Asphalt from Pig Manure Provides a Viable Bio-Alternative

July 15, 2016 | Comments

Obtaining a steady supply of pig manure as a raw material is not a problem. Billions of gallons of pig excrement are produced in the U.S. each year. In modern pig farming practices, the waste often is dealt with by flushing it into lagoons. It then sits there for extended periods of time and poses a serious health threat if these areas become flooded.

Researchers at the North Carolina A&T State University see a better fate for pig manure. They have discovered a method of processing pig waste to create a bio-alternative for road asphalt.

As it turns out, the oils in swine manure have similar properties to petroleum. They are too low grade for gasoline but are perfect for asphalt.


The asphalt undergoes testing from the Department of Transportation. (Image courtesy of the National Science Foundation.)


How Asphalt Oil Is Made

Asphalt is made in an intense refinement process. The crude oil is first desalted to remove sand, rust, minerals, salts and other contaminants, as any small salt content will corrode the distilling column. Fresh water and chemicals are used in this process.

Crude oil is then boiled at varying temperatures and separated into its different hydrocarbon components in a distiller. Asphalt is one of the heavier hydrocarbons, which settles into trays at the bottom where it is removed.

The lighter hydrocarbons, like butane, vaporize at temperatures as low as 90 °F, whereas residuum, including asphalt, requires temperatures as high as 800 °F to vaporize. In a controlled environment with high heat and low pressure, asphalt oils are removed for further refinement.


Bioadhesive from Pig Manure as a Viable Alternative

“Here we produce bioadhesive from breaking biomass molecular structure and resynthesizing the bioadhesive structure,” according to Elle Fini, lead researcher and assistant professor of Civil Engineering. “Bioadhesive is lower in cost, requires less heat for mixing and compaction, and is more durable.”

The adhesive costs $0.56 per gallon to process, which is less than conventional asphalt made from crude oil. Odor is also not a problem, as the compounds in the manure that produce the smell are removed in the process.

The bioadhesive is currently undergoing testing to ensure that it abides by the Department of Transportation standards. This includes the stress of 20,000 consistent passes over the material, which is supposed to simulate truck traffic. So far, the bioadhesive has passed all tests.

The National Science Foundation has funded the research for this project. The research team has filed the necessary patents and has created the Bio-Adhesive Alliance company. It is their hope that the product will reach the market soon.

“We think it’s scalable and cost-wise it’s profitable,” said Fini. “Our vision is to help the farmer and help the construction industry—both sides. We see a win-win approach in the solution.”


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