Turning slash piles into valuable commercial products is an economic challenge; two significant economic hurdles are the cost to process and transport forest residuals and the capital costs needed to build new facilities or retrofit existing ones.
NARA researchers and graduate students associated with the Integrated Design Experience (IDX) course approach this challenge by identifying existing wood processing facilities throughout Idaho, Montana, Oregon and Washington and developing methods to select those facilities that can participate in the supply chain at the lowest cost. In addition, the IDX students provide design options to retrofit existing wood processing facilities, which can in most cases, result in lower capital costs compared to newly built facilities.
Sugar depots are a type of facility that would convert forest residual chips or pellets into simple sugars, which could be concentrated and transported to refineries for conversion into biofuels and other chemical products. Existing pulp mills, which convert wood into paper and lignosulfonates, are ideal candidates to accommodate the role of a sugar depot because much of the infrastructure used to make paper can be also used to produce simple sugars. The addition of simple sugar production capacity could increase a mill’s product portfolio and enhance the facility’s economic sustainability.
Recently, the IDX course, comprised of WSU civil engineering and University of Idaho landscape architecture students, provided regional stakeholders a webinar where they discussed design considerations for retrofitting an existing pulp mill to produce simple sugars.
View the IDX webinar Site Design for Liquid Depot here
Site selection for sugar depot design
Two hundred and fifty potential facility sites were narrowed down to 30 using a mapping approach where assets like biomass availability, port access, social capital, and electricity rates were layered to show “hot spot” regions most suitable for liquid depots.
Assets like total acreage, natural gas rates, transportation options, and water treatment facilities were evaluated for the 30 sites and applied weighted scores. From this ranking process, the Georgia Pacific Wauna Paper Mill in northwestern Oregon scored highest as a potential liquid depot, and this site was chosen as a model site for retrofit design concepts and cost estimates.
Site design
In the webinar, the students identified two locations on the property for potential development and described the advantages and disadvantages for each siting option. All of the design considerations were based on supporting economic, social and environmental sustainability. For the site design, they considered the topography and existing site layout along with potential constraints such as flood zones, wetlands and soil types.
Key design areas described in the webinar focused on a parking lot expansion designed to handle the additional woody biomass storage and transport, the chemical pretreatment area, transportation flows, and accommodations to handle water runoff in an environmentally sustainable manner. For water flow and treatment designs, they incorporated the use of wetlands, sedimentation basins and bio-retention ponds.
The cost for a sugar depot retrofit was estimated at 281 million dollars based on their designs.
Student professional development and stakeholder benefit
The IDX students perform critical data gathering and analyses for the NARA project and for regional stakeholders. Their work to date can be found at https://nararenewables.org/features/supply-chain-analyses, and all of the student work from the past four years will be incorporated into a final supply-chain analysis for the ID, WA, OR and MT region in 2016. A written report for the design analysis described in the webinar will be available soon.
Nearly 100 undergraduate and graduate students with varied study interests including law, engineering, and design have participated in the IDX work for NARA. These students leave with an amazing understanding of biomass and biofuels supply chain issues and how it all works. Already, the students are getting jobs in the region as planners, architects, and engineers and becoming the bioenergy experts in their communities and in business.
The impact from these students entering the bioenergy workforce is a desired outcome of NARA’s bioenergy literacy goal. An additional benefit is that data and outreach accomplished through their efforts educates Pacific Northwest stakeholders.