Estimation of cation and anion leaching characteristics and dissolved BOD-adsorption capacity of homemade charcoal produced by community participation

The cation and anion leaching potential and the dissolved BOD adsorptive capacity of homemade charcoal (made from Japanese cedar trees, salix and cherry) and commercial charcoal (made from white oak (Binchotan) and mangrove species) were examined by laboratory experiments to explore the ways in which charcoal could be applied to improving water quality for use by communities. After the immersion of charcoal in distilled water, EC, pH, and ion concentrations continued to increase in the water for 30 days due to some components of the charcoal leaching from the charcoal. The most dominant ions in the water samples were K(+), Na(+), and Cl(-) depending on plants species from which charcoal were made, but the total amount of ionic compounds leached from charcoal was the lowest in the homemade charcoal made from Japanese cedar. The homemade charcoal had a BOD adsorption capacity equal to that of commercial Binchotan, which has recently attracted considerable attention as an excellent adsorbent. Therefore, it was apparent that the homemade charcoal produced from readily available, discarded lumber has considerable potential for water quality improvement. While Binchotan is considered too expensive for use as an absorbent for local environmental remediation efforts, the homemade charcoal made using our simple iron kiln is inexpensive to produce and can be used continuously. Given that remediation of the regional aquatic environment requires sustainable daily effort, homemade charcoal, which is cheap, easy to produce and exhibits a relatively high adsorption capacity, is more suitable for this purpose than expensive charcoal. Especially, the homemade charcoal made from thinned-out cedar contains only a few materials that are eluted upon being submerged and that it is suitable for elimination of water contaminants when submerged in water, without causing secondary water pollution due to leachate. Given that the thinning of trees in forests of Japanese cedar is indispensable for conservation of soil and water conditions in mountainous areas, the effective use of thinned-out cedar trees is one of the most important subjects for natural land management. However, the change in water quality associated with treatment using charcoal needs to be carefully considered; changes such as an increase in the concentrations of ions and other substances, or the increase in pH associated with leaching from charcoal when it is submerged in the water need to be assessed a priori.