors, and suppliers, and established consultative meetings aimed at stabilizing the supply. Finally, suppliers have considered financial benefit, convenience in providing woody biomass, the market strategies of affiliated organizations, dedicated negotiating personnel at power plants, the confidence in and stability of the business, and unfixed trade. At this time, the approaches taken by power plants and collectors are generally consistent with what suppliers consider important. To maintain a stable supply, current approaches should be continued and strengthened, but cooperation among suppliers needs to be addressed for long-term stability.

　We used a simulator, which can estimate profits of woodland owners from the management of individual forest stands based on numerous sets of forestry-related parameters such as log prices, to identify the most profitable clearcutting rotation age and thinning frequency. We analyzed the effects of rising demand for woody biomass for mainly power generation. The assumed stands are planted Sugi (Cryptomeria japonica) forests in northern Tochigi Prefecture, where ground-based logging systems are predominant. The results showed that soil expectation value (SEV) was negative under many sets of parameters, and long rotation age was preferred in order to postpone the payment of replantation costs after clearcutting. However, because of the assumption that relatively low-cost logging operation was available and the log demand of sawmills was high, there were many sets of parameters where moderate rotation age (e.g., 65 years) and assumed maximum thinning (three times) were chosen as the optimum practice. Assuming a price increase of logs for energy production, the optimum thinning frequency had been scarcely changed, and the optimum rotation age was mostly unchanged or shortened by 5-10 years. The effects of a rise in biomass demand on optimum rotation age and thinning frequency were limited, but the shortened rotation age may support the economic rationality of the recent implementation of clearcutting in this region.

We investigated the effects of bucking methods of crooked Sugi trees on the production volume of low-quality logs for biomass power generation and bucking time. Two methods, i.e., quality bucking and quantity bucking, were examined. In quality bucking, the crooked portion and defects existing within the stem are removed. In quantity bucking, log bucking is performed with a pre-selected log length, irrespective of crookedness or defects. Diameters, lengths, grades (A, B, and C) of the logs, and bucking time produced by the two bucking methods were determined. On average, in quantity bucking, merchantable volumes increased by 5% as compared with those in quality bucking. When quantity bucking was performed, the proportion of grade C logs increased while that of grade B logs decreased, compared with those when quality bucking was conducted. In quantity bucking, bucking time decreased by 20% on average compared with that of quality bucking. Using the statistical models developed in this study, log volumes for each grade were estimated from the tree data for 48 sample stands. Consequently, when quantity bucking was performed, the volume of grade C logs increased 39% on average compared with that when quality bucking was conducted. However, the profits from quantity bucking typically decreased compared with those from quality bucking.

This study estimated the supply potential and availability of unused materials for woody biomass power generation in the Japanese cedar and cypress forests of Tochigi Prefecture. Then, the long-term possibility of supplying fuel woods to the existing power generation plant and the locations of the newly established power generation plants were examined. As a result, supply potentials of used and unused materials were estimated at 1,003,745 m³/year and 394,042 tons/year respectively, whereas those availabilities were estimated at 430,561 m³/year and 169,125 tons/year respectively. Although those availabilities were reduced to 102,835 m³/year and 40,110 tons/year, respectively, while considering profits of forest owners, this availability of unused materials could meet the demand of the existing power generation plant which consumed 35,000 tons/year. Furthermore, small-scale gasification power generation plants could be installed in two cities of Tochigi Prefecture using the surplus availability of unused materials with profits for forest owners.

There are two woody biomass electric power generation plants in Kochi Prefecture, one (T) in the central area and the other (G) in the western area. Both started operation in 2015 with output levels of 6 MW, each requiring 70,000 to 90,000 m³ of biomass per year. Using existing documentation and interviews, we assessed their current and future biomass supply opportunities. With some difficulty, plant T has acquired a sufficient supply of biomass from logging residue, primarily due to its location in which mature plantation forests and logging contractors are abundant. In contrast, most woody fuel for plant G was from timber residue such as saw mill timber waste, due to the lack of matured plantation forests in the western part of the prefecture. However, the area has extensive un-utilized broad-leaved forests and a new trial has begun to supply fuel wood from them under forest management plans based on clear cutting regimes and appropriate rotation periods.