Greeley is home to North America’s largest renewable energy “stomach” | TheFencePost.com

Greeley is home to North America’s largest renewable energy “stomach”

Kathleen Duff

Motorists passing by the series of six domed-top tanks and various outbuildings tucked between two dairy farms near LaSalle might dismiss the development as yet another of rural Weld County's many oil facilities.

But what those drivers don't see is an innovative addition to Weld County's rapidly growing portfolio of renewable energy enterprises.

Resting on that flat piece of rural land is the Heartland Biogas Project, the largest anaerobic digester in North America. There, food waste and dairy cow manure are converted into renewable natural gas that supplies power to more than 35,000 households.

Global renewable energy leader EDF operates the digester, while A1 Organics of Eaton owns the technology and equipment that supplies the food waste for the project.

Every day at the Weld County Road 49 location, trucks haul unwanted food, scraps and grease from area restaurants, meat-packing houses, schools, a cheese factory and grocery stores to the site. Tons of food waste once bound for the landfill are separated from packaging in A1 Organics' Digester Processing System to create feedstock for the digester.

Bob Yost, vice president and chief technical officer of A1 Organics, said of the food diversion, "It makes economic sense, and it's responsible management of waste."

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The United States alone produces more than 70 billion pounds of food waste a year. Diverting even one cubic meter of methane-producing food waste from the landfill is the same as removing 23 cubic meters of carbon dioxide from the atmosphere. A1 Organics, which has focused on recyclables for more than 15 years, has diverted more than 8 million cubic meters of food waste from landfills through this project and several others it operates.

And capturing methane gas from the manure, which is considered the leading source of agriculture's greenhouse gas emissions, is an environmentally responsible approach.

"Every ounce of manure that we can take that reduces the methane is a good thing," he said.

Yost, who described the anaerobic digester as operating much like a "stomach," added the Heartland project has an appetite for even more food waste. The key is educating more businesses and entities about their recyclable options. "Sustainable is do-able. … A huge key to sustainability is generator responsibility," Yost said. "It's so simple to separate this stuff from the beginning."

Yost said the digester project has been 10 years in the making.

"By the end of the year, we think we will have it dialed up to maximum production," he said.

Heartland operates 365 days per year, 24 hours per day with at least 25-30 workers on site, but its employment impact extends beyond that with the contractors who drive the feedstock to the site and other second-tier jobs — accessory industries that Yost expects to grow over time.

The local project itself is becoming something of a media darling throughout the United States. PBS recently produced a feature on Heartland, as has NPR. Yost said he is contacted by community leaders, the media and industry representatives at least once per week for tours. On a recent sunny day, a group of industry representatives from Ohio waited in a vehicle while he wrapped up a media interview.

Here's how it works

Expired milk, cheese, eggs, canned goods, produce, grease, meat scraps — just about any food-based material — is fed into a machine called the Tiger, which is owned by A1 Organics. This machine separates the food scraps from containers, cans and bottles and combines the foods into substrate. That soupy substance is then pumped into a pipe and sent to six large bioreactor tanks located nearby, where it is combined with truckloads of "clean" dairy cow manure free from dirt and grass.

About 1,100 tons of manure and feedstock is fed into the digester every day. Once combined in tanks, known as the anaerobic digester, the mixture ferments and produces methane gas under the watchful eye of engineers who monitor the "recipe" of sugars, fatty acids, proteins and carbohydrates to ensure maximum gas production. More than 1 million BTUs of natural gas are produced every day. The gas is then reconditioned and pumped into a high-pressure 30-inch pipeline, where it can be drawn for use by communities and industry via an off-take agreement.

Once as much renewable natural gas as possible has been removed in the reactor tanks, the remaining substance is separated into a liquid and solids. The water-based liquid is piped to large covered lagoons located just feet away from the digester, where the last remnants of natural gas are siphoned and sent to the pipeline. Meantime, the solids are transformed into a rich soil amendment.

The process is highly efficient and earth-friendly because food and animal waste is turned into natural gas; the cartons, cans and bottles from the original food sources are composted; very little water is used in the process; and the soil amendment, which is rich in nutrients, will be sold as peat moss for gardens and agriculture.

Environmental impacts

Sybil Sharvelle, an associate professor of civil and environmental engineering at Colorado State University, has conducted original research on anaerobic digesters and has been studying the concept for more than eight years.

She said when methane is captured via anaerobic digestion and used for energy generation, there are many benefits to air quality, including reduced greenhouse gas emissions. Sharvelle said in an email "water quality benefits also are achieved because water is contained and treated via anaerobic digestion."

Sharvelle added, "There are really no environmental drawbacks to AD as long as solid and liquid end products are put to beneficial use.

"My understanding is that it is a key goal for the Heartland project to find beneficial uses for these products, e.g. solid products can be used as soil amendments and the liquid can be used as irrigation water."

Anaerobic digestion projects aren't a new concept. European countries have been refining such technology for more than three decades. But the United States has only more recently come aboard because of volatile prices in the oil and natural gas markets. Sharvelle said, "Economics for AD are better in Europe. This is a result of high energy prices and limited space for waste disposal, resulting in high tipping fees."

Yost explained the Heartland Biogas Project is financially feasible because of its dedicated off-take agreement for the renewable natural gas with the Sacramento Municipal Utility District. Unlike similar facilities, Heartland also nets revenue from selling the soil amendment.

An economic boon for Weld County

Although highly regulated by the state and federal government, Yost said Heartland has been well-received in the county and in Colorado. "There are communities that would die to have what we have here," he said.

"When we permitted (the project), it was pretty exciting," said Barbara Kirkmeyer, Weld County commissioner, who called Heartland "phenomenal for Weld County."

She said the renewable energy project was a natural addition to a county that is number one in agriculture and also produces 90 percent of oil in the state, along with 26 percent of natural gas and 25 percent of wind energy.

Heartland's success is just one of the reasons commissioners are looking to expand Weld 49 to four lanes, making it more of a transportation corridor for agriculture and energy businesses in the area.

"(Heartland) is another example where we will be leading the energy industry in Colorado," she said.

Richard Werner, president/CEO of Upstate Colorado Economic Development, agrees. The public/private nonprofit economic corporation loaned $500,000 to A1 Organics for its part of the project.

"This positions Weld County as an energy economy," he said, adding that he appreciates the synergy between area businesses participating in the project. For example, local dairy farms provide milk to Leprino Foods of Greeley, which sends its expired cheese and other products to the Heartland site to be transformed into natural gas and peat moss. Dairy farms also provide the manure. "It's really been such an innovative way to get another form of renewable energy," he said.

And the Heartland Biogas Project is not done yet. A second phase is planned with four more digester tanks, which could make the digester facility the largest of its kind in the world. ❖

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