Energy intensity and energy ratio in producing willow chips as feedstock for an integrated biorefinery

• The willow plantation (10.5 ha) was located in the north-east of Poland.
• The energy input for the production of willow chips ranged 13.7–30.4 GJ ha−1.
• The energy ratio ranged from 23.9 to 10.2, for UWM 006 and UWM 155 cultivars.
• Transport distances increased energy intensity index by 23–53%.
• Energy ratio decreased significantly by 3–35% with increasing transport distance.

This study examined the production of willow at a commercial plantation with an area of 10.5 ha, situated in north-eastern Poland. Its aim was to evaluate the energy intensity and energy ratio of the production of chips of new willow cultivars as feedstock for an integrated biorefinery. This study emphasises the key importance of the selection of a willow cultivar for the production of willow chips and the transport distance to a biorefinery for the energy intensity of the production process and the energy ratio of the supplied biomass. The lowest energy intensity for willow chip production was achieved for the plantation of the highest-yielding cultivar (UWM 006). When the yield exceeded 86 t ha−1 of fresh biomass, the energy intensity was 0.35 GJ t−1 of fresh matter (f.m.). The energy ratio for the product at the farm gate varied depending on the cultivar and ranged from 23.9 to 10.2, for UWM 006 and UWM 155 cultivars, respectively. The distance of biomass transport to a biorefinery significantly affected the energy ratio. When chips were transported for 25 km, the energy intensity for the production of 1 t of chips increased by 3–7% compared to its value at the farm gate. The energy intensity for the longest of the analysed transport distances increased by 23–53%. The energy ratio for each cultivar decreased significantly by 3–35% with increasing transport distance. The values of energy intensity and energy ratio for UWM 006 and UWM 043 were better than those achieved in other studies.