By Jeff VanVoorhis, Project Manager, Symbiont

Case Studies

For many companies, waste-to-energy is proving a viable, sustainable solution to combating stricter environmental regulations and increased wastewater treatment costs related to their high strength organic waste. By converting this waste-to-energy, companies no longer have to contend with the strict environmental regulations or increased costs and liabilities related to handling their high strength waste using land application. Companies can also reduce the amount of high-strength waste sent to their local municipality to treat, and thus, reduce their treatment costs. Waste-to-energy also provides companies with a clean, continual energy source to fuel their operations.

Funding options for waste-to-energy projects

The emphasis on renewable energy has provided multiple funding mechanisms to help companies move their waste-to-energy projects from concept to completion. On the federal level, the Investment Tax Credit and New Markets Tax Credit are potential funding sources. Many states have similar incentive programs available. Utilities, most with goals for increasing power from renewable energy sources, are interested in potentially purchasing power from these projects. Finally, private investors in the energy sector are potential sources of funding.

Biogas powers combustion engines; heat is transferred to an adjacent facility

With more companies using waste-to-energy, numerous projects are currently underway throughout the United States. These projects typically utilize anaerobic bacteria to break down organic matter in the waste stream to produce biogas, which is subsequently burned to generate electrical power. Common project sites include dairy and food facilities that produce a continuous flow of high-strength organic wastes.

Wisconsin, in particular, is home to several new waste-to-energy projects. One such project is being executed by Green Whey Energy Inc. in Turtle Lake. This project collects more than 300,000 gallons per day (gpd) of high-strength wastes from six food processing facilities. Two 2-million-gallon high-rate anaerobic digesters biologically treat the waste stream to produce about 1,000 cubic feet per minute (cfm) of biogas. The treated biogas is burned in two internal combustion engines to generate 3.2 MW of green energy. Heat captured from the engines is transferred to an adjacent food processing facility, reducing its need for natural gas. Effluent from the digester is further treated with a moving bed aerobic bioreactor and via dissolved air floatation prior to discharge to the city sewer.

A Wisconsin cheese producer is utilizing a two-stage digestion process to convert its high-strength waste to biogas while reducing the cost and liability associated with using land application methods to handle its high-strength wastes. Previously, more than 60,000 gpd of high-strength wastewater was trucked to municipality or land applied at a cost of more than $1.5 million per year. The biogas is fired in two 200-kW microturbines to produce electricity for its cheese and whey plants and reduce the amount of energy purchased from the local utility. The anaerobic treatment system currently is producing approximately 120,000 standard cu.ft, of biogas daily. The energy value of the biogas is about 82 million BTU per day.

Biogas is a renewable energy source that is converted to electrical power

The projects described above demonstrate the economic and environmental benefits of waste-to-energy. Anaerobic treatment technologies are a cost-effective means of managing high-strength organic wastes, while avoiding expensive treatment costs imposed by municipalities and contending with increasingly strict environmental regulations. The biogas generated serves as a renewable energy source that can be converted to electrical power, reducing a company’s utility costs and carbon footprint. The electrical power may also be sold back to the local utility, providing the company with another revenue stream. A company can also increase its revenue by charging tipping fees for the waste it receives from outside sources. Due to these operational and financial incentives, waste-to-energy is becoming an increasingly popular alternative companies are evaluating as they assess their high strength waste treatment costs and operational energy needs.

Symbiont is a full-service engineering and consulting firm that plans, builds, controls and improves environments.