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How small trees and woody biomass could limit carbon emissions and curb wildfire

New research out of the University of California (UC) Berkley outlines how creating a market for smaller diameter trees and other forest biomass could support forest managers to reduce wildfire risk without generating extra carbon emissions.

Clearing the state’s forests of dense overgrowth is crucial to mitigating the risk of catastrophic wildfires. However, this approach has typically used prescribed burning — a technique that releases stored carbon back into the atmosphere and reduces the ability of forests to alleviate the effects of climate change.

Scientists behind the research believe if a market for small diameter trees and biomass was created by encouraging the use of innovative timber products with long lifespans, there could be a consequent economic incentive for forest management to pursue thinning without burning.

The study’s first author, Bodie Cabiyo, a PhD candidate in UC Berkeley’s Energy and Resources Group, noted that difficulties currently exist around effectively managing California’s forests without releasing carbon.

“But if we’re really efficient and careful about how we are using the wood and invest in innovative wood products that can use waste wood, we can achieve both net carbon and wildfire mitigation benefits,” said Cabiyo.

California has made a commitment to achieving full carbon neutrality by 2045, mainly by reducing emissions and investing in carbon sinks, such as forests. Conversely, in conjunction with the US Forest Service, two years later the state also committed to the prescribed burning and thinning of one million acres of forest.

“A lot of people are pointing towards forests as a source of sucking carbon out of the air and not adding carbon to the atmosphere,” Cabiyo said.

“If you drive through these forest treatment projects, you’ll see massive burn piles that can be over 20 feet tall — the size of multiple school buses — and they’re just sitting there waiting to be combusted. That’s a lot of carbon that is going to go back into the atmosphere.”

Smaller trees and underbrush residues produced through forest thinning are currently considered to have little market value in California, particularly in comparison to larger trees that can be harvested and sold to sawmills.

However, small trees and woody residues don’t have to end up as redundant waste that needs to be burned. For example, in other parts of the world engineered lumber is produced by mixing these residues with adhesives, before compressing them into large sheets. These sheets are strong enough to be used in construction. In fact, many existing Californian houses were built using imported engineered wood.

In addition, biofuel plants can convert biomass into electricity or liquid fuel. If equipped with carbon capture technology, these plants can produce this energy while still removing carbon dioxide from the atmosphere.

“While the goal to manage a million acres per year is fantastic and absolutely necessary, the reality is that a million acres per year will cost a lot of money to manage, and it’s still unclear where that money is going to come from,” said Cabiyo.

The analysis demonstrates how the right set of state-directed policies and incentives focused on the increased use of innovative wood products could result in private landowners generating the funds necessary to expand forest thinning without the need for prescribed burning, and so limiting carbon emissions and wildfire risk.

Senior author Daniel Sanchez, an assistant cooperative extension specialist in UC Berkeley’s Department of Environmental Science, Policy, and Management, said the research team hopes its study will help align these two goals, while also providing a framework for managing temperate forests across the world to meet the needs of a changing climate.

“When it comes to carbon storage or sequestration, some people focus only on what’s in the forest,” Sanchez said.

“We wanted to assess the carbon emissions associated with the whole lifecycle of these new products.”

The researchers calculated carbon emissions under a hypothetical scenario involving a state-created market for wood residues. This was achieved by analysing emissions and carbon capture associated with a timber product from the moment the wood is harvested to the end of the product’s life. Alongside this, they calculated future carbon emissions under a business-as-usual scenario.

This analysis suggested that by investing in and incentivising industries that create innovative wood products or convert biomass into biofuels using carbon capture technology, a state-supported market for wood residues that would help avoid the need for burning and the generation of significant carbon emissions was preferable.

“If California starts doing thinning treatments at a large scale, then we’re going to be producing a lot more lumber and wood residues, and where that material goes is a question,” Cabiyo said.

“We found that using that new material for building affordable housing could produce massive carbon benefits, largely because those buildings otherwise would be built with steel and cement, which have significant carbon emissions associated with them.”

This research was published in full in the journal The proceedings of the National Academy of Sciences (PNAS).


Source: Phys.org

Posted Date: April 19, 2022

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