I remember the early 90’s when the TMP mill boom was in full swing and new mills were being announced and built, especially across Canada. I had the professional pleasure of working with many of these mills, developing screening and chip prep systems for TMP operations when nobody knew exactly what the right amount of prep needed was. We used a model based on liquor penetration from Kraft cooking, thinking that steam penetration into chips in the preheating column would be about the same and give similar sorts of benefits. The chip thickness screening systems we installed turned out to be overkill for a process that grinds chips between steel plates. But doing more than was needed was better than what most TMP mill operators had known: no chip prep at all! The mantra of Chip Uniformity is Good applied, of course, and chips systems supplied later in the product cycle were trimmed and more appropriate to the process’ needs.
The term I like to use is “leverage”. What we are doing now is taking what we know about material properties and processes and applying this knowledge to a new industry, Biomass for Energy. I wish it had a simpler name, other than Biomass for Energy. Something like Bioenergy sounds good, but really, doesn’t any living process also use some form of bioenergy to sustain life? BioMASS takes the living component out of it, and reduces it to some gross, heaping pile of trash sort of image, like the melding together the ideas of living things (bio) and landfills (mass). Not a pretty image, I admit. And it is so diverse and could include any sort of cast-off plant material (is it always plant matter used?), that the landfill image is an appropriate one. “Truckloads of cast off plant matter” takes too long to say. Biomass is much simpler.
Back to leveraging. Industrial processes have been using waste materials for power generation for years. Just as pulp from wood chips was originally developed as a way to get rid of the residual chips that were left over from lumber production, bark-fueled boilers were developed to use the abundant bark residue. I recall a college professor say one day that whomever developed a process to use bark to product a product would make a killing. At the time teepee burners were still the disposal method of choice! I think we are still waiting for a proper “bark product” to show up, but in the meantime we can treat bark residues as a fuel source and harness the energy it releases, and make something of value of it.
From a forest products perspective where bark is a residual fuel, to a power production perspective where bark is an essential process feedstock, the lowly sawmill residual streams of bark, sawdust, and hogged trim ends have been promoted to a higher status. Those of us who languished at the back of the woodyard lot with our feet in the bark pile and bark dust down our necks can now stand up proud and tall. Our time was spent wisely, time has shown, and our hard-earned knowledge of this difficult material can now be put to good use in an industry that values what we know. Yes, it is nasty stuff, and yes, it takes special equipment and procedures to manage it, but we have been there, done that, and have the t-shirt to prove it.
Desmond Smith