Comparative study of high-pressure homogenization and alkaline-heat pretreatments for enhancing enzymatic hydrolysis and biogas production of grass clipping

• HPH and NaOH-heat pretreatments enhanced enzymatic digestibility of grass clipping.
• HPH pretreated grass clipping can yield more biogas in shorter time.
• HPH is a promising pretreatment method of biomass for biogas production.

High-pressure homogenization (HPH) and alkaline-heat were both used to pretreat grass clipping in order to improve the efficiency of enzymatic hydrolysis and biogas production. Results showed that both methods were very effective. HPH and alkaline-heat pretreated grass clipping yielded 230.39 and 415.93 mg g−1 reducing sugar with enzymatic hydrolysis, showing 37.82% and 148.81% increase respectively. HPH and alkaline-heat pretreated grass clipping produced 418 and 405 ml biogas in anaerobic digestion respectively, both around 2.5 times higher than that of the control. Furthermore, both pretreated samples produced biogas immediately while the control had a two-day delay. HPH could produce more biogas in a shorter time and it could be operated in room temperature and needs no chemical, implying that HPH could be an effective pretreatment of biomass for biogas production.