Systemkostnader, logistik och kvalitetsaspekter för sju försörjningskedjor för stubbränslen: System costs, logistics and quality aspects relating to seven supply chains for stump fuel

The system chains used in association with stump harvest have so far been largely based on experiences from logging residues and roundwood. No analyses have been carried out of whether these systems are actually appropriate. In this study, we compiled data taken from a number of different studies and created a total of seven possible system chains for grinding and transport of stump fuel. We used a simulation tool that considers the random effects that arise in a system chain during the course of one year. The systems tested involved grinding with three different alternatives, and each grinding alternative had two transport alternatives. In the seventh (reference) system, loose stump parts were transported to the recipient where comminution took place. The results show that the reference system quickly loses fi nancial viability as transport distance increases, and should therefore not be used when the distance to the recipient is longer than approximately 50 km. The most cost-effective system involved grinding the stumps at the landing and storing the ground material in piles without sieving. This material is later collected in chip trucks equipped with a knuckle boom loader. This system requires a good availability of chip trucks, particularly if transport distances are long. Grinding and seiving at the landing increases the energy content by reducing the proportion of contaminants in the chips, but the system requires more machines at the landing. For these systems too, chipping on the ground for later collection with chip trucks equipped with a knuckle boom loader is generally more cost-effective than chipping directly into container trucks.