Renewable Energy Global Innovations features: 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.

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 Fuels, 2015, 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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Renewable Energy Global Innovations features: Operation of an inexpensive bipolar alkaline electrolyser producing a mix of H2/O2 fuel

Significance Statement

The objective of this work was to develop a low cost and portable device to produce an alternative form of fuel or a fuel that can be used to improve combustion efficiency on internal combustion engines and reduce emissions of PM, CO, CO2 and NOx with an incentive to users of improved fuel efficiency. A technology suitable for the users of today.

Much research work is available on Hydrogen IC engines, water injection, and emulsified fuel but few have been shown to address suitability for use on heavy goods vehicles and public transport. Water injection has been shown to reduce combustion temperature and thereby reduce harmful NOx emissions but a practical device has not yet materialised. Emulsified fuel (water in diesel) is currently in use for public transport in some European cities and is generally used in conjunction with hydrogen. This emulsified fuel has limited applications as it is unstable and will separate and is therefore only suitable for high fuel users. Its use has been shown to substantially reduce particulates and NOx emissions.

The cost of going “Green” will remain a burden on taxpayers and users of public transport. London Transport are using some electric buses and for every route two buses are required as one must stop to recharge. Governments continue to impose carbon taxes instead of funding a solution.

On most commercial and industrial electrolysers, the catalyst used is 25%/35% wt/wt potassium hydroxide (KOH) and in this volume the gas cannot be used in engines due to corrosion.

The methodology in this work was to identify a balance between the multiple variables involved in water electrolysis which include a suitable low cost electrode, electrode surface area, variable voltage, current density, electrical resistance, temperature and the type and volume of electrolyte. Reliability of such device and with no electrode erosion could only be achieved with minimal electrolyte concentration and with a low current density.

The design result was achieved by using low cost stainless steel electrodes in a bi-polar configuration whereby electrodes are of solid state in the absence of any perforations and with exposed perimeter edges concealed from the electrolyte, to avoid current loss. This was achieved by the slotted gables in the polypropylene enclosure. When power is applied the top edge of electrodes become exposed in a gas void. An electronic controller was developed in-house and is used to control current/ gas volume to a prescribed setting. The initial voltage per electrode is 2.3 volts which ensures a fast warm up of the electrolyte and as it begins to heat, the voltage reduces by change in resistance, which improves energy efficiency as the electrolyte heats to approx. 60 deg C. We are now producing a combustible gas of H2/O2 which has almost three times more heat energy than gasoline but we also have a form of water injection with the vapour.

This result can be achieved with 0.12M KOH catalyst with laboratory analysis showing no trace in the evolved gas and therefore will not cause engine corrosion. This was also confirmed by analysis of the electrolyte after hours of operation when electrolyte had depleted and the catalyst concentration increased. This result is of particular interest to users as replenishment is carried out with de-ionised water only.

The polypropylene enclosure is designed to accommodate a PEM to separate the oxygen from the evolved gas to permit storage of the H2. Due to the high efficiency the gas can now be produced using solar PV. Testing has been carried out on most vehicles types and the result is significant.

The new administration in the Irish Government has shown considerable interest and we are ready to commence trials using the Reformer on Public Transport where efficiency and emissions testing will be carried out by an independent specialist. 

About The Author

Professor John Cassidy was awarded a diploma in Applied Science by Dublin Institute of Technology, his BSc (Applied Sciences) by University of Dublin, and completed his PhD at the University of Utah, USA. He has since lectured in Analytical Chemistry in DIT, Kevin Street. He was appointed Assistant Head of School in 2001 and awarded Professorship of DIT in 2009.

His research interests include Analytical Chemistry and Instrumentation. This involves the theory and operation associated with Modern Analytical Instruments in the area of spectroscopy, electrochemistry and chromatography. 

 

Journal Reference

International Journal of Hydrogen Energy, Volume 41, Issue 4, 2016, Pages 2197-2201.

Cian O’Reilly¹, Michael Farrell², David Harvey³, John Cassidy¹

Show Affiliations

1. School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin D08 NF82, Ireland
2. School of Electrical and Electronic Engineering, Dublin Institute of Technology, Kevin Street, Dublin D08 NF82, Ireland
3. NuNrg Reformers Ltd, Fardrum, Athlone, Co., Westmeath, Ireland

Abstract

This paper describes the operation of a bipolar alkaline electrolyser which is at least 60% efficient at evolving a hydrogen/oxygen mix. The electrolyser consists of 12 stainless steel (SS316L) electrodes of area 5400 cm² in a sealed polypropylene unit. A pulsed potential waveform is applied to the electrodes in 0.12 M KOH electrolyte yielding on the order of 320 dm³/kWh of the hydrogen/oxygen mix. This compares favourably with commercial devices that are designed to yield hydrogen alone.

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Renewable Energy Global Innovations features: Multiscale modeling and performance analysis of evacuated tube collectors for solar water heaters using diffuse flat reflector

Significance Statement

The deployment rate of solar water heaters (SWHs) is rapidly increasing for various domestic, industrial and commercial applications. Among stationary solar collectors, evacuated tube collectors (ETCs) have captivated more attention because of their satisfactory performance, reliability and cost-effectiveness.

However, using ETCs for various solar water heaters may endure deficits in collecting the necessary thermal energy for water heating particularly in cold seasons. This is because of the cylindrical shape of evacuated tubes which makes the upper circumference of the cylinder is directly exposed to sunrays, while the lower circumference usually misses the beam and also most of the diffuse irradiance.

This study highlights the role of installing a diffuse flat reflector (DFR) layer at the back of ETC array to improve heat capture rate. A comprehensive and generic model in computing solar thermal gain, annual fuel/electricity savings, and small-scale technology certificates (STCs) is developed. While this model is optimized for a promising energy saving compared to the conventional ETC-SWHs in four Australian solar zones, it can be custom-designed for any thermal load at any location worldwide.

This model is able to optimize the azimuth/tilt angles and be sized for the highest annual/seasonal achievable performance. The outcome of this research demonstrates a tangible techno-economic feasibility for many solar water heaters applications. 

About The Author

Dr Dia Milani is currently the energy team leader in the Laboratory for Multiscale Systems (LMS) at the University of Sydney. He obtained a M.S. degree in Environmental Engineering Management from UTS in 2006, a Graduate Certificate in Innovation & Enterprise in 2011, and PhD in Chemical Engineering in 2012 from The University of Sydney.

His research focus is at the water-energy-carbon interfaces with primary emphasis on novel technologies in renewable energy, thermal energy storage, carbon capture, CO₂ utilization, waste management, and solar-assisted power cycles.

About The Author

Associate Professor Ali Abbas received both his Bachelors and PhD in Chemical Engineering from University of Sydney, Australia. He has held academic appointments at Nanyang Technological University (NTU), and UNSW Asia in Singapore before joining, in 2007, the School of Chemical and Biomolecular Engineering at the University of Sydney. His engineering research and expertise is in the area of Process Systems Engineering with emphasis on model-based optimal operation of energy, particulate and bio-systems.

In 2008, A/Prof. Abbas was awarded the PSE Model-based innovation prize (London, UK) recognizing his work in model-based optimal process operations. He was later awarded the Australia-Harvard Fellowship in 2011 as well as the Academy of Technological Sciences and Engineering (ATSE) Fellowship (Australia-China Future Leader in Clean Coal Technologies) in 2012.

He has strong interests in engineering science education with particular focus on curriculum design and integration as well as on experiential e-learning and virtual worlds.

Journal Reference

Renewable Energy, Volume 86, 2016, Pages 360-374.

Dia Milani, Ali Abbas

School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia

Abstract

Using evacuated tube collectors (ETCs) in solar water heaters (SWHs) may endure deficiencies (i.e. in winter season) in collecting the necessary thermal energy for water heating. This is because of the cylindrical shape of evacuated tubes which makes the upper circumference of the cylinder is directly exposed to sunrays, while the lower circumference usually misses the beam and also most of the diffuse irradiance.

In this paper, the role of using a diffuse flat reflector (DFR) at the back of ETC array to improve heat capture rate is examined. A comprehensive model to estimate the annual energy savings and small-scale technology certificates (STCs) is developed. This model is applied on four major Australian cities representing four Australian solar zones. The tilt and azimuth angles for these four zones are optimized.

This optimal setting along with DFR presence could improve the STC entitlements by 14.6% for zone 1; 20.2% for zone 2; 25.9% for zone 3; and 27.9% for zone 4, respectively. This specific-tailored model may increase the annual energy saving up to 95.8% for zone 1; 91.3% for zone 2; 81% for zone 3; and 74% for zone 4 correspondingly.

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