Denver Zoo cancels plan to turn animal dung into energy

This is a story that Billy, Dolly and the rest of the elephants at the Denver Zoo will probably never forget: how they almost, but not quite, became not just animals on exhibit, but also sources of renewable energy.

A decade or so ago, zoo leaders had an innovative idea. As part of their quest to become “the greenest zoo in the country” and a zero-waste facility by 2025, they would develop a technique to transform elephant dung and other waste at the zoo such as paper plates and dirty diapers into fuel pellets that would generate electricity through a process called gasification.

The power would help light and heat the 10-acre elephant exhibit and warm pools in which the animals wade and swim in the winter. The zoo estimated it would reduce what it sends to landfills by 90 percent.

The state and the city said yes. The Environmental Protection Agency was interested, as was the National Renewable Energy Lab. Permits were obtained. The gasification plant would be built on the zoo grounds in the heart of Denver’s City Park.

The zoo showed off the project’s potential by powering a blender to make margaritas and, later, a motorized rickshaw that went on a promotional tour to zoos across the West. This green electricity would power an elephant exhibit sponsored by a major consumer of fossil fuels, Toyota.

“Everyone was on board,” said Tiffany Barnhart, a spokeswoman for the zoo. “Everyone loved it.”

Nearly everyone.

As the years passed and plans proceeded, a small but persistent group of neighborhood activists began raising questions and applying pressure to the City Council. Would the plant disrupt peaceful City Park? Would it really meet air quality regulations? The zoo said of course it would – it would have to. The Denver Post stood up for the project this month.

That prompted still more neighborhood reaction. Larry Ambrose of Denver’s Inter-Neighborhood Cooperation wrote back, saying that the project needed more study and had been “unilaterally” approved by a parks manager appointed by the city’s mayor, Michael Hancock.

He noted that his group had been frustrated by a decision several years earlier to take certain park zoning decisions away from the City Council, ostensibly reducing the ability of residents to influence policy.

Barnhart said opponents often mischaracterized the project as an incineration plant when it would have operated through safe and relatively clean gasification.

There were also questions of money, priorities and practicalities. The zoo had spent nearly $4 million during construction. Yet, while the plant was nearing completion, the zoo was still refining the development of the fuel pellets.

“What we were still working on was pellet consistency,” Barnhart said. “How do you create a consistent pellet out of an inconsistent waste stream?”

Another factor: The zoo hired a new president and chief executive, Shannon Block. She started in March and began pursuing a new master plan for the zoo.

Using elephant waste to make energy, it turns out, will not be in it.

On Friday morning, Block and other zoo leaders called the whole thing off. Sort of. Block said the zoo would no longer pursue the project, but hoped another entity, to be determined, would perhaps take the expensive equipment somewhere else and complete the plan.

“This project has elevated the scientific dialogue,” Block said Friday. “We want this technology to succeed. Although this is a difficult decision, it is the one that makes the most sense to ensure the project continues to completion off-site, and to ensure that the zoo achieves our highest priorities moving forward, including implementation of our new master plan.”

Whether the elephant poop is ever made into energy, it and the waste of other herbivores at the zoo will still have a noble second purpose: compost, or in Barnhart’s words, “garden amenities.”

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Local News

City of Everett Engineer Tom Hood, left, and City of Everett Engineer and Project Manager Dan Enrico, right, talks about the current Edgewater Bridge demolition on Friday, May 9, 2025 in Everett, Washington. (Olivia Vanni / The Herald)
How do you get rid of a bridge? Everett engineers can explain.

Workers began dismantling the old Edgewater Bridge on May 2. The process could take one to two months, city engineers said.

Smoke from the Bolt Creek fire silhouettes a mountain ridge and trees just outside of Index on Sept. 12, 2022. (Olivia Vanni / The Herald)
County will host two wildfire-preparedness meetings in May

Meetings will allow community members to learn wildfire mitigation strategies and connect with a variety of local and state agencies.

Helion's 6th fusion prototype, Trenta, on display on Tuesday, July 9, 2024 in Everett, Washington. (Olivia Vanni / The Herald)
Helion celebrates smoother path to fusion energy site approval

Helion CEO applauds legislation signed by Gov. Bob Ferguson expected to streamline site selection process.

Vehicles travel along Mukilteo Speedway on Sunday, April 21, 2024, in Mukilteo, Washington. (Ryan Berry / The Herald)
Mukilteo cameras go live to curb speeding on Speedway

Starting Friday, an automated traffic camera system will cover four blocks of Mukilteo Speedway. A 30-day warning period is in place.

Carli Brockman lets her daughter Carli, 2, help push her ballot into the ballot drop box on the Snohomish County Campus on Tuesday, Nov. 5, 2024 in Everett, Washington. (Olivia Vanni / The Herald)
Here’s who filed for the primary election in Snohomish County

Positions with three or more candidates will go to voters Aug. 5 to determine final contenders for the Nov. 4 general election.

Students from Explorer Middle School gather Wednesday around a makeshift memorial for Emiliano “Emi” Munoz, who died Monday, May 5, after an electric bicycle accident in south Everett. (Aspen Anderson / The Herald)
Community and classmates mourn death of 13-year-old in bicycle accident

Emiliano “Emi” Munoz died from his injuries three days after colliding with a braided cable.

Danny Burgess, left, and Sandy Weakland, right, carefully pull out benthic organisms from sediment samples on Thursday, May 1, 2025 in Everett, Washington. (Olivia Vanni / The Herald)
‘Got Mud?’ Researchers monitor the health of the Puget Sound

For the next few weeks, the state’s marine monitoring team will collect sediment and organism samples across Puget Sound

Cal Brennan, 1, sits inside of a helicopter during the Paine Field Community Day on Saturday, May 17, 2025 in Everett, Washington. (Will Geschke / The Herald)
Children explore world of aviation at Everett airport

The second annual Paine Field Community Day gave children the chance to see helicopters, airplanes and fire engines up close.

A person walks past Laura Haddad’s “Cloud” sculpture before boarding a Link car on Monday, Oct. 14, 2024 in SeaTac, Washington. (Olivia Vanni / The Herald)
Sound Transit seeks input on Everett bike, pedestrian improvements

The transit agency is looking for feedback about infrastructure improvements around new light rail stations.

A standard jet fuel, left, burns with extensive smoke output while a 50 percent SAF drop-in jet fuel, right, puts off less smoke during a demonstration of the difference in fuel emissions on Tuesday, March 28, 2023 in Everett, Washington. (Olivia Vanni / The Herald)
Sustainable aviation fuel center gets funding boost

A planned research and development center focused on sustainable aviation… Continue reading

Dani Mundell, the athletic director at Everett Public Schools, at Everett Memorial Stadium on Wednesday, May 14, 2025 in Everett, Washington. (Will Geschke / The Herald)
Everett Public Schools to launch girls flag football as varsity sport

The first season will take place in the 2025-26 school year during the winter.

A “SAVE WETLANDS” poster is visible under an seat during a public hearing about Critical Area Regulations Update on ordinance 24-097 on Wednesday, May 14, 2025 in Everett, Washington. (Olivia Vanni / The Herald)
Snohomish County Council passes controversial critical habitat ordinance

People testified for nearly two hours, with most speaking in opposition to the new Critical Areas Regulation.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.