Analyzing and estimating delays in wood chipping operations

Whole trees from energy thinnings constitute one of many forest fuel sources, yet ten widely applied supply chains could be defined for this feedstock alone. These ten represent only a subset of the real possibilities, as felling method was held constant and only a single market (combustion of whole tree chips) was considered. Stages included in-field, roadside landing, terminal, and conversion plant, and biomass states at each of these included loose whole trees, bundled whole trees or chipped material. Assumptions on prices, performances, and conversion rates were based on field trials and published literature in similar boreal forest conditions. The economic outcome was calculated on the basis of production, handling, treatment and storage costs and losses. Outcomes were tested for robustness on a range of object volumes (50-350 m 3 solid ), extraction distances (50-550 m) and transport distances (10-70 km) using simulation across a set of discrete values. Transport was calculated for both a standard 19.5 m and an extended 24 m timber truck. Results showed that the most expensive chain (roadside bundling, roadside storage, terminal storage and delivery using a 19.5 m timber truck) at 158 € t d −1 was 23% more costly than the cheapest chain (roadside chipping and direct transport to conversion plant with container truck), at 128 € t d −1 . Outcomes vary at specific object volumes and transport distances, highlighting the need to verify assumptions, although standard deviations around mean supply costs for each chain were small (6%-9%). Losses at all stages were modelled, with the largest losses (23) occurring in the chains including bundles. The study makes all methods and assumptions explicit and can assist the procurement manager in understanding the mechanisms at work. OPEN ACCESSForests 2014, 5 2085

Section: Chippingmentioning

confidence: 99%

Section: Chippingmentioning

confidence: 99%

Systems Analysis of Ten Supply Chains for Whole Tree Chips

Belbo¹,

Talbot²

2014

“…That seems the closest match to the description provided above, and should offer a viable proxy. Previous studies of chipper delays indicate that delay events with a maximum duration of 15 min account for only one-third of total delay time, and therefore the productivity estimates returned by the model are substantially higher than the actual productivity calculated on the basis of total scheduled time [9]. In that regard, one must notice that different machine meters record time in different ways: some simply measure the time when the engine is on-even if idle-while others only record the time when the engine runs above a certain rotational regime, thus excluding idle time.…”

Section: Robust Productivity Modelmentioning

confidence: 80%

Value Retention, Service Life, Use Intensity and Long-Term Productivity of Wood Chippers as Obtained from Contractor Records

Spinelli

Eliasson

Magagnotti

2017

Self Cite

Acknowledging the absence of up-to-date empirical data on the value retention, service life and annual use of chipping machinery, in 2017 the authors surveyed the records kept by 50 contractors offering biomass chipping services. The machine fleet and operations in this survey could be taken as representative for most of Europe, where the biomass sector is well established and is facing further expansion. Data collection included the whole chipping unit, comprised of chipper, carrier and loader. Manually-fed units were excluded from the survey. The data pointed at a service life up to and exceeding 10,000 h and 10 years, which relieved any concerns about poor durability. Value retention was good, and may exceed that of other mainstream forestry equipment. Engine power was the main explanatory variable in any models to predict purchase price and productivity. The effect of this variable could explain most of the variability (>80%) in the purchase price and productivity data. Results also pointed at the essential equivalence in price and productivity between PTO-driven (i.e., tractor powered) and independent-engine chippers, once differences in engine power are accounted for. However, the distribution of purchase price between different components of the chipping unit was different between the two unit types, with the chipper accounting for a larger proportion of the total investment in independent-engine units. Machine power was also different, with most PTO-driven units being significantly smaller than independent-engine units, due to the limitations of existing tractors. Furthermore, half of the carriers assigned to a PTO-driven unit were subject to flexible use, i.e., they were not solely used for chipping work.

“…8 h). More fundamental and accurate statements on delay times can only be obtained by long-term follow-up studies or by combining a larger number of machine category specific time studies [39]. Recent studies on screening machines showed much higher shares of delay times: Spinelli et al [14] found a total share of delay times of ca.…”

Section: Discussionmentioning

confidence: 99%

Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Huber

Kroisleitner

Stampfer

2017

Low harvesting costs and increasing demand for forest-derived biomass led to an increased use of full-tree (FT) harvesting in steep terrain areas in Austria. Logging residues, as a by-product of FT harvesting, present an easily accessible bioenergy resource, but high portions of fine particles and contaminants like earth particles and stones make them a complex and difficult fuel, as they affect storage capability, conversion efficiency, or emission rates adversely. The present research focuses on the productivity and performance of a star screen, which was used to remove fine and oversize particles from previously chipped, fresh Norway spruce (Picea abies (L.) Karst.) logging residue woodchips. Three screen settings, which differed in terms of different rotation speeds of the fine star elements (1861 rpm, 2239 rpm, 2624 rpm) were analyzed. Time studies of the star screen were carried out to estimate screening productivity and costs. Furthermore, 115 samples were collected from all material streams, which were assessed for particle size distribution, calorific value, ash content, and component and elemental composition. Average productivity was 20.6 tonnes (t) per productive system hour (PSH 15 ), corresponding to screening costs of 9.02 €/t. The results indicated that the screening of chipped logging residues with a star screen influenced material characteristics of the medium fraction, as it decreased the ash content, the incidence of fine particles, and the nutrient content. The different screen settings had a noticeable influence on the quality characteristics of the screening products. An increase of the rotation speed of the fine stars reduced screening costs per unit of screened material in the medium fraction, but also lowered screening quality.