Opportunities to Use Bark Polyphenols in Specialty Chemical Markets

Current forestry practice in North America is to transport pulpwood and logs from the harvest site to the mill with the bark on the wood. Approximately 18 percent of the weight of logs from conifers such as southern pine is bark. The majority of this bark is burned as hog fuel but its fuel value is low.1 When compared with natural gas at an average of $2SO/MBTU or electricity at 3.5 cents/KWH, burning wet bark has a gross fuel value of about 1.2 cents/lb on a dry weight basis. Considering the cost of transport as well as the capital and maintenance costs of boilers, processing bark for fuel is a costly business and seems to be practiced only to avoid a large solid waste management problem. One must not lose sight of the fact that one must handle nearly two Ibs of wet bark to recover that I .2 cents. In addition, concerns about air quality, especially increasingly stringent limits on particulate emissions , has stressed the ability of hog fuel boilers to meet regulatory requirements. We need to find ways to produce higher value products from bark. It is instructive to remember that tree barks were the source of high value specialty chemicals in the past. In the early American colonial days, quercetin-3-O-rhamnoside, a bright yellow compound easily obtained from red oak bark, led export trade to Europe where it was valued as a yellow dye.2 From 1900 to WWI, the United States Leather Company, making vegetable tannins from eastern hemlock bark, was ranked in the top ten capitalized companies in the United States. Eastern hemlock forests concentrated from New York to Pennsylvania were harvested for the bark while the wood was often left to rot.3. During the 1950's and 1960's major efforts were made by forest products companies such as ITT Rayoniers and Weyerhaeuser Company " to develop specialty chemical markets for a wide range of products obtained from western hemlock and Douglas-fir barks. Although ITT Rayonier had plants operating in Washington and British Columbia in the 1960's, they were closed just prior to the energy crisis of the early 1970's. Other notable efforts by New Zealand Forest Products and Bohemia Lumber Co were timed better with the energy crisis but were not successful. Wattle tannins from South Africa and quebracho tannins from South America have dominated the vegetable tannin market and the lion's share of this material …