Past, present, and future of the wood preservation industry: wood is a renewable natural resource that typically is preservative treated to ensure structural integrity in many exterior applications
Preservative treatment of wood has a long history in the United States and throughout the world. Even the early settlers to the New World in the 17th century used wood preservatives to protect homes and other structures.
The treated wood industry in the United States is evolving as new products emerge, technology advances, and environmental concerns increase. Recently, chromated copper arsenate (CCA) preservative-treated wood has been a frequent subject in the national news. A voluntary phase-out of CCA-treated wood for non-industrial uses has increased the attention on new-generation, arsenic-free preservatives. In a recent feature article in the Forest Products Journal. Evans (2003) discussed new preservative systems, including copper- and zinc-based and other metal systems, metal-free systems, treatment technologies, wood modification, and natural protection systems. This article examines the past, present, and future of preservative-treated wood with an emphasis on issues in the market-place and treated wood use policy.
The history of humankind is closely intertwined with wood utilization. Some of the earliest uses of wood were for fuel for heating and cooking. Even today, this accounts for the highest demand and use of wood in many developing countries. A period of significant advances in industrial processing occurred during the Industrial Revolution. Among these advances in the United States was the construction of trans-continental railroads, which created the need for crossties and switch ties. As industrial technology advanced, wood was used more frequently in exterior structural applications. Wood species that did not possess inherent decay resistance properties failed in service due to biological attack, creating a need for preservative-treated wood. Several historical treatises on wood preservation can be found in the literature (Hunt and Garratt 1967, Graham 1973, Wilkinson 1979, Barnes and Murphy 1995).
The earliest U.S. patent for a wood preservative was that issued by the Province of South Carolina to Dr. Wm. Crook in 1716 for " ... Oyle or Spirit of Tarr ... " In the 1700s, mercuric chloride and copper sulfate were first recommended, while zinc chloride was recommended as a wood preservative in 1815. A major development in wood preservation history was the use of coal-tar creosote, which was patented in 1836 by Moll, in a pressure impregnation process patented by John Bethell in 1838. Known as the Bethell, or full-cell, process, it was the first major use of pressure for wood treating and remains the basis of most modern wood treating operations. The process utilizes an initial vacuum period followed by filling of the cylinder with preservative and application of a pressure period to inject the preservative. A modern-day modification called the modified fullcell utilizes an initial vacuum of lower intensity and shorter duration along with a final vacuum period. In 1847, a similar pressure system was used with zinc chloride in what would be called the Burnett treatment.
The Boucherie Process developed in 1839 provided the basis for modern-day sap displacement methods such as the SlurrySeal[R] Process, PresCap[R], and Gewecke methods. In 1874, Julius Rutgers of Mannheim, Germany, developed a process for...