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

Go To Energy Fuels

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

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.

Go To International Journal of Hydrogen Energy

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

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.

Go To Renewable Energy

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

Renewable Energy Global Innovations features: One-pot synthesis of hierarchical MnO2-modified diatomites for electrochemical capacitor electrodes

Significance Statement

The hierarchical and porous MnO₂-modified diatomite structures are prepared for the first time by a one pot hydrothermal method. We also demonstrate the synthesis of size- and shape-controlled MnO₂ nanostructures by replica molding from diatom silica structures for high-performance supercapacitors. The results show that birnessite-type MnO₂ nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Three types of hierarchical hollow MnO₂ patterns with different three-dimensional (3D) structures, shapes and large surface areas were successfully prepared from three diatom species by a template-assisted hydrothermal process. The extraordinary precision and nano-scale resolution of 3D replications of complex biological architecture from diatoms to artificial MnO₂ structures are confirmed. The electrochemical results demonstrate that the MnO₂-modified diatomite electrode exhibits highly reversible features, good rate abilities, and good cycle stability (95.92% over 5000 cycles) demonstrating the suitability of the low-cost MnO₂-modified diatomite structure as a potential electrode material for supercapacitors. 

About The Author

Dr. Yu Xin Zhang received his B. Eng. and M. Eng. in Chemical Engineering from Tianjin University in 2000 and 2003, respectively. He received his Ph.D degree in Chemical and Biomolecular Engineering from the National University of Singapore (NUS) in 2008, and continued to work as a research fellow in Prof. Hua Chun Zeng’s group at NUS till 2009. Now Dr. Zhang is a full professor of College of Materials Science and Engineering in Chongqing University. Dr. Zhang’s research interest is self-assembled nanostructures for energy storage materials and photocatalysts. 

Journal Reference

Journal of Power Sources. Volume 246, 2014, Pages 449-456.

Yu Xin Zhang ^1,2,*, Ming Huang¹, Fei Li¹ , their collaborators

Show Affiliations

1. College of Material Science and Engineering, Chongqing University, Chongqing 400044, P.R. China

2. National Key Laboratory of Fundamental Science of Micro/Nano-Devices and System Technology, Chongqing University, Chongqing 400044, P.R. China

Abstract

The hierarchical and porous MnO₂-modified diatomite structures are prepared for the first time by a one-pot hydrothermal method. The morphology and structure of MnO₂-modified diatomite hierarchical structures are examined by focus ion beam scanning electron microscopy (FIB/SEM) and X-ray diffraction spectroscopy (XRD). The results show that Birnessite-type MnO₂ nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Furthermore, the electrochemical properties of the MnO₂-modified diatomite electrodes are elucidated by cyclic voltammograms, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in 1 M Na₂SO₄ electrolyte. The electrochemical results demonstrate that the MnO₂-modified diatomite electrode exhibits highly reversible features and good rate abilities, respectively. Significantly, it exhibits the specific capacitance of 202.6 F g^-1 for the MnO₂-modified diatomite and 297.8 F g^-1 for the MnO₂ nanostructures after etching the diatomite. The capacitance retention of 95.92% over 5000 cycles further indicates the suitability of the low-cost MnO₂-modified diatomite structure as a potential electrode material for supercapacitors.

Go To Journal of Power Sources

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

Renewable Energy Global Innovations features: Self-Assembly of Mesoporous Nanotubes Assembled from Interwoven Ultrathin Birnessite-type MnO2 Nanosheets for Asymmetric Supercapacitors

Significance Statement

 Here, we develop a simple and cost-effective approach to prepare CuO@MnO₂ core-shell nanostructures without any surfactants and ultrathin MnO₂ nanosheets-built nanotubes have been fabricated via a large-scale chemical etching method. An asymmetric supercapacitor with CuO@MnO₂ core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide (MEGO) as the negative electrode yields an energy density of 22.1 Wh kg^-1 and a maximum power density of 85.6 kW kg^-1; the device shows a long-term cycling stability which retains 101.5% of its initial capacitance even after 10000 cycles. The MnO₂ nanotubes in a three-electrode system display much high specific capacitance (377.5 F g^-1 at current density of 0.25 A g^-1), good rate performance.

Moreover, an asymmetric supercapacitor on the basis of MnO₂ nanotubes as the positive electrode and activated graphenes (AG) as the negative electrode produced an energy density of 22.68 Wh kg^-1 and a maximum power density of 4.5 kW kg^-1. Such a facile strategy to fabricate the hierarchical CuO@MnO2 core-shell nanostructure and MnO₂ nanotubes with significantly improved functionalities opens up a novel avenue to design electrode materials on demand for high-performance supercapacitor applications. 

About The Author

Dr. Yu Xin Zhang received his B. Eng. and M. Eng. in Chemical Engineering from Tianjin University in 2000 and 2003, respectively. He received his Ph.D degree in Chemical and Biomolecular Engineering from the National University of Singapore (NUS) in 2008, and continued to work as a research fellow in Prof. Hua Chun Zeng’s group at NUS till 2009. Now Dr. Zhang is a full professor of College of Materials Science and Engineering in Chongqing University. Dr. Zhang’s research interest is self-assembled nanostructures for energy storage materials and photocatalysts. 

Journal Reference

Scientific Reports. Volume 4:4518, 2014.

Ming Huang¹, Yuxin Zhang^1,2, Fei Li¹, Lili Zhang³, Rodney S. Ruoff⁴, Zhiyu Wen² , Qing Liu¹

Show Affiliations

1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, P.R. China,

2. National Key Laboratory of Fundamental Science of Micro/Nano-Devices and System Technology, Chongqing University, Chongqing 400044, P.R. China,

3. Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Jurong Island 627833, Singapore, Department of
4. Mechanical Engineering and the Materials Science and Engineering Program, The University of Texas at Austin, One University Station C2200, Austin, Texas 78712, United States.

Abstract

Porous nanotubes comprised of MnO2 nanosheets were fabricated with a one-pot hydrothermal method using polycarbonate membrane as the template. The diameter and thickness of nanotubes can be controlled by choice of the membrane pore size and the chemistry. The porous MnO2 nanotubes were used as a supercapacitor electrode. The specific capacitance in a three-electrode system was 365 F g21 at a current density of 0.25 A g21 with capacitance retention of 90.4% after 3000 cycles. An asymmetric supercapacitor with porous MnO2 nanotubes as the positive electrode and activated graphene as the negative electrode yielded an energy density of 22.5 Wh kg21 and a maximum power density of 146.2 kW kg21; these values exceeded those reported for other MnO2 nanostructures. The supercapacitor performance was correlated with the hierarchical structure of the porous MnO2 nanotubes.

Go To Scientific Reports

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

Renewable Energy Global Innovations features: Optimization of the CeO2/CeCl3 cycle by cerium IV oxide reductive dissolution catalysis

Journal Reference

International Journal of Hydrogen Energy, Volume 40, Issue 39, 2015, Pages 13272–13280. 

Florent Lemont, Alisée Barbier, Samuel Resin

Commissariat à l’Energie Atomique (French Atomic Energy Commission) – DEN/DTCD/SCDV/LPIC, France

Abstract

While thermochemical cycles can be a way to produce hydrogen, physiochemical studies show that implementing them is often difficult for reactivity reasons. Most of the cycles actually involve solid–gas type systems with limited reactivity due to interface passivation processes. To overcome this difficulty, studies have shown that using the CeO₂/CeCl₃ pair, in which the cerium undergoes a reversible oxidation–reduction cycle, has enormous potential since it may partially be carried out in aqueous phase by reductive dissolution from cerium oxides (IV) to cerium chloride (III).

If the first reaction of the cycle is well known for industrial application, its second and its third reaction still need some investigation. Thus, this article primarily describes the work done on the second reaction to assess the possibility of carrying out cerium reduction in aqueous phase. The extremely positive results have highlighted the possibility of achieving 100% reaction efficiency in systems catalyzed by fluoride ions. Conducting the reaction with in-line distillation of the excess water also helps significantly reduce reaction time which offers good potential for the next stage. A ratio of 8 ml of a 20 w% HCl solution per gram of CeO₂ containing 6w% of CaF₂ leads to ensure a total reaction in a few minutes at 108.6 °C (boiling temperature of the H₂O–HCl azeotrope).

The work presented herein also describes a brief feasibility study for the third reaction cycle which could be carried out by spraying the solution from the second reaction, in a hot column whose temperature will be determined by further work. These results have allowed upgrading the first flowsheet proposed in a previous publication.

Go To International Journal of Hydrogen Energy

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

Renewable Energy Global Innovations features: Performance of mixed LED light wavelengths on biogas upgrade and biogas fluid removal by microalga Chlorella sp.

Significance Statement

Biogas is the most important renewable energy resource that attracts attention all around the world. In Europe, the biogas production increases from 1.18 million MMBtu d^-1 in 2010 to 1.46 million MMBtu d^-1 in 2013, while the total biogas potential is estimated as 16 million MMBtu d^-1. In China, the biogas production of small scale projects raises from 180 million m³ in 1996 to 1000 m³ in 2007, and the medium and large scale biogas projects raises from 12 billion m³ in 1996 to 600 billion m³ in 2007.

Raw biogas usually consists of methane (CH₄, approximately 60 vol. %), carbon dioxide (CO₂, approximately 40 vol. %), and other trace compositions including hydrogen sulfide (H₂S), water vapor, etc. However, the relatively high concentration of CO₂ in raw biogas will lower its heat content as well as increase its energy demand of compression and transportation usage. The biogas upgrading is removing CO₂ from raw biogas. It is the precondition for biogas high efficient usage. When the CO₂ content in the biogas is decreased, the CH₄ concentration in the biogas is increased. The biogas CH₄ concentration should be upgraded to at least higher than 90% (vol. %) to meet the criterion for using as fuel for vehicles or even substitute for natural gas.

There are several biogas upgrading techniques that have been widely applied nowadays, including absorption of liquids with physics/chemical adsorbent, membranes separation, pressure swing adsorption, and cryogenic separation. However, they usually need high capital cost when build construction and consume a large amount of energy during treating process. This makes above mentioned techniques achieve high economic benefit only when they are used in large-scale industrial biogas projects. Most of these techniques also require complicated operating systems, and produce unwanted end products that need further treatment or result in secondary pollution. Further, the CO₂, which removed from the raw biogas, is always discharged into the atmosphere as greenhouse gas in these techniques. In addition, most physical/chemical technologies for CO₂ removal require a prior removal of H₂S.

An alternative technique to upgrade biogas is to use photosynthetic CO₂ uptake by microalgae. Microalgae have high carbon fixation ability and rapid growth rate, and can be adapted to various environmental conditions. When microalgae are utilized for biogas upgrading, the photosynthesis can efficiently convert CO₂ in raw biogas into its biomass. This allows the valorization of biogas CO₂ in the form of a valuable microalgae biomass, which can be used as feedstock to produce biofuels or even high value-added by-product. Anaerobic digestion not only produce raw biogas, but also nutrient-rich waste stream, called biogas slurry, which can be uptake freely during microalgae growth process and made the major contribution to the nitrogen and phosphorus removal from biogas slurry wastewater. Therefore, removing CO₂ from raw biogas by culturing microalgae with biogas slurry is a highly potential technique for simultaneous biogas upgrading and biogas slurry decontamination.

However, as far as we know, there is a little literature available about the simultaneously biogas upgrading and biogas slurry decontamination by using of the photosynthetic CO₂ uptake of microalgae, particularly about its effects under various light intensities and wavelengths. Therefore, this research focused on the effects of various LED artificial light source’s light wavelengths, light intensities, and photoperiods on biogas upgrading and simultaneously biogas slurry decontamination by using of microalgae photo bioreactor. Furthermore, the most appropriate light wavelength was discussed. The lighting control strategy was also optimized by analyzing the microalgae growth, as well as the efficiencies of biogas CO₂ removal and simultaneously biogas slurry decontamination under various light intensities and photoperiod’s treatments.

About The Author

Associate professor Dr. Cheng YAN comes from the Department of Environmental Science and Engineering, School of Environmental Studies, China University of Geosciences (Wuhan), No. 388 Lumo Road, Hongshan District, Wuhan 430074, Hubei Province, PR China.

Dr. Cheng YAN focused on Bioenergy with Carbon Capture and Storage (BECCS). He developed several Negative Emission Technologies (NETs), which involve CO₂ capture by biological processes from diffuse and point sources, atmospheric CO₂ capture by microalgae, microalgae as bio-agent for CO₂ mitigation, and CO₂ emission valorization. He also pays close attention to optimizing microalgae photo-bioreactor with artificial lighting system, and upgrading biogas by microalgae system. The research field about purifying anaerobic fermentation slurry by microalgae is also interested.

Dr. Cheng YAN has already published 17 academic papers (10 as the first author, 1 as the second author, and other 6 as cooperator) in refereed international JCR publications in English. He is keen on academic exchanges and participated in several academic international conferences in Barcelona, Prague, Dublin, and Singapore.

Journal Reference

Applied Energy, Volume 178, 15 September 2016, Pages 9–18. 

Cheng Yan^1,2, Liandong Zhu³, Yanxin Wang²

Show Affiliations

1. Laboratory of Basin Hydrology and Wetland Eco-restoration, China University of Geosciences (Wuhan), Wuhan 430074, China
2. Department of Environmental Science and Engineering, School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan 430074, China
3. Faculty of Technology, University of Vaasa, FI65101 Vaasa, Finland

 

Abstract

Anaerobic digestion not only produces raw biogas which needs to be upgraded, but also nutrient-rich waste stream biogas slurry which needs decontamination. Therefore, this research focused on the effects of various light wavelengths, light intensities, and photoperiods on biogas upgrading and simultaneously biogas slurry decontamination by using of microalgae photobioreactor. The microalgae photobioreactor was a transparent polyethylene bag (80 cm × 60 cm × 11 cm). The results demonstrated that biogas upgrading and simultaneously biogas slurry decontamination was successfully achieved by the use of the photosynthetic CO₂ uptake by microalgae photobioreactor. The optimal light wavelength was the mixed LED red:blue = 5:5; whereas the optimized lighting control strategy was: low light intensity (300 μmol m⁻² s⁻¹) with long photoperiod (16 h light:8 h dark) for the time course of 0–48 h, moderate light intensity (600 μmol m⁻² s⁻¹) with middle photoperiod (14 h light:10 h dark) for the time course of 48–96 h, and high light intensity (900 μmol m⁻² s⁻¹) with short photoperiod (12 h light:12 h dark) for the time course of 96–144 h. Its biogas CO₂ removal efficiency was 85.46 ± 6.25%. Its removal efficiency of chemical oxygen demand, total nitrogen, and total phosphorus were 85.23 ± 8.32%, 87.10 ± 7.55%, and 92.40 ± 3.05%, respectively.

Go To Applied Energy

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)