Alternative Fuels from Landfills
Landfill Gas, Canola, and Biodiesel: Working Towards a Sustainable System
With Snohomish County’s commitment to the use of biodiesel, an ongoing project has helped to lessen dependency on imported petroleum as well as added to the economic diversity of the County by creating new crops and jobs.
Terrill Chang, P.E. and Deanna Carveth
Snohomish County in western Washington State began converting its vehicle fleet to a blend of biodiesel in 2005. As prices for biodiesel rose due to increased demand for this cleaner-burning fuel, Snohomish County looked to its farmers to “grow” this fuel locally. Suitable oil seed crops for biodiesel feedstock include canola, mustard, and camelina. The residue, or meal, has high value as an animal feed. County farmers began with 52 acres of canola and mustard crops in 2006, increasing to 300 acres and 700 tons in 2009.
The team consisted of Snohomish County Public Works, engineering firms (URS Corporation and Parametrix, Washington State University Extension, Wolfkill Feed and Fertilizer (local fertilizer company) and various equipment suppliers, It was necessary to develop local infrastructure for the canola project because canola is not a traditional crop in Snohomish County. To reduce the project’s cost and environmental footprint, the County tapped the methane content in landfill gas from the closed Cathcart Landfill south of the City of Snohomish and about 35 miles north of Seattle as the energy source for the seed dryer, in lieu of propane or natural gas. The canola processing facility is located at the landfill site, adjacent to the existing landfill gas blowers and flares. Project benefits include:
Revitalization of the local agricultural community, increasing the County’s economic diversity, a key goal of County government
Addition of an excellent rotational, low tillage crop that can also convert pasture into row crops
County ownership of a commercial facility suitable for drying other grains and crushing other seeds for oil production
A central location of the dryer and crusher that reduces transportation to processing and to the refinery that converts the canola oil into biodiesel
A beneficial use of a declining landfill gas stream that still contributes to reaching sustainability in vehicle fuel
This paper discusses the challenges of the design and equipment procurement process, permitting, construction and startup, operational results and lessons learned.
The goals of this project are to:
Support the use of biodiesel in Snohomish County’s vehicle fleet
Support local agriculture
Beneficially use landfill gas, an energy source previously wasted through flaring
Create community resiliency by reducing dependence on petroleum-based fuels and shortening supply lines
In 2005, the County’s Fleet Management group committed to using a cleaner fuel in the County’s diesel trucks and began converting its fleet to use a 20 percent biodiesel blend (B-20). In 2009, the County increased the blend to 40 percent (B-40); local farmers “grew” 30 percent of that amount, supporting the County’s “Focus on Farming” initiative (local farmers interested in growing an economically viable crop with a local market were identified).
A supply of unused methane gas was available as landfill gas (LFG) currently being flared at the Cathcart Landfill. The landfill closed in 1992, with about 1.97 million tons of waste in place. Current gas flows are about 700 cfm with a methane content of about 30 percent.
By growing and locally processing fuel for Snohomish County’s diesel fleet, the County has eliminated the risk of supply line disruptions. Further, by strengthening its local agricultural community, the County has preserved farmland for food production.
In January of 2006, a group of Snohomish County farmers approached the County Executive seeking a crop to support the County’s new biodiesel initiative. Working with Washington State University (WSU) Extension offices, growers planted small field trials (52 acres) of two mustard variants and two canola variants to determine which of these Brassica family members would grow best in the wet, overcast climate of the Snohomish River valley. Brassicas were chosen because they favor moist, cooler growing seasons and because the fuel they produce can reach 28ºF before gelling making it preferable for our cooler winters. In contrast, soybeans prefer a hotter growing climate and their biodiesel has a cloud (gel) point of 36ºF.
Both crops grew better than expected. Canola had a higher yield (pounds per acre) than mustard and more viable markets for both the oil (35 percent of total crop weight) and the leftover meal (65 percent of total crop weight), a sought-after animal feed.
The County provided a grant to SnoSky Agricultural Alliance, a grower’s non-profit organization, to manage the field trials, pay WSU staff, and otherwise promote the project in both 2006 and 2007. The Alliance determined that a combine was needed to effectively harvest the crop and used grant funds to procure a Combine.
The growers attempted to field-dry the harvested canola, but western Washington proved to be too rainy and the seed germinated, rendering it useless for oil extraction. Growers decided a crop dryer was essential to successfully harvest and market this crop. Snohomish County and its partners began design work for full-scale infrastructure.
The previous year’s crop trials favored Hyola canola, so three 50-acre plots were planted. Wolfkill Feed and Fertilizer found and transported a used 8-ton batch dryer from Lipton, Saskatchewan, Canada to the Cathcart Landfill. County staff connected it to the LFG system and dried the canola. The LFG-fired dryer was deemed a successful proof-of-concept. Seed samples taken before and after drying showed no changes to seed chemistry due to exposure to LFG.
It became clear that the combine and batch dryer were insufficient infrastructure on which to base a viable enterprise. Also, lack of local processing meant trucking the seed 300 miles east across the Cascade Mountains to Sunnyside, Washington, eliminating profits in 2007.
2008 was the critical year. The County received a $344,400 earmark via the Department of Energy and a $500,000 Energy Freedom Fund Grant from the Washington State Community Trade and Economic Development Department. Along with funds authorized in the solid waste budget, procurement and installation began.
The first purchase was a 15-ton continuous flow commercial seed dryer with centrifugal fans, a 475-bushel holding capacity, screens sized for canola (0.050-inches), natural gas burners, oversized piping for low-BTU LFG, and digital temperature/moisture monitoring to control burners and fans. URS Corporation and the County had hoped to recover heat from an existing LFG flare by re-routing hot exhaust gas through an air-to-air heat exchanger to produce clean, hot air to dry the seed. However, the flare manufacturer declined to place a fin-tube heat exchanger cross-wise in the 8-foot diameter flare, citing concerns about corrosion and restricting the vertical flow of exhaust gas. Ductwork to capture exhaust gas at the top of the flare was also considered, but there was no precedent for such a design. Finally, quotes for a heat exchange system approached $750,000, exceeding the available budget
The next purchase was seed storage silos (356 ton capacity) and handling equipment. Trucks unload on a concrete pad, where the in-ground auger conveys the seed through a seed cleaner and into the bucket elevator. The elevator lifts the seed to the top of the silos, where an 8-way distributor directs the seed to the appropriate silo. Bottom U-trough augers and pipe augers move the seed to the dryer or the elevator. The auger and elevator system provided a continuous feed of canola to the new dryer, which dried 286 tons of canola and 414 tons of mustard in 2008.
Engineering work by URS Corporation and Parametrix included the design of concrete slabs, roadways, drainage, power supply, agricultural equipment specifications and the air permit application. To reduce costs, Public Works crews familiar with the landfill site built the concrete pads and roads, placed the dryer, and connected the LFG piping and electrical power supply. The project used Department of Energy funds to pay for the access road and consulting services, and Energy Freedom Funds for the crusher system.
Solid Waste Division and Specialty Laboratories of Texas determined that using a gas chromatograph/mass spectrometer (GC/MS) analysis showed the most potential contaminants for the least cost. This type of screening would also prevent missing a key constituent of concern by looking for all constituents rather than a few named isomers. Testing in 2007, 2008 and 2009 showed that wet or green seed has exactly the same “fingerprint” as the dried seed, except that volatile organic compounds that naturally occur in the green seed are significantly lower in the dried seed. The landfill gas did not adhere or absorb any contaminants onto the seed.
In spring 2009, a seed cleaner, crusher and extruder were installed. About 12 tons of canola from the 2008 fall harvest was used to test the crusher and extruder, producing about 1000 gallons of oil and 8 “super sacks” of meal used for animal feed. The meal contained about 7 to 9 percent oil, which means that the incoming seed had about 42% oil, much higher than expected. A second grain elevator was installed to improve functionality. Overall, 330 tons of material was dried including 214 tons of mustard, 85 tons of canola and 31 tons of barley; more crops were field dried this year due to an unusually dry summer.
Results and Findings
Two crops per year of canola can be grown successfully in western Washington’s cool and rainy climate. The spring harvest of the winter crop takes place around late-June. The seed must be dried and the oil extracted before the fall harvest (about mid-September) of the spring-planted crop.
Even using low-BTU LFG (~30 percent methane), the dryer functioned properly and met air emissions requirements. A manifold tank was installed between the LFG compressor and the dryer to accumulate enough gas at pressure to start the ignition sequence.
The County Public Works system was not geared to agricultural projects—the atypical equipment and the urgent timing of the crops were a challenge. Because the project was designed and constructed over several years by multiple parties, using new and refurbished equipment from various vendors, funded by grants as well as County funds, the County was forced to act as the system integrator.
Farmers and other members of the local agricultural community worked collaboratively with the County. Their support and continued interest in growing oil seed crops is critical to the long-term success of the County’s biodiesel initiative.
A matter of great interest was whether burning LFG in the dryer would produce compounds such as dioxins that adhered to the seed. The GC/MS methodology allowed comparison of the chemical fingerprints of wet and dry seeds. Complex market economics also affect the long-term viability of the biodiesel system.
One measure of success is the increase in the acres of canola grown for biodiesel. Canola is a great rotational crop and it is anticipated that acreage will grow to about 1,000 acres in production each season.
Available funding provided the window of biodiesel opportunity in Snohomish County. The Solid Waste Division had looked at using landfill gas to generate electricity previously. The Pacific Northwest power market has a very high percentage of hydropower, electricity has historically been inexpensive, making alternative technologies difficult to justify financially. In 2013 the Bonneville Dam bonds will be paid off, allowing the Bonneville Power Administration greater ability to ship “green” power out of the Pacific Northwest. This will increase opportunities for newer technologies to compete in the Puget Sound region as local utilities work to meet green power mandates.
The County is currently looking at Department of Energy ARRA grant dollars to use combined landfill gas and methane from a near by dairy farm for energy. This same grant incentivizes the capture of waste heat which the Division can potentially use to run the dryer, run a boiler to make steam for the de-gummer system and potentially pre-heat the wash water in the nearby truck wash. Local production of fuel promotes local jobs and economy, preserves acres for farming not houses, ensures we have fuel when we need it should supply lines be disrupted.
This project continues to be important on several levels. First, it showed that landfill gas, even from a landfill closed 18 years earlier, can be a viable energy source for an industrial process, the drying of crops. Second, groups interested in promoting local agriculture and the use of alternative, non-petroleum fuels worked together cooperatively to grow a non-traditional (for this geographic area) crop and extract two useful products (oil and animal feed meal) that have local markets. Third, it showed that the technology and equipment for a crop-to-fuel system could be assembled and operated at a County solid waste facility. Fourth, because the County offers tours to interested parties, there is an educational and public outreach component that helps inform students and County residents about sustainability, alternative energy and waste management. Fifth, with the County’s commitment to the use of biodiesel, this project helps to lessen dependency on imported petroleum. And last but certainly not least, it has added to the economic diversity of the County by creating new crops and jobs.
Terrill Chang, P.E. is a Senior Solid Waste Engineer for URS Corporation in Seattle, WA. He has 35 years of environmental and mechanical engineering experience, and has been involved in feasibility studies, planning, design, permitting and environmental impact assessment for landfills, incinerators, transfer stations, recycling and compost facilities for government and private sector clients. Current projects include several county solid waste management plans and the design of two transfer stations. Terrill holds degrees in Mechanical Engineering from MIT and Oregon State University and is a licensed engineer in Washington, Oregon and Idaho. He can be reached at (206) 438-2596 or e-mail [email protected].
Deanna Carveth is a Project Specialist IVfor Snohomish County Public Works (Everett, WA). She is a 21-year solid waste professional, starting her career in San Francisco packing small business and household hazardous waste. Currently a project specialist, she manages the Canola to Biodiesel project for Snohomish County, writes and maintains the FEMA approved Disaster Debris Management Plan, assures compliance with NPDES permits, is starting the Greenhouse Gas reporting program and manages the groundwater modeling program for the County’s closed landfills. Deanna can be reached at (425) 388-7607 or e-mail[email protected].
This material is based on work supported by the Department of Energy under award number DE-FG36-08GO88177. Standard disclaimer applies.
The authors also gratefully acknowledge the support of Washington State Department of Commerce’s Energy Freedom Fund and our private partners including Wolfkill Feed and Fertilizer, Whole Energy, and Snohomish Farms including Sno-Valley Farms and Reiner Farms.
This paper was originally presented by Terrill Chang, URS Corporation, during WASTECON© 2009 in Long Beach, California. Excerpts and information from that presentation are reproduced with the permission of the Solid Waste Associate of North America (SWANA).