Case Study: Energy From Waste Through Anaerobic Digestion

This entec biogas plant installed by Reynolds, Inc. was funded by a $1M grant awarded to Grand Valley State University's Michigan Alternative and Renewable Energy Center (MAREC), and den Dulk Dairy Farm, LLC.

Reynolds, Inc. served as general contractor in the installation of the first entec biogas plant in the US. The plant is designed to produce electric and thermal power from 22,000 metric tons of manure, the waste produced annually by a 1,000 cow dairy operation. This fully operational plant is located at den Dulk Dairy Farm in Ravenna, Michigan.

While reduced utility costs are an obvious benefit of producing renewable energy from waste, owners of these systems also benefit from several environmental factors: reduction in greenhouse gas emissions and reduction of pathogens when land applying. Food processors located upstream from municipal treatment plants would also realize lower BOD/COD values in their digested process streams.

The finished plant converts animal waste to biogas through anaerobic digestion, and a high yield is achieved with the assistance of a continuous stir tank reactor (CSTR). The system contains an in-line hydrogen sulfide scrubber that uses a proprietary bacterial technology, a CHP engine and CHP micro turbine for electric and thermal power generation, and a liquid solid separator. The farmer not only takes advantage of the reduction of utility costs but also uses the solids that are separated as bedding for the barns and the liquids for land application.

SOURCE: Layne Christensen Company Water Treatment Division