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Sludge Plant is Real Gas: $7 Million Facility Turns Sewage Waste into Clean Electricity

December 13, 2007

By Bob Downing, The Akron Beacon Journal, Ohio

Dec. 13–”Taking our brown and turning it into green” was the way Akron Water Pollution Control Administrator Brian Gresser described a new facility that turns the city’s sewage sludge into electricity.

The green-energy project “makes a positive out of a negative,” Akron Mayor Don Plusquellic said of the electricity derived from sludge.

The process will ‘ “save taxpayers a good deal of money . . . and it will be good for the environment,” he said.

The city and its partner, KB Compost Services Inc. of Independence, held a press conference Wednesday to show off the new $7 million facility at the city’s composting plant off Riverview Road.

Since mid-October, Akron and KB Compost have been fine-tuning the plant that turns sludge from the city’s sewage treatment plant into a methane-rich biogas that powers an electric generator.

The new facility is owned by the city and operated by KB Compost, the company that also manages the city’s composting plant.

If the new facility works as well as expected, Akron will look into expanding the operation and shutting down the composting plant, which triggers odor complaints from people living in and at the edge of the Cuyahoga Valley, Plusquellic said.

He said he is unable to say when that might occur.

Akron’s system — the first of its design in the United States — was developed by Schmack Biogas AG in Germany. That company has 200 operations in Asia and Europe.

KB Compost Services has partnered with Schmack Biogas AG to form a new company, Schmack BioEnergy LLC in Independence, to promote the German technology in the United States.

It was outside Zurich, Switzerland, where Plusquellic first inspected a biogas operation four years ago.

“I knew we had the infrastructure largely in place to do this in Akron and it makes sense for us to get the most out of materials we’d otherwise discard,” Plusquellic said. “This has wide-ranging benefits for us.”

Akron’s initial biogas project is designed to handle 5,000 tons of sludge per year, or about one third of the 15,000 tons produced annually at the city’s sewage treatment plant off Akron-Peninsula Road.

Power station

The new system relies on an engine-driven generator. It is producing 335 kilowatts, or enough electricity to power 325 homes. About 30 percent of the power will be used at the sewage plant and the rest will be used by the composting operation.

The city currently spends nearly $1.4 million on electricity for its sewage treatment, and that will be money saved, Gresser said.

The new operation makes Akron’s facility the first sludge plant in the country to produce electricity with the help of bacteria, the city said.

The system relies on bacteria that do not need oxygen, a process known as anaerobic digestion. The bacteria cause the high-solids sludge to ferment.

The bacteria multiply, consume part of the sludge and produce a methane-rich burnable gas called biogas, said Annette Berger, vice president of operations at KB Compost Services.

Key to the system are two tanks — one capable of processing 160,000 gallons of sludge and a second that can hold 450,000 gallons. The sludge will be processed for 25 to 30 days at temperatures of 90 to 100 degrees.

Akron got its start-up bacteria in sludge from the city of Kent, Gresser said.

The biogas will be 60 percent methane, 35 percent carbon dioxide and 5 percent other gases. In comparison, natural gas is 99 percent methane.

Akron paid for 10 percent of the $7 million project, which was funded in part by the Summit County Port Authority.

Evaluation planned

After an 18-month performance evaluation, the city and KB Compost will negotiate a new contract and potential expansion of the system to process all of the city’s sludge.

If the system does not meet agreed-upon performance criteria, then the city’s financial obligation ends.

Gresser said the process will help reduce the city’s escalating costs in handling sewage waste from Akron and its suburbs.

Akron and KB Compost realized that a technology other than composting was needed to stabilize the ever-increasing cost of sludge treatment and disposal.

The composting plant handles 1.2 million gallons of sludge every week, and the city spends $6.2 million annually to handle its sewage sludge.

“We’d like to eventually replace the composting plant,” Plusquellic said. “It has served Akron well for more than 20 years, but it’s getting old and the odors are still an occasional problem for us.”

Before the composting plant opened in 1986, Akron incinerated its sewage sludge. That ended in 1993.

Gresser said the city might be able to shut down the composting operations if the biogas facility is expanded, but the sludge dewatering part of that plant will likely remain open.

Most people give little thought to what happens to their trash or sewage sludge, but those are big and costly issues that cities like Akron must deal with, Plusquellic said.

Bob Downing can be reached at 330-996-3745 or bdowning@thebeaconjournal.com.

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Copyright (c) 2007, The Akron Beacon Journal, Ohio

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