* The debate on the effectiveness and utility of bio-fuels is increasingly broad and often divergent opinions.
The characteristics of a good bio-fuel, be it bio-ethanol or bio-diesel, are threefold:
a) must have a good energy balance, meaning that the energy needed to produce one liter of bio-fuels should be much lower than the energy it can extract liter;
b) must, if produced by crop, requiring little water for irrigation;
c) should not interfere with crops for food to avoid turbulence and speculation on the cereal markets critical to the livelihood of most humans.
The production of bio-ethanol from lignocellulosic seems the most promising. In particular, are promising research on Panicum virgatum , a plant widely used in North America, proprio perchè soddisfa a tutti e tre i requisiti elencati . Scopo della ricerca tecnologica è principalmente quello di sviluppare trattamenti enzimatici a basso costo capaci di convertire la cellulosa in zuccheri e dunque in etanolo.
Uno studio, appena pubblicato su Biomacromolecules da alcuni ricercatori del Oak Ridge National Laboratory e Georgia Institute of Technology, mi sembra a tal proposito molto interessante.
Generalmente la biomassa lignocellulosica è costituita da tre polimeri: 1) cellulosa, polimero formato da catene di glucosio assemblate in strutture fibrose e cristalline, 2) Hemicellulosa, un polimero containing different sugars, 3) lignin, a polymer coating the heavy cellulose fibers.
In order to extract glucose is necessary to decompose the cellulose fibers by enzymatic hydrolysis, but the enzymes can attack the fiber only when the layers of hemicellulose and lignin are removed. This is why it is necessary to treat the biomass mechanically and chemically. These treatments naturally affect the final price of bio-ethanol therefore have to be efficient.
The study referred to analyze, by means of neutron scattering, the structural changes in the lignocellulose of Panicum virgatum induced by a pre-treatment of biomass in hot sulfuric acid. This
treatment is effective in redistributing lignin and hemicellulose to dissolve the increase in the diameter of cellulose. This would facilitate the digestibility of cellulose by enzymes and increase the efficiency in the production of bio-ethanol.
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