Final Report: Biomethane for Transportation

EPA Grant Number: SU833684
Title: Biomethane for Transportation
Investigators: Leonhardt, Eric , Castillo, Anthony , Cruse, Ryan , Freund, Alex , Jopin, Matt , Parent, Sean , Shaw, Todd , Sjodin, Jeremy , Stazel, Jordan , Swazo, Jamin , Welsh, Geoff , Wohlenhaus, Drew
Institution: Western Washington University
EPA Project Officer: Nolt-Helms, Cynthia
Phase: II
Project Period: August 31, 2007 through July 31, 2008
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2007) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Energy , P3 Awards , Sustainability


To demonstrate the ability of dairy farm anaerobic digesters to produce biomethane for use in a vehicle.

To improve the economic value of the anaerobic digester in the Pacific Northwest and therefore increase the number of digesters operating in the region.

To improve regional air, water and soil quality and to reduce the effective greenhouse gas emissions from dairy farming.

This project will create a biomethane upgrading facility and vehicle fueling station at a dairy. The raw biogas will be provided by an anaerobic digester at the dairy. The project will fuel a bus that has been converted to operate on natural gas.

Summary/Accomplishments (Outputs/Outcomes):

The stated purpose was to develop a refining process for an anaerobic digester and then power school buses in a pilot project to demonstrate the feasibility of the refining process.  The goal was to reduce the hydrogen sulfide of the raw biogas from 3500 ppm to less than 15 ppm while increasing the methane content from 60% to 90% or greater.  The scope was to develop a pilot-scale system capable of producing 10 standard cubic feet of biomethane per minute.  Ideally, the cost of the refinery and fuel station infrastructure should be 10% or less of the digester cost—roughly $200,000 at current costs.  The approach was to have the refinery located at the farm with the anaerobic digester.  A compressor and a storage tank array will be located at the farm as well.  A portable tank array for compressed natural gas will be used to transport fuel between the farm and a bus depot. At the school location, another compressor and compressed natural gas fuel tank array will provide a back-up fuel source for the buses during the pilot project.  

Stated goals included: 

  • Displace a minimum of 10 gallons of daily diesel consumption
  • Reduce annual carbon dioxide emissions per passenger by 720 kg
  • Develop a cost/revenue strategy that reduces the 10 year return on investment to 5 years for anaerobic digester projects
  • Collect data on bus performance and emissions
  • Develop a working model with collected data to compare the costs of biomethane transportation with existing diesel and gasoline alternatives on a county wide basis

Data, outputs, outcomes, findings:  The original timeline for the project was to accomplish most of the tasks during the summer of 2007.  This work was delayed until the spring and summer of 2008.  The team created the original timeline based on the mistaken assumption that the Phase II award funding would be available during the summer of 2007.  This setback aside, the team has leveraged the EPA Phase II award for more than $750,000 of additional funding.  The Whatcom Public Utility District provided $20,000 for the installation costs associated with the compressors and refueling infrastructure.  A joint project with Washington State University has provided an additional $52,000 for faculty research salaries and for student research wages.  This funding has provided assistance to resolve challenges encountered with the original design approach.  The state legislature provided this funding to Washington State University, the fiscal manager, during July 2007.  Our program was unable to access these funds until May 2008, which impacted the hiring of researchers. Although the timing of the project has been impacted significantly, the additional resources should ultimately create a better final product.  In addition, the Washington State University Climate Friendly Farming program provided nearly $150,000 of funding from the Paul G. Allen Family Foundation.  In September 2009, a Puget Sound Clean Cities Coalition, Department of Energy grant of $544,000 was awarded to the project with funding to arrive in April 2010. 

Two goals of the project have changed.  Based on studying past results including simulations of refinery efficiency and cost estimates, the design target of the upgrading unit has been increased to provide 25 standard cubic feet per minute (scfm) of biomethane instead of 10 scfm.  This targets an annual production potential of 100,000 gasoline gallons of equivalent energy or one-third the energy used to power the entire Whatcom County Transit Authority buses annually.  The reason for this change is that the cost of materials for the upgrading unit is small relative to the costs required to build a natural gas refueling station.  The upgrading unit is sized to handle the natural gas compressors purchased for the project

The second change is that the new funding helped bring in additional partners and requirements.  Airporter Shuttle/Bellair Charters is a transit provider that operates more than 50 vehicles in Washington State along the Interstate 5 corridor and from Kennewick, Richland and Pasco to Walla Walla.  They have been working with the project to provide buses that could be converted to operate on natural gas or biomethane.  One challenge has been to find vehicles in their fleet that could be converted to operate on natural gas/biomethane.  To meet the needs of the Clean Cities Coalition Petroleum Reduction funding, any vehicle converted to operate on natural gas must meet 2010 EPA emission standards.  After an exhaustive search, an MCI F coach 36 passenger bus has been selected as the first vehicle to be converted. This vehicle can accept a 2010 EPA-compliant, Cummins Westport ISL G engine that is configured for natural gas.  Discussions with Cummins about converting the vehicle have been underway for more than 1 year. Currently, the project team is waiting for a final quote to perform the engine installation.  One difficulty seems to be the sizing of the cooling system for the new engine.  The project team hopes to be ordering the new engine soon.

Airporter Shuttle is located roughly 17 miles from the dairy farm.  Driving tests performed during the summer of 2009 determined that the buses could not refuel at the farm because of the distance and location of the farm.  The farm is located on the U.S.-Canadian border and may be blocked by border traffic.  A fuel tanker truck is required to move fuel from the farm to the bus depot.  This requires adding compressed natural gas tanks to a vehicle with sufficient capacity to fuel a large motor coach bus.  A Blue Bird bus has been purchased to carry the compressed natural gas tanks.  Up to 10 compressed natural gas tanks will reside in the bus with a capacity of more than 200 gasoline gallons of equivalent energy (GGE).  The bus is equipped for a generator and has space for a mobile natural gas compressor.  A bidding process has begun to purchase the tanks for the tanker truck.

The fueling station and upgrading unit consists of a roughly 20’ x 40’ pad of reinforced concrete.  Upon the pad has been placed a 40’ shipping container that has been partitioned into three rooms, dry walled and insulated for sound, fire protection and temperature.  The entire facility is built to National Fire Protection Association code 52 for natural gas fueling stations.  Two 28 scfm compressors have been installed in the container.  Motor shunts are installed to allow the immediate shut down of the compressors from remote mounted emergency shut down buttons.  The container also stores the programmable logic controller and the systems to help process hydrogen sulfide and carbon dioxide. 

The core refinery unit, based on using amine solutions to remove hydrogen sulfide and carbon dioxide from the biogas, is complete.  The unit consists of two 20-foot towers with a 12-inch inside diameter.  The fiberglass tubes were fabricated locally and are connected with stainless steel piping.  A fractional factorial materials study was conducted to select the materials.  A steel framework to hold the towers was constructed and installed.  A large blower pumps raw biogas into the two towers.  The blower is sized to support more than 50 scfm of flow and raises the inlet gas pressure to the two compressors.  Power has been provided to the site with conduit and wires installed.  Final hook-up of the compressors will occur after a full system review with  contract electricians. An amine regeneration heater has been constructed from 316 grade stainless steel and is located outside of the container. 

On the roof of the container, two compressed natural gas fuel arrays have been assembled and installed.  Each array contains 24 cylinders and can hold roughly 88 GGE at 3600 psi.  The steel, type 1 cylinders are connected to a priority panel located in the container.  Up to four fuel arrays may be installed on the roof of the container.  A valuable lesson learned is that anaerobic digester-based fueling stations will tend to require much more storage and smaller compressors relative to conventional natural gas, pipeline-based refueling stations. 

A dual hose fuel dispenser with legal fuel metering capability has been ordered and has been completed.  The team is awaiting final shipment of the dispenser.  A fuel island will need to be constructed to support the dispenser with proper bollards to meet natural gas fuel station requirements.  The final fuel system must be plumbed from the tanks to the dispenser. 

The project requires a dryer to remove moisture from the refined biomethane prior to entering the compressors.  This prevents moisture from freezing in the lines of a natural gas vehicle or the refueling station.  A bidding process was started to purchase a dryer system.  The leading bidder could not meet the insurance and warranty requirements and was disqualified.  The team is looking for another vendor.  This system alone could be $100,000.   

On the vehicle side, a Ford E250 bi-fuel van was purchased with both gasoline and natural gas capability.  A compressed natural gas fuel injection kit also was purchased to update the fuel injection on the Ford van. 

Work remaining for the vehicle side includes the effort required to convert a 2000-2003 year MCI F coach bus to operate on compressed biomethane.  This work involves ordering and installing a Cummins Westport ISL G 8.9 liter natural gas engine.  In addition, new radiators, a torque converter and possibly a rebuilt Allison transmission are required.  This work will be done at Cummins Northwest.  At this point, the team is waiting for an updated and comprehensive quote to transform the bus.  Six compressed natural gas tanks and plumbing for the fuel system then will be added to the bus.  The ISL G engine is a long lead time item.  It is hoped that the engine can be installed during the summer. 

Permits for the facility have been in process since the summer of 2009.  At this point, the team believes it has answered all of the document requests of the county.  Contracts for fuel and electrical power also must be developed between the Vander Haak Dairy, Airporter Shuttle/Bellair Charters, and Western Washington University.  These are being developed as a means of providing a clear understanding of fuel costs, delivery service and expectations for a 5-year window of pilot operations. 

Challenges Facing Similar Projects:

This project is unique in that there is only one operational dairy derived biomethane for transportation facility in North America at the Hilarides Dairy in Lindsay, California.  Hilarides Dairy began operating biomethane trucks in the summer of 2009 from upgraded, digester-derived biogas.  As a result, this is a new type of project for the dairy industry, the communities in which these facilities are based and the potential users of the fuel.  Although these types of projects are new, the technology for upgrading biogas, compressing, storing and dispensing biomethane are well developed.  Technologies for operating vehicles on biomethane continue to evolve, but basic technologies have been in use for more than 20 years. 

The primary challenges that this project continues to face include economic viability of dairy farms, funding relative to project scope, project management or time, and the limited availability of compressed natural gas vehicle conversions.  In trying to meet the needs of Airporter Shuttle/Bellair Charters, the scope and cost of the bus conversion became much larger than anticipated.  It was initially planned that an E450 bus could be converted for about $25,000.  Unfortunately, although Airporter owns several E450 buses, all of them were diesel based and not suited for any available conversion kits.  This left up to five MCI F coaches available for conversion that had relatively low mileage and were in good condition. 

The DOE/Puget Sound Clean Cities Coalition funding promises to meet the funding challenge of converting the MCI F coach.  This American Recovery Act funding places three limits on the project in return for the funding.  The first is that the funding covers the cost of conversion to biomethane, but not the initial vehicle cost.  The second requirement is that the vehicle must meet EPA 2010 emission standards.  The third requirement is that the funding is only for fueling infrastructure such as tanks, compressors, or dispensers, but not for the biogas upgrading or the digester facility. 

Because the Airporter Shuttle/Bellair Charters business model does not involve purchasing new vehicles, the team was unable to purchase a new, natural gas-ready vehicle with the DOE funding.  The second challenge is that the 2010 EPA emission requirement severely limited which vehicles could be converted.  Technically, it is possible to meet the standards with a wide range of kits and or conversion techniques.  However, legally the vehicles must be certified to meet EPA standards.  This process requires several weeks of testing in an EPA approved facility and is cost prohibitive for a one or two vehicle conversion.  It also is time sensitive so that approved vehicle converters may have kits approved by the EPA, but the kits will have a valid EPA certification for only a limited time and for a specific model and year of vehicle.  The costs are amortized over the cost of a certified kit, but they seem to drive the conversion kits to cost about $20,000 installed when the cost of the components should total around $5,000-$8,000 on a Ford E450 size vehicle.  Although it is possible to find a used Ford E450 cutaway bus using a gasoline V-8 and to install an approved conversion kit, the pre-2010 vehicle could not use a 2010 certification. 

These requirements drove the team to select the MCI F coach as a vehicle that could meet the 2010 EPA requirement.  With larger vehicles, the engine is certified to EPA standards and may be used in many different vehicles.  The MCI F coach requires that its 8.3 liter Cummins C series engine be replaced with a Westport Cummins ISL G series natural gas engine.  This engine is one of a very few engines certified for natural gas in larger vehicles.  The challenge the team currently faces is that the coach builders, MCI in particular, are busy with certifying their new vehicles for 2012 standards.  They have not provided the Cummins Northwest team with the desired application data on the radiators and other components.  As a result, we currently are waiting for an updated and comprehensive quote for the conversion.  Once a quote is received, we can commence with a purchase order.  Unfortunately, the engine is a long lead time item and will delay project implementation.  This challenge was compounded by the delay in funding from DOE and by our team's inability to order the engine until funding was in place. 

A challenge for all projects of this nature is the limited availability of compressed natural gas vehicles.  If a project can be flexible and purchase natural gas vehicles that either already exist or can order a new vehicle, then this presents less of a challenge.  Many kits do exist for smaller, cutaway bus chassis, such as those used for hotel shuttle buses.  Kits exist for light duty trucks for both Ford and GM vehicles.  Kits exist for passenger cars, but only Honda has offered new natural gas passenger cars consistently each year since 1998.  For large trucks, Westport Innovations offers a Cummins ISX engine for 18 wheelers.  Both PACCAR and Freightliner offer Cummins Westport products.  Street sweepers and smaller commercial vehicles can use the Cummins Westport ISL G engines and these can be purchased new from a few manufacturers.  Cummins Westport still sells Cummins B series and C series engines around the world, but these lean-burn natural gas engines are not certified for 2010 emissions and are no longer offered directly from Cummins in the United States.  Navistar has proposed offering a Class 8 truck engine, but the engine does not seem to be certified yet. 

For smaller vehicles, the high cost of vehicle certification remains a barrier to entry of compressed natural gas vehicle kits.  If the certification process could be changed so that a manufacturer’s kit could be certified on a wide range of engines and vehicles, this cost could dramatically drop.  At the present time, EPA requirements and California Air Resources Board (CARB) requirements continue to be more stringent.  This limits the entry of compressed natural gas vehicles in the marketplace.  For older, used passenger vehicles, it may be possible to legally convert to compressed natural gas but we are still investigating this possibility.  The high cost of EPA-approved CNG conversion drives our team and the market to look at converting and purchasing larger, CNG vehicles where the CNG cost is a smaller percentage of total vehicle cost.

Timing and project management pose a continuing challenge.  The compressed natural gas vehicle industry is based on a build to order model.  This requires long lead times to procure critical components such as compressors, storage tanks, and dispensing facilities.  For this project, the delay in DOE funding led us to delay the purchase of a dispenser, additional storage tanks and a two chamber dryer.  Trying to match the funding cycle with the purchase of key components will always be challenging for new projects.  As our team develops a better cost and performance model for these types of projects, the timing and funding level can be more accurately gauged. 

Another challenge still facing the project involves contracts.  We will need to develop a contract to buy, sell and deliver compressed natural gas from the Vander Haak Dairy to Airporter Shuttle/Bellair Charters.  This contract is in development and is required to ensure that the interests of all involved parties are protected and that their expectations are met.  The gas sale also is required to help support the ongoing testing and evaluation of the biomethane facility, in addition to providing support to the dairy.  The team is leveraging experience gained from other local governments in buying and selling biomethane.  The team also is working with the Whatcom Public Utility District No. 1. 

The project will need to develop a means of transporting the biomethane to the end user.  Ultimately, this should be through an existing pipeline.  In the very short term, natural gas vehicles can fuel directly at the farm.  Initially the team thought that buses could fuel at the farm.  The team reviewed the proposed routes between Vander Haak and Airporter Shuttle/Bellair Charters and observed traffic at the border crossing adjacent Vander Haak Dairy.  It became apparent that refueling at the farm would add too many additional miles (~34 miles 55 km) on the route.  Border traffic could prevent the bus from refueling on schedule. 

Gas storage presents another challenge.  As a tank array is used to fill a compressed natural gas vehicle’s fuel tank, the two fuel systems come to pressure equilibrium.  At this point, no further gas will flow into the compressed natural gas vehicle’s fuel tank and a significant quantity of fuel will remain in the storage tank array.  Typically up to 40% of the fuel in the storage array may not be used.  To address this issue requires either larger storage facilities or a booster compressor that regulates the fuel pressure down to an inlet pressure of a pump before compressing it back into a vehicle tank.  Either solution is costly, requires additional space and weight on a mobile vehicle and uses additional energy for the booster pump.  This issue would not occur if the vehicle could be fueled at the farm, where the compressor could be used to top off the vehicle. 

Proposed Pilot Scenario:

Following resolution of the above challenges, the MCI F Coach will be driven, full of fuel, from Ferndale to the SEATAC airport at the beginning of the work week, Monday.  The bus will have six 15.9 inch (404 mm) diameter, 85 inch (2159 mm) long tanks with 18.3 GGE capacity per tank providing nearly 110 GGE of fuel providing 660 miles of range at 6 miles per gallon gasoline equivalent (mpge).  The 218 mile roundtrip could be traveled for 3 days without filling but most likely the tank would be filled every 2 days.  Meanwhile, on the prior Friday, the bus would have been filled by the mobile tank array.  A conservative estimate for the bus would provide it with 240 miles of range each day for 40 GGE/day.  This would require 200 GGE per week.  A mobile refueling rig that could deliver 200 GGE would have to have a minimum of 333 GGE of capacity.  With 15.9 inch (404 mm) diameter and 123 inch (3124 mm) long tanks that store 26.9 GGE each, this would require a bit more than 12 tanks.  The mobile refueling rig would be returned to the farm on Friday for the entire weekend and then pick up again on Monday.  At the farm, the fast fill tank array would initially fill the mobile array from 160 GGE of storage.  As pressures equalized between the two systems, the 160 GGE array would be able to provide about 96 GGE of fuel to the mobile array.  The remaining 104 GGE would be filled by the compressor over time.  The compressor, pumping at 25 standard cubic feet per minute or roughly 12 GGE/hour would refuel the mobile tank array in under 9 hours.  The compressor would work an additional 8 hours to refuel the stationary storage array mounted at the farm.  Fueling one bus requires an operator to refuel the mobile tank array once per week on the weekend.  With a larger tank array, the system could supply six MCI F coaches with fuel with the compressor running 100 hours per week.  With daily refueling of the mobile tank array, a minimum of 400 GGE or 15 storage tanks would be required.  Filling more than six buses would require a larger compressor. 


The team will strive to complete the unit so that full-scale testing can occur during the summer of 2010. The pilot operation of the MCI coach might begin as soon as the fall of 2010. If the testing is successful, we believe that this approach will provide a relatively low-cost means of dramatically reducing the global warming potential of Whatcom County while improving dairy farm economics and reducing the environmental impacts from dairy waste. The Whatcom County goal for reducing annual carbon dioxide emissions is 1.1 million tons (lbs) by 2020 . If this project were implemented across the county, more than 10% of this goal could be achieved. The opportunity for exporting this technology also is significant with a pilot test potential for the Philippines and interest from Costa Rica as well.

Supplemental Keywords:

RFA, Scientific Discipline, Sustainable Industry/Business, POLLUTION PREVENTION, Environmental Chemistry, Sustainable Environment, Energy, Technology for Sustainable Environment, Environmental Engineering, sustainable development, environmental sustainability, alternative materials, biomass, alternative fuel, biodiesel fuel, energy efficiency, energy technology, alternative energy source

P3 Phase I:

Biomethane for Transportation  | Final Report