Carbon stock estimations for buildings have been examined by many studies. In almost all studies, carbon stock quantity was calculated by the floor area multiplied by wood / floor area ratio which was actually measured. The number of buildings, however, which have been constructed and demolished without registrations or reports, is still so many in Japan that it cannot be neglected in order to estimate carbon stock correctly. This is a main problem in carbon stock estimation for buildings. To estimate carbon stock more correctly and efficiently, quantities of wood products made in Japan and imported ones were used in this report. Quantity of wood products has been surveyed as each figure; lumber, plywood, glulam, etc. The quantity data obtained for each figure was sorted as its uses; for building, civil engineering, packing, furniture and the rest. Lifetime of wood products was set on each use. Year-by-year variation of still-used wood products was approximated as a logistic curve. Half-lives of logistic curves were set as lifetimes of products. If a lifetime of a building has been 25 years, the result was obtained that 147 million ton-C would be stocked as wood products in Japan from 1990 until 2012.
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