71. 下水に含まれる肥料資源と廃熱・排出CO₂を供給し甘藷の光合成効率を高めメタン・水素生産に利用する資源循環システム

抄録

For mass-produce methane from sweet potatoes as a hydrogen fuel resource, we investigated a method to increase photosynthetic efficiency by supplying fertilizer, exhaust heat, and CO₂, contained in wastewater. When treated wastewater was applied to sweet potatoes as a liquid fertilizer, part of the leaves turned yellow and the photosynthetic activity of the sweet potatoes tended to decrease. In addition, it was found that the Ca content, which is supposed to suppress the decomposition of chlorophyll by UV, was low.

On the other hand, the yield of sweet potatoes increased by nearly 30% when shielding with a film that attenuates the UV and heat rays of the sun. These results suggest that in order to increase the photosynthetic efficiency of sweet potatoes, it is necessary to suppress strong UV rays and overheating in summer, and to supply additional Ca fertilization.

It was found that the CO₂ concentration increased when exhaust gas was supplied from the wastewater aeration treatment tank, and sweet potatoes grew vigorously. So far, we have reported that sweet potatoes can be cultivated even in winter when treated wastewater is supplied, and it was suggested that the introduction of exhaust gas will increase the heating effect beside the CO₂ fertilization.