Environment

Pig manure may pave the way to sustainable road building

Pig manure may pave the way to...
Chunks of asphalt made with binders derived from pig manure, which can replace the petroleum found in traditional asphalt
Chunks of asphalt made with binders derived from pig manure, which can replace the petroleum found in traditional asphalt
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Chunks of asphalt made with binders derived from pig manure, which can replace the petroleum found in traditional asphalt
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Chunks of asphalt made with binders derived from pig manure, which can replace the petroleum found in traditional asphalt

Researchers from North Carolina A&T State University have developed a process that uses pig manure as a low-cost replacement for petroleum in the production of road asphalt. In searching for bio alternatives, the group discovered that swine waste is especially rich in oils very similar to petroleum, at a grade too low to make gasoline but suited for asphalt.

With funding from the National Science Foundation, the group developed a process that turns the waste into a black crude – the sticky binder that can be used to make asphalt. The cost to process the manure oil is US$0.56 a gallon, which is much cheaper and greener than current petroleum binders.

"It is different from petroleum refinery, which distills crude oil to produce mainly fuel and leave the residue for asphalt," Ellie Fini, lead researcher and assistant professor of civil engineering, told Gizmag. "Here we produce bio-adhesive from breaking bio-mass molecular structure and re-synthesizing the bio-adhesive structure. Bio-adhesive is lower in cost, requires less heat for mixing and compaction and is more durable."

For drivers concerned about the odor of their roads, the compounds that give pig manure its uniquely pungent smell – a stew of volatile fatty acids – are filtered out during processing. And the dry matter left over from the process can be used as fertilizer.

Meanwhile, the bio-asphalt is being put through rigorous testing to see how it will hold up under real world road conditions, including a simulation of truck traffic making 20,000 passes over it. The tests have so far been successful, passing Department of Transportation specifications, which led the group to form the company Bio-Adhesives to scale up their research.

"We think it's scalable and cost-wise it's profitable," says Fini. "Our vision is to help the farmer and help the construction industry, both sides. We see a win-win approach in the solution."

Asphalt made from pig manure could alleviate what's become a huge environmental issue – effluence from factory farm feedlots – especially in large swine-producing states like North Carolina.

"We generate 43 billion gallons of swine manure in the world every year," says Daniel Oldham, graduate student researcher on the project, who adds that China produces 10 times the amount of pig manure as the U.S.

At the same time there are around 2.3 million miles of asphalt paved roads in U.S., with the cost of paving an urban two-lane road with traditional petroleum asphalt costing over $800,00 per mile.

Source: National Science Foundation

Pig manure paves road to sustainable asphalt - Science Nation

9 comments
spicedreams
Got to wonder whether pig manure is not too valuable to turn into roads...
windykites
This reminds me of that old saying: "where there's muck there's brass!" Here is a new saying: "one man's meat is another man's roadway" As it requires lower temperatures for processing, I hope that doesn't mean that it will go soft and sticky in the heat of the day. This is a terrific idea. Let's hope it stays on the ground. Pigs might fly!
Non-Compos_Mentis
Re, "The tests have so far been successful ..." : All tests are successful. The product may pass or fail, but the test is always successful. Re, "It is different from petroleum refinery, which distills crude oil to produce mainly fuel and leave the residue for asphalt," Ellie Fini, lead researcher and assistant professor of civil engineering, told Gizmag. "Here we produce bio-adhesive from breaking bio-mass molecular structure and re-synthesizing the bio-adhesive structure. Bio-adhesive is lower in cost, requires less heat for mixing and compaction and is more durable." Not. By the end of the paragraph, Ellie Fini seems to have forgotten that two or more products are obtained from crude. He/she implies that the cost of asphalt is the cost of refining crude, which it is not.
eMacPaul
@Non_Compos_Mentis, a poorly-designed test may fail.
noteugene
Oh man, how'd you like to have to do that job, paving roads out of pig shit? All this was informative but you could have told us the estimated cost per mile to resurface a road using this method don't you think? What was the point of telling us the cost per mile using the current method & omitting the cost with this alternative method?
KGN
Unfortunate -- pig manure is already used as a low-cost and effective fertilizer due to its high Nitrogen content. I don't know about other areas of the country, but I doubt the Midwest has any effluence issues. It's actually pumped out from below hog barns and spread onto nearby fields, returning the Nitrogen lost from growing crops in the first place. If this is used in roads, it may raise food production costs due to the potential reduction in low-cost fertilizer. So you're not getting the cost/benefit ratio you think you're getting, and may even be environmentally damaging...
ErstO
just stay off the road when it rains, yuchhhh
Mr_X
If a certain amount of unprocessed pig manure is retained in the mix, it could help in reducing traffic.
WagTheDog
Now mix ground up tires into the asphalt to get cheap, quiet, smooth, and long-lasting roads. Unfortunately, the road construction industry just won't let that happen.