April 26, 2007 | General

Cayuga County, New York Pioneers Community Digester Program

BioCycle April 2007, Vol. 48, No. 4, p. 56
New project of Soil And Water Conservation District will help control odors and improve water quality while generating biogas with an innovative system.

A BIOENERGY VISION that started several years ago is finally being built at the Cayuga County Soil and Water Conservation District headquarters in Auburn, New York. Jim Hotaling, Executive Director, has long envisioned a community digester facility that would address the community concerns of manure storage and land application odor, and improve the water quality in Cayuga County. He recently investigated his idea in Europe and was further convinced that importing European anaerobic digester technology would allow his agency to better serve its constituents. However, it was not until 2004 that he found a U.S. company, ECO Technology Solutions, LLC (ECOTS), that could help him bring his vision to a reality.
The Cayuga County Soil and Water Conservation District (“District”) is a unique agency that has worked on numerous projects to better the agricultural industry in New York and to improve the water and air quality in Cayuga County. While many environmental agencies regulate activities, the District actively pursues new concepts and approaches to help farmers and others implement environmental improvement projects. The Cayuga Regional Digester Facility is just one of many projects that have been championed by the District.
“I was impressed by the European digester technology when I visited Europe a few years ago,” says Hotaling. “Not only had the Europeans built hundreds of working digesters, they had pioneered the concept of community digesters, which allows multiple farms to pool resources to better handle manure disposal. The community digesters in Europe not only processed manure but other organic waste making them much more efficient at biogas production. The risk and rewards are shared among the participants and the size of the digesters make it possible to hire a professional staff to operate the facility.”
The European community digester concept has been very successful. In fact, digesters of all types have been quickly embraced and integrated into the electric generation system throughout Europe. In Germany alone, more than 2,500 digesters are operating on both a community and farm level. The German program has been so successful that little manure is available for new digesters. Instead, food waste from grocery stores and processing plants has been contracted, and many of the new digester facilities are processing household and commercial organics and energy crops grown exclusively for digester applications.
The Cayuga Regional Digester first phase construction program will build a 625 kW facility that will process 39,000 gallons/day of manure. A screw press will separate the 39,000 gallons/day of sludge material produced, yielding approximately 34,000 gallons/day of liquids that will be land applied, and 25 tons/day of solids material that will be composted.The facility has contracts with several farms in the area, and is actively pursuing an additional 50 tons/day of food processing waste. The food waste will supercharge the gas production at the facility creating the biogas needed for the 625 kW of generation.
The District will use a contract transportation company to initially pick up the manure at each farm, and to return processed liquid fertilizer to the same farms. Strict requirements on safety, loading and unloading procedures, cleanliness of vehicles and travel routes will minimize community concerns and on-farm biosecurity issues. Separate manure and food processing unloading facilities at the bioenergy facility eliminate the potential for cross-contamination between the different delivery vehicles, eliminating biosecurity concerns for the food processors’ facilities. The bioenergy facility design has provisions for future expansion, with a future plant potential of almost 2 MW.
The electricity and heat produced by the bioenergy facility will be used primarily for the Cayuga County buildings housed at the District campus. Some of the remaining energy will be used by the digester and the excess sold to the grid and other facilities.
The county buildings served by the bioenergy facility will include a nursing home, jail, maintenance shop and administrative offices. Several county agencies will benefit from the reduced energy cost of the bioenergy facility, which will allow the agencies to redirect the money saved to additional services.
The creativity at the District does not end with the construction of the bioenergy facility. The final project has numerous innovative ideas, including: 1) Aggregation of electric loads on the campus to reduce electric cost while the bioenergy facility is being constructed; 2) Building of satellite liquid by-product storage to reduce the hauling distance to the field of the liquid fertilizer produced by the bioenergy facility; 3) Final composting of the solid by-product produced by the bioenergy facility with wood chips and similar organics to produce a new ground cover stabilizer for planted areas after road repairs and grading have been completed; 4) Permeable asphalt type materials in the bioenergy facility parking areas to provide surface water drainage to maintain nearby wetland areas.
The digester being built by the District is equally innovative. It will be the first hydraulic-mix digester constructed by GBU (a German digester company) in the U.S. ECO Technology Solutions, LLC is the exclusive licensee in the U.S. for this innovative technology, which is a continuous stir type technology that has no internal moving parts. The substrates processed in the digester are thoroughly mixed using the pressures from the inflow and outflow of the raw and processed materials and the biogas. Carefully calibrated pressure and timing mechanisms control the hydraulic movement of the gas and liquids which results in a complete mixing of the substrate approximately every five to ten minutes.
“The hydraulic pressures used for mixing are not very high but are very powerful – creating a whirlpool inside the digester that not only mixes the substrate thoroughly, but ejects debris through a special slot in the side of the digester, eliminating the need to clean the digester in the future,” explains Kamyar Zadeh, ECOTS Vice-President of Technology Development and Transfer. “It was this unique mixing and self-cleaning feature that attracted ECOTS attention and resulted in our licensing of the technology.”
Bill Cetti, ECOTS President and CEO, notes that the digester is slightly more expensive to construct than a standard continuous stir digester. “It basically consists of two vessels in one, with the internal vessel providing some of the final polishing treatment of the substrate,” he says. “While the initial capital costs are more, the life-time maintenance cost is much lower. For example, the electric stirring motor is eliminated, which eliminates the bearing replacements and motor maintenance, as well as electric use and scheduled downtime. Internal cleaning of the digester is eliminated, further saving downtime and eliminating employees having to work in the hazardous confined space of a digester vessel.”
The hydraulic-mix digester is also very flexible, according to Cetti. It can easily transition between feedstocks providing a safety net for the digester owner when a waste provider changes processing and the resulting waste stream is different or a waste provider goes out of business and another provider is contracted that has different waste materials.
The Cayuga Regional Digester has already broken ground. The road into the site and the receiving building is almost complete. The District is assisting with the actual construction of the facility and will be trenching and helping to build parts of the facility as the project moves forward. Construction is expected to be completed by the end of 2007.
Hotaling summarized the project by saying, “It has been a challenge for a public agency like our District to undertake a project of this size, but the results will improve not only our water quality in the county, but the quality of life in the surrounding communities. I appreciate the help of the various grant and funding agencies that have made it possible for our District to build this project. I anticipate that it will become a model for other Soil and Water Districts throughout the country, and other communities will benefit from our program.”
ECOTS is a technology facilitation company located in Leesburg, Virginia. It specializes in the development, implementation and deployment of new energy and related technologies that focus on conservation and distributed generation.

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