Researchers presented their results at the 255th National
Meeting & Exposition of the American Chemical Society.
The idea for the
project germinated on Crete, where Alexander Bismarck, Ph.D.,
noticed goats munching on summer-dry grass in the small village
where he was vacationing. "I realized what comes out in the end
is partially digested plant matter, so there must be cellulose
in there," he recalls.
After working with goat
manure, Bismarck, who is at the University of Vienna, Austria,
his postdoc Andreas Mautner, Ph.D., and graduate students Nurul
Ain Kamal and Kathrin Weiland moved on to dung from horses, cows
and eventually elephants.
The supply of raw
material is substantial: Parks in Africa that are home to
hundreds of elephants produce tons of dung every day, and
enormous cattle farms in the U.S. and Europe yield mountains of
manure, according to Mautner.
The researchers treat
the manure with a sodium hydroxide solution. This partially
removes lignin, which can be used later as a fertilizer or fuel,
as well as other impurities, including proteins and dead cells.
To fully remove lignin and to produce white pulp for making
paper, the material has to be bleached with sodium hypochlorite.
The purified cellulose requires little if any grinding to break
it down into nanofibers in preparation for use in paper, in
contrast to conventional methods.
"You need a lot of
energy to grind wood down to make nanocellulose," Mautner says.
But with manure as a starting material, "you can reduce the
number of steps you need to perform, simply because the animal
already chewed the plant and attacked it with acid and enzymes.
You inexpensively produce a nanocellulose that has the same or
even better properties than nanocellulose from wood, with lower
energy and chemical consumption," he says.
The dung-derived
nanopaper could be used in many applications, including as
reinforcement for polymer composites or filters that can clean
wastewater before it is discharged into the environment.
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