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’Flower Crusher Helps Resolve ‘Stinky’ Issue

Tuesday, September 1, 2009
filed under: Utilization/Trade

With the right vision and circumstances, sometimes a problem can be transformed into an opportunity.

Such was the case several years ago for North Dakota’s largest city. As Fargo grew, so too did the size of its sanitary landfill, located in what once was a rural setting on the city’s western edge. An ever-increasing volume of methane gas, created by the decomposing garbage, was escaping into the atmosphere. Concerns about the unpleasant odor increased as commercial development nudged closer and closer to the large landfill. The city began exploring the feasibility of landfill gas collection, but a passive flaring system to burn off the gas was not very effective.

The answer to the odor problem came from the west — about 1.5 miles to the west, to be exact. That’s the location of the Cargill, Inc., oil sunflower crushing plant and refinery (which actually has a West Fargo address). About the time Fargo was struggling to manage its landfill odor, Cargill was contending with skyrocketing prices of natural gas — the primary feedstock for its process boilers.

The proverbial “light bulb” came on. Cargill plant management approached the city with the idea of capturing the methane gas and transporting it to the sunflower plant for burning in its boilers. If feasible, the city would solve its odor problem, Cargill would save money on fuel — and the environment would benefit as well.*

Working with Wenck Associates, an environmental engineering firm, Cargill and the city of Fargo came up with a plan to collect the landfill gas, pressurize it at a compressor station, and pipe it to Cargill. Cost analysis considerations for the city included the gas collection, extraction and pressurization system, along with half the cost of the underground pipeline. For Cargill, the initial costs included the other half of the pipeline, plus significant modifications to its boilers.

The 1.5-mile underground pipeline, built in 2002, is now owned by the city (up to the Cargill property line). Originally there were 20 wells; now the number is up to 40. Driven down into the landfill, the wells suck in the methane gas. The gas then goes to the compressor building, from which it is piped into the Cargill plant’s boiler burners. (Some gas also is utilized to help heat a transfer station at the landfill. The gas runs an electric generator, and exhaust heat off the generator is then captured and used to heat the building.)

According to Terry Ludlum, solid waste director for the city of Fargo, the energy value of the methane gas utilized by Cargill is approximately 100 billion BTUs per year. That translates into roughly $100,000 in annual revenue for the city.

Ben Mauch, refinery supervisor for the Cargill facility, says the burning efficiency of methane gas is not as good as that of natural gas, due to a certain amount of air being drawn in by the wells along with the methane. However, given the boiler modifications the company has made to burn the methane, it works quite satisfactorily.

Kevin Clausen, commercial manager for Cargill’s West Fargo operation, says the plant’s energy needs are now about evenly divided among natural gas, methane from the landfill and the sunflower hulls that the plant has burned for many years. “We can adjust our burn accordingly, based on what’s most economical and what’s available,” he points out. “Though methane doesn’t burn as efficiently as natural gas, it’s still a 100% benefit [for both Cargill and Fargo]. And, it’s still better to use it for this purpose than to emit it into the air.”

“We see it as a real win-win for the city and us,” Mauch remarks. “Now that they’re controlling [the formerly emitted gas], they get rid of their odor problem, and we pay them for it.”

Both Cargill and the Fargo Solid Waste Division regularly receive inquiries from other cities and companies looking for solutions to odor and/or other landfill problems. “I think we’ll see this [type of partnership] continue to evolve” in other cities, Clausen says. “It’s definitely a success model that other people are looking to capture.” — Don Lilleboe

* Upon its completion in 2002, EPA estimated that the Fargo-Cargill methane gas collection and utilization project would, in each year of its operation, equate to eliminating carbon dioxide emissions from 16,000 cars, planting 23,000 acres of forest, or preventing the use of 185,000 barrels of oil.

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