Ethanol production from industrial hemp: Effect of combined dilute acid/steam pretreatment and economic aspects

• Combined dilute acid and steam treatment as an effective method of hemp pretreatment.
• Optimal hemp pretreatment conditions: 180 °C and addition of 1% H2SO4 as a catalyst.
• Biomass pretreated at the optimal conditions indicated positive economic results.
• Cultivation type had no significant effect on pretreatment and ethanol fermentation.
• Hydrolysis of hemp cultivated organically proceeded quicker compared to conventional type.

In the present study, combined steam (140–180 °C) and dilute-acid pre-hydrolysis (0.0–2.0%) were applied to industrial hemp (Cannabis sativa L.), as pretreatment for lignocellulosic bioethanol production. The influence of the pretreatment conditions and cultivation type on the hydrolysis and ethanol yields was also evaluated. Pretreatment with 1% sulfuric acid at 180 °C resulted in the highest glucose yield (73–74%) and ethanol yield of 75–79% (0.38–0.40 g-ethanol/g-glucose). Taking into account the costs of biomass processing, from field to ethanol facility storage, the field-dried hemp pretreated at the optimal conditions showed positive economic results. The type of hemp cultivation (organic or conventional) did not influence significantly the effectiveness of the pretreatment as well as subsequent enzymatic hydrolysis and ethanol fermentation.