Carbon Negative: How Modern Sawmills Maximize Efficiency and Eliminate Environmental Impact

Today’s lumber industry wastes nothing. It’s pretty remarkable and it makes wood one of the most sustainable building material choices we have available. As they enter the mill, every log is properly purposed down to the last 2x4, furring strip, shim, chip and splinter, and it all happens with impressive efficiency in one centralized location, with lumber neatly packaged for its final destination. Thanks to technology and the nature of wood, modern sawmills are yielding renewable products carrying negative carbon footprints, and how they do it is nothing short of amazing.

It Starts With the Logs

Just consider a dozen trucks—or even just one—rolling in laden with logs, and someone has to size up those logs, grade them, and do it quickly enough and accurately enough to turn a profit. Traditionally, saw millers assessed a log’s value by what they could see, determining three key characteristics:

  • Tree Species. Discriminating between pine, softwood, for example, versus oak or walnut, hardwood, is important because they’re often processed at different mills, have different uses and hold different values simply because of what they are.

  • Log Quality. While the highest quality logs are often destined to become veneers, others may become sawlogs for boards, pallet stock or even pulp wood. It all depends on factors like color and heartwood-to-sapwood ratios, for example, as well as defects like cracks, knots, rot, wormholes, spots and streaks.

  • Log Scale. Considering the log’s quality, scale addresses how many usable board feet the log holds. A standard calculation uses diameter and log length to determine the yield of lumber in board feet.

Now, sawmills use grand-scale computerized systems of laser scanners, x-rays and optic sensors to analyze each individual log in its entirety, and they do it all in greater detail, with greater accuracy and quicker than ever before. Within mere seconds, systems can identify a log’s wood species as well as its length and diameter, curvatures, taper, bucking, irregularities, internal flaws and even potential metal fragments. Sophisticated algorithms can even evaluate woodgrain properties for tensile strength and their ability to withstand compression and shear.

Once scanned as virtual 3D models, each log gains an identity and personal profile that becomes key in determining a plan—whether they’ll become 2x12s bound for the rafters, 2x4s for roof trusses or wood chips for engineered wood products like OSB. Armed with each log’s unique metrics, the system sorts the logs so that each is used to maximum benefit throughout every step of the process.

Technology Takes Over

It may be hard to grasp that, in the midst of more logs per hour and larger scale full-cycle operations, individualized analysis and algorithms enable a more customized approach, but that’s exactly what happens. Throughout the rest of the milling process, machine stations will read the data they’re sent, adjust it according to the tasks that they perform and send it on to the next stop. A log and its resulting pieces of wood may be scanned 50 times or more as they flow through a seamless network of conveyors.

  • Long logs are automatically cut to optimal lengths based on their diameter, taper and interior conditions. They’re then grouped and stored, ready for runs of particular wood species or board cuts.

  • Debarking removes only the tree bark, without wasting layers of usable sapwood. Harvested bark often becomes mulch or fuel for a sawmill’s drying kilns, for example.

  • Gang saws use multiple blades and computerized precision to get the maximum value from each log. There’s no guessing or miscuts. Within seconds, one slim 12-foot section of pine may become two 2x4s and a 2x6, with the outside edges collected for further processing. Likewise, large-diameter logs may yield an assortment of 4x4s, 4x6s, 6x6s, 2x10s, 2x12s, 2x4s, 1x6s or 1x1s—whatever the quality of the log or board allows.

  • Curved lumber, which used to be problematic and the epitome of waste and frustration, becomes manageable thanks to flexible guided saws. Instead of fighting the grain, the blade follows it, resulting in a long board that can be weighted, kiln-dried flat, sold and used.

  • On-site kilns bake the sawn lumber, using biomass collected from the mill processes—bark, for example—as an energy source.

  • Planers and edgers give boards that smooth finish—why 2x4s are actually 1½x3½s—and the shavings become prime bedding material for horses.

  • Trimmers take another look at the boards, ensuring standard lengths and searching for any final imperfections that merit turning a 24-foot 2x10, for example, into two shorter pieces.

  • Stackers ration out boards in sets, building neat bundles that are packaged in weatherproof wrap and stored onsite, ready for delivery to a work site or lumberyard.

  • Meanwhile, odds and ends, chips, shavings and sawdust don’t go to waste. They’re collected to serve as key components in composite and engineered wood products like OSB board, MDF board, LSL board and particleboard as well as composite sidings, roofing and flooring, for example. Low-quality scraps can be finger-jointed or repurposed. Also, don’t forget pulp for paper products, cardboard and cardstock products.

All the while, systems are inventorying and accounting for every board foot, every piece of structural or dimensional lumber created and sorted, and every bit of byproduct bound for repurposing. It’s a protocol that’s taken accountability and efficiency to the point of being able to generate a responsible, green plan for every tree harvested.

High-Tech Sawmills Aim for Negative Carbon Footprints

In achieving a negative carbon footprint, modern sawmills and their wood products are actually aiming to remove carbon dioxide from the environment. It sounds like an awfully tall order, but they’re starting with a natural, environmentally friendly raw material that is readily renewable and sustainable. Then, they’re using technology to eliminate one of the worst generators of greenhouse gases in our world—waste, energy needlessly expended.

Just by existing, our forests are carbon sinks—that is, they accumulate, store and consume more available CO2 while alive than they release when harvested or decomposing. To maintain that overall balance, voluntary forest certification programs like the Sustainable Forest Initiative work to ensure that certified wood products come from well-managed forests that are sustained and renewed.

Once trees are harvested, technology allows for full-cycle sawmill complexes that are able to transform raw logs into neatly packaged bundles of finished lumber all at one site with a minimum of damage or waste. In fact, “waste” is used either as biofuel during processing or is collected and used in creating wood fiber composites, engineered wood building components or paper products. Even transportation costs are mitigated because of the breadth and scale of the workflow.

For wood products, their use continues to reduce environmental impact. Researchers for the Consortium for Research on Renewable Industrial Materials compared the life cycle assessment—LCA—of wood versus other building materials like aluminum, steel or concrete. LCA takes into account the amount of energy expended in harvesting, manufacturing, maintaining and disposing of a material. In comparisons evaluating solid waste generation, air emissions, wastewater, noise and CO2, wood was the solid winner, with wood-framed homes using significantly less energy, releasing less CO2 and having less environmental impact over the long term than identical homes framed in steel or concrete.

The new, high-tech approach of modern sawmills is part of a growing recognition that our forests—whether mountainsides or plantation fields of standing timber—are not only our most sustainable renewable building resource but also the one that leaves the smallest carbon footprint on our world. Idaho is a leader in the new age of modern sawmill complexes, and here at Franklin Building Supply, we carry certified, sustainable wood products and building components. Before you design or buy for your next building project, come see us. Support Idaho’s investment in smart, modern sawmills, and reduce your environmental impact. Choose wood.