Wastewater treatment plants (WWTP) which have anaerobic digested sludge tank have the problems of the clogging of piping and the equipment troubles by MAP (ammonium magnesium phosphate). Higashinada WWTP in Kobe is annoyed by MAP. To solve the problems, we constructed phosphorus recovery system (239 m³/d) in Higashinada WWTP and demonstrated by B-DASH in 2012. PO₄-P removal rate from digested sludge was about 90％ and the performance was continued good and stable. The suppressant of scale generation of MAP was suggested. In addition, we aim the local production for local consumption of recycling phosphorus and developed and sell the fertilizer including recycling phosphorus, which is called KOBE Harvest. Shipments of MAP from Higashinada WWTP and KOBE Harvest fertilizer gradually increase and the recirculation of phosphorus was constructed in Kobe city. In addition, these fertilizers are used for vegetables and rice used for the school lunch in Kobe and contributes to food education and the environmental education for the children carrying the future.

The purpose of this study is to estimate the carbon absorption in artificial seaweed bed and seagrass bed to confirm the effect of blue carbon by the artificial seaweed bed substratum created in the Seto Inland Sea. The artificial seaweed bed substratum was constructed four times from February 2013 to February 2018, and the total area was 36,500 m². The wet weight of seaweed increased from 1,251 to 2,916 g·m² with seasonal fluctuation from 16 to 40 months after creation. Before the creation of the artificial seaweed bed substratum, the average seagrass bed area on the shore was 1,259 m² from 1981 to 2012. After the creation, the average seagrass bed area from 2014 to 2020 expanded 4.7 times to 5,934 m² due to controlling the flow and waves, and the shoot density of seagrass also increased. The annual carbon uptake by the artificial seaweed and the seagrass bed on its shore was estimated to be 3,200 kgC and 1,458 kgC, respectively. The total annual carbon absorption was estimated to be 4,658 kgC due to the creation of the artificial seaweed bed substratum and confirmed the effect of blue carbon.

In this study, we investigated effects of dilution on (i) removal of dissolved organic carbon (DOC) and nitrogen (DN) from the miso-processing (MP) and bean-boiling (BB) wastewaters by cultivation of Aurantiochytrium sp. strain L3W, (ii) its biomass yield in terms of the DOC and DN consumptions, and (iii) production of lipid and fatty acids including docosahexaenoic acid (DHA). Dilution resulted in the less biomass and lipid productions; however, the remarkable increase of biomass yield was attained. By diluting more than 5 times, the DN concentration in the BB and MP wastewater samples was maintained within the range in the sewage discharge standard for nitrogen set by the municipal government of Higashi-hiroshima City. However, the remaining DOC after cultivation was estimated to exceed the sewage discharge standard for biochemical oxygen demand in spite of 20 times dilution. The DHA content in the biomass of strain L3W was 10.7 mg/g in the 10 times diluted BB wastewater sample and 16.8 mg/g in the 20 times diluted MP water sample.

We proposed solid-state anaerobic digestion (SSAD) and high-yielding rice cultivation as pig manure management to produce renewable energy (biogas) and recycle nutrient in the manure as fertilizer for grain of high-yielding rice. In this study, carbon and nitrogen mass balances were calculated in the conventional and proposed pig farming systems and environmental loadings were compared; such as NH₃, greenhouse gas emissions and N discharge into the water environment.

NH₃ emission from the entire system was 1.5 kg N/head/year for conventional system, while it was reduced to 1.1 kg N/head/year for proposed system by replacing 10％ wet of pig feed with grain rice harvested from the high-yielding rice filed. In the proposed system, 3.0 kg N/head/year of nitrogen was emitted to the water environment in the proposed system, which was lower than that of 4.3 kg N/head/year in the conventional one.

Greenhouse gas emission was 396 kg CO₂-eq/head/year for conventional system. Gross greenhouse gas emission from the proposed system was 437 kg CO₂-eq/head/year. On the other hand, renewable energy utilization by co-generation with biogas yielded net 298 CO₂-eq/head/year. These results suggest that SSAD and high-yielding rice cultivation is promising approach to reduce environmental loading in the pig farming system.

We quantified nitrate (NO₃⁻), chloride (Cl⁻) and water hardness concentrations in stream water catchments in the Koza River within the Shimanto Belt, where low nitrate concentrations in precipitation are reported. We conducted water sampling at nine sites in the Koza River’s stream waters in southern Wakayama at ordinary water levels, and the elevations range from 35 to 410 m. The mean concentrations of nitrate and chloride of the samples were 90.7 μM and 4.27 μM, respectively. The mean water hardness concentration was 9.12 mg L⁻¹, which is significantly low values. These results show that the chloride concentrations in stream water catchments had the elevation dependency. The nitrate concentrations in stream waters of the Koza River were substantially low, and the samples fell below the detectable limits in the upper reaches of the Shichikawa Dam in summer. Thus, sampling of stream water catchments in the Koza River can be used as control to monitor cross-border pollution in Japan.