California North Coast agencies wonder what to do with all the wood waste
As California ramps up attempts to reduce woodland fuels for destructive wildfires a parallel effort has been emerging to both keep that woody waste out of landfills and perhaps help with the state’s need for always-on renewable energy.
In Marin County, a coalition of clean-energy, waste and natural-resources organizations is looking into how much woody green waste there is, where it’s coming from, what’s currently happening to it and what are other and potentially better things to do with it.
As part of that effort, the Marin Resource Conservation District in September was awarded $500,000 for one of five pilot studies statewide on local biomass.
That’s the term for shrubbery, trees and other vegetation. The agency inked a $285,000 contract with TSS Consultants to talk with waste managers, foresters and land managers about how they collect, process and use biomass waste.
Beyond compost and mulch, potential uses for biomass waste include fertilizer, engineered wood products, securing renewable gases such as hydrogen and methane (natural gas), and generating electricity, according to Chad White, Ph.D., manager of the district’s 3-year-old Marin Biomass Project.
“We’re looking what Marin has and look at what is most practical to build on existing infrastructure and meet carbon goals of Marin,” White said.
This parallels the Marin Carbon Project, a district effort since 2008 to research and undertake carbon sequestration on farmland. The district has completed 19 carbon farm plans, which lay out how practices will trap carbon into the soil, and 68 properties are on the waiting list.
“Landfill diversion and carbon farming are pillars of the project to help the biomass and carbon projects come together,” White said.
That merging could happen along the state’s 2030 and 2045 timelines for a zero-net-carbon economy, he said.
The Marin Biomass Project is partly an outgrowth of two state laws and a county parcel tax.
Assembly Bill 1383, a June 2021 law that requires a 75% reduction in food and plant waste going into landfills by 2025. The goal is to reduce the amount of human-produced methane, considered a potent greenhouse gas and generated by decomposing biomass in the landfills.
That followed Senate Bill 1385, which as of last year required curbside collection of organic waste.
And in 2020, Marin voters passed Measure C, a parcel tax that raises an estimated $19.3 million annually for 10 years to establish the Marin Wildfire Prevention Authority. From this comes a drive to create defensible spaces around homes, clearing brush and reducing fire fuel.
Throughout this year, the Marin Biomass Project will be completing draft findings, wrapping the report by mid-2024.
Marin Sanitary Service currently takes in 25,000 tons a year of woody material, enough to fill three to five big trucks full daily that go to biomass-burned power plants in the Central Valley, in Woodland and Stockton, according to Justin Wilcock, director of operations.
“We receive that material from all over North Bay and other parts of the Bay Area,” Wilcock said. “They come from homeowners who bring loads in, to landscapers to tree companies doing bigger projects. We get green materials and clippings to big trunks and cut-down trees.”
Smaller material can go to the composting operation at Redwood Landfill north of Novato, he said.
At Napa Recycling & Waste Services, part of the same ownership as Marin Sanitary, the operation is about to go out with a request for proposals for a biomass gasification plant, according to Tim Dewey-Mattia, recycling and public education manager.
Gasification is a process that uses high heat without combustion and a certain amount of oxygen or steam to turn organic matter into carbon monoxide, hydrogen and carbon dioxide gases that can be captured. Hydrogen gas can be used for clean combustion or used in fuel cells to generate electricity.
Another conversion method for synthesizing such gases (called, syngases) is pyrolysis, which doesn’t use oxygen and generates carbon dioxide and hydrogen gases.
A joint project with the city of Napa, the estimated $20 million project would generate synthetic hydrogen that could be used to generate electricity and also biochar, a charcoal-like substance that has multiple industrial and agricultural uses.
“Generating green electricity from our wood still makes sense, and we will only need more electricity when we electrify our trucks,” he said.
In 2018, the company replaced its fleet of 40 trucks with compressed natural gas models, but now the organization is looking at the proposed state phase-out of combustion heavy vehicles in favor of electric models. Those currently cost $500,000 each and don’t have enough torque to be suitable, he said. Hydrogen fuel cell trucks, which use the gas to produce electricity and output water vapor, could be an alternative.
