Optimization of Enzyme Hydrolysis of Seafood Waste for Microwave Hydrothermal Carbonization

Significance Statement

Seafood processing operations generate enormous quantities of waste in the form of solid residues and liquid effluents. Currently there is an increasing demand for attractive seafood waste utilization strategies that could minimize environmental pollution while recovering products that are of commercial interest. Hydrothermal carbonization (HTC) is a technique that utilizes wet biomass to produce a solid product called hydrochar that has potential for wide applications in the field of energy, agriculture, and material science. Hydrothermal carbonization has been in use mainly to treat lignocellulosic biomass such as wood or agricultural waste. Recently, the Hydrothermal carbonization process has been gaining attention as an efficient waste management tool that can utilize high-moisture-containing complex waste streams, a mixture of lignocellulosic and nonlignocellulosic biomass, such as sewage and municipal waste. However, there is limited knowledge on the effectiveness of Hydrothermal carbonization on purely nonlignocellulosic industrial wastes such as seafood waste.

Here, we prove for the first time that purely nonligocellulosic wastes such as fish and shrimp waste could be utilized by Hydrothermal carbonization to produce a solid coal-like biofuel called hydrochar. By using an enzyme cocktail of Viscozyme, Lipase, and Protease, it was found that an enzyme ratio of 1:1:1 (w/w/w), and an enzyme concentration between 10 and 20% with a treatment time of 6 h, resulted in maximal hydrolysis of fish and shrimp waste. Subsequently, hydrochar and biocrude liquor were generated from hydrolyzed fish and shrimp waste by microwave hydrothermal carbonization (MHTC) using a high-pressure MiniWAVE Digestion Module (SCP Science, Canada) with quartz vessels at conditions of 150 °C for a 1 h reaction time.

The unique aspect of this method is the use of microwaves as the source of thermal energy required to drive the process.  Microwaves provide volumetric heating which minimizes heat transfer limitations and is also more rapid, energy efficient, and easier to control. Thus this study would potentially expand the use of Hydrothermal carbonization to other nonlignocellulosic wastes such as meat waste, and  leather industry waste.

Optimization of Enzyme Hydrolysis of Seafood Waste for Microwave Hydrothermal Carbonization, Renewable Energy Global Innovations

About the author

Shrikalaa Kannan is a PhD candidate at the Department of Bioresource Engineering, McGill. Her research combines two global challenges – increasing sustainability in the current energy technologies and reducing environmental pollution from bio-waste. Her work focuses on the generation of biofuels from bio-waste. 

About the author

Yvan Gariepy is a professional associate in the Department of Engineering, McGill. He is a senior engineer with expertise in a wide range of fields ranging from food security and food safety to microwave assisted thermal processes.

About the author

Dr. Vijaya Raghavan is a James McGill Professor at the Department of Bioresource Engineering, McGill University. He is presently the President-Elect of the Royal Society of the Canada Academy of Science, the Director of the Applied Science and Engineering division of Science of the Royal Society of Canada, and the President of the Canadian Society for Bioengineering.

Dr. Raghavan is involved in a wide range of research areas which includes post-harvest or post-production processes and technologies, food safety and security, electrotechnologies for food drying and storage, microbial fuel cells and biofuel production. 

Journal Reference

Energy Fuels2015, 29 (12), pp 8006–8016.

Shrikalaa Kannan, Yvan Gariepy, Vijaya Raghavan

Department of Bioresource Engineering, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec H9X 3V9, Canada

Abstract

Hydrothermal carbonization (HTC) is a promising technique that converts wet biomass into a coal-like material and has a wide application to the fields of energy, material science, and nanotechnology. Hydrothermal carbonization has been primarily used to treat a limited number of feedstocks, mainly lignocellulosic biomass such as wood. Recently, the Hydrothermal carbonization process has been utilized to treat high-moisture-containing complex waste streams, a mixture of lignocellulosic and nonlignocellulosic biomass, such as sewage and municipal waste. However, there is limited knowledge on the effectiveness of Hydrothermal carbonization on purely nonlignocellulosic industrial waste like seafood waste. Processing of seafood generates enormous amounts of waste in the form of solid residues and liquid effluents. Currently there is a demand for attractive seafood waste utilization strategies that minimize environmental pollution while recovering products that are of commercial interest to the industry. In this study, we have devised one such strategy where seafood waste is pretreated by enzymatic hydrolysis for subsequent Hydrothermal carbonization to produce hydrochar and biocrude liquor. Enzyme hydrolysis conditions including enzyme concentration, incubation time, and enzyme ratios were carefully optimized for maximal hydrolysis of seafood waste. By using an enzyme cocktail of Viscozyme, Lipase, and Protease, it was found that an enzyme ratio of 1:1:1 (w/w/w), and an enzyme concentration of 10–20% with a treatment time of 16 h, resulted in maximal hydrolysis of fish and shrimp waste. Subsequently, hydrochar and biocrude liquor were generated from hydrolyzed fish and shrimp waste by microwave hydrothermal carbonization (MHTC) using a high-pressure Mini WAVE Digestion Module (SCP Science, Canada) with quartz vessels at conditions of 150 °C for a 1 h reaction time. The results of this study show for the first time that MHTC can be successfully employed to produce valuable products from pure nonlignocellulosic waste like seafood waste. This would pave the way for effective utilization of other moisture-rich nonlignocellulosic industrial wastes.

Copyright © 2015 American Chemical Society

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