To perform the conversion into compost or aerobic decomposition of organic waste by preparing a waste content adjusting material for the biotreatment of organic waste containing coir pith.

Coir pith is the residue left after fibers being removed from the mesocarp of coconuts, rich in lignin and cellulose, porous, and water absorbent, has a good water-retaining effect, and demonstrates a good reinforcing effect due to its fibrous structure. A water content adjusting material for biotreating organic waste is produced by using coir pith, organic waste is mixed with the coir pith. By ventilation and fermentation, the organic waste is composted or decomposed aerobically. The water absorption per unit weight of coir pith is 12 g-water/g-coir pith which is nearly five times as large as that of sawdust. By using coir pith as a water content adjusting material, the reduction of addition percentage of the material can be attempted.