Biomass Pretreatment with the Szego Mill™ for Bioethanol and Biogas Production

Merlin Raud,Lisandra Rocha-Meneses,Vahur Rooni,Olev Träss,Timo Kikas,Kaja Orupõld

doi:10.3390/pr8101327

Abstract

Results from an investigation of the mechanical size reduction with the Szego Mill™ as a pretreatment method for lignocellulosic biomass are presented. Pretreatment is a highly expensive and energy-consuming step in lignocellulosic biomass processing. Therefore, it is vital to study and optimize different pretreatment methods to find a most efficient production process. The biomass was milled with the Szego Mill™ using three different approaches: dry milling, wet milling and for the first time nitrogen assisted wet milling was tested. Bioethanol and biogas production were studied, but also fibre analysis and SEM (scanning electron microscope) analysis were carried out to characterize the effect of different milling approaches. In addition, two different process flows were used to evaluate the efficiency of downstream processing steps. The results show that pretreatment of barely straw with the Szego Mill™ enabled obtaining glucose concentrations of up to 7 g L−1 in the hydrolysis mixture, which yields at hydrolysis efficiency of 18%. The final ethanol concentrations from 3.4 to 6.7 g L−1 were obtained. The lowest glucose and ethanol concentrations were measured when the biomass was dry milled, the highest when nitrogen assisted wet milling was used. Milling also resulted in an 6–11% of increase in methane production rate during anaerobic digestion of straw.

Highlights

According to revised Renewable Energy Directive published in 2018, the European Union (EU)set a goal to become a global leader in the field of renewable energy
Size distribution of straw samples ground with a cutting mill and the Szego MillTM are given in Effect of Milling
The Szego MillTM was more efficient for particle size reduction than the cutting mill, which can be whereas with the Szego MillTM size fractions 0.5–1 mm and 0.25–0.5 mm were dominant (Figure 3)

Summary

Introduction

According to revised Renewable Energy Directive published in 2018, the European Union (EU). Set a goal to become a global leader in the field of renewable energy. To gain this target, the directive establishes a new and binding target for renewable energy for the EU for 2030 of at least 32%. As the goal is to shift the transport sector from fossil fuel use to the use of different fuel mixtures with a larger fraction of different biofuels, such as bioethanol and biodiesel. Biofuel target in transport sector is planned to be covered with biomethane produced by anaerobic digestion of local biomass. Shows potential in laboratory conditions, the large-scale and cost-effective production of cellulosic biofuels is still hindered by several technical barriers. There is an urgent need for research and development of new and Processes 2020, 8, 1327; doi:10.3390/pr8101327 www.mdpi.com/journal/processes

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