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6. COST-EFFICIENCY OF A SYSTEM WITH ONE
HARVESTER THAT LOADS TWO FORWARDERS IN
COMPARISON TO A TRADITIONAL HARVESTER-
FORWARDER SYSTEM
Ola Lindroos 1 *
1 Swedish University of Agricultural Sciences, Umeå, Sweden
* ola.lindroos@srh.slu.se
In the cut-to-length system, some alternative machine systems have lately challenged the
conventional harvester-forwarder system. In the so called “Beast-system”, manned forwarders
take turns to remote control one un-manned harvester. In this system logs are loaded directly on
the forwarder, and hence, less crane work is needed, logs are kept clean and do not risk to be
forgotten. Moreover, each log is handled by only one operator and the unmanned harvester can
be made cheaper than the cabin equipped manned harvester. The backside is that the system
becomes completely integrated (“hot”), as the harvester cannot conduct work without a forwarder,
and a forwarder cannot load without the harvester. Any numbers of manned forwarders could take
turns in using the un-manned harvester, but two forwards were assumed in this study as other
numbers of forwarders only rarely were more cost-efficient. Below this method of integrated cooperation
between one harvester and two forwarders is called integrated forwarder loading (IFL).
Because harvester productivity is mainly affected by tree size and forwarder productivity is mainly
affected by forwarding distance, there are intrinsic difficulties to balance the work time required by
the machine types. In the conventional harvester-forwarder system, this can be handled in such a
way that it does not necessarily cause delay time on machines, through changes in work time or
alternative work tasks. For the IFL-system, delay time is only avoided when it for one forwarder
takes as long time to transport, unload and return to the harvester as it takes to fill the other
forwarder. If the forwarding distance is to short in relation to the harvester productivity (loading
time), the forwarder will return before the other forwarder is loaded and will, thus, have to wait for
its turn to use the harvester (to be loaded). If the distance is too long, the harvester will be left
unused. As a consequence, the margin for balance between machines is thin and delays occur for
most combinations of tree sizes and forwarding distances. Moreover, delays will occur due to
machine down-time and unplanned interruptions even with perfect balance. Such delays happen
to both conventional and IFL-machines, but in the IFL-system the delays to one machine affect
also other machines. Thus, the level of machine availability will be considerably lower in the IFLsystem.
In this study of theoretical potentials, the work method of an IFL-system with two forwarders was
compared with a conventional harvester-forwarder system in final felling. The analysis shows that
the integrated work method used by the IFL-system is considerably less cost-efficient than what
has been previously estimated. When assuming the unrealistic mechanical availability of 100%
(i.e. all main work time is productive work time), the IFL-system was the most cost-efficient system
when the mean tree size was larger than 0.6 m 3 at a mean forwarding distance of 100 m when
harvesting 300 m 3 /ha. At 700 m forwarding distance, the trees had to be larger than 0.3 m 3 .
However, when assuming more realistic levels of mechanical availability, the IFL-system became
less cost-competitive. At 100 m forwarding distance the trees had to be at least 0.9 m 3 , and at 700
m at least 0.4 m 3 .
The analysis of suitable combination of mean stand characteristics was applied to data on
harvested stands in different Swedish regions. The results show that the volume of final felling on
which the IFL-system is the most cost-efficient system is very limited, especially if also the
system’s extra cost for road transport of machinery is included (three machines to transport
instead of two). The results showed that less than 15% of the volume of final felling is costefficiently
harvested with the IFL-system under the conditions assumed in the analyses.
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