Water scarcity will become a serious problem due to climate change and population growth. In this research, we have introduced a water-saving mist cultivation system, comprising a sealed container and an ultrasonic mist generator. One of the features of this system is the intermittent supply of nutrient solution in mist form. We confirmed that optimization of water supply frequency enabled operation with about 70% less water, 65% less CO2 emission, and 84% less nutrients compared to conventional hydroponics without scarifying the yield of lettuce. In addition, we found that the sugar content in tomato could be increased by controlling the watering frequency and time.

Kandelia obovata, one of the mangrove species, provides a low-cost solution for recovering heavy metals and improving water quality, which could be useful, especially in developing countries with limited wastewater treatment. In this research, we found that heavy metals such as arsenic, cadmium, and lead accumulate in the fallen leaves of Kandelia obovata.

Fallen leaves contain six times more cadmium than young leaves. By collecting these fallen leaves, along withother toxic heavy metals, about 2.01 kg of arsenic and 1.29 kg of cadmium can be recovered per 1 km2 of yellow mangrove forest per year. This method would provide a practical means of addressing heavy metal pollution in water bodies.

The annual cycle of dry and rainy seasons causes soil salinization to become major abiotic constrains limiting agricultural production in arid and semi-arid regions. With the climate change, population booming and increasing global food demand, developing countries are experiencing severe food crisis. The salinity issue remains as major challenge. We developed a low-cost water-efficient salinity prevention system through capillary barrier (CB). The objectives of our study were to introduce an artificial CB, which made up of lime (e.g., calcium chloride, converter slag, and plant and wood ash), gravel and plant residue. We found the salinization suppression without requiring huge amount of water by the CB application.

This low-cost and water-saving system will surely pave a new path for sustainable agriculture.

We’d like to utilize contaminated water treatment for the reconstruction of Fukushima and to prevent environmental pollution. I took over the research from the predecessors and have attempted to develop a treatment system using these indigenous plants for the treatment of radioactively contaminated water, with the final goal of proposing a novel alternative to a current approach: discharge of treated water into the ocean.

In this research, by applying “Ta-Ta-Ki” soil, a traditional Japanese soil solidification technology, we developed a novel multifunctional water collection system to control soil runoff and increase food production with low environmental impact and low cost, and this system can be adapted to developing countries, especially in the arid and semi-arid areas.
(1) the water storage by collection and retention of rainwater during the rainy season; (2) the supply of trients to poor soil; and (3) the control of soil runoff caused by rainfall.
This inexpensive solidification technology with high operability can be an effective solution to environmental problems around the world, besides the areas with the demand for food production, as mentioned above.

Eutrophication is mainly caused by oversupply of nitrogen and phosphorus, and exerts negative impacts on ecosystem and safe drinking water source all over the world. In this project, a novel system was developed by combining energy-saving H2O electrolysis with an eco-friendly iron carbon battery, which continuously removes nitrate and phosphate. This system utilizes the oxidation/reduction of iron to realize low-voltage H2O electrolysis to produce H2 and can collect phosphorus, as well as it reuses solid waste (used tea leaves) and uses solar energy. The simple structure of this system also enables us to easily apply to on-site treatment of eutrophicated water in lakes and ponds in addition to the possible incorporation into the conventional wastewater facilities or septic tanks.

In both kidney beans and maize systems, the combination of nitrifying bacteria and mycorrhizal fungi can eliminate the nitrogen concentration effectively, and the growth of maize and kidney beans was enhanced by the existence of nitrifying bacteria.
On-site pilot experiments indicated that maize and kidney beans in the local lake provided an energy-saving and cost-effective alternative instead of conventional energy-intensive systems for water purification.