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Bioresour Technol. 2015 Nov;196:129-35. doi: 10.1016/j.biortech.2015.07.051. Epub 2015 Jul 21.

Techno-economic evaluation of conditioning with sodium sulfite for bioethanol production from softwood.

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Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden. Electronic address:
SP Processum AB, SE-891 22 Örnsköldsvik, Sweden.
SEKAB E-Technology AB, SE-891 26 Örnsköldsvik, Sweden.


Conditioning with reducing agents allows alleviation of inhibition of biocatalytic processes by toxic by-products generated during biomass pretreatment, without necessitating the introduction of a separate process step. In this work, conditioning of steam-pretreated spruce with sodium sulfite made it possible to lower the yeast and enzyme dosages in simultaneous saccharification and fermentation (SSF) to 1g/L and 5FPU/g WIS, respectively. Techno-economic evaluation indicates that the cost of sodium sulfite can be offset by benefits resulting from a reduction of either the yeast load by 0.68g/L or the enzyme load by 1FPU/g WIS. As those thresholds were surpassed, inclusion of conditioning can be justified. Another potential benefit results from shortening the SSF time, which would allow reducing the bioreactor volume and result in capital savings. Sodium sulfite conditioning emerges as an opportunity to lower the financial uncertainty and compensate the overall investment risk for commercializing a softwood-to-ethanol process.


Cellulosic ethanol; Conditioning; Simultaneous saccharification and fermentation; Sodium sulfite; Techno-economic evaluation

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