Eco-efficient technologies in forestry

In addition to safety, small hand-operated forestry machines can be criticised for affecting the
operators’ health, especially because of high levels of exhaust gas emissions, noise and vibrations.
In this study, gas emissions, noise and hand-arm vibrations (HAV) levels have been measured
on chainsaws, hedge cutters and blowers fuelled with two different types of fuel: a commercial
RON 95 gasoline with the addition of 2% of synthetic oil suitable for two-stroke engines and,
as an alternative, a specific advanced mixture available on the market, based on alkylate gasoline.
For two different running conditions, i.e. with the engine at idle speed and when executing a
typical working routine (maximum speed with load), tests were carried out for:
Þ gas emissions, using a gas analyser, for measuring the volatile organic compounds (VOC)
values
Þ noise, using a sound level meter, to record the levels at both of the operator’s ears
Þ HAV, using a tri-axial accelerometer fixed on the handgrip(s) of the machines.
The results demonstrated that, when using the alkylate fuel, the VOC emissions were reduced,
in the considered machines, from 23 to over 77%, while for noise and HAV, the differences in
level were not statistically significant. The present study confirms that the reduction in the
amount of emissions can be remarkably improved by adopting advanced fuels that lead to a
more efficient combustion process.

Stora Enso Wood Supply Finland (WSF) was certified to the ISO 50001 Energy Efficiency
Management System standard in 2015. At Stora Enso WSF, the goal is to improve energy
efficiency by 4% by 2020 from 2015. Improving the energy efficiency of wood procurement
(i.e. logging and timber trucking) enterprises is currently one of the main focus areas for energy
efficiency development at Stora Enso WSF. In order to clarify its state-of-the-art in the
business of wood procurement enterprises at Stora Enso WSF, logging and timber-trucking
entrepreneurs were interviewed in November and December 2017. The survey data consisted
of 25 logging and 25 timber-trucking entrepreneurs. The coverage rate of both entrepreneur
groups was 73.5% in the survey. The results indicated that timber-trucking enterprises highlight
more energy efficiency and fuel efficiency than logging enterprises. For instance, the
timber-trucking entrepreneurs underscored more energy efficiency in their acquisition decisions
of new vehicles and the greater role of fuel efficiency in the energy-efficient business than
logging entrepreneurs during 2016 and 2017. Furthermore, the survey results revealed that
logging and trucking enterprises can improve energy efficiency in their business by organizing
more energy efficiency education (i.e. economical and anticipated driving training) for
their machine operators and truck drivers. There is a positive attitude towards energy efficiency
among both logging and timber-trucking entrepreneurs. This creates a solid background
to deepen and continue energy-effective work in the wood supply chain between the enterprises
and Stora Enso WSF in the future.

Climate change affects forest ecosystems, impacting timber production and eco-services. Conversely, sustainable forest management has been identified as a means to help mitigate carbon dioxide emissions, a greenhouse gas and contributor to climate change, while also maximizing multiuse benefits through close-to-nature silviculture. In this study, a life cycle assessment was performed on forest harvesting operations at three research sites to provide real-world understanding of the selected environmental impacts associated with harvesting systems typical of Germany: motor-manual (chainsaw and forest tractor), semi-mechanized (single-grip harvester, chainsaw, and forwarder), and fully-mechanized (single-grip harvester and forwarder). Environmental impact categories assessed included greenhouse gas emissions, particulate matter emissions, and non-renewable energy consumption. Results from the three research sites were estimated on a machine basis. The semi-mechanized system resulted in the lowest environmental impact, the majority of which was attributed to felling and processing operations. Next, the environmental impacts were estimated for a complete rotation period and compared amongst the different harvesting systems. According to results, semi-mechanized harvesting systems had the lowest impact over the full rotation period as well as for thinning treatments when compared to motor-manual and fully-mechanized systems. The fully-mechanized system performed the best for final felling treatments. Considering variability between the research sites as well as the system boundary assessed, a diversified approach to harvesting operations may be considered, integrating semi-mechanized and fully-mechanized systems for different treatments throughout the rotation period.

Farm tractors are still widely used in many forestry operations. Predicting fuel and lubricant costs is difficult because their consumption depends on a number of factors such as hours worked and operations performed. Fuel and lubricant consumption is important since it can have an impact at both the economic and environmental level. Many fuel models have been studied in the last decades, but few studies have focused on oil consumption. The ASABE (American Society of Agricultural and Biological Engineers) Standard suggested a model for predicting engine oil consumption of farm tractors of the 1980s, which are potentially different from modern tractor engines. In addition, the recent widespread application of semi- and full-power-shift and continuous variable transmissions and the high number of hydraulic applications increased the amount of lubrication oil for transmission and hydraulic systems.

For these reasons, we analysed 133 4WD recent model farm tractors used in forest operations with the aim to study:

Þ   engine, transmission and hydraulic system oil capacities

Þ   engine oil change intervals as recommended by the manufacturers.

A new equation for engine oil consumption, as a function of the rated engine power, was first used and statistically analysed. It was similar to the equation developed by other authors (with a mean difference of 28%, decreasing to 11% at the highest engine power), but well below the ASABE model (with an average engine oil consumption three times higher). Another equation of total oil consumption related to the rated engine power was then studied and compared with a recent study. The results showed an average difference of 18%, decreasing to 8% at the highest engine power. The differences, due to a different machine dataset (only 4WD farm tractors that can be used for forestry operations were analysed) are, however, minimal also in the engine oil consumption model if compared with the oldest ones: a new proposal is therefore necessary, with new and affordable models for correctly evaluating economic and environmental forestry operation costs when using farm tractors.

Ground contact pressures exerted by elements of the machine chassis on the ground in the forest are associated with the machine impact on the soil during its operation. In the case of a crawler system, determining the ground contact pressure appears simple, which is not entirely true. The aim of the study was to analyze the loads on the ground (forest soil) exerted by the MHT 8002HV crawler harvester chassis. The measurements were made in Forest School Enterprise in Kostelec nad Černými Lesy, Central Bohemia Region in the Czech Republic, on brown soil made of clay on stony formations, fresh mixed mountain forest (FMMF), with the use of a hydraulic scale when extending the harvester crane forward along and perpendicular to the longitudinal axis of the machine. The calculations were carried out with a simulated load of the crane on the tree in question, assuming that the impact on the ground of the crawler system is heterogeneous and that the point impact comes from the crawler support wheels. As it was shown, the average ground contact pressures under the crawler track of the analyzed harvester generally do not exceed 70 kPa. The crane extension with a simulated load, which would have caused the crawler track to act on the ground with an average pressure exceeding 70 kPa, was limited by machine stability. On the other hand, high ground contact pressures may occur under a more loaded section of the crawler track if the active length of the crawler track is shortened. As it was shown in the case of a weak track tension, the course of ground contact pressures exerted on the soil deviates from the assumed usually homogeneous impact over the entire length of the crawler.

The impact of machines on forest soils is regularly assessed and quantified using absolute bulk density, which is most frequently obtained by soil cores. However, to allow for repeated measurements at the exact same locations, non-destructive devices are increasingly being used to determine soil bulk density and moisture content in field studies. An example of such a device is a nuclear moisture and density gauge (NMDG), originally designed as a control measurement for soil bulk density and moisture content in geotechnical applications. Unlike road construction or foundation projects that use mineral soil or gravel, forest soils have complex structures and the presence of organic matter, which can skew moisture and density readings from a NMDG. To gain further knowledge in this respect, we performed controlled tests in a sandbox to quantify the influence of varying amounts of saturated organic matter (3, 5, 10, and 15%) mixed with mineral soil in different layers (0–5, 0–10, 0–20 and 0–40 cm) on the accuracy of soil moisture content obtained by a NMDG and soil theta probe at varying depths. Main results illustrated that the presence of saturated organic matter per se was not problematic but moisture content overestimations and related underestimation of dry bulk density occurred when the tested measurement depth was below the created organic layer. Since forest soils often exhibit higher organic matter contents in the upper horizon, correction factors are suggested to minimize the moisture content variations between NMDG and reference method. With the use of correction factors, NMDG can present a non-destructive, fast, and accurate method of measuring soil moisture and bulk density in forestry applications.

Forest operations often enhance runoff and soil loss in roads and skid trails, where cut slopes and fill slopes are the most important source of sediment. This study evaluated the effectiveness of four erosion control treatments applied to cut slope and fill slope segments of forest roads of different ages in the Hyrcanian forest in northern Iran. The treatment combinations, each replicated three times, included four classes of mulch cover (bare soil [BS], wood chips cover [WCH], sawdust cover [SC], and rice straw cover [RSC]), two levels of side slope (cut slope and fill slope), two levels of side slope gradient (20–25% and 40–45%), and three levels of road age (three, 10 and 20 years after construction). Mulch cover treatments significantly reduced average surface runoff volume and sediment yield compared to BS. Regardless of erosion control treatment, greater surface runoff volume and soil loss under natural rainfall occurred on steeper slope gradients in all road age classes and decreased with increasing road age on both slope gradients. On cut slopes, average runoff and soil loss from the plots covered with WCH (17.63 l per plot, 2.43 g m–2) was lower than from those covered with SC (22.81 l per plot, 3.50 g m–2), which was lower than from those covered with RSC (29.13 l per plot, 4.41 g m–2 and BS (34.61 l per plot, 4.94 g m–2). On fill slopes, average runoff and soil loss from the plots covered with WCH (14.13 l per plot, 1.99 g m–2) was lower than from plots covered with SC (20.01 l per plot, 3.23 g m–2), which was lower than from plots covered with RSC (24.52 l per plot, 4.06 g m–2) and BS (29.03 l per plot, 4.47 g m–2). Surface cover successfully controlled erosion losses following road construction, particularly on steep side slopes with high erosion potential.

The EU’s climate and energy framework and Energy Efficiency Directive drive European companies to improve their energy efficiency. In Finland, the aim is to achieve carbon neutrality by 2035. Stora Enso Wood Supply Finland (WSF) had a target, by 2020, to improve its energy efficiency by 4% from the 2015 level. This case study researches the use of the forest machine fleet contracted to Stora Enso WSF. The aims were to 1) clarify the forest machine fleet energy-efficiency as related to the engine power; 2) determine the fuel consumption and greenhouse gas (GHG) emissions from wood-harvesting operations, including relocations of forest machines by trucks; and 3) investigate the energy efficiency of wood-harvesting operations. The study data consisted of Stora Enso WSF’s industrial roundwood harvest of 8.9 million m3 (solid over bark) in 2016. The results illustrated that forest machinery was not allocated to the different cutting methods (thinning or final felling) based on the engine power. The calculated fuel consumption totalled 14.2 million litres (ML) for harvesting 8.9 million m3, and the calculated fuel consumption of relocations totalled 1.2 ML, for a total of 15.4 ML. The share of fuel consumption was 52.5% for harvesters (cutting), 39.5% for forwarders (forest haulage), and 8.0% for forest machine relocations. The average calculated cubic-based fuel consumption of wood harvesting was 1.6 L/m3, ranging from the lowest of 1.2 L/m3 for final fellings to the highest of 2.8 L/m3 in first thinnings. The calculated fuel consumption from machine relocations was, on average, 0.13 L/m3. The calculated carbon dioxide equivalent (CO2 eq.) emissions totalled 40,872 tonnes (t), of which 21,676 t were from cutting, 16,295 t were from forwarding, and 2,901 t from relocation trucks. By cutting method, the highest calculated CO2 eq. emissions were recorded in first thinnings (7340 g CO2 eq./m3) and the lowest in final fellings (3140 g CO2 eq./m3). The calculated CO2 eq. emissions in the forest machine relocations averaged 325 g CO2 eq./m3. The results underlined that there is a remarkable gap between the actual and optimal allocation of forest machine fleets. Minimizing the gap could result in higher work productivity, lower fuel consumption and GHG emissions, and higher energy efficiency in wood-harvesting operations in the future.

Forest operations can lead to increased runoff and soil loss on roads and skid trails. The aim of this study was to evaluate the effectiveness of two erosion control treatments applied to different segments of skid trails following six natural rainfall events. A total of 162 plots 10 m long by 4 m wide were established in a Hyrcanian deciduous forest to assess soil runoff and soil loss following ground-based harvesting traffic. The experimental setup consisted of three levels of traffic intensity (three, eight and 16 skidder passes), two levels of slope gradient (≤20% and >20%), three classes of curvature (narrow = high deflection angle, 60°–70°; wide = low deflection angle, 110°–130°, and straight trail segments), and three classes of mulch cover (bare soil, sawdust cover, and rice straw cover). Each treatment combination was replicated three times, yielding 972 soil samples. The average surface runoff volume and soil loss differed significantly between the switchbacks and the straight trail segments and depended strongly on the degree of curvature, with severity of adverse effects increasing with curve tightness. Mulch cover treatments had a significant ameliorating effect on the surface runoff volume and soil loss throughout the skid trail. The average runoff and soil loss from the skid trails treated with sawdust cover (SC) (0.24 g m-2 (mm) and 0.49 g m-2, respectively) were lower than on trails covered with rice straw (RSC) (0.45 g m-2 and 1.19 g m-2, respectively), which were, in turn lower than on untreated bare soil (BS) trail segments (0.70 g m-2 and 2.31 g m-2, respectively). Surface runoff volume was significantly positively correlated with soil loss and both were positively correlated with dry bulk density and rut depth and negatively correlated with litter mass, total porosity, and macroporosity. Surface cover is a successful measure for controlling erosion losses following skidding disturbances, particularly in the switchback curves of trails on steep slopes where erosion potential is high.

The behavior of the vehicle-soil interaction and reduction of the possible soil damage to an acceptable level is one of the goals of forest engineering. This study aimed to analyze the impact of a 6-wheeled forwarder on water-physical soil characteristics on lowland soil – pseudogley. The research was conducted using a 17-ton Timberjack 1710B forwarder, which forwarded 694.1 m3 volume of oak (Quercus robur L.) assortments. Soil characteristics were measured after each of the eight passes of the loaded forwarder. Bulk density measured on the surface layer ranged from 1.01–1.23 (Me=1.10) g/cm3 (undisturbed soil); 1.14–1.70 g/cm3 (multiple passes of the loaded forwarder). The highest soil density increase was observed after the first pass of the loaded forwarder (16%). Soil solid phase ranged from 2.49 to 2.73 g/cm3 with no statistically significant difference between undisturbed soil and soil after multiple passes of the vehicle. The highest porosity decrease was observed after the first pass of the loaded forwarder (10%). The highest soil water retention capacity decrease was observed after the first pass of the loaded forwarder (3%). The highest soil air capacity decrease was observed after the first pass of the loaded forwarder (30%) compared to the undisturbed soil of the forest stand.

Deforestation and erosion are important indicators of the beginning of land degradation. This study aimed to present the changes in some physical, chemical, and microbial characteristics of the soil on sloping land on which deforestation has led to gully erosion. The study was conducted on dam slopes on which the forest cover had been removed, and gullies subsequently formed. Nine soil samples were taken from deforested and eroded slopes (SDE) and six soil samples were taken from slopes with forest vegetation (SF) for physical and chemical soil analysis. Thus, a total of 15 samples were taken from the study area to determine physical and chemical properties. To determine microbial biomass and activity, a total of 30 samples were taken from the same locations in duplicate. The results revealed that sand particles, bulk density, soil temperature, >2 mm/<2 mm fraction ratio, pH, and electrical conductivity increased markedly, whereas total porosity and organic carbon decreased (p≤0.05) in SDE soils. Moreover, it was found that the average organic carbon content of SDE soils decreased by more than five times compared to SF soils. Microbial biomass carbon and basal respiration in SDE and SF soils indicated a significant difference (p≤0.05). While the metabolic quotient indicated a marked difference (p≤0.05) between SDE and SF soils, the microbial quotient showed no significance (p>0.05). Furthermore, it was found that the most relevant physical and chemical soil characteristics of microbial biomass and activity were bulk density, pH, and organic carbon.