The population of Japan is decreasing, particularly in rural areas. The amount of sewage to be treated has decreased with the decrease in population. However, the current sewage treatment process is designed for the higher population and does not fit the lower population. In this study, five scenarios were considered and compared in terms of the economy and carbon dioxide emission. Taking a typical Japanese rural area as an example, we evaluated the effects of population changes on sewage sludge treatment.　　

This study targeted Akita City, Akita Prefecture, Japan, and aimed to design a district heating and cooling system using renewable energy to decarbonize heat. A heat demand map was created, and target buildings that were candidates for demand were selected from areas with high heat demand density. A district heating system based on the available supply of waste heat from waste incineration and the heat demand of the target buildings was designed. The heat loss, cost, and carbon dioxide reduction of the designed system were evaluated.

The NPV of a gasification CHP project of less than 50 kW was calculated for the case where a subsidy for the installation of equipment was utilized. Under this set of conditions, we were able to confirm the generation of monetary value from the investment. However, the probability of a positive NPV is slightly more than 50% when considering the price fluctuation of heat and electricity, and it is necessary to plan on the implementation of this investment project with the understanding that the project is strongly affected by the prices of electricity and heat.

The objective of this study is to estimate the potential of woody biomass, taking into account forestry management costs, based on forest inventories. It also optimizes the use pattern and determines the amount of electricity generated and the unit cost of electricity generation at that point in time. Although subsidies have a large impact, the maximum amount available was 350,000 m³, 1.68 times the actual production. The supply chain consists of 84 million kWh from single-firing power plant in Akita City and 10.2 million kWh from distributed CHPs, for a total of 186 million kWh. This is 3% of Akita Prefecture's annual electricity consumption, at an average cost of 28.8 yen/kWh.

Woody biomass power generation plants exsert significant amounts of ash during operation. Although powder-ash has been used as fertilizer, there has been little use of clinker-ash, which is hard and usually has different size distributions. A company operating a woody biomass power generation plant in the western part of Kochi Prefecture, Japan, started to distribute clinker-ash for use as a paving material for secondary/spur roads in forested areas, especially where the soil is prone to erosion. In order to obtain approval from a local government to use clinker ash as a road paving material, a series of field tests were conducted to certify the strength of the road surface. The result showed that the road surface had sufficient strength compared to the control, i.e. unpaved road surface with bare soil. There may be a chemical influence around the areas where the spur roads are paved with clinker ash because it has rather high alkalinity. While tests for alkalinity around the paved spur roads are underway, it seems that the alkaline effect would be negligible, partly due to the intrinsic nature of low acidity over forest soils.

We have developed a model for assessing the potential wood biomass in artificial forests within non-restricted forest areas, with the aim of ensuring sustainable, long-term utilization of forest resources. We applied a bottom-up approach to this evaluation. Using forest inventory and area data for all prefectures, we extracted information on area, timber volume, tree species, and age of forests for each forest unit. From these analyses, we calculated the volume of woody biomass per forest area and aggregated the results for each of the 1,741 municipalities.

In this study, the effect of ambient gas on the decomposition behavior of chlorine was investigated by changing the ambient gas during the torrefaction treatment of agricultural waste. Superheated steam was used as the ambient gas during the torrefaction process, the yield of char and elemental compositions were compared. And the surface of the char was observed by SEM. As a result, it was found that the char yield was lower in the case of pyrolysis with superheated steam than in the no-steam torrefaction. There was no difference on the surface observation of the chars by SEM. And the superheated steam made the yield of chlorine lower than no-steam torrefaction process.