NCASI studies address wet storage of roundwood

In the southeastern U.S., mills often store roundwood for up to a year in facilities known as “wet decks” where water is typically applied continuously with sprinklers to reduce the risk of fungal decay or damage by insects. Wet decks also allow mills to increase inventory of roundwood during periods when weather conditions are favorable.

However, mills in the southeastern U.S. are interested in refining water application strategies and developing methods for regulating water use in wet decks. 

Recently, investigators with the University of Georgia (UGA), NCASI, and other cooperators reported results from studies investigating methods for monitoring wood moisture content in stored roundwood and implications of potential reductions in water application. Dr. Erik B. Schilling managed NCASI’s participation in these studies and is a co-author on two publications.

In the first publication, investigators with UGA, Oregon State University, and NCASI evaluated the use of time domain reflectometry (TDR ) for monitoring moisture content of wood stored in wet decks.

TDR has traditionally been used to detect faults in cables and to estimate soil moisture content. However, the investigators successfully used TDR to monitor moisture content in loblolly pine and sweetgum.

The abstract for the paper by Joseph Dahlen and others follows.

“Time-domain reflectometry (TDR) can be used to predict the moisture content of porous materials, including soil, and is an exciting tool that could be used to measure the moisture content in wet-stored wood. Three-rod probes with 127 mm- or 152 mm-long rods were inserted into 62 loblolly and 34 sweetgum saturated bolts. The bolts were air dried over a span of five weeks. TDR waveforms and moisture content were periodically recorded. In total, 534 and 482 readings were taken for the loblolly pine and sweetgum bolts, respectively. An algorithm in R was written to automatically analyze the apparent length of the TDR rods. Calibration models were developed between moisture content and X (apparent length / actual rod length). A three-parameter logistic model was developed for loblolly pine (R2=0.64) and sweetgum (R2=.084). The process was repeated using shorter bolts and 152 mm-long rods, resulting in improved models for loblolly pine (R2=0.99) and sweetgum (R2=0.97). Overall, TDR and the algorithm written to analyze the waveforms were accurate in predicting moisture content and could be used to monitor moisture in wet-decks.”

In the second publication, investigators with UGA, the U.S. Forest Service, International Paper, and NCASI reported results from studies at two woodyards that confirmed TDR can be used to monitor moisture content of southern pine logs stored over an extended period (15 months) and that log moisture content was not adversely affected when water application rates were decreased by 30%.

The abstract for the paper by Heath Raybon and others follows. 

“Wet storage of logs under sprinklers is a common method for maintaining log quality and consistent fiber supply to wood production facilities. Because of increased concerns regarding water use, mills in the southeastern United States are interested in refining water application strategies. To do so, we need to examine how log moisture varies with time and in response to differing water application rates. We used time domain reflectometry (TDR) to examine variation in log moisture of southern pine logs in response to nominal water application (100 mm/day) and a 30% reduction in water use at two woodyards (Santee in South Carolina and Dry Creek in Alabama) over a 15-month period. Initially significant differences between treatments were observed, but differences only existed for a short period, indicating that a 30% reduction in the amount of water applied results in little change in log moisture or quality.”

  

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References 

Dahlen, J., F. Antony, A. Li, K. Love-Myers, L. Schimleck, and E.B. Schilling. 2015. Time-domain reflectometry for the prediction of loblolly pine and sweetgum moisture content. BioResources 10(3):4947-4960. http://dx.doi.org/10.15376/biores.10.3.4947-4960 

Raybon, H., L. Schimleck, K. Love-Myers, F. Antony, J. Sanders, R. Daniels, E. Andrews, and E. Schilling. 2015. Examination of the potential to reduce water application rates in pine wet decks. TAPPI Journal 14(10):672-679.