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Gas from wastewater facility to soon power garbage trucks in Boulder/Broomfield

by Allen Best

BOULDER, Colo. – Seeds planted by Congress in 2005 are now bearing fruit in Boulder. The city is the newest among four jurisdictions in Colorado to use a financing tool created by the federal legislation to create new uses for biogas from wastewater treatment plants, and more such projects are being studied

Boulder’s late this month will begin converting biogas from its wastewater treatment plant into compressed natural gas for use in 38 trash trucks operated by Western Disposal in Boulder and Broomfield counties.

Biogas from Boulder is piped from the plant’s anaerobic digester to BioCNG™ System, called Tetra Tech. It removes the (pee-ew!) hydrogen sulfide, moisture, siloxanes, volatile organic compounds and carbon dioxide from the biogas. The cleaner fuel is then piped—in this case using Xcel Energy pipes—to a station for fueling of the trash trucks with the compressed natural gas, or CNG.

Having a customer for the gas was crucial for Boulder, says Carolyn Elam, Boulder’s energy strategy program manager.

The city will sell the gas at a 5% discount from the monthly energy index.

Boulder conducted two calculations. One was how much the city’s carbon footprint might be trimmed. The net-savings comes to 265,000 gallons of diesel fuel per year.

The other calculation was financial. The biogas had been used to produce electricity, for use at the wastewater plant. That equipment needed to be replaced. Electricity is relatively cheap, and renewable generation has flattened cost increases. The better economics were in creating a transportation fuel.

This takes the money trail back to the Energy Policy Act of 2005 and a 2007 revision, the Energy Independence and Security Act. Congress wanted to instigate greater domestic production of transportation fuels. Keep in mind that this was before application of fracking and other techniques that have allowed the plentiful extraction of hydrocarbons from shale formations.

The most discernible outcome came quickly: a great ramping up of biofuels, mostly from corn. In Colorado, 32% of corn goes to ethanol plants, the most prominent source being a plant near Yuma.

In its energy legislation, Congress created the Renewable Fuels Standard Program. To implement the intent, the Environmental Protection Agency created the RIN credits, which can be sold to refiners such as Suncor, which is located north of downtown Denver, to satisfy their requirements of meeting the federal obligations to have a percentage of produced fuel from renewable sources. The financial device is called the renewable identification number, or RIN, which operates much like a renewable energy credit, or REC.

These credits come into play at Boulder’s program and also the other three biogas projects in Colorado.

Grand Junction was first

Grand Junction was the first city in the nation to create a transportation fuel from its biogas. Before, nearly all the biogas was flared. Around 2006 city employees began asking themselves whether there was a more productive way to avoid the problem of emitting dangerous gases into the atmosphere.

Flaring biogas eliminates methane but produces carbon dioxide. Both are greenhouse gases, but methane has 84 times as much heat-trapping potential in the first 20 years than does carbon dioxide. But then disintegrates, while C02 very slowly breaks down over hundreds, even thousands of years.

“We were wasting a valuable resource,” says Kurt Carson, wastewater services manager for Grand Junction.

The thought process included some consideration of the environmental impacts of flaring. Those impacts, if important, can’t be monetized. In fact, creating the ability to produce compressed natural gas to power 62 vehicles for Grand Junction has resulted in the reduction of 3 million pounds of carbon dioxide per year. The net effect is to produce the equivalent of 400 gallons of gasoline.

“Each utility will have different financial drivers. For us, the RINs are an important aspect, I couldn’t say whether they would make or break the project, but they are a significant factor on the economic return on investment,” says Carson.

With aid of the RIN credits and the reduced need for diesel fuel, the return-on-investment of the new infrastructure was reduced to eight years.

Carson also notes that the size of the project influences its feasibility. His district serves a population of 85,000 to 90,000 people.

Longmont, South Platte projects

Two projects along the Front Range went  on line last fall.

Longmont also tapped biogas to create what it calls renewable natural gas. Of the city’s 21 diesel-powered garbage trucks, 11 can burn the fuel. The remaining are expected to be replaced in 2024,

The city’s website lays out the finances: Assuming diesel fuel of $3 per gallon, the city saves $270,000 in fuel costs. The RIN credits produce $150,000 to $250,000 per year. The conversion project completed in 2019 got a $1 million grant from the Colorado Department of Local Affairs.

Colorado’s biggest biogas conversion project lies near the intersection of Santa Fe Drive and Dartmouth in southwestern metropolitan Denver. There, the South Platte Renewal Partners treated sewage from 300,000 people in Englewood, Littleton and 19 other, smaller districts. It’s the third-largest wastewater treatment facility in Colorado.

This is from the July 23, 2020, issue of Big Pivots. Subscribe for free to the e-magazine by going to Big Pivots.

Unlike other biogas conversions in Colorado, however, South Platte Renewal Partners produces natural gas that is injected into Xcel Energy pipelines for use in buildings and other purposes. The facility produces about 500,000 cubic feet a day.

Anna Schroeder, an engineer at the wastewater plant, says the district lacked a partner, such as the three municipalities have, for the compressed natural gas. But the payback on this still looks good – perhaps even better than some others: 4 to 6 years, she reported in a telephone conversation. The credits for the renewable fuels standard program were a “big driver.”

Equipment goes into place for biogas conversion along the South Platte River in metro Denver.

In the conversion, South Platte had to merge the specialists of “two different worlds, the gas world and the water world,” she says.

“There was an initial barrier, where people were more comfortable working within their own sector, to overcome.” Once the barriers were overcome and the ground rules established, “it worked pretty well,” she says.

Becky Luna, a consultant with Corrola Engineering, says the economics work out best at larger plants. Longmont is relatively small, though, and found a way to make it work, she observed.

RIN payments are crucial to the districts, if finances matter—as they always seem to. Reduction of greenhouse gas emissions is also driver among some districts.

In addition to the four existing biogas conversions in Colorado, two more are being studied. This puts Colorado roughly equal with California in the adoption of this technology and well ahead of surrounding states.

More yet may come if Colorado ultimately adopts a renewable fuels standard. Senate Bill 20-150, which was introduced by Sen. Chris Hansen, D-Denver, would have required Public Service Co. of Colorado, a subsidiary of Xcel Energy, to use 5% renewable natural gas by 2025 and 15% within a decade. The proposal would also required the state’s Public Utilities Commission to develop renewable natural gas programs for smaller utilities and require municipal utilities to report emissions from natural gas.

The bill was shelved in the rushed session in May after legislators returned from an extended covid-caused recess.

Hansen says he plans to reintroduce the bill next winter. If it gets adopted, says Luna, it would have result in more and also smaller plants converting. It would also encourage more landfill operators to tap the methane, as Fort Collins and several others already do, instead of flaring the gas.

Allen Best
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