Guest Editorial: R&D Needs in Wood Drying Technology

It is my opinion that at the present time solid wood drying has become a relatively mature industrial process. Anecdotal information from colleagues around the world persuades me to believe that it is getting more and more difficult to access funding for basic research in solid wood drying. I have the impression that some scientists that have been traditionally very active in the field are now being forced to look for alternative research opportunities. To make things even more difficult, the wood manufacturing industry does not seem to perceive drying technologies as a priority for future investment. If one would ask sawmill personnel about the priorities for solid wood drying, the most probable answers would be reducing drying time, production costs, energy consumption, and the amount of wood downgraded after drying because of high moisture content (MC), checks, and distortion. It would be very difficult to find wood manufacturing companies eager to invest in new and more sophisticated drying technologies. On the contrary, most people would agree that the majority of the solid wood products available in the market today can be dried in a cost-effective manner by using a wellestablished drying technology commonly known as conventional kilns; that is, batch driers in which the solid wood is exposed to hot air at controlled temperature and relative humidity. It could be argued, however, that my previous statement is a paradox in itself. There are innumerable tree species around the world that cannot be commercially processed into wood products just because they are very difficult to dry in conventional kilns. A good example is Eucalyptus nitens in Chile. It is predicted that by 2040 there will be more than 7 million m=year of E. nitens in Chile available for commercial uses, but the prospects of developing solid wood products are limited because of the inherent difficulty of drying this particular species. There is not any doubt that researchers around the world will continue improving the current drying practices and developing new drying technologies for local species that are still a challenge for the wood manufacturing industry. Just by looking at Drying Technology, for example, the reader will find recent studies for acacia, paulownia, canelo, and sugi wood, to mention a few. Nevertheless, conventional kilns are a remarkably simple and robust technology for an industrial environment, and there is not any reason to believe that its predominance will be challenged anytime in the near future. In my opinion, the threat to conventional kilns would not come from new and more sophisticated drying technologies, but rather from their own need to become more efficient than they are today. One of the question marks for the future of conventional kilns is energy consumption. Industrial wood drying is not really an offender when considering carbon footprint. It was reported, for example, that the softwood manufacturing industry in Canada emits less than 200 kg of CO2 per m of sawn wood, but the amount of carbon sequestered in that wood is more than 750 kg of CO2 per m . On the other hand, energy cost may be a problem in certain areas of the world. For instance, an international survey showed that the total energy required to dry softwood in northern Europe is approximately 1.5GJ=m, including electricity and transportation within the sawmill. If one could use the price of natural gas as a quick reference for the energy cost, let’s say $10=GJ in Europe today, then energy may erode 10% of a commodity value that fluctuates around $150=m. More importantly, the value of softwood as a commodity has been constantly reducing during the last two decades. According to the United Nations Economic Commission for Europe, wood product prices have remained relatively constant or have reduced slightly since the early 1990s, thus resulting in a reduction of approximately 50% of the real wood value after adjusting for inflation. The reality is that wood producers in the developed world are constantly pushed to increase production and reduce costs, thus basically working more for less. A large sawmill in northern Europe or North America can process around 1 million m=year of sawn wood, thus having a few percentage points increase in production rate or reduction in production costs would normally result in a very attractive value proposition for their business. That is also true from the corporate stand point, as the top 12 companies alone produce more than 50m=year of the approximately 400m=year of sawn wood that is consumed worldwide. Consequently, some companies are now starting to believe that progressive kilns could be an alternative for running their drying operations more efficiently and at a lower cost. Progressive kilns are based on the same principle as conventional batch kilns, but they are designed to work on a continuous basis by drying wood packages as they gradually move through a sort of tunnel. Progressive kilns have proven to increase productivity in comparison to batch kilns because they do not need to be Drying Technology, 32: 629–630, 2014 Copyright # 2014 Taylor & Francis Group, LLC ISSN: 0737-3937 print=1532-2300 online DOI: 10.1080/07373937.2014.895141