EN :

The fight against climatic change has introduced a new dimension to Finnish forestry. Renewable forest fuels play an important role in the national climate strategy, which is aimed at reducing the greenhouse gas emissions in accordance with Finland's international commitments. According to the Action Plan for Renewable Energy Sources, 5 million solid m3 forest chips or 0.9 Mtoe energy is to be derived annually from low-quality forest biomass by 2010: two thirds from logging residues from final fellings and one third from small trees from early thinnings.

The production of fuel chips from early thinnings is a challenge, but provides the opportunity to improve the tending of young forests. To make the use of chips competitive, the cost of harvesting must be reduced, and the yield of biomass per hectare must be increased. Therefore, in industrial operations the chips are produced from whole trees rather than delimbed stems. The intensive recovery of biomass can result in the accelerated loss of nutrients from forest soils, and this has to be taken into account in site selection and system development.

In 1999, the National Technology Agency Tekes launched a five-year Wood Energy Technology Program to develop efficient procurement systems for large-scale production of forest chips from residual forest biomass. The ongoing program is reviewed in this paper from the viewpoint of early thinnings. Among the topics discussed are the resource and its biomass composition, background problems, cost of production, silvicultural impacts, benefits from the program, and future prospects.

EN :

A comparison is made of energy usage and the contribution made to the global warming potential (GWP) by present (1997) and past (1972) forestry operations (including secondary haulage) in Sweden. The results are expressed in units of one cubic metre (solid u.b.) of harvested timber.

The results indicate that, since 1972, improvements in fully mechanized forestry operations, particularly logging, have led to a reduction in total energy use from 1972 (236 MJ). In fact, the energy used by today's (1997) mechanized logging systems (147-200 MJ) is roughly the same as that used by motormanual systems back in 1972 (156-177 MJ). The same is true as regards the contribution made to global warming potential: more fossil carbon was released in mechanized forestry (22 GWP) in 1972 than in 1997 (13-17 GWP). What's more, the contribution to GWP in 1997 is on the same level as that made by motormanual systems in 1972 (15-16 GWP).

It is accepted that forest management in Sweden mitigates the global warming potential. This is because the resulting sequestration effect in forest biomass is greater than the level of emissions from forestry operations.

EN :

Cut-to-length harvesting systems offer an alternative to conventional mechanical systems for thinning mixedwood stands. We evaluated the performance of a single-grip harvester and forwarder in a poplar-dominated mixedwood stand in Southern Ontario to quantify the effect of tree size and tree form on harvester productivity and harvesting cost, and to assess the damage caused by the harvesting operation to advance regeneration and residual trees. A single-tree selection silvicultural system was used. Individual trees were assigned a form index based on their visual estimates of limb size and stem form. The cut-to-length harvester produced 23.1 m3 per productive machine hour (PMH). Forwarder productivity was 17.2 m3/PMH. The results indicate a significant and positive relationship between harvester productivity and tree size (dbh) and tree form. Tree size (dbh) has the greatest influence on the unit cost of harvesting. At an average 27 cm dbh and extraction distance of 200 m, the stump-to-landing cost was approximately 10 US$/m3. As tree size increased, the unit cost of wood produced decreased. Damage to residual trees and advance regeneration was minimal. The results suggest that single-grip cut-to-length harvesting systems can be effective in managing poplar-dominated mixedwood stands.

EN :

A silvicultural project encompasses tasks such as site-level planning, regeneration, harvest, and stand-tending treatments. An essential problem in managing silvicultural projects is to efficiently schedule the operations while considering project task due dates and costs of moving scarce resources to specific job locations. Transportation costs represent a significant portion of the total operating cost. The main difficulty in developing such a management system is finding an optimal transport schedule while handling complicated constraints, such as precedence and temporal relations among project tasks, project due dates, truck routing, weather, and other operational conditions. It is well known that finding an optimal solution to these types of problems involves high computational complexity. They are usually NP-hard. For this reason, we propose to use simulated annealing -a meta-heuristic optimization method- that interacts with a network simulation model of the system in which the precedence and temporal relations among project tasks and logistics are explicitly accounted for. The approach has been tested using data provided by a silvicultural contractor located in Alabama. The results obtained solving one instance of a small size problem with five worksites showed that the best solution could be found in less than four minutes using a personal computer with a processor Pentium III (1 GHz). A good solution for a larger problem with twenty worksites was found in thirty minutes. Also a resource analysis is performed to evaluate the impact of each resource on the best solution.

EN :

The grabbing forces of log grapples were modeled and analyzed mathematically under operating conditions when grabbing logs from compact log piles and from bunch-like log piles. The grabbing forces are closely related to the structural parameters of the grapple, the weight of the grapple, and the weight of the log grabbed. An operational model grapple was designed and tested to validate grabbing forces of the mathematical models while grabbing logs from five alternative diameter classes under two different working conditions. The working conditions and log sizes affected the grabbing forces significantly. Validation results suggest that the mathematical models developed can be used to estimate the grabbing forces required in the design process of log grapples. The results can be used by equipment manufacturers and researchers involved in the engineering design of grapples used in harvesting operations.