Assessment highlights about the effects 

of harvest slash collection on carbon and 

soil productivity - projects of the Northwest 

Advanced Renewables Alliance

USDA is an equal opportunity provider, employer, and lender.

November 2016: 

Alaska Airlines made the first commercial flight 

powered in part by renewable fuel made from wood 

waste salvaged from tribal and private lands in 

Washington, Oregon, and Montana.

These assessments were 

projects of the Northwest 

Advanced Renewables 

Alliance (NARA). 

Using residual biomass 

from logging operations 

as feedstocks, NARA aims 

to create a sustainable 

industry to produce 

aviation biofuels and 

value-added co-products.

About NARA 

https://nararenewables.org 

Led by Washington State University, the NARA project includes a broad 

alliance of private industry, government laboratories, and educational 

institutions throughout the United States. The project includes study 

sites affiliated with the North American Long-Term Soil Productivity 

Network (Fall River, Matlock, and Molalla) which were established with 

support from the forest industry and U.S. Forest Service Research and 

Development through the Agenda 2020 Program. 

United States Department of Agriculture

NARA was funded from 2011 through 2016 by the Agriculture and Food 

Research Initiative competitive grant no. 2011-68005-3016 from the 

USDA National Institute of Food and Agriculture.

WOOD TO WING

The Economics of a 

Wood-based Biorefinery 

in Longview, Washington
Do avoided emissions from slash pile burning offset 

emissions from collecting, transporting, and using 

post-harvest biomass residuals?

About 40 percent of a tree (excluding roots) is left behind 

during timber harvests in the Interior West. This residual 

biomass is generally piled and burned or left to decompose, 

it could be used as feedstock for wood-based biofuel. 

Burning it releases the embedded carbon with air pollutants. 

The machinery used to collect and transport the feedstock to 

the treatment facility also emits carbon—but comparatively 

how much? 

A planted Douglas-fir following whole-tree harvesting. 

NARANARA

 A researcher measures the efflux of carbon dioxide from the soil near 

a planted Douglas-fir to determine soil microbial activity. 

Tim Harrington

Residual Biomass Harvesting and 

Soil Productivity 

A slash pile: it can be burned, left to decompose, or used to produce biofuel. 

Is residual biomass harvesting detrimental to the 

long-term productivity of the soil? 

Four study sites in the Pacific Northwest are helping to 

answer this question.

KEY FINDINGS 15 YEARS IN

Soil type matters

• Removing biomass residuals has little effect on tree 

regrowth at sites with rich, highly productive soil.

• Tree regrowth was negatively affected at sites with coarse, 

lower productivity soil. 

Competing vegetation fills void, resulting in reduced 

tree growth

• Residual biomass can act as mulch by conserving soil 

water and cooling the soil, which inhibits germination 

of invasive species, such as Scotch broom, that compete 

with Douglas-fir for water, nutrients, and light. Residual 

biomass also provides habitat for native vines that help 

exclude non-native forbs, grasses, and shrubs.

Soil compaction isn’t an issue

• Standard harvesting practices did not negatively affect 

tree regrowth. A positive response was seen at sites with 

coarser soil, likely because compaction increased waterretention capacity of soil.

Residual Biomass Harvesting and 

Carbon Emissions 

KEY FINDINGS

Harvesting residual biomass rather than burning it: 

• Reduces greenhouse gases 

• Improves local air quality 

Collecting, grinding, and transporting residual biomass 

comprise 20 to 30 percent of the global warming potential 

associated with the conversion of biomass to jet fuel.

How does the global-warming potential of wood-based 

jet fuel compare to petroleum-based jet fuel?

KEY FINDINGS

A 70-percent reduction in global-warming potential can be 

achieved by substituting 100-percent petroleum-based jet fuel 

with 100-percent wood-based jet fuel.

Co-products that displace other coal-based products would 

further improve the environmental footprint of the residualbiomass-to-jet-fuel conversion process. Activated carbon, used 

in water and air filters, is one such possible co-product.