Acid-Catalyzed Wet Torrefaction for Enhancing the Heating Value of Barley Straw

Antonios Nazos,Elias Sakellis,Dimitrios Sidiras,Panagiotis Grammelis

doi:10.3390/en13071693

Abstract

In the present study, the possibility of improving the higher heating value (HHV) of lignocellulosic biomass, especially barley straw, was examined. The research deals with the treatment of barley straw by acid-catalyzed wet torrefaction (ACWT), also called acid hydrolysis, in a batch reactor (autoclave) Parr 4553 3.75 L. In this case, two different simulation approaches were applied: (i) combined severity factor (CSF) and (ii) response surface methodology (RSM) based on Box–Behnken design of experiments (DoE). Sulfuric acid (SA) concentration, temperature and time were the ACWT parameters examined herein. An oxygen bomb calorimeter was used for the HHV measurement. The findings indicated that the composition changes of the straw due to ACWT had a significant effect on the HHV of the pretreated material. In this study, treatment conditions were 10–35 mM SA, 160–200 °C and an isothermal reaction time 0–40 min (preheating period not included in these values). In conclusion, there was a significant increase in the HHV up to 24.3 MJ/kg for the ACWT barley straw, compared to 17.5 MJ/kg for the untreated straw, at optimal conditions of 200 °C for 25 min (isothermal period) and 35 mM SA. This resulted in a 1.39 enhancement factor (EF) and 68% energy yield (EY).

Highlights

The increase in worldwide energy demand has a significant effect on the fossil fuel contribution to environmental pollution and climate change, provoking a global interest in the use of environmentally friendly, renewable fuels [1,2]
The surface of the solid residue of untreated barley straw (Figure 6a,c,e) and the acid-catalyzed wet torrefaction (ACWT)-treated one Figure 6b,d,f) was observed by a Scanning electron microscopy (SEM), in the order to observe the physical changes in the structure of barley straw
It was shown that ACWT has the potential to convert biomass such as barley straw into biofuel with enhanced thermal, chemical and physical fuel properties compared to raw barley straw

Summary

Introduction

The increase in worldwide energy demand has a significant effect on the fossil fuel contribution to environmental pollution and climate change, provoking a global interest in the use of environmentally friendly, renewable fuels [1,2]. Renewable biomass is one of the emerging energy resources with high potentials that can balance CO2 emissions [3]. Lignocellulosic biomass is currently a major energy source for fossil fuel partial substitution [4,5,6]. Biomass contributes about 10% of the global annual energy production [7,8]. Biomass attracts considerable research interest in order to meet the increasing future sustainable energy demand [9]. Electricity, fuel, chemicals and other high added value products can be produced from biomass [7,9]

Methods

Results

Conclusion