North Carolina State University, Ph.D.
EREF Scholar 2021
Enhancing Volatile Fatty Acid Production from Anaerobic Co-Digestion of Food Waste
As the human population grows rapidly, food waste has become a concerning challenge. The USDA reported that in the United States, 31 percent of food went to wastage in 2010. This wastage was equal to 1.2 lb of food per person per day and amounted to $162 billion dollars lost. EPA encourages the recycling of food waste to reduce greenhouse gas emission and recover nutrients and energy. Interest in the use of anaerobic co-digestion (AcoD) to treat food waste is increasing.
Hezhou’s research investigates how to recover the resources from food waste in the form of volatile fatty acids (VFAs) through the process of AcoD. During AcoD, hydrolytic bacteria first break down the solids in food waste to soluble compounds, such as sugars, amino acids and alcohols. Fermentative bacteria then further utilize these solubilized nutrients, producing hydrogen, carbon dioxide, and VFAs. The gases and acetic acid (a kind of VFA) are picked up by methanogens to generate methane.
In traditional AcoD process, methane is the final product for resource recovery. However, VFAs have much higher commercial values and are used for various industrial applications including food, pharmaceutical, plastics, textile industries, and others. Therefore, many scientists have shifted the interest from methane to VFA production. To accumulate VFAs in an anaerobic digester, methane production must be inhibited. Hezhou’s project explores how to suppress methanogenesis and maximize VFA production from food waste in AcoD.
Hezhou’s team proposes a heat treatment strategy to inhibit methanogenesis, as methanogens and fermentative bacteria respond differently to the environmental stresses due to their physiological differences. This project also looks at the impact of heat treatment on microbial populations in the digesters.
Hezhou received her BEng in environmental engineering from Jiangnan University in 2017, where she spent two years working closely with ecotoxicology studying the effects of different external factors on the photosynthesis of soybeans. After that, Hezhou earned her MS from University of Arizona in the same major. During her master’s degree, she studied the growth of Anammox bacteria. She designed a protocol for the measurement of bacteria growth rates. Hezhou is now a Ph.D. student in environmental engineering at NC State University (2019-present). Her research interests involve resource recovery from food waste using biological treatments.