Sugarcane Bagasse Pyrolysis in a Carbon Dioxide Atmosphere with Conventional and Microwave-Assisted Heating

Bo-Jhih Lin,Wei-Hsin Chen

doi:10.3389/fenrg.2015.00004

Abstract

Pyrolysis is an important thermochemical method to convert biomass into bio-oil. In this study, the pyrolysis of sugarcane bagasse in a CO2 atmosphere under conventional and microwave-assisted heating is investigated to achieve CO2 utilization. In the microwave pyrolysis, charcoal is used as the microwave absorber to aid in pyrolysis reactions. The results indicate that the yields of pyrolysis products are greatly influenced by the heating modes. In the conventional heating, the prime product is bio-oil and its yield is in the range of 51-54 wt%, whereas biochar is the major product in microwave-assisted heating and its yield ranges from 61 to 84 wt%. Two different absorber blending ratios of 0.1 and 0.3 are considered in the microwave pyrolysis. The solid yield decreases when the absorber blending ratio decreases from 0.3 to 0.1, while the gas and liquid yields increase. This is attributed to more energy consumed for bagasse pyrolysis at the lower blending ratio. Hydrogen is produced under the microwave pyrolysis and its concentration is between 2 and 12 vol%. This arises from the fact that the secondary cracking of vapors and the secondary decomposition of biochar in an environment with microwave irradiation is easier than those with conventional heating.

Highlights

To date, the increasing concentrations of greenhouse gases (GHGs) in the atmosphere are a remarkable issue
It was reported (Yang et al, 2007; Chen et al, 2012) that the decomposition temperatures of hemicellulose, cellulose, and lignin were in the ranges of 200–315, 315–400, and 160–900°C, respectively, stemming from their inherent difference in lignocellulosic structure
It follows that the first peak exhibited at 319°C (Figure 2) is due to the thermal decomposition of hemicellulose in raw bagasse, while the second peak observed at 366°C is owing to the thermal degradation of cellulose

Summary

Introduction

The increasing concentrations of greenhouse gases (GHGs) in the atmosphere are a remarkable issue. Carbon dioxide has the biggest share of GHG emissions, so it is the most important contributor to the global warming, which has a serious impact on social, environmental, and economic costs (Bilgili, 2012; Chen, 2014). Biomass even acts as an atmospheric CO2 sink if it is associated with the carbon capture and storage (CCS) technology (Chen et al, 2013; Huang et al, 2013;Yin et al, 2013). A variety of thermochemical and biochemical methods have been developed for bioenergy. Pyrolysis is one of the thermochemical methods where biomass is thermally degraded to produce biofuels in the absence of oxidants or in a nitrogen environment. The operating temperature of pyrolysis is normally between 500 and 800°C (Carrier et al, 2011; Akhtar and Amin, 2012)

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Conclusion