Biogas - New and Same Olde
Posted: June 11, 2009
We estimate as of June first that there are 17 Pennsylvania farms with operable digesters; 14 dairy farms approximately 10,000 cows (www.biogas.psu.edu). Various Pennsylvania and US government assistance programs have encouraged much of this activity. A discouraging feature of recent visits to digester projects in Pennsylvania and neighboring states is that we are still seeing many of the “same olde mistakes and problems” on our digester projects.
Electrical interconnection issues:
- Failure to involve power supplier early in the project. Common problems have included - delays in interconnection; misunderstanding of interconnection equipment requirements; issues with high voltage utility lines serving the farmstead.
- Utility contract negotiation, execution and payment - including unexpected low payment, lengthy periods of time before payment is received and making assumptions as to what the power company will decide.
- General lack of understanding of all the items on a monthly utility statement and what items are included in net metering arrangements.
- Failure to make use of the PA Public Utility Commission and the procedures in place for helping with relations between investor owned utilities and customers. Find information about the PUC at http://www.puc.state.pa.us/electric/electric_alt_energy.aspx Select Net Metering Standards and Interconnection Technical Contacts
- Assuming every utility agreement to be the same. There is variability among and within power suppliers based on the location on any given suppliers grid and the time of day power is delivered to the utility. Be careful of rules of thumb or assumptions when making business plans.
Forty years ago farmers were having problems with power companies because they bought a brand new big silo unloader, grain dryer or some other electric motor driven device without checking to see what the power supplier’s rules were for size of load on the line or the cost and time involved with upgrading lines to the farm. Sounds like a similar “olde problem.”
Design, Construction and Operation issues:
- Building a digester is a complicated, expensive and for many components a specialized process. Unlike with milking centers or feed centers we do not have a service and support infrastructure that provides one stop shopping for design, equipment, construction and perhaps most important follow up service, support and troubleshooting. Misunderstandings about who to go to, what cost to expect for this consultation and the expected response time for trouble shooting are common. We are beginning to develop a small group of subcontractors who have experience with components of the systems.
- Failure to have clear contracts and scope of work developed and executed with designers and suppliers. Employing a designer who is also a supplier or receives commissions from suppliers may result in surprises during the project. Be sure to have a complete contract and to read and understand what it says. Anytime you assume a liability, don’t be afraid to involve your legal and business team in reviewing the contract.
- No one (project manager, general contractor…) responsible for day-to-day project management regularly at the site.
- Parts and service availability for items and components that are not from traditional local suppliers or that these venders are not familiar with.
Digester heating and excess heat:
- Poor performing digester heating due to build up of scale and deposits on the outside of heat exchanger pipes and deterioration of pipes located in the digester.
- Total energy utilization efficiency for engine generator sets will vary from 22- 40%. The first use for excess heat should be the digester. Finding other uses to replace purchased heat energy makes good economic sense.
Owners and operators have traditionally been most generous in sharing their time and knowledge about digesters. Those of us who take advantage of this generosity should be careful not to wear out our welcome and understand when someone responds “not today” when we want to visit or pick their brains. We continually balance the desire to provide good and helpful information to those interested in digester systems with the concern that we not wear out our welcome with these folks. Thanks you to all -- the digester owner, operators, designers and suppliers who provide us with information we can share with others.
Robert E. Graves, Deborah Topper, and Patrick Topper, Department of Agricultural and Biological Engineering