Pennsylvania Water Pollution Control Plant to Convert Recalled Ice Cream into Energy

Pennsylvania Water Pollution Control Plant to Convert Recalled Ice Cream into Energy

Every day, companies are faced with safety concerns and determining if recalls are necessary on their products due to possible defects or the likelihood of injury or harm to the consumer.

In March, Blue Bell Creameries, a private, family-owned ice cream company based in Brenham, Texas, recalled all of their products due to the discovery of listeria. In April, Columbus, Ohio-based Jeni’s Splendid Ice Creams destroyed more than 250 tons of ice cream and closed its shops in at least seven states after listeria was discovered in two of its products by the Nebraska Department of Agriculture.

The two ice cream manufacturers have faced difficult times over the past several months as Blue Bell has announced a massive 1,450 layoffs and has closed its distribution center in Richmond, Va., after seven people fell ill and three died because of the listeria contamination.

Jeni’s has fared a little better, as it recently released a statement saying it plans to reopen all of its 21 shops on May 22. It also has received good news from the Hermitage Water Pollution Control Plant in Pennsylvania, who plans on converting 290 tons of the recalled ice cream into biogas energy thanks to a recent upgrade at the plant.

“In planning for the upgrade, it was decided to add the capability to utilize food wastes as a supplement to feeding of the anaerobic digesters,” says Thomas W. Darby, manager of the Hermitage Municipal Authority. “For the last year the plant has been receiving wastes from local sources, such as Dean’s Dairy Facility located about seven miles away, Joy Cone Company located in Hermitage as well as other local liquid and semi-liquid food wastes.”

Jason Wert, consultant and project engineer for RETTEW Inc., an engineering design firm based in Lancaster, Pa., says the Hermitage Municipal Authority utilizes a two-stage anaerobic digestion process to convert food waste and wastewater sludge to renewable energy and a soil product.

“The food waste is separated from its packaging materials and the mixed with the community's wastewater sludge. Recyclable packaging materials are separated and recycled by a third party,” he says.

The combined sludge and food waste is heated over a period of 12 days in anaerobic digesters. The first stage heats it at 131 degrees to kill any pathogens and boost biogas production. The second stage lasts approximately 10 days and is heated to 95 degrees, where the majority of our biogas is produced. The biogas, a combination of methane, carbon dioxide and trace gases, is a byproduct of the bacteria that consume and eliminate the waste, according to Wert, who designed the system at the Hermitage Water Pollution Control Plant.

The authority has begun exploring other sources of food wastes to help to increase the production of methane gas in the digesters. 

“The methane gas is pulled off the digesters and blended with natural gas to operate a 600 KW biogas Caterpillar generator,” says Darby. “That energy is sent back to the grid and results in a credit to the plant’s overall electric bill. For the most part we are able to zero out our usage of electrical usage.”

Darby says the authority began investigating the possibility of using certain kinds of recalled foods and even contacted Blue Bell. 

“Their plant is located in Texas so it wasn’t economically feasible to transport the wastes here. When we saw the Jeni’s Ice Cream voluntary recall we contacted them to offer our unique service of being able to utilize the product in an environmental way.  By using Hermitage as a disposal point for their waste products, they help produce electric through our renewable energy facility,” he says. 

The energy becomes available in just a short few days after feeding the digesters the melted ice cream.  The high content sugar and organic matter are quickly broken down by the digesters.

“It’s anticipated that the amount of product we are receiving will be capable of producing up to 45 days of electrical energy when blended with our wastewater sludge in the digesters,” says Darby. “The benefit to the city and its residents are that the plant can operate at reduced energy costs.   In addition the City continues to reduce its own carbon footprint by utilizing a renewable by product such as the biosolids of the water pollution control plant.”

According to Wert, the authority collects the biogas from the anaerobic digester and removes the impurities so the biogas is "clean" for combustion in the on-site electrical generator. The generator burns the biogas to produce renewable electricity that offsets the authority's electric bill and also produces heat that is used in the anaerobic digestion process.  The biogas is similar to natural gas, but produced from a renewable source.

“After the process, the food waste has been reduced by more than 70 percent and any residue has been heated and treated so it's a soil product that can be used for turf and greenhouse applications,” he says. “The authority is not distributing that material yet to the public, but expects to have the necessary approvals later in the year for public use.”

Darby says the environment is the authority’s first concern and priority. 

“Everything we do impacts someone downstream.  So our goal is to minimize that to our best ability.  By reusing food recalls and expired products we are reducing the impact to landfills and utilizing the energy producing capabilities of that material to operate an existing water pollution control plant,” he says. “We have future plans to pull some of the methane gas from the digesters and begin to produce renewable compressed natural gas for use in (Hermitage) city vehicles which we plan to phase in as part of the city’s vehicle replacement plan.” 

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