Rendering Wastewater for Electricity Generation?

By Annel K. Greene, PhD, Professor and Center Director
Clemson University Animal Co-Products Research and Education Center

It was with great sadness that the Clemson University Animal Co-Products Research and Education Center (ACREC) faculty, staff, and students learned of the passing of dear friend and supporter Carl Wintzer of G.A. Wintzer & Son Inc. in late December 2016. Roughly 18 months after Dr. Gary Pearl first approached Clemson University about the ACREC concept, the ACREC Steering Committee was formed. In 2004, Wintzer was a member of that committee and visited Clemson University on what would be the first of many visits. He became a well-known and much respected contributor to ACREC programs and was greatly adored by the faculty, staff, and students. For 13 years, his quiet wisdom, intense love of science, delightful sense of humor, and always happy demeanor set the tone for ACREC projects. Wintzer had a special passion for wastewater treatment systems along with scientific facts and figures.

Upon hearing of his passing, everyone at ACREC echoed the same sentiments – what a wonderful, true gentleman Wintzer was and how greatly he will be missed. The spring 2017 ACREC meeting was dedicated to him. Prayers and sincere condolences go to the entire Wintzer family from Clemson University and ACREC. We will miss our dear friend.

Rendering Wastewater to Generate Electricity?
At the spring 2017 ACREC meeting, proposals were reviewed for both continuing research as well as new projects. Eight of the 13 proposals submitted were selected for funding. Dr. Sudeep Popat, a new assistant professor in the Clemson University Department of Environmental Engineering and Earth Sciences, was selected to conduct an exploratory ACREC project to investigate the use of microbial fuel cells (MFCs) to further clean rendering wastewater while also generating electricity and/or value-added chemical products. 

In an MFC, unique bacteria known as anode-respiring bacteria grow on an electrode submerged in wastewater. The bacteria use the chemical components in wastewater as food. During their growth and respiration under anaerobic conditions (without oxygen), the bacteria create an electrical current that can be used for power. In addition to generating electrical power, other by-products such as hydrogen gas, hydrogen peroxide, and sodium hydroxide (caustic soda) as well as valuable chemicals can be produced by different modifications to the system.

Although MFCs have been studied extensively for use in domestic wastewater treatment, these units have not been investigated for use in rendering wastewater applications. In general, domestic wastewater treatment involves low-strength wastewater meaning it contains low levels of organic components. Previous studies using low-strength domestic wastewater have shown the proof of concept of the MFC system, but the electrical power produced has been low. However, rendering wastewater contains higher-strength wastewater meaning it contains higher concentrations of organic components. It is hypothesized that a potential advantage to using rendering wastewater in an MFC will create a greater amount of electrical current that could lead to production of electrical power or other products at high rates. Popat will be examining this hypothesis by building an MFC and using rendering processing plant wastewater as the feed for the bacteria.

Based on his preliminary work, Popat expects good removal and conversion of wastewater components that will result in further cleaning of the water. It is not known what impact high fats, oils, and greases will have on the process; therefore, he will examine how these components affect electrical current output from the MFCs. Popat hypothesizes that high protein content in the wastewater will likely be an advantage for the MFC bacterial populations.

In addition to electricity generation, one of the major advantages of MFCs in biological wastewater treatment is the production of a range of chemical by-products in addition to or as an alternative to electrical power. For instance, development of hydrogen peroxide from the process could provide a value-added product that might be used within the rendering plant for cleaning, disinfection, and/or odor control. Other products, such as ammonium-based fertilizer could be possible as value-added by-products, creating a new profit center for renderers from their wastewater. If this preliminary proof of concept project is successful, it could lead to further work on development of MFCs for eventual pilot-scale testing and commercial use. 

June 2017 RENDER | back