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Energy crops can increase biomass availability for large-scale biomass-fired heat, power and CHP plants, which can contribute greatly to mitigation of greenhouse gas emissions. Industrial fibre hemp ( Cannabis sativa L.) is a potential high biomass and energy yielding crop intended for use as solid biofuel, but its fuel properties are insufficiently characterised. Hemp was grown in two independently planned field studies 900 km apart, in southern and northern Sweden. The northern field trials comprised two seasons, two locations and four different cultivars of hemp, while the southern field trial included one hemp variety and one season. Mineral elemental composition (C, H, O, N, S, Cl, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Se, Si, Sn, Sr and Zn), heating value, moisture content and initial ash deformation temperature were determined on samples taken between autumn and spring. Spring harvesting significantly improved relevant combustion fuel properties such as moisture content, alkali and ash content and heating value in comparison with autumn harvest. Major fuel properties were not influenced by choice of cultivar or geographical location. Spring-harvested industrial hemp was found to have high initial ash deformation temperatures and a mineral composition similar to that of willow and coniferous wood, indicating that the ash resulting from its combustion will have a low risk of slagging and fouling. Relevant combustion fuel properties were superior to those of other available agricultural biomass feedstocks, such as cereal straw, miscanthus and reed canary grass (straw fuels). Therefore, hemp is a suitable solid biofuel for large-scale CHP plants and small-scale heating boilers as pellets or briquettes. This study characterised hemp as a solid biofuel, but large-scale combustion tests and an economic analysis are needed to determine the competitiveness of hemp compared with other sources of biomass. |
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