Biochar blocks are a new material that is expected to be used as a greenhouse gas reduction measure called carbon recycling, a negative emission technology that reduces CO2 emissions by capturing CO2, which is considered a cause of global warming, as a carbon resource and reusing it as a variety of carbon compounds. We believe that the development of materials utilizing biological resources such as biochar, rather than fossil resources, will become increasingly important for building a sustainable society.
Development of biochar blocks as carbon stock and Regeneration Architecture project for water purification of Lake Sanaru.
Until a few years ago, Lake Sanaru was one of the worst water quality lakes in Japan, and various water quality improvement efforts are being actively undertaken by the government, universities, and organizations. In order to contribute to the purification of the water quality, we focused on biochar, which is made by reusing mandarin tree branches, an unused local resource. Biochar has a high function in water purification. In collaboration with a paving block manufacturer, they succeeded in developing Japan’s first “biochar block” inlaid with biochar made from carbonized branches and trees. The biochar blocks were used for the exterior and interior, and approximately 21 tons of biochar was utilized. The biochar blocks finished on the exterior walls promote rainwater purification, and the rainwater flows through the copper plate roof, which has the same water purification properties as the biochar, and is discharged into the exterior planting area, percolates underground through the biochar also laid in the soil, overflows into the wetland, and flows to Lake Sanaru. This is a regenerative material development and architectural approach to carbon neutrality that utilizes unused local wood resources and positions biochar as a means of regenerating the water resources of Lake Sanaru.
The mountains surrounding Lake Sanaru are home to mandarin oranges, and we asked a charcoal artisan who converts the waste branches and trees cut down there into biochar, and a pavement block manufacturer to collaborate in the development of biochar blocks. Instead of blending the biochar into a powder, the biochar blocks were inlaid into the cement in their original organic form, creating a beautiful expression. To prevent the biochar from peeling off from the cement, the biochar was first coated with noro paste, allowed to dry, then laid out on a pamphlet and poured with cement. Furthermore, by mixing the rice husk smoked charcoal with cement, the charcoal was utilized as an admixture that reacts with the calcium hydroxide produced by the hydration reaction of the cement, resulting in greater strength and durability than blocks with no admixture.
To verify the effect of the biochar blocks on lake water quality improvement, water quality was measured at a total of 60 points along the seawall of Lake Sanaru, and COD values dropped from about 8.0 mg/L three years ago to about 6.0 mg/L, showing the effect of water quality improvement. In addition, the use of 21 tons of biochar resulted in 59 t-CO2 of CO2 storage, a value 1.4 times higher than that of a wooden structure of the same size and 5.4 times higher than that of an RC structure, contributing to CO2 reduction.
