Larch Biorefinery:
Technical and Economic Evaluation
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Abstract
In
this study a forest biorefinery concept based on larch wood
was technically and economically evaluated. Two slightly different
cases of a larch-based biorefinery were compared to conventional kraft
pulping. The wood chips of Larix sibirica (Lebed.) were pre-extracted (PE) and washed with water prior to
pulping, in order to generate an additional sugar side-stream. The
sugars were hydrolyzed into monosugars, which were then fermented
by Bacillus coagulans into lactic acid.
The lactic acid needs to be purified before sold to the market. By
pulping the pre-extracted wood chips with anthraquinone (AQ) and polysulfide
(PS), the pulp yield loss was reduced. The pulp was then bleached
(O-D0-Ep-D1-P). The products of this larch biorefinery are bleached
softwood pulp and lactic acid. Three process cases were simulated:
conventional kraft pulping, PE-PSAQ with 0.5% PS, and PE-PSAQ with
2% PS, in terms of mass and energy balances. Considering the availability
of larch resources, this kind of a biorefinery could suitably be located
in Siberia, Russia. Market prices were collected, and based on the
simulation results, cash flows were determined. Sensitivity analysis
was carried out, and investment costs were estimated. Based on the
simulation with the addition of a lactic acid production line to an
existing pulp mill, the payback time for the investment costs would
be about 16 months