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Wednesday, February 8, 2012

Wood Science 101(3) - Lignin

http://shakib-biology.blogfa.com/8708.aspx
You'd be hard pressed to find a material more universally researched right now than lignin. Let's talk about it a little today. It's the second most abundant organic polymer on earth, behind cellulose. It's what makes trees stand upright, what makes wood hold its shape, and what makes furniture support your weight when you sit on it. It's been called "God's glue", and "nature's plastic", because it fills the space between plant cells, called the middle lamella, where the lignin is highly concentrated, and binds to the cell walls (which themselves have a lower concentration of lignin mixed with the cellulose and hemicellulose fibrils that make up the primary and secondary cell walls).  It's really sticky, durable stuff, and that's what all the research is about.

It seems that today's scientists, in trying to reverse-engineer plant materials, would like to have an easy way to break down the lignin bonds that hold the other plant constituents together, so that they can then re-assemble those components into various other things. Over the last century or so, various processes have been developed, mostly by paper companies, to de-lignify wood pulp, and the lignin by-product that remains has been burned for energy in the paper-making process, or further refined into other products, such as:

  • forms of sugar
  • water reducers in concrete and gypsum wallboard admixtures
  • mineral pelleting and granulating production aid
  • oil drilling additive
  • animal feed additive
  • road dust control
  • additive for certain yeasts and pet foods
  • dispersant in brick manufacturing

Technical description, from Wikipedia:
"Lignin, or lignen,is a complex chemical compound; most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word 'lignum', meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose and constituting from a quarter to a third of the dry mass of wood. As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Its most commonly noted function is the support through strengthening of wood in trees.
...
Lignin plays a significant role in the carbon cycle, sequestering atmospheric carbon into the living tissues of woody perennial vegetation. Lignin is one of the most slowly decomposing components of dead vegetation, contributing a major fraction of the material that becomes humus as it decomposes. The resulting soil humus, in general, increases the photosynthetic productivity of plant communities growing on a site as the site transitions from disturbed mineral soil through the stages of ecological succession, by providing increased cation exchange capacity in the soil and expanding the capacity of moisture retention between flood and drought conditions."
http://en.wikipedia.org/wiki/Lignin
Lignin is everywhere in the biological realm, plays a huge part in maintaining the earth's carbon cycle, and therefore, the environmental stability of the world, and is still one of the primary foci of the world's scientific community. More reasons to appreciate the role of wood in our world.

And those reasons continue to mount as the scientists make progress. You've heard of carbon-fiber technology, and how it improves the strength-to-weight ratio of everything from body armor to Formula One racing cars? Well, one problem with carbon-fiber materials are that they are expensive when produced from petroleum-based raw materials, or precursors. So, guess what? Scientists are striving to make them cheaper using lignin, from wood! Sound familiar? Check out the great video below from the scientists at the Oak Ridge National Laboratory.



So, just as scientists and entrepreneurs envision fast-growing plantations for the farming of cellulose for various energy and bio-refinery products, so too are they working on high value-added uses for the lignin as it is separated. And fortunately for lignin-production values, the lignin content of softwoods is typically higher (23 to 33%) than in hardwoods (16 to 25%), so faster-growing softwood plantations of warmer climates will increase the viability of any future lignin markets.

When you consider all the potential uses of cellulose and lignin already under development, it's really not difficult to envision a day in the not too distant future when practically everything we wear, ride, build with, or use for energy will come from a wood or woody plant derivative. Those old woodies of the 1940's may have George Jetson style successors made from wood, after all.

3 comments:

Anonymous said...

Chuck- really nice BlogSpot Contribution today. Too bad no longer any new lignin plants being built in the USA! Great compounding agenta and surfactant precursor!
WoodDoc

Chuck Ray said...

Thanks, Doc. Yes, too bad all the investment dollars are going into that really important technology, like Facebook :-)

Anonymous said...

If you know of a company interested in commercializing lignin-based products, or if there is serious interest in building a lignin production plant in the U.S., we'd like to hear from you:

http://www.itascadv.org/eco_web/