Final Report: Biomethane for TransportationEPA Grant Number: SU833169
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
Project Period: September 30, 2006 through May 30, 2007
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2006) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Energy , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability
The objective of this project is to construct a small scale biomethane fuel production and purification facility, which will process biogas retrieved from local dairy farms. The resulting fuel will be tested for the amount of CO2 (carbon dioxide) and H2S (hydrogen sulfide) removed and then used in a high-efficiency hybrid natural-gas powered engine.
Dairy waste in Whatcom County presents an economic burden to farmers and an environmental burden to the region. The Nooksack River basin has had a history of state bacterial standard violations with significant fecal coliform loading; dairy waste production rates are not environmentally sustainable using current techniques. Biomethane digesters can reduce the water and air pollutants in dairy waste while making a commercially useful fuel. However, the installation cost of an anaerobic digester is prohibitively expensive for most farmers.
The Vander Haak dairy farm in Whatcom County is currently facing a 10 year payback period, based on the $1.2 million construction cost and the $112,828 yearly revenue. The economic significance of the project is determined by the value of the electricity produced by the Vander Haak digester. Based on the current rate of $.05/kWh, including Green Tag premium, that Puget Sound Energy pays to purchase power from the digester, the Vander Haak’s yearly revenue is $112,828 based upon the calculations below.
The digester can produce 280 kWh of power more than 90% of the time. If that power is sold for $.05/kWh then the plant earns $336/day gross or $112,828/year.
$.05/kWh*280kWh/hr*24hrs./day = $336/day
$336/day*365days/year*92% operation = $112,828
As of 4/2/2007 national average gasoline prices were at $2.71/gal. If this same volume of biogas were instead used as a gasoline substitute the Vander Haak farm’s revenues could be substantially higher. The following calculation outlines the potential value of the gas if it were utilized for transportation.
The Vander Haak dairy farm processes effluent equivalent to that created by 1200 cows per day. Each cow produces approximately 60 scf of pure methane (CH4) each day after the energy overhead of the digester. This amount of methane is worth $567,283.94 per year if used as a gasoline substitute.
1200 cows*60scf/day =72000 scf/day
72000scf/day*1000BTU/1scfCH4 = 72x106BTU/day
72x106BTU/day*1gal. gasoline/115,500 BTU = 623.38 gal. gasoline equivalent/day
623.38 gal. gasoline/day * $2.71*365day/year*92% operation = $567,283.94
Currently, the Vander Haak farm is facing a 10 year payback period, based on the $1.2 million construction cost and the $112,828 yearly revenue. If the biomethane was used for transportation the payback could be as low as 2.1 years given the $1.2 million construction cost and the $567,283.94 potential yearly revenue. It is expected that a balance between supply and demand will allow biomethane to be a less expensive alternative to gasoline for local consumers while providing increased profits to its producers.
Biogas, although corrosive to engine components in its unrefined state, can be cleaned and used as a viable fuel in CNG (compressed natural gas) motor vehicle applications. Biomethane as a fuel for energy efficient motor vehicles is likely to be a cost-effective application for farm-produced biomethane that can generate financial revenues to improve the economic stability of Whatcom dairy farms. It is important to note that this process can be also be applied to landfills and waste water treatment facilities which can supply biomethane and exist in nearly every municipality.
The Biomethane for Transportation project will demonstrate and document the economic benefits to farmers of reduced manure management costs and increased revenue potential from biomethane production. It will also document the multiple sustainable economic and environmental benefits that accrue to farmers, community, and businesses from production and use of biomethane to power a high-efficiency motor vehicle. The completed small-scale production facility will provide the basis for future hands-on education and research for faculty, students and members of the community.
During phase I of this project we designed and built two different small-scale biogas refineries. The first design used a caustic absorption system. Our initial results showed an increase in CH4 (methane) content from 60.50 Mol% in the raw biogas to 93.62 Mol% in the scrubbed gas. We achieved a reduction in CO2 (carbon dioxide) from 36.03 Mol% in the raw biogas to 2.05 Mol% in the scrubbed gas. Lastly, we achieved a reduction in H2S (hydrogen sulfide) from 0.34% Mol% to a value too low to be picked up by the gas chromatograph. Subsequent dräger tube tests showed levels of ~850ppm to ~900ppm.
Our second design is an amine absorption system. The best initial sample showed a composition of 94.88 Mol% CH4 (methane), 0ppm H2S (hydrogen sulfide), 0ppm CO2 (carbon dioxide) and 4.25 Mol% nitrogen. Nitrogen was our purging gas and proved to be problematic in some of the other samples accounting for 53.22 Mol % in one particular sample. This was due largely to operating error and was most likely caused by not completely venting the nitrogen used for purging the system from the drying tower before taking samples. However, all samples taken registered 0ppm H2S (hydrogen sulfide) and all but one registered less then 2% CO2 (carbon dioxide). Therefore the second design was considered as success. The amount of CO2 and H2S scrubbed by the second design showed an improvement over the first design and were well below are initial goal.
We have demonstrated the ability to successfully remove carbon dioxide and hydrogen sulfide from a raw biogas stream. We exceeded our expectations in our second design by removing all of the hydrogen sulfide and substantially more carbon dioxide than we had initial set out to remove. Most importantly, we have shown that this can be done with a small-scale scrubbing facility costing under $10,000.00 dollars. This is a relatively low cost given the potential revenues and percentage of the total cost of the digester.
This shows that producing and utilizing unconventional energy sources can be done at a local level for a relatively low cost. In order for a system such as this to be implemented we need to demonstrate a continuously operating scrubber. Our previous designs were based on a batch system and have not been run for more than six hours at a time. It should also utilize automated controls.
Proposed Phase II Objectives and Strategies:
For Phase II the Vehicle Research Institute will design and build a pilot transportation system that utilizes the refined biomethane from a dairy cow based anaerobic digester. The system will include a biogas scrubber, a natural gas compressor, a refueling gas cascade and two buses converted to run on natural gas. The system will be sized for ten standard cubic feet per minute of gas flow, which represents roughly 10% of the anaerobic digester’s biomethane production. The purpose of the system will be to demonstrate the viability of a biomethane fueled transportation system and how this system can improve the economic viability of an anaerobic digester. In Phase II we demonstrated how it is possible to refine raw biogas for low cost and use that fuel in an emission controlled vehicle. Phase II would require that we can reliably refine the biogas for use in a transportation system.
The purpose of phase II would be to improve the economic value of the anaerobic digester. If we can reduce the payback period for the digester from 10 years to 3-5 years, then dairy farmers will be able to afford to install anaerobic digesters. Increasing the number of digesters will help resolve a dairy waste issue. The If we can improve the economics of the anaerobic digester, than we can.