Biocycle laboratory

Overview of laboratory

Study in the environmental engineering department is sub-divided into two fields, environmental coexistence and remediation, and prevention technologies targeting environmental pollutants.

  Biocycle laboratory is attached to the latter. We deal with wastewater and solid waste discharged from households and factories with a view to solving the environmental problems discharge causes. In this laboratory, the treatment technologies utilizing microorganism’s ability are being studied.

  An example of this is the technology of biogas generation from food waste which can contribute to a sound material-recycling society by reducing consumption of fossil fuel. Parallel to this, if it is difficult to recycle, we seek ways to minimize environmental loading by employing appropriate technology.

Introduction of research

"Methane fermentation employing biological ethanol fermentation as pretreatment"

  Methane fermentation of food waste is an attractive technology to jointly tackle waste treatment and energy production.  Methane fermentation is a biological treatment process which decomposes organic matter in waste using anaerobic microorganisms.  Biogas is generated in the decomposition process. It contains approximately 60% methane and is predominantly used for steam and electricity production.

  In this laboratory, we focus on food waste from restaurants having a high starch concentration, such as boiled rice.  Such waste has a practical use in bioethanol production.  The current process incorporates ethanol extraction and the residue is sent for methane fermentation.  In our process, there is no ethanol collection extraction process. Instead, ethanol rich fermented liquid is sent directly for methane fermentation.

Figure1 Methane fermentation system in this study

In the saccharification reactor, starch content in food waste is decomposed to monosaccharide by adding saccharification enzyme. Subsequently, monosaccharide in saccharified liquid is decomposed to ethane by adding yeast.  In the ethanol reactor, carbon dioxide is released to atmosphere as biproduct of ethanol. Next, ethanol fermented liquid is sent to methane fermentation. In this process ethanol is decomposed to methane and carbon dioxide. Stoichiometry, 2 mol of carbon dioxide from ethanol fermentation reactor and 3 mol methane and 1 mol carbon dioxide from methane fermentation reactor from starch content in food waste are generate from whole process.