A Compound From Plants Could Replace Bitumen To Make Roads Greener

A Compound From Plants Could Replace Bitumen to Make Roads Greener

Construction teams around the world rely on bitumen — an incredibly sticky by-product of crude oil production — as the main binding agent for asphalt. But a team of scientists reckon that a compound found within plants could help replace it, making road-building a greener, more sustainable practice.

Ted Slaghek and his colleagues form TNO, a non-profit from the Netherlands that develops science into sustainable real-world applications, suggest that a plant molecule known as lignin could replace bitumen. Lignin — which keeps water out of plants and binds them together, too — is chemically quite similar to bitumen: it has a large number or carbon rings in its structure. Indeed, some have suggested that the similarities could allow the two to be simply mixed together to produce a mixture that swaps some bitumen out of the usual construction mix.

Such attempts haven't worked. But Slaghek explained at the 249th National Meeting & Exposition of the American Chemical Society yesterday that integrating lignin into the bitumen at the molecular level does produce a useable mixture for road-laying. In fact, PhysOrg reports, it's possible to produce a 50-50 mix of bitumen and lignin that works well for such applications, halving the demand for bitumen. Slaghek's team explain that lignin can be used to improve the material qualities of bitumen mixtures, making it harder in warm weather or more pliable in the cold. In turn, it could create asphalt better suited to extremes of temperature.

There's certainly enough lignin in the world. It accounts for up to a third of all the the dry material in trees. In fact it's removed as a waste product during the production of paper — meaning there's a ready supply of 50 million tons of the stuff around the world every year.

The next step is to turn the lab work into practice. Indeed, Slaghek is to begin construction of cycle paths made from the new lignin-bitumen mixture later this year. If that's a success, we may all soon be driving on tree matter. [PhysOrg]

Picture: Trey Ratcliff/Flickr

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