Estimating hardwood sawmill conversion efficiency based on sawing machine and log characteristics

Increased problems of hardwood timber availability have caused many sawmiller, industry analysts, and planners to recognize the importance of sawmill conversion efficiency. Conversion efficiency not only affects sawmill profits, but is also important on a much broader level. Timber supply issues have caused resource planners and policy makers to consider the effects of conversion efficiency on the utilization and depletion of the timber resource. Improvements in sawmill conversion efficiency would favorably impact sawmill profits, and would be equivalent in effect to extending existing supplies of standing timber. An equation was developed to estimate lumber recovery factor for hardwood sawmills based on the characteristics of sawing machines and log resources. Variables included in the model were headrig type, headrig kerf, average log diameter and length, and the influence of total sawing variation. The estimated coefficients significantly influenced lumber recovery factor. The model should be helpful in assessing conversion efficiency trends and potential benefits from gains in sawmill efficiency. The efficiency with which hardwood sawmills convert logs to lumber has become increasingly important. Sawmillers are experiencing problems in the availability of hardwood logs and standing timber (3,9-11). Competition for hardwood timber has increased due to export and domestic demand growth and increased use of hardwoods for pulp and reconstituted panels. Competition has also increased due to reduced timber availability from growing pressures on forests for non-timber uses (3,9-11). On a broader level, hardwood availability and conversion efficiency is of interest to those concerned with the utilization and supply of the nation’s timber resources. Because of increasing concerns over timber resources, federal and state organizations have prepared assessments of the nation’s future hardwood timber supply, as initiated by the Forest and Rangeland Renewable Resources Planning Act (16). Projections estimate an annual yield increase of 0.2 percent for timber industries as a result of technological change. Actually, the current level of technology in the hardwood sawmilling industry is unknown. The level of technology in hardwood sawmills may be best determined by the conversion efficiency of raw material to lumber. Better information on current hardwood sawmill conversion efficiency and the factors that influence it should aid in developing more accurate estimates of future improvements in technology and the influence of this technology on the timber resource. Lumber recovery factor (LRF) is a measure of the conversion efficiency of sawmills. LRF is calculated as the nominal board feet (BF) of lumber recovered per cubic foot volume of log input to a sawmill. LRF has been used as a measure of conversion efficiency past research on sawmill efficiency (1,13-15). The objective of this study was to quantify the relationship between LRF and hardwood sawmill and log characteristics. Results would thus allow expected and potential changes in hardwood sawmill and log characteristics to be evaluated with respect to their influence on conversion efficiency. Steele and Wagner The authors are former Graduate Research Assistant and Associate Professor, Dept. of Forestry, Mississippi Agri. and Forestry Expt. Sta., P.O. Drawer FR, Mississippi State, MS 39762; and Associate Professor, Mississippi Forest Prod. Util. Lab., Mississippi State Univ., P.O. Drawer FR, Mississippi State, MS 39762; and Project Leader, USDA Forest Serv.. Brooks Forest Prod. Center. Blacksburg, VA 24061-0503. This paper was received for publication in January 1992. © Forest Products Research Society 1992. Forest Prod. J. 42(11/12):21-26. FOREST PRODUCTS JOURNAL Vol. 42, No. 11/12 21 Figure 1.—Locations of SIP studies used in the analysis. (14) developed a similar model that estimates LRF for softwood sawmills by region.