Fire Chief for East Bay Regional Park District, Aileen Theile, and other park staff spoke at a press event about the carbonator on Tuesday, Oct. 24. Credit: Callie Rhoades

A new climate-conscious machine is helping reduce excess and dead vegetation in East Bay parks. The machine is called a carbonator and is capable of turning as much as 80 tons of trees and shrubs into biochar in a matter of several hours. The biochar—a mostly carbon substance created by burning organic material in an oxygen-limited environment—can then be spread around the land to improve soil quality.

“We realized that we basically had a public safety emergency because we had dead and dying trees all due to climate change that we needed to deal with,” said Aileen Theile, fire chief for the East Bay Regional Park District. “We had to start thinking outside the box and thinking of new and innovative ways to process that.”

Park staff started noticing a significant tree die-off in the fall of 2020. Upon investigation, they found over 1,500 acres of dead trees within the parks, which include thousands of acres of land in Alameda and Contra Costa counties. Most of the trees were eucalyptus and had succumbed to climate change-induced drought and other stresses. 

In one of their first large-scale uses of the carbonator, the park district hopes to clear excess vegetation from 365 acres of land in Anthony Chabot Regional Park, part of which borders East Oakland. The project started in May and is expected to last approximately eight more months. 

A man walks in front of a massive metal box with a gaping steel door.
The carbonator looks like a shipping container crossed with an oven. Credit: Callie Rhoades

The carbonator is a large, truck-like machine with a metal chamber that reaches high temperatures, around 1,300 degrees Fahrenheit, but in a low oxygen environment. While the machine does create some smoke, it is far less than what was emitted by their previous process of shipping downed trees to Sacramento where they were burned for fuel. When it’s done burning the wood, the carbonator dumps out charcoal.

In 2021, the district received around $10 million in state funding to clear dead and dying trees. However, a new challenge emerged as the district began felling and transporting mass quantities of trees out of impacted areas: The carbon emissions from using large trucks to transport the trees out of the parks to Sacramento were significant. Additionally, the large semi-trucks were polluting the air in the parks with their exhaust. According to the park district, the new onsite processing will now significantly reduce the carbon emissions that would have typically been produced in transit. 

The park district has a stockpile of trees in Anthony Chabot Regional Park waiting to be processed. The carbonator can only be run from November to March when the weather is colder and wet and there’s less of a risk that embers could land in surrounding vegetation and cause a wildfire. 

The park district initially tested the new machine with an 80-acre pilot project in Anthony Chabot Park in 2022. After that project’s completion, they started the new project, which is the largest eucalyptus reduction effort in the area to date. 

A tractor works in a dense stand of eucalyptus trees in Anthony Chabot Regional Park.
Park staff work to fell large quantities of eucalyptus trees in Anthony Chabot Regional Park’s dense forest. Credit: Callie Rhoades

Eucalyptus trees have presented a unique problem in Northern California parks for some time. The tree was initially planted in droves in the area in the late 19th century, mainly as a proposed solution to a high demand for timber, but also to serve as windbreaks, improve farmland, and beautify cities. While the trees ended up being unsuccessful as building material, they have since thrived in the California environment and taken over many of the Bay Area’s forested spaces. 

Eucalyptus tends to burn extremely fast during wildfires, spreading dangerous embers far and wide. They also shed dry bark that leaves piles of potential fuel on the ground. 

“Eucalyptus stands, especially unmanaged, are rated, in the general scale of things, a very high fire hazard,” said Givonne Law, fuels reduction coordinator for East Bay Regional Park District. “Their leaves and their bark and a lot of their smaller limbs are producing and covered in volatile chemicals that light on fire. They burn very hot, and that’s because they’re supposed to, that’s how they reproduce. Gum nuts, the seed pods, will pop open in fire.”

Richer soils that sequester carbon

Fire Chief Aileen Theile, Assistant Fire Chief Khari Helae, and Fire Captain Patrick McIntyre chat in Anthony Chabot Regional Park on Tues. Oct. 24. Credit: Callie Rhoades

The carbonator not only eliminates eucalyptus, it also produces a beneficial product for the parks: biochar. According to the United States Department of Agriculture, biochar can be added to soil to help mitigate a wide array of environmental, agricultural, and forestry-based challenges. “Applications of biochar include improving soil health, raising soil pH, remediating polluted soils, sequestering carbon, lowering greenhouse gas emissions, and improving soil moisture.”

So far, most of the biochar created by the park district’s carbonator has been taken to the Ardenwood Historic Farm in Fremont. All biochar created by the project will be dispersed throughout the parks. Park officials say that while they still have a ways to go on this current project in Anthony Cabot, the carbonator may be utilized in other park areas in the future. 

“When you don’t do the kind of work that we’re doing, you have a catastrophic wildfire,” said Khari Helae, assistant fire chief for East Bay Regional Park District. “So we’re thinning the forest, making the area safer, it’s better for the environment, creating the product of biochar for the park district which can now reuse it for other beneficial uses all from this product that really had no good use for us unless it was removed.”

Callie Rhoades covers the environment for The Oaklandside as a 2023-2025 California Local News Fellow. She previously worked as a reporter for Oakland North at Berkeley Journalism’s Investigative Reporting Program. She has also worked as an intern for Estuary News Group, as an assistant producer for the Climate Break podcast, and as an editorial intern for SKI Magazine. Her writing has appeared in Sierra Magazine, Earth Island Journal, and KneeDeep Times, among others. She graduated from The University of California, Berkeley’s Graduate School of Journalism in 2023.