CES Spotlight Blog
Colby College Biomass Facility
I had the good fortune to attend the NNECERAPPA conference at Colby College in Waterville Maine on October 15th. (NNECERAPPA stands for Northern New England Chapter Eastern Region Association of Higher Education Facilities Officers). Besides winning the award for conference with the longest and most confusing acronym, the conference was notable for an excellent presentation about, and tour of, Colby’s state-of-the-art wood chip combined heat and power plant.
Waterville is located in a part of Maine that currently has no access to pipeline natural gas. Colby has historically used #6 residual oil for its thermal needs. Residual oil is a relatively dirty fuel--it is literally the oil that remains after the crude oil refining process has removed cleaner distillate products such as jet fuel, gasoline and #2 heating oil. Colby has plans to be carbon neutral by 2015 and was therefore highly motivated to find an alternative to oil.
Colby’s new biomass plant went online in January 2012. Consisting of 2 new 500 hp boilers – each de-rated to 400 hp when fired on biomass – the new plant can provide 27,000 lbs of steam per hour. Wood chips are delivered into an underground bunker (pictured) and a Chiptec gasification system turns the wood into gas. It is the gas that is actually burned in the boilers. An existing 600 kW backpressure steam turbine produces electricity at the plant as well. Particulate emissions are kept in check by cyclonic dust collectors and an electrostatic precipitator. Because the wood chips are sourced from sustainable forestry operations they are deemed to have zero net carbon emissions.
Although it cost more than $11 million to build, Colby estimates that it could save this much in lower fuel costs in as little as 5 years. Residual oil costs more than $20/MMBtu today while wood chips are in the $5/MMBtu to $8/MMBtu rage. Colby’s plant will displace about 1 million gallons of oil each year with 22,000 tons of wood chips. The existing oil plant was kept for redundancy and about 100,000 gallons of #6 oil will continue to be used to meet peak winter heating demand. The plant operates all year, providing cooling in the summer and heat in the winter. The wood chips are sourced locally, mostly from within 50 miles of campus, keeping money and jobs in the Maine economy.
Plant operation has not been without issue. Patricia Whitney, Colby’s Director of Physical Plant and Chris Shumway, President at Rist-Frost-Shumway Engineering, gave a very comprehensive overview of the lessons learned after a partial year of operation. As might be expected, fuel handling and storage was the hardest part of the process. Colby recently had to empty and bleach the storage bins due to an unwanted microbial bloom. A boiler refractory had to be replaced after being worn through in just a few months time by abrasive fly ash. The impressive labyrinth of conveyors, screw augurs and moving grates has also taken a fair bit of tweaking to get right.
Situated on the edge of campus the LEED (Leadership in Energy and Environmental Design) plant is ideally located. Easily one of the more attractive boiler plants around, large glass windows and nearby walkways invite a close inspection. Despite seeming to be a part of the campus, trucks carrying wood chips have easy and non-obtrusive access. This is key, as wood chips have a much lower energy density than oil and Colby will require 4 to 5 times the number of tractor trailer deliveries compared to oil.
There are many options for clients looking for alternatives to oil, including: wood chips, wood pellets, geothermal, compressed natural gas, liquefied natural gas and propane. The best choice is highly dependent on geographic location, environmental goals and access to capital. It is important to evaluate all the alternatives before making a decision. Colby, for one, seems to be very happy with its impressive new biomass plant.
(Tags: Biomass, Wood Chips, Colby College, Waterville Maine)