[in Japanese]

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A method was investigated to provide logs to a woody biomass electric power generation facility in the western part of the Kochi Prefecture, Japan, where unmanaged broad-leaved tree stands are periodically clear cut and allowed to naturally regenerate over a defined rotation period. We carried out a trial project in which a coastal broad-leaved tree stand of ca. 10 ha was prepared as a test site, the stand was clear cut, and logged via a cable logging system. The average stock volume at the site was estimated as being approximately 300 m³ /ha as determined using a series of sample plots. A total of 572 tonnes of logs were extracted during a four month period, from an area of ca. 3 ha. The operation was not economically viable: the average logging cost was 12 thousand yen/t including rigging up and logging, whereas the income was only 4.8 and 3.7 thousand yen/t for logs and logs including twigs, respectively. The average efficiency was 2.6 and 2.1 t/man-day for logging only and logging and rigging up, respectively. A minimum two or three fold increase in efficiency would be required to avoid a cost deficit. The low efficiency in the logging operation was due to the time required to perform lateral logging for cut trees dispersed throughout the coup. Logging efficiency would be enhanced by up to 20 percent if a threshold was set to utilize only larger diameter trees.

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