Biogas: Harnessing Energy from Wastewater

 Coupling new technology with conservation projects, WLSSD is headed toward generating electricity to meet about half its needs by 2018—keeping regional wastewater treatment costs stable and contributing to Minnesota’s renewable energy goals. Capitalizing on “biogas”, a methane-rich by-product of wastewater treatment, WLSSD will produce both clean water and clean, renewable energy.

Reliable, effective and affordable wastewater treatment is a cornerstone for business and industry and vital to quality of life for the people in our region. It is crucial the success of new and existing businesses competing in a tough, global economy and rate stability is critical for the region to thrive.

WLSSD ELECTRICITY

However, wastewater treatment is energy-intensive. At $3 million a year, electricity accounts for nearly 40 percent of non-payroll costs at the wastewater treatment plant, driving tough budgetary decisions and increased rates to the businesses and residents in the community. An astounding 53.6 percent increase in electricity rates over the past eight years has added to the challenge of stabilizing rates.

To address this problem, WLSSD embarked on a project to ensure the organization fully understood its energy issues and was equipped to deal with them.  In 2013, WLSSD finished an energy policy to help guide its decisions. The plan is essentially a roadmap that outlines near-term and long-term actions throughout the organization to conserve energy and generate energy, and facilitate a stepwise process toward the ultimate goal of energy self-sufficiency. The objectives of the energy policy are to improve energy consumption efficiency, reduce cost, decrease capital investment, reduce environmental emissions and conserve natural resources.

Energy conservation and an eye toward self-sufficiency aren’t new for WLSSD. Conservation has always been a priority and WLSSD has implemented many projects to increase energy efficiency and reduce electrical consumption.  In fact, WLSSD has reduced its overall electrical consumption by 18 percent since 2011.  To achieve energy self-sufficiency, the energy impact of every project must be considered. In other words, energy conservation will be built into every reliability project.

While conservation continues to be important, the energy planning process revealed that the best “bang for the buck” would be derived from a large investment in technology to fully utilize the biogas produced at the facility.

Currently, WLSSD only uses a portion of the methane-rich biogas it produces and excess biogas is flared off. This use of biogas for heating meets about 8 percent of WLSSD’s energy needs. A plan is now underway to use all of the biogas currently produced to generate electricity to meet about 35 percent of treatment plant electrical needs.  Additionally, WLSSD plans to reclaim other high-strength wastes to produce more biogas and more electricity—allowing WLSSD to generate electricity to meet about 50 percent of treatment plant needs.

Through its pursuit of an energy self-sufficient facility, WLSSD will reduce operating costs and improve the environmental stewardship of the campus.  WLSSD’s 5-year plan will cut its electricity purchases in half and includes three phases: 1.) Replace an existing inefficient boiler and some associated equipment, 2.) Install 2 engine generators that will use the biogas to generate electricity, and 3.) Increase biogas and electricity production by adding other wastes into the system to maximize the use of existing equipment.

If future biogas production exceeds WLSSD’s electricity needs, the organization will explore other options to use the gas including compressing it for use in powering WLSSD fleet vehicles or selling it as a biofuel to another source.

Until recently, WLSSD’s capital funding has focused primarily on improvements related to system integrity, reliability, cost effectiveness and capacity leaving few funds to devote to strategic investments in efficiency and energy improvement projects.  Even with potential payback associated with energy projects, WLSSD has found it difficult to take on additional capital expenditures due to the impact of debt on the community.

WLSSD is responsible for providing the region with reliable, effective, and affordable wastewater treatment. Now, not only clean water plans, but also clean energy plans will address conservation, continuous improvement and utilization of modern technology to ensure WLSSD can meet customer needs into the future.