Robert W. Rice

Characteristics of Wood Fuel Pellet Manufacturers and Markets in the United States, 2010

The wood fuel pellet industry has been growing rapidly in recent years. The survey results reported here are focused on the annual production, raw material, production cost rankings, market radius, barriers to market expansion, and other data that give an overview of the industry during a very difficult economic period. Eighty-four mills across the United States were contacted and 53 responded. The average volume of production was over 59,000 tons per year. Raw materials for pelletizing and labor were the principal costs of production according to respondents. Market demand and capital costs were cited as the chief barriers to expansion. The industry is clearly subject to market forces that influence the cost and availability of raw materials as well as the cost of heating fuel alternatives such as oil. Despite the economic difficulties, demand continues to grow for pellet fuels both in the United States and in Europe.

Cytotoxicity and genotoxicity of wood drying condensate from Southern Yellow Pine: an in vitro study

We tested condensates from Southern Yellow Pine for potential cytotoxicity and genotoxicity in CHO-WBL and human peripheral blood lymphocytes (PBL) in the absence of S-9 activation. Cytotoxicity was evaluated by the Trypan blue exclusion assay, mitotic index (MI) and proliferative rate index (PRI). Genotoxicity was measured by the chromosome aberration (CA) assay and sister chromatid exchange (SCE) analysis. Both cytotoxic and genotoxic effects were observed. Laboratory-generated Southern Yellow Pine condensate reduced the viability of CHO-WBL cells. The number of viable cells was roughly inversely proportional to dosage over a range of 100% to 31% in treated groups, in both experiments, as compared to 2.6 x 10(5) (100%) in the control. The MI data in both CHO cells and PBL also showed an inverse correlation. The highest scorable dose limited by toxicity was determined to be 1 ml of Southern Yellow Pine condensate in 10 ml total of medium. Lastly, a dose response curve was observed in CHO cells, as well as in PBL, using the CA assay and also with the SCE analysis. The present findings corroborate the results from Ames testing and represent the only information currently available on the genotoxic potential of these chemicals.

Demand Drivers and Price Supports for Bioethanol Use as Fuel in the United States: A Brief Review

Fuel ethanol, especially cellulosic ethanol, is likely to play an important role in renewable fuel development. This article reviews the main factors that currently drive fuel ethanol demand in the United States. In the short term, the phaseout of methyl tertiary butyl ether (MTBE) is important. In the long run, federal and state price support policies will play a dominant role in fuel ethanol demand. Both major demand factors and the current status of cellulosic ethanol manufacture are discussed. The current state of technology and the high capital cost for cellulosic ethanol production when compared with corn-based ethanol are major barriers to expanding the markets.

Detection of Structural Damage in Medium Density Fiberboard Panels using Neural Network Method

This research assessed the feasibility of using a neural network to detect low levels of damage in small samples of medium density fiberboard (MDF). The neural network was a three-layer back-propagation network. The undamaged stress wave frequency spectrum patterns were trained by the neural network. The trained patterns were then compared to stress waves patterns taken from MDF samples loaded to various percentages of their estimated failure load. In this experiment, if an application load is below the proportional limit, a small change in wave patterns occurs. The neural network has the unique ability to train data to recognize spectral patterns and has been used with success for the detection of structural damage.

Guest Editorial: Theoretical and Experimental Studies Leading to Improved Wood Drying Practice

This special issue of Drying Technology presents a peerreviewed collection of selected papers, presented at the 10th International IUFRO Division 5 Wood Drying Conference held in Orono, Maine, in August 2007. What began many years ago as the first IUFRO Wood Drying Working Party conference in Skelleftea, Sweden, continues as one of the premier meetings for specialists in all phases of wood drying and related topics. Since its inception, there have been ten conferences organized to date. They are:

Comparative DOC Estimates from the Heartwood and Sapwood of Five Hardwoods

Across North America, increasing attention is being paid to the quantity and nature of the volatile organic compounds (VOC) released when lumber is being dried or processed. A number of studies have estimated the VOC emissions from a variety of species and a few researchers have identified and quantified the major chemical compounds released during the drying process for certain species. The previously reported data often show substantial variation. The purpose of this research was to investigate the differences in dissolved organic carbon (DOC) between heartwood and sapwood as potential sources of the variation. The results show that some differences in the DOC exist between the heartwood and the sapwood among the five species tested but these differences do not fully explain the variation seen in VOC estimates.

An assessment of the feasibility of ultrasound as a defect detector in lumber

Abstract This study investigated the limitations of certain attributes for use in detecting internal defects using ultrasonic methods in spruce dimension lumber. Wave propagation in the radial direction and the effect of induced defects on ultrasonic wave characteristics were examined. Ultrasonic velocity, a parameter often applied, was found to be ineffective due to changes in wavelength and frequency when large defects were present. Amplitude, peak frequency magnitude and the area under the frequency spectra showed statistically significant differences between clear and defect-bearing samples, but among-sample variation was found to be too high because of localized density differences and microstructure, so that these methods were not consistently reliable. When sound intensity level was calculated, the variation among samples decreased and distinctions could be made between clear and defect-bearing wood, both within and among the samples tested. Certain attributes of the frequency spectra also showed clear changes with the introduction of defects.

Heat Capacity and Its Variation with Moisture Content for Plywood and Oriented Strand Board Sheathing Produced by North American Mills

Abstract The heat capacity of panels used for house sheathing is an important property that allows the hygrothermal modeling of thermal mass and the calculation of heating and cooling rates of certain types of walls. To our knowledge, this article presents the first data in over four decades for the measurement of heat capacity across a range of moisture content values. Although some estimates of panel heat capacity exist, few, if any, have been reported for mills across North America and across a range of moisture contents. The data clearly show the dependence of heat capacity on moisture content. They also show that solid wood and panel heat capacity values are similar at low moisture contents but diverge as moisture content increases. The variation in heat capacity with moisture content is large enough so that it should be considered when determining hygrothermal efficiency in walls containing plywood or oriented strand board or when developing hygrothermal models.

Changes in Thermal Energy with Moisture Content for Representative Wood Pellet Fuels in the Northeast

Gross heating values for densified wood residues made in the northeastern United States are shown as a function of moisture content (MC). As expected, the trend is clear, and the fuel values decrease sharply as MC increases. What is also clear is that storage time and storage conditions are important considerations for those using pellet fuels as an energy source. Typically, large quantities of pellets are purchased and stored for months before use. Moist storage conditions or long storage times could substantially change the quantity of pellets required to heat a structure.

MEASUREMENTS OF DELAYED WARP IN EASTERN SPRUCE STUDS

ABSTRACT Nearly eighty percent of the lumber manufactured in the United States is softwood dimension lumber used for the manufacture of housing. The principal quality related problem with softwood dimension lumber is that it is subject to warp related degradation. Much of the degradation occurs during the initial drying process, however, residual stresses and moisture content changes that occur after kiln drying can either reduce or increase the amount of warp. The magnitude of post kilning warp change, here termed delayed warp, has not been well quantified. Measurements of twist, bow, crook and moisture content were taken from eastern spruce (Picea spp) studs immediately after drying and planing. The wood was allowed to sit without restraint for a period of two weeks after which the measurements were repeated. Of the 1224 studs measured, over 76 percent experienced changes in twist, over 84 percent experienced changes in bow and over 73 percent experienced changes in crook. Increases in warp generally exceeded decreases, although a surprising percentage of the studs showed decreases in warp. Attention was focused on finding a correlation between moisture content and the changes in warp, but the correlation coefficients were low for both the increases and the decreases. The most likely cause of the warp was the high percentage of juvenile wood present in the raw material. The most likely causes for the changes in warp during the two-week period were stress relaxation aggravated by a change in the moisture gradient.