Economic evaluation of Hemp's (Cannabis sativa) residual biomass for production of direct energy or biochar.

• Economic evaluation of the residual hemp biomass for energy or biochar production. • The hemp variety 'Fedora and CS' were selected as the best for multipurpose production. • The highest surface area revealed biochar prepared by slow pyrolysis at 700 °C. • The use of residual hemp biomass improves farmer economy of hemp growing. The aim of the article is to present the results regarding a comprehensive evaluation of the efficiency of Cannabis cultivation with an emphasis on the economic evaluation of the use of residual biomass either for direct energy use or for biochar production. The results of field experiments conducted in the Czech Republic showed great variability and adaptability of six tested varieties, out of which 'Fedora' and 'CS' were selected for further evaluation for energy and biochar production due to favourable yields of stem biomass (5.5 – 8.5 t DM/ha). Biochar produced from hemp biomass revealed texture properties which corresponded to quality commercial sorbents and met the limits related to the use in a variety of applications, e.g. soil amendment or water treatment. The economic analysis showed the advantage of residual biomass exploitation for the production of biochar, resp. for energy use as a by–product of the primary production of bioactive substances from Cannabis plants. The cost of obtaining 1 GJ of heat in the fuel is between 4.1 and 5 EUR, while another economic effect relates to the income from the sale of flowers for the extraction of bioactive substances. Concerning the conditions of the Czech Republic, the cost of biochar production from hemp biomass ranges, assuming the pyrolysis technology with the capacity 250 kg of raw biomass per hour, from 452 to 667 EUR/t (without excess heat utilization), and from 381 to 596 EUR/t (with excess heat utilization). [ABSTRACT FROM AUTHOR]