NIST researchers have identified a method of refining pig manure into a fuel source for vehicles and heating.

Photo courtesy of NIST (www.nist.gov).

After a close examination of crude oil made from pig manure, chemists at the National Institute of Standards and Technology (NIST, www.nist.gov) have developed the first detailed chemical analysis revealing what processing is needed to transform pig manure crude oil into fuel for vehicles or heating. Mass production of this type of biofuel could help consume a waste product overflowing at U.S. farms, and possibly enable cutbacks in the nation’s petroleum use and imports. But, according to a paper detailing the NIST’s analysis on this matter,* pig manure crude will require a lot of refining.

The ersatz oil used in the NIST analyses was provided by engineer Yuanhui Zhang of the University of Illinois Urbana-Champaign (www.aces.uiuc.edu). Zhang developed a system using heat and pressure to transform organic compounds, such as manure, into oil.

As described in the paper, the pig manure crude contains at least 83 major compounds, including many components that would need to be removed, such as about 15 percent water by volume, sulfur that otherwise could end up as pollution in vehicle exhaust, and lots of char waste containing heavy metals, including iron, zinc, silver, cobalt, chromium, lanthanum, scandium, tungsten, and minute amounts of gold and hafnium. Whatever the pigs eat, from dirt to nutritional supplements, ends up in the oil.

The measurements were made with a new NIST test method and apparatus, the advanced distillation curve, which provides detailed data on the makeup and performance of complex fluids. A distillation curve charts the percentage of the total mixture that evaporates as a sample is slowly heated. Because the different components of a complex mixture typically have different boiling points, a distillation curve gives a good measure of the relative amount of each component in the mixture. NIST chemists enhanced the traditional technique by improving precision and control of temperature measurements and adding the capability to analyze the chemical composition of each boiling fraction using a variety of advanced methods.
NIST researchers analyzed the graphite-like char remaining after the distillation by bombarding it with neutrons, a non-destructive way of identifying the types and amounts of elements present. Two complementary neutron methods detected the heavy metals listed above.

For more on the process of making pig waste in crude, see “Converting Manure to Oil: U of I Lays Groundwork for One-of-a-Kind Pilot Plant”.

* L.S. Ott, B.L. Smith and T.J. Bruno. Advanced distillation curve measurement: Application to a bio-derived crude oil prepared from swine manure. Fuel (2008), doi:10.1016/j.fuel.2008.04.038.