Features Research & Innovation
Converting to a Biorefinery: The Path Forward

Biorefining continues to be a hot topic in paper industry circles. An afternoon session hosted by the Biorefinery Special Committee at the PAPTAC Annual Meeting featured presentations from Canadian and U.S. universities.

Richard Phillips of North Carolina State University presented a work he co-authored with Shu-Fang Wu, Trevor Treasure, Hou Min Chang and Hasan Jameel entitled, “Technical and Economic Feasibility of Repurposing Uneconomic Softwood Kraft Pulp Mills to Ethanol Production.” Beginning with the basic acknowledgement that slumping demand for key paper grades has prompted numerous mill closures, Phillips emphasizes that repurposing a softwood kraft mill to produce ethanol offers a number of advantages, not least of which includes avoiding a complete write-off and demolition of uneconomical mills.

The study indicated that attractive investment returns can be achieved with green liquor pretreatment, blowline refining of pretreated chips, oxygen delignification, wash press washing after oxygen delignification, additional pulp refining to open up the softwood fibres to allow efficient subsequent enzyme treatment which are fermented and distilled to 95% ethanol concentration, and then dehydrated to 99.5% ethanol content with molecular sieves. As Phillips noted, this process reuses existing wood-yard, cooking, washing, oxygen delignification and bleaching towers, as well as power and waste treatment plant systems that are already in place.

Adriaan van Heiningen of the University of Maine presented his work entitled “Kinetics and Mechanism of Autohydrolysis of Hardwoods,” which he co-authored with Martin Lawoko and Xiaowen Chen. With an emphasis on extraction of hemicelluloses from wood prior to pulping in order to make co-products such as ethanol and acetic acid, Heiningen’s work expands on previous studies conducted in batch reactors, using a continuous mixed batch reactor to obtain the intrinsic kinetics of dissolution of hemicelluloses from a mixture of hardwoods. Autohydrolysis presents an inexpensive and environmentally-friendly alternative to depolymerising the structural polysaccharides of woody biomass into fermentable monosugars in the woody biomass conversion process.

Evaluating ethanol feedstocks.

Controversy abounds regarding the economic and environmental viability of ethanol production. While there is wide recognition that a number of renewable resources can be used to produce ethanol, emphasis on the source of the feedstock is critical to undertaking an informed environmental evaluation. As Paul Stuart and Mahasta Ranjbar, the NSERC Environmental Design Engineering Chair highlighted in their work, “Comparative Life-Cycle Assessments for Different Feedstocks-to-Ethanol Production,” life cycle assessment (LCA), or the systematic approach to evaluating the environmental performance of a process, product or activity, is a methodology available and able to reveal the environmental performance of ethanol production. In their study, the authors apply the LCA methodology in order to evaluate the environmental ‘friendliness’ of ethanol produced from different feedstocks.