• Energy Research

AbstractRed pine (Pinus brutia Ten.) is the most common tree species in Turkey, where it covers almost 6 million hectares. The first thinning of red pine stands is a fundamental tending measure that may yield between 4 and 12 dry tons of biomass per hectare. While this is not a very large amount per se, it is larger than obtained from the recovery of logging residues from final felling operations, which have represented the main subject of previous studies. What is more, valorization of the non‐commercial biomass component can boost work productivity and increase owner revenues, with strong benefits on the financial sustainability of an operation that normally incurs substantial cost and tends to be neglected. Therefore, increased use of biomass can support proper tending of young stands and a general improvement of their quality and future value. The study also indicates that small‐tree size favors whole‐tree harvesting, even when performed with animal or manual power, as customary in Turkey and in most developing economies. Whole‐tree chipping is probably the best option in stands growing on poor yield sites, whereas multi‐product harvesting is advisable on good yield sites. This study addresses specifically Turkish red pine, but it frames a general paradigm that applies to most forest stands and countries, and as such it can be generalized to a great extent. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd

AbstractA new shredder was designed for comminuting small‐size rootstocks from the termination of orchards and short‐rotation plantations. The new shredder is lighter than any similar models available on the market and is fitted with an integral star screen: these innovative characteristics allow the machine to work in‐field, leaving dirt on site and packing denser loads. The preliminary test conducted in this study lasted 13.2 h and produced 15 full containers, or 123 t of fresh chunks. Researchers measured the time required to fill each container, and associated it with its net weight. Samples were collected from each load in order to determine product moisture and dirt content. Productivity ranged most commonly between 8 and 10 t of fresh chunks (or 38 and 50 m3 of loose chunks) per scheduled hour, inclusive of all delays. Net shredding productivity was much higher and peaked at 17 t of fresh chunks or 80 m3 of loose chunks per hour, excluding delays. The shredding cost varied between 24 and 30 € t−1 of fresh chunks, including transportation to the plant yard. Prolonged storage at the field edge and effective screening resulted in a dramatic reduction of water and soil content, which were measured at 23% and 1% respectively. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

The authors report on 6 years of tests with systems used to harvest pulpwood from the SRF poplar stands in the Pacific Northwest USA. Four systems are described and analyzed. All can produce in excess of 400 green tonnes per day and return delivered cost varying from $15-30 per green tonne. Transportation is a major item: depending on distance, it may represent 30-70% of total delivered cost. Two opposing strategies proved the most cost-effective. System 1-felling and bunching, forwarding and delimbing/debarking/ chipping-is simplest and easiest to implement. System 4-the central yard option-is more complex and has higher stump-to-truck costs, but these are more than offset by substantial savings on transportation.

The experiment determined the technical and financial efficiency of five storage techniques, specifically designed for SRF poplar chips stored at the farm site in small (20 m3) piles. The treatments on test were: uncovered storage, storage under a temporary roof structure, cover under a semi-permeable fleece sheet, cover under two types of plastic sheet (i.e. white and black). Each treatment was replicated 3 times. Researchers monitored temperature and moisture content trends inside the piles, and determined dry matter losses at the end of the 170 days storage period. In general, piles under plastic cover presented opposite trends compared to all other piles. They acquired moisture rather than losing it, and showed gradual temperature trends instead of a typical peak-and-drop behaviour. Dry matter losses varied from 5.1% to 9.8%, and were highest for the uncovered treatment, and lowest for the plastic cover treatment. Under the conditions of north-western Italy, uncovered storage was a cost-effective option. Protecting the piles with some cover incurred more cost than it saved, resulting in a higher storage cost per unit energy. Although more expensive, sheltering the piles under a simple roof structure offered the benefit of a higher reduction of moisture content, which may turn the chips into a higher quality fuel. Of course, these results were closely related to the Southern European climate, and the specific year of the test. Occasional wetter years may overturn these results. © 2013 Elsevier Ltd. All rights reserved.

The success of short-rotation coppice (SRC) will rise with increasing biomass prices. One of the main constraints for establishing SRC today is the unpredictable cost of (whip) harvesting. Therefore, the harvest of a 9 ha SRC in Belgium was monitored, in order to develop a whip harvesting cost model to estimate harvesting productivity and costs as a function of various input data. The harvest was executed in February 2017 with a Stemster MkIII, after a three-year rotation of SRC with poplar. A biomass inventory was combined with a time-motion study and an economic analysis. The field stocking (fresh weight basis) ranged from 40 to 100 Mg ha(-1). The average load of 2.4 Mg was obtained from a 220 m long double row and took 6.4 min, resulting in an average productivity of 26 Mg h(-1) (excluding delays). Genotype, field stocking and their interaction significantly affected the harvester's productivity. Border limited headlands (<8 m width) had a significant impact on turning time and, thus, increased the total harvesting cost by 6%. The offload time was stable at 23 s Mg-1, while the harvesting cost varied from 7 to 22 (sic) Mg-1, depending on work conditions and costing assumptions. Even though the Stemster MkIII produces whips instead of wood chips, its productivity is still lower than the modified foragers' productivity, but the Stemster MkIII is lighter and may offer better mobility. Optimal performance can be obtained with a high field stocking, appropriate spacing and adequate headlands.

We conducted a comparative study of chipping logging residues at the roadside landing or at the yarder pad, the latter inaccessible to heavy road vehicles. Field data was collected from real operations in the Italian mountain, and it was used for building a simulation model that could generalize the results of the study. The model was built with Arena 14 and carefully reflected interaction delays between individual units along the chain. Chipping at the pad with a chipper and two shuttles was the best compromise solution of low supply cost and fuel consumption. At a mean cost of Euro22.7 per fresh tonne, this solution was 10% cheaper than chipping at the landing. Using three chip shuttles did not allow a meaningful reduction of supply cost over a two-shuttle chain, but resulted in a 7% increase of fuel consumption. The distance between the pad and the roadside landing was by far the most important factor in determining supply cost, and accounted for 80% of the variability in the data, for both systems. Under these circumstances, the higher speed and payload of the chip shuttles made it preferable to chip at the pad, provided enough shuttles are available.

Moisture content (MC) is the most important quality parameter for energy wood. Unfortunately, checking MC under operational conditions is difficult, because the standard method for MC measurement requires up to 48 h. The bioenergy industry needs alternative methods allowing fast and reliable MC determination, but most of the commercial devices require biomass-specific calibration models. This is an important limitation, particularly in Mediterranean areas, where mixed forest dominate and feedstock loads can include multiple species. In this study a moisture meters based on Magnetic Resonance (MR) was tested for assessing its reliability as an alternative to oven drying. For this purpose, a stress-test was performed at the premises of an energy facility in Southern Italy, using a commercial MR analyzer. Thanks to the non-destructive action on the biomass of MR technology, the MC of 350 samples was measured with both MR and standard gravimetric techniques. Results confirm the validity of the MR analyzer as an alternative to oven drying. Accuracy and precision of the machine are both satisfactory, with over 95% of values within±2.5% of deviation and a Standard Error of Performance of 1.2%. Furthermore, the analyzer processes over 15 samples per hour, coping with frequent deliveries.

Vineyards cover about eight millions of hectares worldwide and their annual pruning generates a large amount of ligno-cellulosic biomass, potentially available for industrial and energy use. Commercial pruning residue harvesters are now available, which may allow cost-effective recovery. The study aimed at determining the quantity and the quality of pruning residues potentially derived from vineyard management. Data were obtained from 17 fields in Northern and Central Italy. Fields were harvested with seven different machines. The experimental design adapted to the necessities of field trials, but was adequate for testing the main sources of variability. Net residue yield varies around 1 oven dry tonne per hectare, with minor differences between grape varietals and harvesting technologies. Losses are still high, and are generally related to ineffective management techniques. Moisture content at harvest varies between 40% and 45%, whereas the higher heating value is slightly lower than that of forest fuels. Comminuted vineyard residues are unsuitable for firing residential boilers, due to the frequent presence of oversize and/or undersize particles. The application of pesticides does not result in any significant contamination with noxious chemicals, because these products are almost completely weathered before residues are recovered. In wine-producing regions, the recovery of vineyard pruning residue may represent a substantial source of industrial bio-fuel. © 2011 Elsevier Ltd.