From Waste to Fuel
From Waste to Fuel
A stinging acronym has often attached itself to the placement of facilities where municipal solid waste gets sent: NIMBY, as in “Not In My Back Yard.”
But for a PepsiCo business on the east coast of Florida living next door to this sort of site, proximity proved key to cultivating what has become a genuine environmental asset.
Tropicana’s juice-producing facility in Fort Pierce, Fla., borders the St. Lucie County Baling and Recycling Center, a complex that receives more than 600 tons of household waste during an average day.
Once recyclables and hazardous materials are removed from the incoming waste stream, what remains is primarily organic refuse that is then compressed into nearly 4,000-pound bales.
Those bales are transported to a section of the landfill where they are stacked and buried. As the waste decays it produces landfill methane gas.
According to the Environmental Protection Agency (EPA), methane “is a very potent greenhouse gas that is a key contributor to global climate change.” In terms of global warming, methane gas is considered 22 times more potent as a greenhouse gas than carbon dioxide.
A Renewable Energy Source Next Door
In something of a twist on Robert Frost’s oft-cited line regarding good fences, Tropicana’s Fort Pierce facility has learned that an operation that produces such a substance can actually make for a very good neighbor in the area of sustainability.
Tropicana has worked diligently with St. Lucie County to secure its landfill methane gas and use it as a fuel source to help power its Fort Pierce plant.
Because Tropicana is purchasing the landfill methane gas from the county and is using it to fuel its facility, it is limiting the amount of methane released into the atmosphere.
The EPA, through its Landfill Methane Outreach Program (LMOP), embraces the concept of beneficially using landfill gas, deeming it a “reliable source of renewable energy” that can replace fossil fuels that would otherwise be needed to operate the manufacturing facility.
The average of 33,000 kilowatt hours of electricity produced daily using the methane gas is expected to provide about 20 percent of the plant’s annual electrical power, trimming the plant’s utility bills.
St. Lucie County benefits too, as it now receives funds for what was previously a waste product. “This project is a win for everybody,” said Glenn Johnson, PepsiCo Americas Beverages’ senior principal engineer for sustainability. “It reduces the emission of the more potent methane greenhouse gas, reduces fossil fuel use, provides needed revenue to the county and provides a good financial return for PepsiCo’s shareholders.”
From Landfill to Plant Energy Source
So how does the project work and how are these objectives achieved?
As soon as a section of the county landfill is completely filled with bales, it is covered with a membrane and buried to trap the methane gas that is being continuously generated by the decaying organic waste. Meanwhile, below ground, 90 horizontal and vertical wells siphon the methane gas from the decomposing waste bales into a 50-horsepower compressor.
The landfill methane gas is compressed, de-watered to reduce moisture and sent through an underground pipeline to Tropicana’s boiler room.
There, Tropicana’s investment in the project is critical. The plant’s boiler, which produces steam that is essential in juice pasteurization, was modified to use a varying blend of landfill methane gas and traditional pipeline gas as its fuel source.
By installing a new fuel train, a new burner and sophisticated controls, the burner can be adjusted to a changing ratio of lower energy-content landfill methane gas and higher energy-content pipeline gas.
“We spent a number of years on that boiler and learned landfill gas chemistry,” said Johnson. “After some years of experience, we developed an even better project that makes more efficient use of the gas throughout the year, so we’re pretty proud of that.”
Concurrent with the boiler modifications, construction of a versatile 1,600-kilowatt cogeneration facility, which generates electricity and creates heat for steam, began next to the boiler room.
“Think of the internal combustion engine in your car,” Johnson suggests, “but instead of turning a transmission and making your car go, it turns a generator and makes electricity. The heat recovery steam generator recovers heat from the exhaust gas while the jacket water heat recovery system recovers heat that would otherwise be sent to the radiator.”
The result of the process is the creation of an extraordinarily energy efficient use of a renewable resource.
With this highly efficient renewable fuel initiative making a positive difference in its operation, Tropicana Fort Pierce is producing high-quality orange juice while serving as a sustainability model throughout the industry.
“I believe this project is a great example of PepsiCo’s Performance with Purpose in action,” Johnson said. “It is also a great example of what is achievable when government works as a team with manufacturing.”