Solar‐powered microwave pyrolysis of corn stover for value‐added products and process techno‐economic assessment

Abstract

Microwave pyrolysis, powered by the solar photovoltaic (PV) electricity has been studied for safe and effective disposal of one of the abundantly available agro-residues that is, corn stover (CS) in India. The study focuses on maximizing the yields of value-added products that is, wood vinegar and biochar, because of their several applications in the agriculture and easy trading among the farmers with a scope of earning higher economic benefits. The effects of different levels microwave power, reaction time, and various concentrations of additive (biochar) on the yields of the pyrolytic products have been investigated. Under the optimal conditions of pyrolysis (input power of 700 W for microwave, pyrolysis reaction duration of 20 minutes and use of 5% additive from biochar), the yields of wood vinegar and biochar were measured to be 31 and 34 wt%, respectively, with the lower yields of both tars (9.64 wt%) and gas (25.2 wt%). The wood vinegar, obtained from the study, contained about 28%-32% acids, 10%-15% phenols, 18%-20% ketones, and 12% alcohol with the pH in the range of 2.94-3.21. The lower heating value (LHV) of biochar ranged from 22-27 MJ/kg. From the techno-economic and environmental assessment, the monthly income, payback period and quantity of CO 2 mitigation are estimated to be USD 44, 3.5 years and 25.6 tones in case of lab-scale set up and USD 44114, 1.7 years, and 20 549 tones for scaled-up production systems, respectively. These findings would contribute to diminish the greenhouse gases emissions, mitigate climate change, and help to derive economic benefits for the farmers along with the effective utilization of agro-residues.

Process optimization and technoeconomic environmental assessment of biofuel produced by solar powered microwave pyrolysis

“…The current study used a modified domestic microwave oven (LG, 28 L convection oven) with a 1-L cylindrical quartz reactor. The diagram of the experimental set-up, as well as other essential information on the experimental set-up and procedures followed, are detailed in our previous work 28 – 30 . Based on our prior work 4 , the experiments were conducted under different microwave powers of 500, 700, and 900 W and different ratios of AC additive (10, 20, and 30%) with a constant reaction time of 15 min.…”

“…For the calculation of the quantity of CO 2 emissions, it has been reported that about 1.5 kg of CO 2 is emitted into the environment by burning 1 kg of CS feedstock 1 , 2 . This quantity of CO 2 can be mitigated by applying the MAP process for the safe disposal of agricultural wastes like CS 28 , 29 . In addition, the coal-based thermal power plant generally produces about 0.98 kg of CO 2 /kWh.…”

“…Moreover, increased use of grid-electricity results in the indirect emission of harmful pollutants because its generation is mostly from coal-based thermal power plants, where the burning of coal produces greenhouse gases into the environment. Therefore, the integration of other sources of renewable energy, especially solar energy, as an input power for the MAP process has been found to be more feasible 28 , 29 .…”

Conversion of biomass into biofuel by microwave pyrolysis: Assessment of energy and exergy aspect

“…A modified domestic microwave oven (LG, 28 L convection oven), with 1-liter cylindrical quartz reactor was used in the current study. The microwave oven was operated at 2.45 GHz frequency with a maximum input power of 1200 W. 27 Figure 1 presents the diagram of the experimental set-up and other relevant information about the experimental set-up and the procedures followed as described in detail in our previous work. 34 A fixed amount of 60 g of feedstock without or with additive (10% of feedstock) was introduced into the reactor.…”

“…26 Thus, only the chemical energy and exergy have been included in the current study based on calorific values for bio-oil and biochar. 27 On the other hand, the bio-oil produced from MAP of CS has low quality in terms of low calorific value, 28 high oxygen contents 29 and poor chemical composition. 30 Also, biochar needs more improvements 31 in terms of improving its calorific 32 and its elemental composition.…”