The impact of mechanical log surface damage on chip size uniformity during debranching and debarking Eucalyptus pulpwood logs using a single-grip harvester

Mechanised harvesting operations are becoming more prevalent in South Africa with the realisation that motormanual and manual harvesting operations pose significant health and safety risks to workers. The damage inflicted by single-grip harvester feed rollers and delimbing knives on log surfaces during debranching and debarking eucalypts, may affect eventual chip quality. Chip quality influences pulp quality and recovery in the kraft pulping process. This study investigates the influence of two mechanised debranching and debarking treatments on Eucalyptus pulp logs (threeand five-feed roller passes along the stem surface) by feed rollers and delimbing knives on chip uniformity, size and purity. The two mechanised treatments to three log classes (base, middle and top logs) were compared with chips produced from manually debarked logs. Manually debarked logs produced significantly less undesirable-sized chips than both three and five-pass processed logs. The volume of undesirablesized chips produced during chipping also increased with decreasing log size. Manually debarked logs produced chips with significantly less bark than three-pass-processed logs (0.008% vs 0.062%), and five-pass-processed logs produced chips with significantly less bark than three-pass-processed logs (0.018% vs 0.062%). Middle logs also produced chips with significantly less bark than base logs (0.016% vs 0.056%), and top logs produced chips with significantly less bark than base logs (0.017% vs 0.056%). In all cases the bark content on logs was considerably less than the maximum of 1.0% generally specified by kraft pulp mills.     

The impact of log surface damage caused by harvester Eucalyptus debarking on pulp value recovery

Mechanised harvesting operations are growing in popularity in South Africa, as motor-manual and manual harvesting operations pose significant health and safety risks to workers. Potential damage inflicted by single-grip harvester feed rollers and delimbing knives on the log surface during debranching and debarking of eucalypts may affect chip size distributions during chip production. Chip size is important as it influences pulp quality and recovery in the kraft pulping process. The study investigated the influence of two mechanised debarking treatments in eucalypts (three feed roller passes and five feed roller passes along the stem surface) with feed-roller-induced log surface damage on pulp value recovery. The two mechanised treatments were compared against chips produced from manually debarked logs with no surface damage. In addition, the effect of two log drying periods (one week and two weeks) and three log classes (base, middle and top logs) on chip quality were also analysed. An economic evaluation was conducted to quantify potential recoverable pulp value losses associated with debarking treatments and log drying periods. Logs subject to manual debarking produced significantly less undesired sized chips than both three-pass and five-pass mechanically debarked logs and therefore had significantly greater pulp value recovery. Mechanically debarked logs had a projected pulp value recovery of R62, R86 and R123 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a one-week log drying period. Mechanically debarked logs also had a projected pulp value recovery of R77, R40 and R59 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a two-week log drying period. Logs dried for two weeks also produced significantly less under-sized chips than chips produced from one-week-dried logs and therefore had greater pulp value recovery. However, two-week-dried logs produced wood chips with significantly more over-thick chips than logs dried for one week. The volume of undesirable-sized chips produced during chipping increased with decreasing log size.     

Rapid estimation of kraft pulp yield and lignin in Eucalyptus camaldulensis and Leucaena leucocephala by diffuse reflectance near-infrared spectroscopy (NIRS)

Near-infrared spectroscopy has been used to develop calibration models for the rapid determination of kraft pulp yield (KPY) and lignin in Eucalyptus camaldulensis and Leucaena leucocephala. The correlation coefficient for cross-validation is 0.90 for KPY and 0.95 for lignin prediction, while the root mean square error for cross-validation for KPY and lignin prediction are 1.46 and 0.77, respectively. The method has been validated with 37 samples of E. camaldulensis and 18 samples of L. leucocephala. The root mean square error of prediction for KPY (1.53) is higher than for lignin (0.77). The method is rapid and can be used for screening a large number of samples.     

Fibre volume losses of eight softwood clearfell harvesting systems in South Africa

A study of both fibre volume loss and related opportunity cost was performed across the South African softwood sawtimber industry to gain information on the actual utilisation of useful fibre and potential loss or gain of opportunity in terms of potential revenue from both field practices and policy. The study quantified volume losses from high stumps, felling and crosscut saw kerf, log allowances, excessive removal of merchantable wood, incorrect log trimming allocation, and utilisable wood left in-field. Eight treatments were examined: four terminated with merchandising at roadside landing and four at merchandising yards. Within the treatments, felling was either motor-manual or mechanised and compartments were classed by average compartment tree size (less than or greater than 1 m³). Total wood utilisation was found to be 92.07%. Stumps were found to be 7 cm higher than necessary and volume losses because of high stumps were 0.79% and 0.07% for mechanical and motor-manual felling, respectively. For felling saw kerf losses, mechanical felling showed 0.92% loss, whereas motor-manual felling resulted in only 0.15% loss. Incorrect log trimming allowance provided for 0.60% loss. Excessive trimming of logs resulted in 2.02% loss. Volume lost because of crosscutting saw kerf was low at 0.20%, but tops not being extracted resulted in 2.57% loss. Using SIMSAW 6 simulations, these volume losses translated into an additional annual harvested volume of 421 722 m³ or additional 1 278 ha harvested area, R166 million log value and R393 million net lumber value loss. Total loss was lowest (6.49%) in the average tree size class less than 1 m³, which was mechanically felled regardless of merchandising location. For the majority of volume loss categories, motor-manual felling caused greater loss when compared to mechanical felling methods. Log trimming allowance consumed 80 604 m³ annually. The results indicate that the human element may have a greater impact on fibre and value losses than the system choice. Further research is recommended to quantify the effect of the human element.     

Crop losses and their economic implications due to growing of Eucalyptus on field bunds — a pilot study

The paper presents evidence, collected mainly through interviews with farmers in north-west India, regarding crop losses suffered by the farmers planting Eucalyptus on farm bunds. Farmers experienced that the crop remained weak in a width of strip measuring 2 to 10 metres next to the tree line. These losses drastically reduced the profits farmers were expecting from the sale of trees. The average B-C Ratio at 15% discount rate would have been 9.2 without these losses, but came down to just about 2, when crop losses were taken into account. The reduced profit margin was not perceived to be sufficiently high to cover risk of production and of fluctuating output prices, and therefore none of the farmers replanted Eucalyptus after sale. Many even uprooted the coppice roots and went back to annual cropping.     

Rapid assessment of wood chemical properties and pulp yield of Eucalyptus camaldulensis in Thailand tree plantations by near infrared spectroscopy for improving wood selection for high quality pulp

Near-infrared (NIR) spectroscopy has been demonstrated as a means for rapid nondestructive determination of the chemical composition and final pulp yield of Eucalyptus camaldulensis in Thailand tree plantations. Multiple linear regression (MLR) analysis and partial least squares (PLS) analysis were introduced to develop statistical models in terms of calibration equations for total pulp yield, screened pulp yield, and contents of -cellulose, pentosans, and lignin in wood. In MLR analysis, a reasonably good calibration equation was found only for pentosans (standard error of prediction (SEP): 0.98%). The PLS analysis improved the accuracy of prediction for every criterion variable, especially for pentosans (SEP: 0.91%) and lignin (SEP: 0.52%). Also, in the case of screened pulp yield, we were able to use such a statistical result as an indicator of the characteristics of the pulp and paper. Thus, NIR spectroscopy could be satisfactorily used as an effective assessment technique for Eucalyptus camaldulensis plantation trees.     

蓝桉不同整地方式造林水土流失监测初报

采用径流小区定位观测法，对保山砂页岩发育的山地红壤进行不同整地方式营造蓝桉林，经过三年的监测研究表明：未整地自然土壤侵蚀量达１．６５７～１．４０２ｔ／ｈｍ２·ａ，有机质流失量达８０．４８３～６８．１１３ｋｇ／ｈｍ２·ａ，土壤肥力退化显著；撩壕整地及挖塘整地造林当年土壤侵蚀量分别达３．３６６ｔ／ｈｍ２·ａ及２．４６４ｔ／ｈｍ２·ａ，均属轻度侵蚀级，第二年土壤侵蚀量为０．５９２ｔ／ｈｍ２·ａ及０．３６７ｔ／ｈｍ２·ａ为微度侵蚀。有机质流失量为７５．８１１ｋｇ／ｈｍ２·ａ及４７．１２２ｋｇ／ｈｍ２·ａ。随着桉树幼林生长，林地覆盖度和地表稳定程度增加，土壤侵蚀急剧下降。     

Sulfuric acid bleaching of kraft pulp II: Behavior of lignin and carbohydrate during sulfuric acid bleaching

The purpose of this study was to investigate the behavior of lignin and carbohydrates in kraft pulps during sulfuric acid bleaching. Beech kraft pulp and red pine kraft pulp were bleached with dilute sulfuric acid at pH 1.3 with addition of sodium nitrate and sodium nitrite at 100°C for 1 h. The pulps were then extracted with aqueous sodium hydroxide solution at 70°C for 1 h. Lignin and carbohydrates in the acid effluents and the alkali effluents were analyzed. The carbohydrate compositions of unbleached and bleached kraft pulps were also determined. The residual lignin in kraft pulp was degraded to a molecular size similar to that of milled wood lignin during sulfuric acid bleaching without additives, and it was further degraded to a much smaller molecular size during sulfuric acid bleaching with additives. It was found that the amount of carbohydrate dissolved in the bleach effluents were only about 1 of the dry weight of the kraft pulp under these bleaching conditions. The carbohydrates dissolved during bleaching were mostly of hemicellulose origin.Part of this report was presented at the 8th International Symposium on Wood and Pulping Chemistry, Helsinki, July 1995     

Species richness and biomass of understory vegetation in a Eucalyptus globulus Labill. coppice as affected by slash management

The aim of this study was to assess the effect of different slash management practices on understory biodiversity and biomass in Eucalyptus globulus coppices in Central Portugal. The experiment consisted of four treatments: (a) removal of slash (R), (b) broadcast over the soil (S), (c) as in S but concentrating woody residues between tree rows (W) and (d) incorporation of slash into soil by harrowing (I). Understory vegetation was surveyed during 1–6, 9, and 10 years, the proportion of soil cover by plant species estimated, and diversity and equitability indexes determined. Above ground understory biomass was sampled in years 2–6, 9, and 10. The highest number of species in most years occurred in plots where slash was removed. Differences between treatments in the proportion of plant soil cover were never significant, whereas differences in diversity index were only occasionally significant and apparently related to the number of species. Thus, differences in the equitability index were not significant. Understory biomass did not decrease during the rotation period, and was usually highest in R and I, and lowest in S, but not significantly different. At the end of the rotation period, understory biodiversity indices and biomass were apparently independent of slash treatment.     

尾巨桉中大径材立地指数编制及施肥对立地指数的影响

本文采用了连续12次16年生标准地的观测数据,以模型H=a+b/(c+A)作为导向曲线,标准年龄为7 a,编制了尾巨桉中大径材立地指数表.经过x2? 检验和标准差检验综合得出,所编制的立地指数合理,科学可行.本研究提出培育桉树中径材的立地指数不应小于20,培育桉树大径材的立地指数不应低于24.施肥提高了林地的立地指数,施肥量越多,立地指数提高的幅度越大;这种提高幅度在施肥量少的时候较大,当施肥量逐步增大的时候,立地指数的提高幅度逐渐变小.     

Examination of polychlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins and polychlorinated dibenzofurans in process water of kraft pulp bleaching mill using chlorine dioxide from the aspect of environmental water quality

Process water of a pulp mill with extended kraft cooking, two-stage oxygen delignification, and chlorine dioxide bleaching was examined from the aspect of a new standard for environmental water quality in Japan. According to the new standard, the concentration of dioxins – polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, coplanar polychlorinated biphenyls – in environmental water is restricted to less than 1pg TEQ/l. We clarified that the concentrations of the dioxins in sewers in the chlorine dioxide stage and the alkali stage were less than 1pg TEQ/l and that the 2,3,7,8-tetrachlorodibenzofuran concentrations were 0.5pg/l or less. In addition, a main source of 1,3,6,8- and 1,3,7,9-tetrachlorodibenzo-p-dioxins in the process water seemed to be an agrochemical in water supplied from a river.