Comparing the LCA’s of fossil-based jet fuel to biojet fuel from forest residuals. The image is from CINTRAFOR's publication of "Environmental Assessments of Woody Biomass Based Jet-Fuel".
Comparing the LCA’s of fossil-based jet fuel to biojet fuel from forest residuals. The image is from CINTRAFOR’s publication of “Environmental Assessments of Woody Biomass Based Jet-Fuel”.

Replacing fossil fuel-based products with bio-based products are good for the environment…right? How do we know? A technique used to answer this question is a life cycle assessment (LCA), which assess the overall environmental impacts associated with a product or activity throughout its life cycle. LCAs can be used to compare the environmental impact of one product to another, and standards are adopted to ensure that the assessments are complete and relevant.

NARA is conducting a life cycle assessment of forest residual-based biojet fuel. The LCA-based global warming potential (GWP) impact assessment has economic implications for the overall feasibility of the project. A 60% reduction in GWP potential associated with NARA biojet fuel, as compared to fossil based jet fuel, ensures that the forest residual-based biojet fuel meets the greenhouse gas reduction target specified in the US Energy Independence Act and is a necessary step to qualify for renewable identification numbers (RINs) and for public procurement eligibility.

To review a report on the renewable fuel standards, RINs, and how they relate to NARA, view here.

In a recent newsletter published by the Center for International Trade in Forest Products (CINTRAFOR), NARA researchers at the University of Washington provide the framework and preliminary findings for an LCA on producing woody biomass-based biojet fuel.

To read Environmental assessments of woody biomass based jet-fuel, click here.

Key findings

The paper describes the overall scope of the LCA and lists the assumptions, benchmarks and scenarios used to evaluate the environmental implications of producing biofuels in the NARA sub-region of western Montana, northern Idaho and eastern Washington (previously titled the western Montana corridor (WMC)). Listed below are key findings and assumptions expressed in the paper.

  • Sixty one percent of the above ground biomass harvested from a mature forest in the WMC region consists of sawlogs and pulp logs; 39% is considered forest residuals (branches and tops). Approximately 58% of those forest residuals are available for use as feedstock while the remaining residuals are left on the forest floor or at the landing site.
  • Hauling forest residuals over forest roads from the landing to a secondary landing where the residuals are ground to chips produced significantly more smog and CO2 than harvesting and chipping activities and chip transport on paved roads to a depot or conversion facility. The use of a roll-off containers verses a dump truck to transport residuals on forest roads greatly reduced CO2 emissions.
  • The avoided environmental impacts derived from using forest residuals to produce biojet fuel rather than burning them in slash piles result in a 62.2% reduction of the global warming potential. After accounting for the avoided emissions from slash pile burning, Harvesting, processing and hauling feedstock from the harvest site to a conversion facility produces approximately 15% of the total CO2 emissions generated in using forest residuals to make biojet fuel. The remaining 85% emissions are generated at the biorefinery.
  • The assessment assumes that 6.857 kg of bone dried woody biomass produces 1 kg of iso-paraffinic kerosene (jet fuel).
  • Depending on the transportation scenario used, 56% to 70% less CO2 and 35% to 89% less smog are produced when forest residuals are used to produce biojet fuel rather than jet fuel made from petroleum.

More LCA refinement

The LCA is a work in progress as more data becomes available. Since this paper’s publication, a preferred pretreatment protocol has been chosen, and harvesting and logistical information has been updated for the west side of the Cascades. The NARA research project will conclude in the summer of 2016, and a more complete and refined LCA will be available then.

NARA just concluded its third annual meeting in September at Seattle. At this meeting, the LCA lead researcher Indroneil Ganguly presented an update, which can be viewed on NARA’s YouTube page.

To view Indroneil’s presentation “Life Cycle Assessment of Biomass Scenarios” click here.