Case Study of a Biomass-Fired Cogeneration Plant
Case Study: Dow Corning
Corporation Biomass Cogeneration Plant
Presentation by Terry DeBlaay,
Forester, Dow Corning Corporation
Contents
Plant
History
The rise in energy costs in the late 1970s led Dow Corning Corporation to plan for
a new source of power for its manufacturing plant in Midland, Michigan. The plant
is located near Saginaw Bay, an area with a well-developed road network and
abundant supply of wood. In addition, the Midland area is in nonattainment with
national air quality standards, so cleaner-burning fuels and technologies were
needed.
Previously, the plant (a joint venture of Dow Chemical and Corning Corporation)
had purchased electricity and burned #6 fuel oil to produce steam, but the
worldwide energy crisis had caused prices to increase sharply. After considering
many different alternative energy sources including coal, natural gas, and nuclear
power, Dow Corning settled on wood power.
After a feasibility study to assess the fuel supply, the 22 megawatt Steam &
Electric Cogeneration plant (SECO) was constructed in 1982. The plant continues to
operate today, making use of wood harvested from forest stands as well as waste
wood. At present, 60% of the fuel supply comes from wood harvested from forest
sources. The remainder comes from industrial and commercial waste wood.
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Early Fuel Procurement Strategies
Feasibility studies for SECO revealed that there were 4 million acres of forested
land within a 75-mile radius of the plant. (Seventy-five miles was considered to be
the most economical distance to haul wood.) Ten percent of that land was owned
by the United States Forest Service, 21 percent was owned by the Michigan
Department of Natural Resources, and the remainder was private. Those land
ownership patterns continue to the present. It was the 69 percent of the land
owned by private landowners that was considered as appropriate for fuel supply.
Dow Corning established a staff of foresters and wildlife biologists to work out
forest and wildlife management plans with private landowners. At no cost to the
landowner, SECO staff visit a landowner's property and produce a
Comprehensive Forest Management Plan that meets the needs of the
landowner regarding establishment of wildlife habitat, maintenance of timber types
and generation of income from timber sales.
The typical landowner is an absentee landowner who owns over 160 acres. Many
landowners are interested in providing habitat for game animals such as deer,
turkey, grouse, rabbit and other animals. The actual harvest is determined by the
goals of the landowner. Aspen, the primary timber type found in the region, is
harvested and managed using the clearcutting silvicultural technique to encourage
regeneration of the next forest.
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Fuel Harvesting and Transport
Dow Corning contracts with logging crews to carry out the harvest
recommendations. Trees are harvested with feller-bunchers, machines which cut
the trees and lay them in piles known as skids. These skids are then brought out of
the woods to a central landing location, where they are chipped and the chips
blown into a semi-trailer for shipment to the plant. In order to avoid picking up
stones or sand while removing wood, contract terms require the landing area use a
paved surface or a 12-inch bed of wood.
Terry DeBlaay refers to some of the difficulties in balancing multiple land use goals
as "biopolitics." For example, landowners often want small stands of trees to serve
for deer stands. However, these trees limit the regeneration of the forest due to
competition for sunlight.
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Marketplace Changes
Early on in the plant operation, one-half of the fuel supply was met with sawmill
waste wood. As the Michigan wood power industry grew, additional plants were
built closer to the sawmills that produced much of the waste wood. As competition
grew, supplies were reduced for SECO. The result was that SECO had to adjust
their procurement plan to new sources.
As a result of the shift in supply, Dow Corning moved to use of urban and
industrial waste wood from the southeast part of the state, mostly from the
automotive industry. At present, 85-90% of the urban and industrial waste used by
the plant is from scrap pallets. These pallets are ground up in a tub grinder to
uniform sizes of 1/4 to 3-inch pieces. Sizes smaller than this generate airborne wood
dust, which becomes a nuisance. Wood dust can clog air filters used in the
production plant. All nonforest sources of wood must be magnetically separated
before being delivered to the plant. Non-wood contamination (plastic or cardboard)
is currently removed by hand, but SECO is investigating air separation. Plastics are
not allowed by regulation into the boilers of the SECO plant.
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Fuel storage
"Just-In-Time" inventory is standard Dow Corning procurement practice. Due to
this practice, the company maintains a maximum five day inventory, and two to
three days inventory on average. The fuel is stored in three cement silos to reduce
fugitive dust. The silos have the added benefit of protecting the fuel stores from the
elements. On the other hand, outdoor piles of wood allow larger supplies to be
stored.
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Other fuels
As SECO had to adjust to changing market conditions, they experimented with
many different types of biomass resources. SECO's experience illustrates many
challenges of using biomass fuels.
Waste corn was available in large supply at certain times of the year. However, the
equipment used by SECO was not designed to handle corn, which would have
rolled back down the inclined conveyor belts. Because of the seasonal nature of the
corn supply, it didn't make sense to modify the system to accommodate the corn.
Agricultural residues, in general, are very seasonal and provide an inconsistent
supply. Other examples of agricultural residues include sugar beet pulp, which was
difficult to handle and had high moisture content, and paprika grindings, which
were too dusty to handle. Horse manure was high in energy content, but became a
pungent nuisance after rainfall. Also, the waste from race tracks contained
chemicals that had been given to the horses.
SECO purchased 4,000 acres to provide a backup fuel supply and demonstration
harvest sites. Hybrid poplars were planted on some of this land, but were not able
to compete with natural vegetation. The energy crops require cultivation in early
years that absentee landowners do not provide, so the experiment was not
successful.
Tire-derived-fuel (TDF) was tested at the plant and found to work well. However,
due to regulatory prohibitions, TDF could not be used.
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Ash disposal
The SECO plant generates 40 cubic yards of ash per day. The plant has a ready-
made market for the ash in the acid quench ponds at the chemical plant on the
premises. Recently, SECO received an agricultural land use permit to spread the
ash in dry form on farm land as a fertilizer.
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Lessons
The SECO plant is considered a success by the Dow Corning Corporation. The $36
million cogeneration plant was paid off in energy savings in less than four years. In
addition, many thousands of tons of wood wastes were kept out of landfills. Terry
DeBlaay shared a number of lessons that SECO has learned:
- Work closely with a few number of larger suppliers rather than a large
number of small suppliers. Supplies are more reliable with these long-term
contracts. Working with more suppliers is more difficult and is a less efficient use of
resources.
- Be careful in accepting resource assessment studies which promise huge
supplies of unused wood. There is a big difference between gross volumes and
what is economically viable to recover and use. DeBlaay cited the example of the
Michigan DNR in Lansing stating there was room for two to three more wood-fired
powerplants while one plant had to temporarily suspend operations due to fuel
shortages.
- Maintain a public information program. The SECO plant sent out staff to
address local citizens groups such as the Lions' Club, Ladies Garden Club, Kiwanis
and others on a regular basis. In the first five years they made presentations to over
10,000 people. This was especially important for Dow Corning as chemical plants
tend to be regarded as less than perfect environmental stewards by the public.
DeBlaay described their efforts as being very "up-front" with the community.
- Agricultural residues don't "travel well," and require special fuel handling
systems. These modifications reduce the economic attractiveness of these supplies.
- When purchasing fuel, the moisture content must be accounted for. This is
often done through a "moisture deduct" where payments are based on the green
ton and the payment is adjusted for the moisture content. However, this often leads
to bad feelings as suppliers feel the plant is "taking money from them," so DeBlaay
advises sampling shipments for moisture and adjusting payments on the front end
for "the BTUs that you use."
- SECO staff have adjusted to staff reductions with efficiency improvements.
These include use of computerized mapping through global positioning systems
(GPS), geographic information systems and field computers.
Speaker Information
Terry DeBlaay is Fuel Supply Manager with Dow Corning
Corporation. He is actively engaged in fuel procurement for its 22 MW wood fired
power plant in Midland, Michigan. Mr. DeBlaay works on managing private forest
land to harvest, submitting bids on timber sales on state and federal forests, and
developing forest management plans for subsequent regrowth of forests.
He also oversees the urban/industrial waste wood program, and manages the
inventory and scheduling for the wood fuel. His professional training is in wildlife
and forest management.
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Last updated on August 9, 1995.
This document is based on a presentation made at the Biomass
Energy Infrastructure Workshop in Madison, Wisconsin on June 6-7, 1994.
This was written by Andy Olsen, who also organized the workshop. To contact Andy, send email to:
AndyO@inxpress.net
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