Wastewater treatment is a multi-step process in which organic matter, nitrogen and phosphorus compounds are removed by degradation methods to produce activated sludge as a by-product. The activated sludge is precipitated and incinerated as waste, consuming a large amount of energy in the process. The Tohoku-Recovery Next-generation Energies for Tohoku Recovery project (NET) will install a new energy-efficient process at Sendai's Minamigamo wastewater treatment plant, which sustained massive damage during the Great Tohoku Earthquake.
The NET process will produce energy from wastewater by using oil-yielding heterotrophic algae Aurantiochytrium and autotrophic algae Botryococcus. Together with laboratory-scale research on algae biofuels, an outdoor test plant will be set up at the Minamigamo purification center. Implementation of the new microalgae process will allow water to be purified and biofuels to be produced from waste organic matter contained in the wastewater.
Laboratory-scale research is in progress and results such as effective algae strains, nutrient recovery methods from sludge and defatted algae residues, pretreatment methods for extraction, extraction methods from living algae cells and catalysis for fuel upgrading have been developed. Life-cycle analysis (LCA) of the entire wastewater treatment and microalgae cultivation is being conducted.
 Toshiyuki Nonaka, Ryoma Maruta, Masayuki Iguchi, Taku Michael Aida, Masaki Ota, Richard Lee Smith, Jr., "Extraction and Liquefaction of Microalgae with Hot and High Temperature Water", International Symposium for the 70th Anniversary of the Tohoku Branch of the Chemical Society of Japan, Sendai, Japan, September 28-30 (2013)
 Masaki Ota, Kagakukougaku, 77(4), 248-251 (2014)
 Shun Tsutsumi, Takehiro Shibuya, Kouhei Baisho, Yasuhiro Saito, Yohsuke Matsushita, Hideyuki Aoki, Comparison of High-pressure Homogenizer and Disc Mill in Microalgae Oil Extraction, 10th International Conference on Flow Dynamics, Sendai, Japan, November 25-27 (2013)
 Hideo Watanabe, Dalin Li, Yoshinao Nakagawa, Keiichi Tomishige, Kunimitsu Kaya, Makoto M. Watanabe, Characterization of oil-extracted residue biomass of Botryococcus braunii as a biofuel feedstock and its pyrolytic behavior, Applied Energy, 132, 475-484 (2014)
 Shin-ichi Oya, Daisuke Kanno, Hideo Watanabe, Masazumi Tamura, Yoshinao Nakagawa, Keiichi Tomishige, Catalytic production of branched small alkanes from biohydrocarbon, submitted.