Biodiesel Frequently Asked Questions

What is biodiesel made from?
According to the National Renewable Energy Laboratory (NREL), biodiesel can be made from a variety of renewable sources, such as vegetable oils (soybeans or other crops), recycled cooking grease, or animal fats. These feedstocks are used to manufacture a mixture of chemicals called fatty acid methyl esters (biodiesel).

Biodiesel blends are mixtures of diesel fuel and biodiesel produced from one of the above feedstocks. The blend is identified according to the proportion of biodiesel fuel it contains. For example, B20 is equivalent to 20% biodiesel fuel, and 80% diesel fuel.

Does using biodiesel void my warranty?
Major manufacturers of stationary generators are aware of biodiesel and often have official positions on its use in their engines.  Check with your manufacturer for the most current information.

According to NREL, Original Equipment Manufacturers (OEMs) provide a material and workmanship warranty on their products. Such warranties do not cover damage caused by external conditions, such as fuel. Thus, if an engine using biodiesel experiences a failure unrelated to the biodiesel use, it must be covered by the OEM’s warranty. Federal law prohibits the voiding of a warranty just because biodiesel was used—it has to be the cause of the failure. If an engine experiences a failure caused by biodiesel (or any other external condition, such as bad diesel fuel), it will not be covered by the OEM’s warranty.

Where can I get biodiesel?
The Iowa Soybean Association has a list of soy biodiesel distributors by county. They also have a list of locations where you can get biodiesel at the pump.

What blends of biodiesel can I use in my utility's stationary generators?
The Iowa Department of Natural Resources (IDNR) has recently made a rule change to allow all stationary generators in Iowa to use blends of up to 2% biodiesel (98% diesel).  Currently, any utility can burn 2% biodiesel without having to notify the IDNR or modify any permits. Additionally, a small number of municipal utilities are already permitted to burn up to 5% biodiesel.

What if I want to burn blends higher than B2 in stationary generators?
You will have to modify the operating permits for your facility. These include Voluntary Operating Permits (VOP), Small Source Operating Permits (SSOP), Title V Operating Permits, and construction permits. The IDNR will allow utilities to modify their permits so they can burn up to 10% biodiesel. The necessary permit modifications will slightly decrease the amount of operating hours or total amount of fuel consumption that your facility is allowed. This is because the emissions factor will have to be adjusted for biodiesel. Below is an example calculation adjustment for using 5% biodiesel fuel:

Original Calculation (before using biodiesel):
NOxdi = (VOLoil x 140,000 Btu/gal x 1 MMBtu/10⁶ x 3.85 lbs NOx/MMBtu x 1 ton/2000 lbs)

NOxdi = total NOx emissions emitted from engine
VOLoil = total amount of oil burned in engine

Modified Calculation (to allow use of 5% biodiesel):
NOxdi = (VOLoil x 140,000 Btu/gal x 1 MMBtu/10⁶ x 3.85 lbs NOx/MMBtu x 1 ton/2000 lbs) + (VOLbio x 140,000 Btu/gal x 1 MMBtu/10⁶ x 4.04 lbs NOx/MMBtu x 1 ton/2000 lbs)

VOLbio = total amount of B5 burned in engine
NOxdi = total NOx emissions emitted from engine
VOLoil = total amount of oil burned in engine

Here the term in red and blue has been added to the permit calculations. It represents NOx emissions from biodiesel. The blue term 4.04 lbs NOx/MMBtu is 5% higher than the 3.85 lbs NOx/MMBtu term that is used for diesel fuel. This modification is linear. In other words, if the permit was to be modified to allow use of 10% biodiesel instead of 5% biodiesel, the coefficient would than be 4.24 lbs NOx/MMBtu instead of 4.04.

Making these coefficients bigger than 3.85 results in a larger amount of NOx emissions coming from the facility. In order to compensate for this increase, there would likely be reductions in VOLoil and VOLbio, which is the amount of fuel that the facility is allowed to burn.

For burning blends higher than 10%, the IDNR has indicated that additional stack testing may be needed. If you have questions concerning this, please contact the IDNR Air Quality Division.

Contact – IAMU Biodiesel Program
Anne Kimber, P.E., Director of Energy Services, 515-289-1999