A Molecule from plant to make roads 'greener'!

Use of a plant molecule in asphalt and sealant mixtures of roads and roofs could help them withstand various weather conditions, also making them environmentally friendly.

  

The plant molecule called lignin could one day replace bitumen, a by-product of crude oil production which is currently used as the main sticky ingredient in asphalt and roof sealants, noted the study presented at the 249th National Meeting & Exposition of the American Chemical Society (ACS) in Denver.

As oil is a non-renewable resource and fluctuations in the oil market have made it more difficult to get high-quality bitumen, manufacturers have been forced to look for alternatives, said Ted Slaghek, senior scientist at TNO, a non-profit organisation in the Netherlands.

"In the long term, we have to move to renewable products that we can harvest every year," pointed out Slaghek.

Slaghek explains that lignin is a renewable resource that makes up as much as a third of the dry material in trees, where it keeps out water and binds together other components of plant biomatter, like cellulose. Lignin is also plentiful—and therefore, inexpensive—because it is removed as a waste product during the paper-making process. More than 50 million tons are produced globally as waste each year. Most of this is burned to generate electricity to run the paper mills. Burning lignin is not only wasteful, it releases soot and other pollutants, he says.

Because lignin shares many characteristics with bitumen, it could become an environmentally friendly additive to help reduce the amount of bitumen needed for construction activities. Like bitumen, lignin is a large molecule with a number of carbon rings.

To use it as an additive, the researchers said, lignin must be integrated into the bitumen on the molecular level, not just mixed into it. By integrating the lignin, it is possible to reduce the amount of bitumen needed by as much as half, Slaghek said.

Slaghek's team developed a number of lignin-bitumen mixtures that make the asphalt harder in warm weather, preventing rutting and adding several years to a road's lifespan."We have also developed lignin-bitumen mixtures that keep the bitumen more tacky, so at lower temperatures it is still a good road," Slaghek added. The mixtures contain differing amounts of lignin, as well as lignin with various chemical modifications.

To demonstrate how well these mixtures can work in the real world, Slaghek and partners are planning to build a 100-meter stretch of bicycle path this year using one of the lignin-based asphalt mixtures.

The advantages of lignin go beyond quality, cost and performance benefits, Slaghek notes. It's also safe to handle—and consume. "You might be surprised to learn this, but you're eating lignin every day if you're eating vegetables," he says.

Sources:
http://timesofindia.indiatimes.com
http://phys.org