A BIOGAS - TOLERANT ENGINE - GENERATOR FOR ADVANCED AGRICULTURAL WASTE MANAGEMENT SYSTEMS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: SMALL BUSINESS GRANT
• Reporting Frequency: Annual
• Accession No.: 0213545
• Grant No.: 2008-33610-18929
• Proposal No.: 2008-00316
• Project Start Date: May 1, 2008
• Project End Date: Dec 31, 2009
• Grant Year: 2008
• Program Code: [8.11]- Animal Waste Management

Recipient Organization
MAINSTREAM ENGINEERING CORPORATION
200 YELLOW PLACE
ROCKLEDGE,FL 32955

Performing Department
(N/A)

Non Technical Summary
Anaerobic digesters are capable of producing methane-rich biogas from animal manure and also offer the advantages of controlling odors, reducing pathogens, and minimizing the environmental impact of the waste. The biogas produced from anaerobic digesters is a renewable, distributed source of energy that can be used to generate electricity to offset power consumption on farms. Unfortunately, biogas is highly corrosive and quickly embrittles the cast iron and steel used for many engine components. As a result, conventional engines fail after several months of exposure to biogas. The objective of this project is to develop an inexpensive, low-maintenance, high-efficiency, biogas-tolerant engine that can be used for generators at these biodigester installations. Our approach will be to modify the engine to minimize the flow of corrosive gases into the crankcase and to replace critical engine components with ones fabricated from corrosion-resistant materials.

Animal Health Component

100%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
403	5399	2020	50%
511	5399	2020	50%

Knowledge Area
511 - New and Improved Non-Food Products and Processes; 403 - Waste Disposal, Recycling, and Reuse;

Subject Of Investigation
5399 - Structures, facilities, and equipment, general/other;

Field Of Science
2020 - Engineering;

Keywords

anaerobic digester

renewable energy

generator

biogas

corrosion

hydrogen sulfide

Goals / Objectives
Anaerobic digesters are capable of producing methane-rich biogas from animal manure and also offer the advantages of controlling odors, reducing pathogens, and minimizing the environmental impact of the waste. The biogas produced from anaerobic digesters is a renewable, distributed source of energy that can be used to generate electricity to offset power consumption on farms. Unfortunately, biogas is a sour gas that is rich in hydrogen sulfide (H2S), a highly corrosive gas that quickly embrittles the cast iron and steel used for many engine components. As a result, conventional engines fail after several months of exposure to the high levels of H2S in biogas. No small (<25 kW) engines are currently available that can use this fuel without pretreatment to remove the H2S--a process that adds complexity, cost, consumables, and maintenance. As a result, many smaller biodigester installations simply flare the biogas rather than extracting any useful work from the fuel. The objective of this project is to develop an inexpensive, low-maintenance, high-efficiency, biogas-tolerant engine that does not require preconditioning of the biogas to remove H2S.

Project Methods
The overall approach is to modify an existing gasoline engine to replace susceptible iron and steel components with corrosion-resistant materials. Because reliable materials compatibility lists for H2S do no exist, corrosion testing will be performed to identify the most appropriate materials. Also, custom engine components will be designed and fabricated to reduce transmission of H2S from the combustion chamber to the crankcase and subsequent acidification of the engine oil. Because some blowby is unavoidable, experiments will be performed to identify oils that have low solubility for H2S and can resist acidification. Initial testing of the prototype engine will be performed using biogas collected from a local biodigester and more extensive life testing is envisioned for Phase II.

Progress 05/01/08 to 12/31/09

Outputs
OUTPUTS: 1. Life testing was performed to identify the failure mode of engines run with biogas containing elevated levels of hydrogen sulfide. 2. The optimal compression ratio, spark timing, and fuel-air equivalence ratio for the biogas engine were determined from a review of published data. 3. Corrosion testing was performed to identify materials and coatings that exhibit good corrosion resistance to acidified engine oil. 4. The optimal engine oil for the prototype biogas-tolerant engine was identified through a review of available vendor information. 5. A test method for monitoring the acidification of engine oil was developed based on ASTM guidelines. 6. Testing of a specialized piston ring pack was performed to measure the blowby of gases from the chamber to the crankcase. 7. A prototype biogas-tolerant engine was developed that included a modified carburetor, piston, piston ring pack, crankshaft bearings, cylinder liner, ignition system, and engine oil. 8. A small anaerobic digester was constructed and used to produce biogas from horse manure. 9. The prototype biogas-tolerant engine is now undergoing extended life testing. The results of this SBIR program have not been disseminated because we have not yet filed for patent protection. PARTICIPANTS: The individual from Mainstream Engineering that participated in this program are Dr. Paul Yelvington (PI) and Andrew Carpenter. Prof. Ann Wilkie from the University of Florida IFAS participated in this program as a consultant. TARGET AUDIENCES: The target audience for this project is owners of dairy, swine, and poultry operations that employ anaerobic digesters for manure management. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The failure mode for engines fueled with biogas containing elevated levels of hydrogen sulfide was identified. Our findings contradict other reports of the failure mode in the published literature. A inexpensive, low-maintenance, high-efficiency, biogas-tolerant engine that does not require preconditioning of the biogas to remove hydrogen sulfide was developed. Development of this prototype engine was enabled by the life testing, corrosion testing, component development, and oil analysis performed in this program. The seed money provided by this Phase I SBIR program facilitated the development of this product, which Mainstream Engineering intends to transition to a commercial product in Phase III.

Publications

• No publications reported this period