Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Dr. Franco Berruti

Abstract

Miscanthus, an invasive crop, has recently gained attention as an emerging energy crop because of certain features such as adaptability to lower temperature, efficient use of water and nutrients, low or no need of nitrogen fertilizers, high biomass yield, fast growing cycle and less intensive agricultural cultivation practices than other energy crops, such as corn.

The literature review is focused on the value-added applications and conversion of Miscanthus for bioenergy and biomaterial applications. The thermochemical conversion technologies reviewed in this chapter include pyrolysis, liquefaction, torrefaction and gasification, whereas biochemical conversion technologies include enzymatic saccharification and fermentation.

In this work, Miscanthus was selected as the feedstock for fast pyrolysis carried out in a mechanically fluidized bed reactor at three temperatures (400, 450 and 500°C) and three vapor residence times (1.4 s, 2.7 s and 5.2 s). Miscanthus was efficiently converted to energy-rich bio-oil and value-added biochar through fast pyrolysis. Fast pyrolysis performed at 450°C with 1.4 s of vapor residence time gave the highest yield of bio-oil (> 50 wt%). The biochar obtained at variable pyrolysis temperatures were also activated at 900°C for 1.5 h under CO2 atmosphere to enhance its value as a potential adsorption agent for pollutants.

Several characterization techniques were used to study the bio-oils, biochars and activated biochars obtained from the pyrolysis of Miscanthus. The absorption of methylene blue as a model dye (wastewater pollutant) was done to evaluate the performance of activated biochar versus the biochar precursors. Both pyrolysis and physical activation complemented each other as new technologies for energy extraction and material synthesis from Miscanthus.

Summary for Lay Audience

There are several environmental concerns relating to fossil fuels, increasing energy demands and pollution problems. In order to address these issues, alternative green fuels produced from biomass and wastes seem to be a sustainable option. In this study, Miscanthus was used as an energy crop to produce biofuels and bioproducts. Miscanthus, which is an invasive plant is considered energy crop due to some salient features such as adaptability to lower temperature, efficient use of water and nutrients, low or no need of nitrogen fertilizers, high biomass yield, fast growing cycle and less intensive agricultural cultivation practices than other energy crops. Thermochemical conversion technology such as pyrolysis was used to extract value out of this energy crop. Pyrolysis is a process in which thermal decomposition of biomass and organic wastes occurs in the absence of oxygen to produce condensable vapors (bio-oil), biochar and non-condensable gases. Pyrolysis can be slow, fast or intermediated depending upon the vapour residence time, heating rate and temperature used during the process. Maximum bio-oil yield from Miscanthus was obtained at higher heating rates and short residence times, whereas higher yields of biochar were obtained at longer residence times and short heating rates. The biochar was further activated at higher temperatures to produced activated biochar for use in environmental remediation. Various characterization techniques were used to study the bio-oils, biochars and activated biochars obtained from the fast pyrolysis of Miscanthus. The absorption of methylene blue as a model dye was done to evaluate the performance of activated biochar versus the biochar precursors. Both pyrolysis and physical activation complemented each other as new technologies for energy extraction and material synthesis from Miscanthus.

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