Energy requirements for wood chip compaction and transportation

Wood chips represent one of the most popular biomass fuel in latest cogenerating plants and in small heating systems. This fuel, being characterized by low bulk density, requires high transportation costs. This obstacle can be overcome by wood chips densification. The authors investigated the energy benefit of wood chips densification for transport operations for "short supply chain" as defined by the Italian government for the biomass fuel subsidy scheme. Three different woods (poplar, chestnut and a mixture of spruce and eastern white pine) chips and six different tractor's trailed trailers were investigated. The total specific energy (kJ kg-1) required to transport a defined quantity of wood chips, the energy saving ratio (%) from chips' compaction and the breakeven distance (km) between raw and compressed chips were calculated. The results highlights that densification process of wood chips is an interesting opportunity to improve the transport energetic convenience. The benefit of wood chips densification is strongly affected by raw wood chips density values and by trailer characteristics: the benefit is maximum when the density of compressed wood chips to be transported attains the vehicle theoretical density