Sawmill Residue, Sawdust, and Chip Yield

About half a log does not become lumber, and where that half goes decides whether a mill has a revenue stream or a disposal cost. The kerf share is the part a mill can change and the part that is directly computable: every cut turns a kerf-width slice into sawdust, so on 1 in boards a 0.180 in kerf is 15.3% of the wood cut and a 0.125 in thin-kerf band is 11.1%. FOUR POINTS OF THE LOG move from sawdust to lumber, and on a mill cutting 10 million board feet a year that is 414,000 board feet of additional lumber from the same logs -- a far larger number than the saw upgrade costs. THE SAME CHANGE IS WORTH HALF AS MUCH ON THICK STOCK, which is the part that gets missed before a capital request: on 2 in stock the denominator is twice as large, the shares fall to 8.3% and 5.9%, and the gain is 0.57 times what it is on boards. A mill cutting mostly timbers has much less to gain from kerf than a mill cutting boards. WHERE THE REST GOES. A mill at 55% recovery sends 45% of the log to residue: 12 points of bark, 13.4 points of sawdust at this kerf, and 19.6 points of chips -- the largest stream and the only one with a market. That market's size distribution, bark content, and moisture requirements decide whether slabs are worth chipping or are simply fuel, and the revenue per ton differs a lot. Bark is nearly always a cost, and bark in the chip stream downgrades the whole load, which is what debarking exists for. A volume split from recovery and kerf figures the user supplies. Residue proportions vary widely with log size and quality, product mix, and equipment, and the bark fraction is species dependent. Bulk densities for sawdust, chips, and bark differ substantially and change with moisture, so any volume-to-tonnage conversion must use the mill's own measured figures rather than table values if the result is going to a scale ticket. It does not evaluate chip quality against a mill specification -- size distribution, fines, overs, and bark content determine whether chips are saleable at all -- or the moisture content that pulp and fuel buyers pay on, and it does not address dust collection, combustible dust hazards, or the fire and housekeeping requirements residue handling carries. The residue buyers' specifications, the mill's own scale records, and NFPA 664 for wood processing dust hazards govern.

sawdust share of the wood cut = kerf / (kerf + board thickness); residue fraction = 100 less the entered lumber recovery percentage; sawdust as a share of the log = the kerf share applied to the wood inside the bark; chips = the residue less bark and sawdust.

The kerf sawdust relation by name, with NFPA 664 named for the wood processing dust hazard. The residue buyers' specifications, the mill's own scale records, and NFPA 664 govern.

A volume split on the recovery, kerf, and bark figures the user enters; no buyer specification or density table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: lumber_recovery_pct, kerf_in, target_kerf_in, board_thickness_in, alt_board_thickness_in, bark_fraction_pct, annual_lumber_mbf, sawdust_share_pct, target_sawdust_share_pct, gain_pts, alt_gain_pts, gain_ratio, residue_pct, sawdust_of_log_pct, chips_of_log_pct, annual_gain_bf

• Sawdust is kerf over kerf plus thickness so the thin-kerf gain is largest on the thinnest stockfirst principles
• Chips are the stream with a market where a pulp or panel buyer exists; otherwise it is hog fuelresidue market practice
• Densities are the mill's own table values are not good enough for a scale ticketthe mill's scale records