Fuel Consumption of Forwarders in Lowland Forests of Pedunculate Oak

Sa？etak Background and Purpose: Fuel consumption in timber harvesting operations is significant for both economic and environmental reasons. In economic sense, one significant part of timber harvesting costs is reduced to fuel costs, and in environmental sense 80% to 95% of exhaust emissions and soot particles in forest machinery are in fact associated with fuel consumption. Materials and Methods: The research object was a 6-wheel Valmet 840.2 forwarder and research was conducted in Forest Administration Vinkovci (lowland part of Croatia) during seeding felling in a stand of pedunculate oak and narrow-leafed ash. For the purpose of measuring fuel consumption on the researched forwarder a differential flow device was installed together with FMS (Fleet Management System) which was used for data transfer. Results: Fuel consumption is expressed in six different ways concerning: cycle, extraction distance of 100 m, time (hour), load mass (tons), gross load volume (m3) and product of mass and transporting distance (tkm). Fuel consumption amounted to 0.56 l·tkm-1 during the extracting of logs and 0.78 l·tkm-1 during the extraction of energy wood. The results also show an increasing trend of fuel consumption expressed per ton of transported load with the increase of travelled distance during the extraction. Conclusions: Fuel consumption expressed in l·tkm-1 is the most accurate fuel consumption indicator because it allows a realistic comparison of different types of machines with different loads (t, m3) at different extracting distances. The higher fuel consumption of an unloaded forwarder compared to a loaded forwarder can be explained with an increased wheel slip of an unloaded forwarder due to reduced traction between wheels and the soil both in the extraction of logs and energy wood