New Jersey Village Turns Heat into Power

Ridgewood, N.J., builds a model for energy sustainability at its wastewater treatment plant.

by / July 25, 2012
Courtesy of Village of Ridgewood, New Jersey

Editor’s Note: Michael Greenhouse is a writer and a member of the Ridgewood Environmental Advisory Committee, which advises the New Jersey village on environmental concerns, energy reduction and sustainability.

For years, Ridgewood, N.J., engineer Chris Rutishauser would look at the bio-gas flare coming from the water pollution control facility he oversees and lapse into a troubling thought: “There goes a lot of wasted energy — a lot of money.”

Now, thanks to some creative thinking by Rutishauser and facility superintendent Robert Gillow, and some careful planning by leaders in Ridgewood, a project is under way that will capture that energy, shrink the facility’s carbon footprint, and cut its operating costs.

Ridgewood’s Sustainable Energy Project will cost the village’s 26,000 residents  nothing. And it reaches beyond the energy needs of the water pollution control facility itself, potentially serving as a catalyst for the village’s longer term vision for sustainability.

An Anaerobic Overhaul

From 2002 to2005, the facility was completely overhauled to meet stricter federal and state environmental standards. It now features two anaerobic “digesters” that break down and reduce the amount of organic waste that must be processed and disposed of by the plant. The digesters create methane bio-gas. Some of this gas is cycled back into the digesters to heat and break down the sludge. The rest is safely burned off into the air.

Despite these improvements,  Rutishauser and Gillow still felt they could better harness the energy flowing through the facility and perhaps  reduce the cost of running it in the process.

“It’s the largest consumer of energy that the village owns, costing upwards of $250,000 a year for natural gas and electricity,” Rutishauser said. “That’s a big cost and a big opportunity.”

The two began looking into an innovative new system that turns digester gas into reusable heat and electrical power. This Combined Heat and Power (CHP) system uses the bio-gas produced by the anaerobic digesters to both heat the sludge entering the digesters and produce power to run the plant. A number of waste water treatment plants in Europe have used CHP to become energy self-sufficient. A few large facilities in the U.S. are also using CHP to get closer to energy self-sufficiency.

Economically Feasible

The U.S. Environmental Protection Agency (EPA) has been evaluating the feasibility of CHP since the mid-2000s. In 2007, it published a report on CHP implementations at more than a dozen wastewater treatment facilities. The EPA concluded that “CHP is a reliable, cost-effective option for [wastewater treatment facilities] that have, or are planning to install, anaerobic digesters.”

At the time, the EPA said that CHP was a good option only for large plants with flow rates greater than 5 million gallons per day. However, in October 2011, an updated EPA report concluded that CHP could also be viable and cost-effective for smaller plants like the 3 million-gallon-a-day facility in Ridgewood.

Officials in Ridgewood believed they could get the same results with CHP. They also believed a CHP project could be a model for good environmental practices in the community and a platform for adopting renewable energy throughout the village.

And, just as importantly, they believed it could be done without any upfront capital outlays by the village — an important criterion for village officials.

In October 2011, New Jersey-based Natural Systems Utilities was selected and approved by the Ridgewood Village Council to perform project engineering and construction.

Engineering and hardware installation for the CHP system began this year. Natural gas-powered turbines will capture the excess gas, and generators will power the facility and keep the sludge heated at an optimal temperature.

Several New Energy Saving Technologies

During construction, the team will also install a new, chemical-free system for disinfecting the liquid effluent that is discharged from the plant after it has been treated. The system uses ultraviolet lights and eliminates the need to use chemical disinfectants during the treatment process.

An array of solar panels will also be installed on the front lawn of the plant, providing yet another source of energy.

According to Rutishauser, they are also considering a third source of energy: a turbine inserted into the facility’s outflow pipe. “This water flows 24/7,” he said. “If we can install a turbine without causing any backflow in the pipe — and I believe we can — we will have another very reliable source of energy.”

Even without this turbine, staff members expect the system to generate most, if not all, of the energy needed to run the facility. It will greatly reduce the amount of natural gas they will need to use, thereby reducing the plant’s carbon footprint substantially.

The project has another energy benefit as well: solar energy at four large properties in Ridgewood including the village hall and the main fire house will be captured by solar arrays installed on these buildings at the vendor’s expense. The energy savings will accrue directly to the village.

Natural Systems Utilities COO Don Rodgers explained that the company will potentially recoup its investment and turn a profit through a long-term contractual arrangement with the village. The company will raise the $4 million needed to engineer and build the system, including the solar arrays. In exchange, the Ridgewood will purchase the energy the new system generates at 12 cents a kilowatt hour for a period of 20 years, with a 3 percent increase per year for inflation.

According to an estimate, the village will save about $1.7 million in energy costs over the term of the contract. This is achieved by locking in a fixed rate for 20 years and “saving” the expected increase.

A Renewable Energy Platform

Rutishauser believes many aspects of the Sustainable Energy Project — and its business model — can be replicated elsewhere in the village. “The idea is to build sustainable energy into the whole village using the three proven technologies we’re utilizing at the facility: solar, bio-gas and hydraulic movement,” he said.
Solar is seen as a viable option for some of the village’s smaller municipal facilities, such as the municipal garage, fleet services and Ridgewood’s second firehouse. The business model would be the same as it is at the water pollution facility: the vendor installs the panels at no charge in exchange for an agreement to purchase the electricity generated from them.

Utilizing hydro power would be a relatively simple matter of installing a turbine in a flowing river, stream or brook. “Theoretically, we could take advantage of all the elevations we have in the village to utilize hydraulic energy,” Rutishauser  said. “Technically, it’s really very simple.”

With some changes to state laws governing energy usage, specifically permit aggregation, Rutishauser believes the village can also leverage the anaerobic digestion concept. For example, the village could potentially collect food waste and other organic waste and digest it to create methane and, thus, another source of power.

Rutishauser believes the key to expanding sustainability more broadly throughout the village is to execute the project at the water facility successfully.

“We need to get this project up and running successfully first — demonstrate success, so everyone can see how these systems work. Models like this start people thinking about what else is possible,” he said.

“The facility is a great venue, a great model. But people in this community are going to see this is just the start.”

Michael Greenhouse

Michael Greenhouse is a writer and a member of the Ridgewood Environmental Advisory Committee, which advises the New Jersey village on environmental concerns, energy reduction and sustainability.