Could ‘liquid wood’ replace plastic?

Germans engineer an organic alternative from a paper waste product.

Scott Wallace/Staff

Almost 40 years ago, American scientists took their first steps in a quest to break the world’s dependence on plastics.

But in those four decades, plastic products have become so cheap and durable that not even the forces of nature seem able to stop them. A soupy expanse of plastic waste – too tough for bacteria to break down – now covers an estimated 1 million square miles of the Pacific Ocean.

Sensing a hazard, researchers started hunting for a substitute for plastic’s main ingredient, petroleum. They wanted something renewable, biodegradable, and abundant enough to be inexpensive.

Though they stumbled upon a great candidate early on, many US chemists had given up on it by the end of the 1990s. The failed wonder material: lignin, the natural compound that lends strength to trees. A waste product from paper production, much of the lignin supply is simply burned as fuel.

But while many scientists turned to other green options, a German company, Tecnaro,  says it found the magic formula. Its “liquid wood” can be molded like plastic, yet biodegrades over time.

Now, Tecnaro’s success could revive interest in lignin and propel the search for better and cheaper bioplastics.

“The lignin itself was misunderstood completely by [leaders in the field] and the majority of people,” says Simo Sarkanen, an environmental science professor at the University of Minnesota.

The formula is everything
This past holiday season, nativity figurines made from Tecnaro’s “liquid wood” raised eyebrows among the bioplastic community. Sold as Arboform, the tough mixture is chock full of lignin – sometimes more than 50 percent, compared with the 30 percent threshold where many researchers would max out. The rest is fiber from wood, flax, or hemp, as well as a few additives.

Raw Arboform consists of dark brown pebble-sized pellets. It is processed using the same equipment used to make conventional plastic. The granules are dropped into a barrel and heated until they melt. Then the contents are highly pressurized and forced into a rigid mold – that of a figurine, perhaps.

As the liquid cools, Arboform actually conforms better than most plastics to the boundaries of complex molds, says Benjamin Porter, a researcher with Tecnaro. The 10-year-old, 10-person operation based in Ilsfeld, Germany, is very secretive about its ­liquid-wood formula – so proprietary that Dr. Sarkanen is a little skeptical. In 2001, his lab
patented a simpler lignin-based plastic, one that lacks the secret combination of additives in Arboform.

With several years of successful sales, the company takes on one or two new employees annually. And as the company grows, so does the catalog of Arboform products, according to Mr. Porter. The current lineup includes watches, keyboards, hairbrushes, and, recently, caskets. Future possibilities include car interiors and furniture. “We haven’t built a house though – yet,” Mr. Porter jokes.

Arboform’s nativity figurines showcase a new grade of the material. Its sulfur content is much lower than Tecnaro’s original recipe, says Emilia Regina-Inone of the Franhoefer Chemical Institute, which works with Tecnaro to test Arboform. And it can be broken down and reused eight or 10 times without wrecking the material’s mechanical properties, such as its relatively high fire-resistance and durability.

But there are tradeoffs. All versions of Arboform are heavier, more brittle, and more expensive than conventional plastics. Arboform costs about $1.60 per pound when purchased in bulk, compared with less than a dollar for a pound of polypropylene, a traditional plastic. Tecnaro produces about 6.6 million pounds of Arboform each year, a capacity that Porter says consistently increases 10 percent each year.

America has a taste for starch
Tecnaro’s products sell in Australia, Brazil, and Colombia, but mostly in Europe, where consumers are more willing to pay for environmentally conscious products – and producers must pay to recycle petroleum-based plastics.

The US mostly backs a different plastic substitute. After giving up on lignin, American scientists focused on starch – a cheap and renewable resource, though one also important to food production.

Cereplast, based in Hawthorne, Calif., harnesses starch from corn, tapioca, wheat, and potatoes to produce a resin capable of replacing at least 50 percent of the petroleum in conventional plastics. Dwarfing upstarts like Tecnaro, the company’s California facility can pump out 50 million pounds of starch-based plastic a year for compostable forks and biodegradeable containers.

But tapping the potential of long-neglected lignin could not only cut the amount of plastic thrown away each year, but could also slow current greenhouse gas emissions. In trees, lignin naturally stores carbon dioxide during photosynthesis, in which plants use sunlight to turn that CO2 into oxygen.

When papermakers discard unwanted lignin, the carbon is still trapped inside it – until they burn the lignin. At that point, much of the CO2 is released into the atmosphere.

“If you can make plastics, or any useful kinds of polymeric materials from lignins … this, of course, would help reduce the rate of global warming quite significantly,” Sarkanen says.

And the question of what to do with lignin instead of burning it is quickly becoming an urgent one. The US Department of Agriculture has mandated that 30 percent of transportation fuels must come from plant materials by 2030.

Producing those “green” fuels involves stripping the lignin from the cellulose in plant matter, an arduous task. Federal funding totaling $375 million over five years now backs three research centers dedicated to efficient biofuel production, one of which is affiliated with Sarkanen’s project to find the enzyme that naturally dissolves lignin without the assistance of a fungus.

“The question of what we’re going to do with lignin besides burning it is coming to the fore,” Sarkanen says. “It’s of enormous potential importance.”

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