Development of Low-Cost Portable Spectrometers for Detection of Wood Defects.

Portable spectroscopic instruments are an interesting alternative for in-field and on-line measurements. However, the practical implementation of visible-near infrared (VIS-NIR) portable sensors in the forest sector is challenging due to operation in harsh environmental conditions and natural variability of wood itself. The objective of this work was to use spectroscopic methods as an alternative to visual grading of wood quality. Three portable spectrometers covering visible and near infrared range were used for the detection of selected naturally occurring wood defects, such as knots, decay, resin pockets and reaction wood. Measurements were performed on wooden discs collected during the harvesting process, without any conditioning or sample preparation. Two prototype instruments were developed by integrating commercially available micro-electro-mechanical systems with for-purpose selected lenses and light source. The prototype modules of spectrometers were driven by an Arduino controller. Data were transferred to the PC by USB serial port. Performance of all tested instruments was confronted by two discriminant methods. The best performing was the microNIR instrument, even though the performance of custom prototypes was also satisfactory. This work was an essential part of practical implementation of VIS-NIR spectroscopy for automatic grading of logs directly in the forest. Prototype low-cost spectrometers described here formed the basis for development of a prototype hyperspectral imaging solution tested during harvesting of trees within the frame of a practical demonstration in mountain forests.

Exposure of mobile chipper operators to diesel exhaust.

The current boom of forest biomass is making mobile chippers increasingly popular among forest operators. This motivates concern about the potential exposure of chipper operators to noxious chemicals derived from diesel fuel combustion. The objective of this study was to determine operator exposure to BTEX (benzene, toluene, ethylbenzene, and xylenes) and polycyclic aromatic hydrocarbons (PAHs) generated from diesel combustion. This study sampled 28 mobile chipping operations in the Italian mountains, in order to determine professional exposure to BTEX and PAHs among chipper operators. IOM, Radiello®, and XAD2 samplers were used for the purpose. Operations were divided into industrial and small scale, the former based on powerful chippers with enclosed cabs and the latter on smaller machines without enclosed cabs. We could not detect any measurable exposure to BTEX, while exposure levels for PAHs were very low, especially for what concerned recognized cancer agents. That is likely related to work environment and organization because mobile chippers work in the open-air forest environment and in the presence of very few other machines. PAH concentration was significantly higher inside cabs than outside. None of the operators involved in this research was exposed to BTEX or PAHs above occupational exposure limits.

Technology alternatives for tapping the pruning residue resource.

Four commercial harvesters were compared with respect to recovery of pruning residues for energy conversion. These harvesters were tested side-by-side on 17 test fields, totaling 15 ha. The test fields consisted of vineyards and apple and pear orchards. The residue yield was between 0.7 and 9 green tonne per hectare, at a moisture content from 37% to 48%. Yield was highest for the orchards, and lowest for vineyards. Harvesters collected the residues and moved them to the roadside at a cost of between 11 and 60€ per green tonne, depending on field conditions and technology choice. Single-pass harvesting was the cheapest, especially if applied through a dedicated tractor and a towed unit with a large integral container. Two-pass harvesting was the most flexible, but also the most expensive: it should be favored only when space, weather or other management constraints limit the application of the other systems.

Performance of a mobile mechanical screen to improve the commercial quality of wood chips for energy.

The study analyzed the performance of a mobile screening device for upgrading coarse wood chips to residential user standards, by removing oversize particles and fines. The machine was designed for transportation to forest landings, logistic terminals and plant chip yards. Average productivity was 1.9 oven-dry tons (odt) h(-1), corresponding to a screening cost of 28.5€ odt(-1). This figure was lower than the price increase obtained by upgrading industrial chips to residential user standards. Hence, screening offered a profit of 4.7€ odt(-1), or 16% of the original screening cost. The screening process was capable of upgrading chips from industrial to residential specifications, by reducing the incidence of oversize particles below the 1% critical threshold. Screening also allowed a substantial reduction in the content of fines. A similar effect was not verified for crushed wood, which failed to meet the specifications for residential fuel.

Relating safety, productivity and company type for motor-manual logging operations in the Italian Alps.

The study compared the performance of four different logging crews with respect to productivity, organization and safety. To this purpose, the authors developed a data collection method capable of providing a quantitative analysis of risk-taking behavior. Four crews were tested under the same working conditions, representative of close-to-nature alpine forestry. Motor-manual working methods were applied, since these methods are still prevalent in the specific study area, despite the growing popularity of mechanical processors. Crews from public companies showed a significantly lower frequency of risk-taking behavior. The best safety performance was offered by the only (public) crew that had been administered formal safety training. The study seems to deny the common prejudice that safety practice is inversely proportional to productivity. Instead, productivity is increased by introducing more efficient working methods and equipment. The quantitative analysis of risk-taking behavior developed in this study can be applied to a number of industrial fields besides forestry. Characterizing risk-taking behavior for a given case may eventually lead to the development of custom-made training programmes, which may address problem areas while avoiding that the message is weakened by the inclusion of redundant information. In the specific case of logging crews in the central Alps, the study suggests that current training courses may be weak on ergonomics, and advocates a staged training programme, focusing first on accident reduction and then expanding to the prevention of chronic illness.

Industrial harvesting of olive tree pruning residue for energy biomass.

In Mediterranean countries, olive tree pruning residue represents an abundant source of energy biomass, still largely unexploited for lack of cost-effective harvesting technology. The authors tested two industrial pruning harvesters, capable of overcoming the limits of lighter units appeared in the past years. One of the machines was designed for application to a powerful farm tractor, whereas the other was a self-propelled dedicated harvester. Data were collected from 10 operations, covering a total of 69 hectares and producing over 190 tonnes of wood fuel. Recorded productivity varied between 3 and 9 tonnes per scheduled machine hour (SMH), or 2-7 oven dry tonnes (odt) SMH(-1). Harvesting cost varied from 17 to 52 euro t(-1), with an average value of 28 euro t(-1): these values correspond, respectively to 22, 70 and 40 euro odt(-1). This compares very favourably with the average 1-1.5 ton SMH(-1) offered by lighter commercial units. Productivity was related to residue density, row length and forwarding distance. Mechanical availability was high and over 90%, for both machines. The authors also developed a simple deterministic model capable of predicting harvesting productivity and cost, as a function of significant site and economic conditions. The model can also be used to determine the break-even utilization level, below which the operational flexibility of a tractor-mounted operation becomes preferable to the higher productivity of a specialised unit.