And powdered lignin can be added to pulverized coal for burning in power plants.
To be fermented, cellulose must first be broken away from a plant stiffener called lignin.
In particular, this industry wants to reduce the amount of lignin in the wood it uses.
The hope is that trees can be modified to make less lignin, and more cellulose.
The powdery lignin, once separated from the cellulose, is a very useful substance in its own right.
The lignin pellets, says KL, have 20% higher energy content (for the same weight) than wood pellets.
Dr Chiang therefore inserted into his aspens a gene that makes antimessengers to the lignin gene in question.
Lignin is one of the structural elements in the walls of the cells of which wood is composed.
Trees contain not only the cellulose that papermakers want, but lignin crudely, the stuff that makes a tree a tree which they don't.
An analogy: think of a pencil, where the lead in the middle is the cellulose fiber, surrounded by unwanted lignin and hemicellulose.
Pure Power processes the woody biomass to produce ethanol for fuel, xylitol for food sweetening and lignin for the production of biopolymers.
Because KL's process does not chemically alter the lignin with acids, it can be formed into pellets and burned in wood pellet stoves.
Pound for pound lignin contains nearly as much energy as coal.
Removing lignin is one of the messiest bits of pulp production.
The lignin acts as a glue, binding the cellulose fibres together, so an enormous amount of chemical and mechanical effort has to be expended on removing it.
The trick Dr Chiang and his colleagues used was to suppress the activity of one of the genes in the biochemical pathway that trees employ to make lignin.
They produced aspens, another species of poplar, that have 45% less lignin and 15% more cellulose than their wild brethren, and grow almost twice as fast, as well.
Tough lignin in cellulose structures help plants fend off attacks.
Researchers at the State University of North Carolina have bred aspens with only half the lignin of ordinary ones and, it turned out, they have the additional advantage that they grow faster.
The mixture the team achieved leaves the combined mass of lignin and cellulose in the trunk more or less unchanged and, contrary to the expectations of many critics, the resulting trees are as strong as unmodified ones.
Claire Halpin, of Dundee University in Scotland, and her colleagues have been looking into the question of environmental interactions using hybrid poplars that contain antisense versions of two other genes for enzymes involved in the production of lignin.
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