Lessons Learned in Forest Biorefinery Pilot Trials in Maine

A novel pre-pulping extraction technology uses an existing chemical stream (“green liquor”, available at all Kraft pulp mills) to recover hemicelluloses from hardwood chips prior to conventional sulfate pulping in order to produce bio-based chemicals. Instead of being degraded and burned as a part of black liquor, the hemicelluloses can be recovered on a commercial scale as a valuable renewable feedstock for biorefineries. The green liquor extraction technology can (i) prevent pollution at its source by recovering hemicelluloses that would otherwise be wasted, (ii) improve energy efficiency by off-loading lime kiln fossil fuel demand, and (iii) use existing pulp mill facilities to create a new high-value, renewable chemical feedstock. The pre-pulping extraction process has been demonstrated at full commercial scale at the Old Town mill in Maine through over 800 hours of trials. Several million gallons of extract have been produced while maintaining quality pulp output.

UMaine researchers had invented a process modification to the Kraft pulping process that allows recovery of hemicelluloses and acetic acid from hardwood chips at concentrations of commercial importance while minimizing degradation of wood fibers so they can be further processed into bleached hardwood pulp suitable for paper making and other uses. This concept provided the basis for the wood extract based biorefinery studies. This scale-up and mill trial collaboration is an excellent example of University-Industry activity focused on technology demonstration.

This presentation deals with materials handling issues that are often not apparent at bench scale work but pose challenges up on scale-up. This presentation focuses on lessons learned in recent mill trials involving production of wood extracts and wood sugars. Production of wood-derived fermentation ready sugars allows one to co-produce chemicals and fuels at pulp mills. The National Environmental Policy Act (NEPA) requires that evaluation of potential impacts of such mill conversion production to the environment be done, when federal funds are to be used.