Low-value Wood Research Articles

The economic potential of wood pellet production from alternative, low-value wood sources in the southeast of the U.S.

The global demand for wood pellets used for energy purposes is growing. Therefore, increased amounts of wood pellets are produced from primary forestry products, such as pulp wood. The present analysis demonstrates that substantial amounts of alternative, low-value wood resources are available that could be processed into wood pellets. For three resources, test batches have been produced and tested to qualify for industrial pellet standards. These include: primary forestry residues from premerchantable thinning operations, secondary forestry residues from pole mills and post-consumer wood wastes from discarded wooden transport pallets. The total wood potential of these resources in the southeast of the U.S. (Florida, Georgia, North Carolina, South Carolina), was estimated to be 1.9 Tg y−1 (dry) available at roadside (excluding transport cost) for 22 $ Mg−1 (dry) increasing to over 5.1 Tg y−1 at 33 $ Mg−1 (dry). In theory, 4.1 Tg y−1 pellets could be produced from the estimated potential. However, due to the geographically dispersed supply of these resources, the cost of feedstock supply at a pellet plant increases rapidly at larger plants. It is therefore not expected that the total potential can be processed into wood pellets at costs competitive with those of conventional wood pellets. The optimal size of a pellet plant was estimated at between 55 Gg y−1 and 315 Gg y−1 pellets depending on the location and feedstock supply assumptions. At these locations and plant sizes, pellets could be produced at competitive costs of between 82 $ Mg−1 and 100 $ Mg−1 pellets.

Effect of thermal modification by hot pressing on performance properties of paulownia wood boards

The goal of this study was to investigate the effects of thermal modification by hot-pressing on the performance properties of paulownia wood boards. The boards were thermally modified by hot-pressing method under different pressure and temperature levels. As two boards for each modification group plus two for unmodified, totally 10 experimental wood boards were prepared in this study. Main density, vertical density profile (VDP), thickness swell (TS), water absorption (WA), moisture content (MC), and hardness tests were carried out to evaluate the performance properties of the thermally modified or unmodified wood boards. The results obtained in this study indicated that surface density of the boards increased with increasing press pressure. The thermal modification negatively affected the TS and WA values of the boards. Hardness values of the wood boards were significantly improved by the thermal modification. The results of this research revealed that the thermally compressing method could be used to improve end-use properties of low-density wood materials made from fast-growing tree species such as paulownia, poplar, eucalyptus etc. Thus low-value wood materials could be converted to value-added products. In addition, sustainable management of natural resources could be achieved by using the thermal modification method.

Commercialization Potential of Viscoelastic Thermal Compressed Wood: Insights from the US Forest Products Industry

The increasing demand for forest products and restricted use of natural forests has resulted in a shortage of high-strength wood fiber. The area covered by plantation forests is steadily rising, but the fiber produced by these forests is often unsuitable for high-strength applications. One attempt to combat this problem is the viscoelastic thermal compression (VTC) process, which can dramatically increase the strength and stiffness of any wood species. To advance VTC wood from the concept evaluation stage to the development stage, concept testing interviews were conducted with individuals in the forest products industry. Opinions, ideas, and insights were gathered from interviewees concerning potential applications for VTC wood, as well as advantages and barriers to commercialization. As a whole, interviewees thought the most viable uses for VTC wood were laminated veneer lumber, plywood, concrete forms, transportation components, and flooring. The most frequently mentioned advantages to commercialization included increased mechanical properties and the utilization of a low-value wood species; barriers to commercialization were cost and the forest products industry's resistance to change. Overall, interviewees thought VTC wood would be successful as long as it was not markedly more expensive than similar products.

A financial evaluation of two contrasting silvicultural systems applicable to Pinus taeda grown in north-east Uruguay

The Loblolly pine (Pinus taeda L.) plantation area in north-east Uruguay was 108 000 ha in 2008. Recent industrial capacity developments have resulted in major structural changes. Silvicultural system selection depends on site productivity, costs, timber prices and public policies. This study aimed to assess economic returns for two silvicultural systems in north-east Uruguay, in scenarios with and without a plantation subsidy: System I, with a short, 12-year rotation, primarily for small logs; and System II, with a longer, 24-year rotation. For System I, the underbark volume was 198 m3 ha−1 (mean annual increment16.5 m3 ha−1 y−1) and land expectation value (LEV) at a 9.7% discount rate was US$561 ha−1 and US$442 ha−1, with and without subsidy, respectively. System II resulted in 318 m3 ha−1 underbark volume (13.2 m3 ha−1 y−1) and the LEV was US$860 ha−1 and US$771 ha−1, with and without subsidy, respectively. System I was more profitable than extensive cattle husbandry only when the distance to mill was equal to or less than 60 km and wood millyard prices were equal to or higher than US$27.8 m−3 and US$28.8 m−3 with and without subsidy, respectively. Values for System II, in which the main product was a mix of sawlog diameters, were positive and higher than those for System I, both with and without subsidy. If a company invested in forest plantations without due provision for early silvicultural treatments, such as pruning and precommercial thinning, a high risk of financial loss would ensue. Long-rotation sawtimber regimes similar to System II would be more profitable and offer a lower risk of financial losses. The results suggest subsidy withdrawal in Uruguay should not lead to changes in silvicultural systems; in fact, it rendered regimes designed for low-value wood, such as System I, even less advisable.

Burned wood in the pulp and paper industry: A literature review

Fires play an integral part in Canadian forest architecture. Low-value wood, from burned stems, is an important source of fibre for the pulp and paper industry. Although wood chemistry changes induced by fire are substantial, burned stems exhibit a demarcation layer between the char and undamaged wood which is only a few cells thick. The loss of stem moisture content requires that burned wood is processed within one year. Aggressive debarking will minimize charcoal contamination and careful metering of chips from burned wood into any pulping process is essential. Chips with low moisture content must be pre-steamed prior to kraft cooking, and chemical pre-treatment may improve mechanical pulp quality. Key words: burn intensity, wood chemistry, charring, stem moisture content, charcoal contamination, chip metering

Nutrient Content of Leaf Litter of Trees in the Northern Rocky Mountains

Considerable interest has been directed to the study of the chemical composition of tree leaves. It was discovered long ago that species differ in their abilities to extract nutrients from the same kind of soil, and that the minerals are not similarity disposed in the tissues, with a result that their litter varies considerably in composition. The silviculturist sometimes finds it desirable to maintain in a mixed stand certain trees that produce low-value wood, only because they are useful in maintaining soil fertility for associated valuable species. The speed of rehabilitation of waste-lands and eroded areas varies with the species used in reforestation. Game management must often take into account the nutrient content of foliage available for browsing. Some analyses have been made in the hope that a reliable method of evaluating soil fertility could be discovered. Although nutrient content often appears unrelated to soil fertility as indicated by chemical analyses of soil or by vigor of growth, special correlations of local significance have found with sufficient frequency that this relationship always deserves study. In any inquiry into why trees grow where they do, the varied influences of the different species must be given careful consideration, for small initial differences in environment may cause differences in the pioneer vegetation, then the contrasted floras add so much more difference as to obscure the primary factor that caused initial divergence (Chandler 1939). Despite the importance attached to the subject, only indirect information was available for just one species of the tree flora of the northern Rocky Mountains, when the present study was undertaken. In summarizing North American literature on the chemical composition of litter of about 60 trees that have been analyzed, Kittredge (1948) listed PopuIts tremuloides, studied in other parts of the continent, as being low in N (in the group with 0.4-0.8%)) medium in P (0.150.3% ), medium in K (0.3-0.6%), and medium in Ca (1.5-3.0%c). Tarrant, et al. 1951 have recently published analyses of fresh leaves and of weathered litter for ten trees along the Pacific coast, four or five of which are taxonomically identical with trees included in this report. Since the chemical composition of foliage varies progressively throughout the summer, and their report does not indicate the time of year when the foliage collections were made, their data cannot be compared with the present study. Although the primary objective of this study has been to evaluate species influences upon soil through the character of the litter they produce, several subsidiary problems were recognized. With the fundamental associations of eastern Washington and northern Idaho defined (Daubenmire 1952), material could be collected according to habitat types and thus make a preliminary exploration of the possibility that chemical composition may be related to variations in undergrowth (the Finnish forest types) and rate of tree growth (the North American site index). Also, the phytosociologic study showed two major discontinuities in undergrowth. A rich xerophytic undergrowth in the lower zones