Raffaele Spinelli

A survey of Italian chipping operations

Abstract We observed over 100 wood chipping operations, using time-and-motion methods to quantify their productivities, and interviews and observations to subjectively evaluate the factors that affect their existence and character. Productive time per green tonne decreased with increases in both chipper power and piece size. In Italy, chipping has evolved from a primary business for contractors who processed whole trees, to a secondary activity for loggers who dispose of residues by chipping them for particleboard. In recent years, biomass-fueled district heating plants in northern Italy have been added to the mix of users, and larger electric power plants may expand the chipping industry in the near future. Operators who heavily utilize chippers prefer self-propelled machines. Tractor-powered and towed chippers are used in a wide range of conditions, but the latter are restricted to landings while the former are employed at landings and within stands. Disc chippers have dominated the industry, but drum chippers are making inroads, especially in fuel supply operations. Chips are transported by farm tractors and powered trailers when distances are short (up to 3– 4 km ), by high-speed tractors for intermediate distances, and by trucks for distances over 30 km .

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.

Analyzing and Estimating Delays in Harvester Operations

Abstract Time and motion studies have been and still are frequently used to describe, understand, and improve forest operations. Delays are recognized as being one of the major factors that limit productivity in most operations and are, therefore, an integral part of most time studies. But, delay events are erratic in both occurrence and magnitude and are, therefore, difficult to precisely quantify within the relatively short observation period of a typical time and motion study. Thus, delay information from individual studies have limited transferability. This paper analyzes the delay component of 34 harvester time study data sets that were recorded between 1998 and 2006. All of the studies were designed and carried out with the same principal investigator. The data sets were all based on harvesters either harvesting and or processing. Three delays categories were used: mechanical, operator, and other. Delays averaged 28.9 percent of the total scheduled time for all 34 studies, comprising of 7.1 percent mechanical, 4.7 percent operator, and 17.1 percent other delays. Delay averages were compared within category descriptions assigned to each data set for statistical significance. Example results include: total delays were higher for operations working on hot decks versus cold decks and operations working in mixed stands had more than twice the overall delays compared to operations in plantations. Considering only mechanical delays, machines that both felled and processed, compared to just processing, had higher mechanical delays. Interestingly, dedicated harvesting machines versus harvesting heads mounted on an excavator base had on average higher operator delays.

Comparison of two harvesting systems for the production of forest biomass from the thinning of Picea abies plantations

Abstract This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed €25 t−1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds €40 t−1. If the delivered price of sawlogs increases to €50 t−1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds €35 t−1. The CTL system is less sensitive to long extraction and transport distances than the WTH system.

Determining the shape of the productivity function for mechanized felling and felling-processing

Productivity studies in forest operations are often carried out on new equipment, or on equipment being used in new conditions. Understanding how stand and terrain parameters impact the productivity of harvesting machines is important for determining their optimum use. Such information is normally presented as a productivity or efficiency function; that is, a regression equation that best represents the data. Most studies establish that piece size is the dominant predictor that impacts overall productivity. A common concept known as the “piece-size law” is that productivity increases at a decreasing rate with increasing piece size. What is not well understood is the upper limit to this piece-size law. That is, as the trees get “too” large, we can expect the machine to start to struggle, resulting in a decrease in productivity. Four different data sets—two based in New Zealand and two in Italy—are presented that clearly show an “optimum” piece size for maximum productivity. On average, productivity tended to decrease gradually, not drop off suddenly beyond the optimum. Using more complex statistical functions, it was possible to correctly correlate piece size to productivity.

Upsized Harvesting Technology for Coping with the New Trends in Short-Rotation Coppice

Since 2003, Italian farmers have planted over 4000 ha of short rotation coppice (SRC), established almost exclusively with poplar clones and harvested every second year. Currently, there is a strong interest towards extending rotation age and diversifying tree species, in order to increase product quality and to exploit less fertile sites. That implies harvesting larger and harder trees, which may prove challenging for existing harvesting units. This study offers preliminary data on the productivity, efficiency, and cost offered by two new harvesting units, specifically designed for handling larger trees. These were a Krone Big-X forage harvester fitted with the HTM header and a John Deere 7400 forage harvester fitted with the Biopoplar header. The machines were tested on poplar, robinia, and willow. Gross machine productivity ranged from 15 to 50 green tonnes per scheduled machine hour. The actual harvest rate (the productivity of cutting and chipping only) reached 60 t h-1. Both harvesters offered reasonable harvesting costs, generally in the range of 14 € t-1 (1.8 € GJ-1). Both machines were pre-commercial prototypes and their performance will be further improved in the eventual commercial versions. The study also highlighted the excellent performance of robinia, which proved superior to poplar on the same fields, and reached yields in excess of 15 odt ha-1year-1. A further advantage of robinia is the low moisture content at harvest, which may help solving the fuel moisture issues inherent to the current single-pass cut-and-chip harvesting systems.

Testing Mobile Chippers for Chip Size Distribution

Abstract Nine chippers were tested for particle size distribution, in order to a) see how chips produced with these machines matched the quality specifications set by the district heating plants of Northeastern Italy and b) detect significant differences between machines. The benchmark was set by collecting chip samples from fourteen district heating plants in the region of interest. The effect of operator skill was minimized and all machines were fed with the same assortment: logs, supplied in lengths varying between 2.4 and 6 m. All logs had similar moisture contents, which typically ranged between 33 and 37 % on a fresh weight base. Mobile in-woods chippers fed with limb-free logs produce high-quality chips, whose particle size distribution matches that of the best chips normally fed to the Italian district heating plants. Indeed, all the tested machines produced chip samples containing almost no oversize particles, very little fines (0.5 to 1 %), and a large majority of chips within the 3–45mm range (95 to 99 %), except the auger-equipped Laimet, which is designed to produce larger chips. There were statistically significant differences between machines and machine types, which were not affected by possible variations of the tree species processed.

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.

Productivity Standards for Harvesters and Processors in Italy

The authors developed a general productivity model for the harvesters and processors currently used in Italy. The model consists of a set of mathematical relationships that can estimate the product...