The Yuba I FRB: Reducing landscape fuel risk and turning woody biomass into a green energy source

Forest restoration treatments in semi-arid western North America include a comprehensive suite of activities such as aspen regeneration and meadow restoration but primarily focus on fuel reduction to reduce the risk of catastrophic wildfire.

Written by: Annapurna Holtzapple, Project Associate

Forest restoration treatments in semi-arid western North America include a comprehensive suite of activities such as aspen regeneration and meadow restoration but primarily focus on fuel reduction to reduce the risk of catastrophic wildfire. Due to decades of fire suppression, these western forests are overstocked, which has made them denser than they were historically and is contributing to extreme fire hazard. Suppressed, diseased, or immature trees are particularly hazardous agents of wildfire spread and severity.

Vegetation such as brush and smaller trees are considered a “ladder fuel” when their height acts as a ladder for wildfire to climb from the ground into the canopy of trees, creating crown fire. Crown fires produce more intense burn conditions that these ecosystems and tree species are generally not adapted for, resulting in higher mortality and more significant forest damage. While some trees removed for restoration treatment can be taken to a mill, many of these ladder fuels are too small to be processed into lumber. These small trees are a high priority for thinning but are considered “non-merchantable timber,” meaning that they aren’t big enough to be used by existing mill facilities.

As restoration work progresses, it creates a new challenge: figuring out where to take or what to do with these small trees and other debris produced during forestry operations like branches and tree tops. There are typically two lowest-cost options for these by-products. They can be scattered around the ground at a low level to break up vertical fuel continuity on the landscape, or they can be piled to dry out and burn later, known as “pile burning”.

The Yuba I Forest Resilience Bond (FRB) Project initially intended to chip some of the material for bioenergy production and pile burn the remaining biomass. Despite being functionally and ecologically distinct from “broadcast burning,” which is the practice of applying prescribed fire across the forest floor, pile burning also requires safety measures and precautions. Due to safety considerations, the piles can only be burned under specific conditions, considering variables such as temperature, humidity, and wind. Recently, it has become increasingly difficult for the U.S. Forest Service to meet burn obligations. The hotter and drier effects of climate change have decreased the window of time that burn conditions are safe, making the conditions for a burn window even more fleeting.

Moreover, staff capacity limitations and permit requirements create administrative hurdles and challenges to burning, including the May 2022 national moratorium of prescribed fire on National Forest System Lands issued by U.S. Forest Service Chief Randy Moore. While more controlled than broadcast burning, pile burning is not entirely without the risk of escaped fire. It would be remiss not to emphasize that this rarely happens. As Chief Moore said in his review statement, “Let me be clear. Prescribed fire is an important tool, and we conduct an average of 4,500 prescribed fire projects annually: 99.84% go according to plan.” Still, pile burning inherently requires concentrated areas of dry fuel to remain on the landscape until they can be consumed in fire, thereby leaving that fuel in the forest and posing a fire risk until a burn window aligns.

In the Yuba I FRB, the project team has had a contract to underburn since 2018, and thousands of forest acres are prepped and ready for treatment. However, there has yet to be a window when conditions and staff capacity align to burn at that scale.

In addition to traditional fuel reduction, woody biomass is also generated through meadow restoration treatments. This project has several different ecological components to support a holistic treatment approach. One crucial aspect is meadow and aspen grove restoration. As coniferous trees begin to grow in a meadow area, their water demand alters the hydrologic processes of the meadow. This process, known as “conifer encroachment,” can dry out the ecosystem. In the case of ecologically inappropriate tree growth, a direct and effective restoration treatment is to remove those trees.

In the aspen restoration units of the Yuba I FRB, most of those encroaching trees are lodgepole pine. However, this species currently has almost no merchantable value. At today’s rate of about $1 per tree, transporting and processing these trees is more expensive than their worth. As a result, these trees were initially intended for pile burning. Fortunately, because of funds available from the Forest Resilience Bond, a new innovative solution is underway to address the issue of pile burning challenges across the landscape.

Instead of simply leaving piles of fuel on the landscape, risking a long waiting period before a burn window becomes available, the Yuba I FRB Project is turning that material into a green energy source. With the additional funding made available by the Forest Resilience Bond, the National Forest Foundation has brought massive machines into the forest to grind and cut down those fuel materials into small chips and transport them to Honey Lake Power. At Honey Lake Power, the biomass is burned for steam generation, producing a cleaner source of energy than through traditional fossil fuel production. To date, 8,500 green tons of biomass have come out of the landscape.

While the original planning-phase estimate for the amount of material to be transported for power was 10,000 tons of woody debris, the on-the-ground operations crew now anticipates that the project will haul around 16,000 tons of total biomass for power production. This immediately reduces the fuel hazard on the landscape, rather than leaving the fuel to dry while waiting for a burn window. Additionally, by not having to burn piles in the treatment landscape, the U.S. Forest Service can redirect human resources to do treatment work in another area when a burn window eventually opens. Moreover, this clean energy production offsets fossil fuel consumption of natural gas or coal power emissions.

Blue Forest and our project partners are excited about these co-benefits and will continue to explore creative solutions around wood innovations that can support forest restoration work.