The Herald, Sharon, Pa.

April 23, 2014

Not even waste will be wasted

Dean Dairy products put digester to test

By Joe Pinchot
Herald Staff Writer

HERMITAGE — Tom Darby admits he wishes the startup of the anaerobic digestion process at the Hermitage Water Pollution Control Plant had moved along much faster.

However, the plant superintendent also acknowledged that each step creates something new for him and his workers to learn, with guidelines to be developed along the way.

Plant workers on Tuesday dumped their first shipment of goods from Dean Dairy Products into the digestion process, the organic matter from the food waste an essential part of the process.

Dean delivered a truckload of about 30,000 pounds of damaged and expired white and chocolate milk, iced tea, yogurt and orange juice in plastic jugs, paper cartons and plastic bags.

Workers dumped each milk crate full of material into a hopper. A conveyor belt carried the containers into a crusher that freed the food content, and the leftover packaging was compressed and baled for eventual recycling.

The food waste is being treated through the normal water treatment process before entering the digesters.

“Eventually, we’ll be putting it directly into the digesters,” said Darby, who also manages Hermitage Municipal Authority, which owns the plant.

While treating the food waste robs the material of some of its gas-generating capability, workers chose not to enter the material directly into the digesters to give themselves the opportunity to learn to use the equipment, and make sure it is functioning properly while still under warranty, Darby said.

Waste batter from Joy Cone Co. has been dumped into a manhole upstream of the plant for six to eight months, and it also eventually will be pumped directly into the digesters.

At some point, waste from Charlie’s Specialties will be brought in, and plant officials will look for other food waste.

The digesters “cook” the food waste and sludge to kill pathogens. When the process is completed, the so-called class A sludge could be handled for landscape application. Currently, the plant trucks its treated sludge to a landfill.

The digestion process also produces a biogas that can be burned to create electricity to sell to the power grid.

Dean’s waste is significant because the company expects to deliver one or two truckloads a week, a steady stream of organic material ideal for optimum digestion, Darby said.

The digesters currently are being loaded with sludge and the cooking process has begun.

“They’re producing a very minimal amount (of gas) that we’re flaring off at the moment,” Darby said.

No gas will be flared off when the process is working at full capacity, a benchmark Darby said he hopes to reach in about six months.

The implementation process has been slowed by the loss of key people, including John Vornous, project manager for consulting engineer Herbert, Rowland and Grubic, who died last summer; material delivery delays; and the slow pace of getting permits. Darby noted the state Department of Environmental Protection had to determine what air-quality permits were needed before Hermitage Municipal Authority could apply for them.

“It’s such a new process,” Darby said. “We’re all learning as we’ve gone along. Even what we’re doing today, no municipal treatment plant is doing this in Pennsylvania, that I know of.”

To help ease the learning curve, the authority last month hired Jason Wert as a consultant. Wert, who used to work for Herbert, Rowland and Grubic, was the lead design engineer for the digestion expansion project. He now works for Rettew and Associates, Lancaster, Pa.

Darby said he expects Wert will work for the authority for eight months to a year working with plant employees and contractors on the startup and implementation.

When the digesters are functioning at full capacity, it will be worth the effort, he said, from creating usable product from what has been considered waste to helping out local food industries.

“I’m excited about it: the whole environmental aspect of it; keeping a quarter million tons (of sludge) from a landfill; getting to a class-A biosolid, which allows land application,” Darby said.