Quaker Oats needs to dispose of 350 tons per day of oat hulls, a cereal making by-product. They have the capacity to store 3 days of oat hulls, but after 3 days there is nowhere to put them. Failure to move the oat hulls out of storage results in reduction in plant production. Inefficiency of oat hull removal results in inefficiency of plant productivity, which, of course, leads to bad business.
Past solutions
Since around 1921, oat hulls have been transformed into Furfural, which has a variety of industrial uses. A byproduct of Furfural production is Resifil, which is a fine black powder that can be used as a coal substitute. Quaker had sold Resifil to Alliant Energy to use as a substitute for coal for 70 years. However, new permit requirements led Alliant to use low sulfur coal as their fuel source. Thus, Quaker Oats had to find a new market for their oat hulls.
Some Options for Oat Hull Disposal
1. Send oat hulls to a landfill.
2. Development of other chemical applications.
3. On site co-generation using oat hulls or Resifil as fuel.
4. Off site co-generation using oat hulls or Resifil as fuel.
Sending oat hulls to a landfill would cost up to $15 a ton, and the economics and logistics of developing other chemical applications and of on-site power generation using oat hulls led Quaker to consider option 4 as the best option. Quaker found a willing and able partner at The University of Iowa.
Co-generation at The University of Iowa Power Plant
The proximity of the University of Iowa, located 25 miles south of the Quaker Oats plant in Cedar Rapids, and the University of Iowa’s history of working with alternative fuels made the University an ideal choice. However, there were several obstacles to overcome before the plan to burn oat hulls could be implemented.
Burning Resifil
Since Quaker at the time was still converting oat hulls into Resifil, the University experimented with mixing Resifil with coal in the summer of 2002. A 90 day test burn was performed. With these tests, the University learned a lot about what worked and what did not work. However, Quaker soon discontinued the production of Furfural and the problem became one of dry oat hull disposal.
Burning Dry Oat Hulls
Once the decision to burn dry oat hulls was made, several issues had to be addressed:
Economic and Environmental Benefits
Fluidized Bed Boiler
Test Burn
Transportation and Material Handling
Air Quality Permitting
The first problem was interruptions in the flow of the hulls into the pneumatic injection system. The solution to this problem was to install a new silo to hold and deliver the oat hulls to the injection system. This new system was installed in the fall of 2002.
A related issue concerned the injection of oat hulls as fuel into the pre-existing coal-fired burners. The fact that oat hulls are lighter and burn at a different temperature than coal created the need to inject oat hulls into the burner at a different location than where coal is injected.
The University had to obtain a temporary permit from the Iowa Department of Natural Resources to test burn the oat hulls and make any necessary alterations to the facilities. The University was able to obtain a temporary PSD (Prevention of Significant Deterioration) permit for a 90 day test burn that began on January 6, 2003, and funding to make alterations to the fuel injection system of their fluidized bed burner.
The next hurdle was to determine the best means of transporting the oat hulls from Cedar Rapids to Iowa City. It was not feasible to transport the oat hulls by rail, so a decision was made to retrofit tanker trucks with pneumatic equipment to maintain compliance with the no dust requirement stipulated in the University’s and Quaker Oats’ permits. The long-term transportation solution is to build an indoor unloading facility for 53ft “moving bottom” trucks in order to take advantage of their increased hauling capacity.
The final step was to convert from a temporary PSD permit to a permanent permit. Both the Iowa Department of Natural Resources (DNR) and EPA Region 7 must approve the substitution of oat hull biomass for coal. New Source Review requires permitting when modifications and repairs are made to sources of air pollution to insure that air quality will not deteriorate. Iowa is in an attainment region of the country where the prevention of significant deterioration (PSD) applies. However, a provision in the legislation allowed for Governor Tom Vilsack to grant a waiver of the EPA permit review thus allowing for the power plant to burn oat hulls. The Governor did this because of the obvious benefits resulting from the substitution of up to 50% oat hulls for dirty coal.
