1. Chemical & Biological Engineering ‘Engineering from Molecules’ Microbubbles: an energy-efficient way to accelerate biofuel production Will Zimmerman Professor of Biochemical Dynamical Systems Chemical and Biological Engineering, University of Sheffield with Dr Hemaka Bandulasena and Dr Jaime Lozano-Parada, with Mr Kezhen Ying and Mr James Hanotu and special thanks to Professor Vaclav Tesar, Dr Buddhi Hewakandamby, and Mr Olu Omotowa (all formerly University of Sheffield researchers).

2. Chemical & Biological Engineering ‘Engineering from Molecules’ Outline Why and how microbubbles? ALB concept Performance studies Steel stack gas trials Advantages for microbial and mammalian cell ALBs Ozone plasma microreactor in the lab (oxidation, lysing cells) Prototype designs

3. Chemical & Biological Engineering ‘Engineering from Molecules’ Why microbubbles? Nine fundamental processes intensified including Faster mass transfer -- roughly proportional to the inverse of the diameter Flotation separations -- small bubbles attach to particle / droplet and the whole floc rises Steep mass transfer enhancement.

4. Chemical & Biological Engineering ‘Engineering from Molecules’ The Fluidic oscillator Mid Ports Inlet Outlets Linked by a feedback Loop What is it? No moving part, Self-excited Fluidic Amplifier.

5. Chemical & Biological Engineering ‘Engineering from Molecules’ Fluidic oscillator makes microbubbles! 20 micron sized bubbles from 20 micron sized pores Rise / injection rates of 10 -4 to 10 -1 m/s without coalescence: uniform spacing/size Watch the videos! Same Diffuser

6. Chemical & Biological Engineering ‘Engineering from Molecules’ Relatively large coalescent and fast rising bubbles Production of Mono-dispersed Uniformly spaced, non-coalescent Microbubbles Gas Inlet Conventional Continuous Flow Oscillatory Flow

7. Chemical & Biological Engineering ‘Engineering from Molecules’ Bubble size distribution Fine mist of bubbles rising from Micropore Technologies Metallic membrane diffuser Median: 47 microns Standard deviation: 20 microns 20 micron sized pores

8. Chemical & Biological Engineering ‘Engineering from Molecules’ Energetics from pilot plant Suprafilt layout for 30m^3/h Master-slave amplifier system for fluidic oscillator Oscillatory flow draws less power than steady flow at the same throughput ! Current draw with varying volumetric flowrate and feedback loop length

9. Chemical & Biological Engineering ‘Engineering from Molecules’ Air lift loop bioreactor design Schematic diagram of an internal ALB with draught tube configured with a tailor made grooved nozzle bank fed from the two outlets of the fluidic oscillator. The microbubble generator is required to achieve nearly monodisperse, uniformly spaced, non-coalescent small bubbles of the scale of the drilled apertures. Journal article has won the 2009 IChemE Moulton Medal for best publication in all their journals. Designed for biofuels production First use: microalgae growth Current TSB / Corus / Suprafilt grant on carbon sequestration feasibility study on steel stack gas feed to produce microalgae.

10. Chemical & Biological Engineering ‘Engineering from Molecules’ Construction Body / side view Top with lid Inner view: Heat transfer coils separating riser /downcomer. Folded perforated Plate  -bubble generator. Replaced by Suprafilt 9inch diffuser

11. Chemical & Biological Engineering ‘Engineering from Molecules’ Growing algae in the lab Internal of the ALB The gas separator section links the riser to the downcomer at the top, permitting gas disengagement and recirculation of fluid. Consequently, this drives a flow from the top of the riser to the bottom. Dunaliella salina

12. Chemical & Biological Engineering ‘Engineering from Molecules’ Gas Dissolution Day 10 Day 3

13. Chemical & Biological Engineering ‘Engineering from Molecules’ Biomass Concentration Algal biomass / bioenergy production (~30% extra biomass from CO 2 microbubble dosing for only 1 hour per day).

14. Chemical & Biological Engineering ‘Engineering from Molecules’ Algal bioreactor challenge and market AIMS - To investigate the feasibility of growing microalgae using CO 2 rich steel plant exhaust gas - To investigate the performance of an airlift loop bioreactor (ALB) with microbubble technology Potential markets Carbon capture in biomass (worst case: fertilizers!) Integrated waste management Nutraceuticals (food additives) Fish and animal feed Bioplastics and other organic / fine chemical co-products Biofuels

15. Chemical & Biological Engineering ‘Engineering from Molecules’ Methodology Challenges in Algal Cultivation Carbon dioxide supply Oxygen removal Light limitation Mixing Contamination This photobioreactor is designed to facilitate high algal growth within a short period of time by improving its transport processes. For best possible carbon capture and biofuel production, high biomass concentrations are preferred. Key design features CO 2 dissolution and O 2 stripping is substantially improved by microbubbels. Air lift loop design promotes vertical mixing of algae – keeps all algae suspended in the reactor while bringing them to lighted surfaces regularly. Designed as a closed system to avoid contamination. Airlift loop effect Volume = 2m 3 ( 1.5m X 1.3m X 1m )

16. Chemical & Biological Engineering ‘Engineering from Molecules’ Field trials Corus: steel plant algal culture Aecom: separation/harvesting Oxyfuel integration with CLCC. Approximately 1 cubic metre cube design with 0.8 m 2 square ceramic microporous diffusers.

17. Chemical & Biological Engineering ‘Engineering from Molecules’ Key Findings/results Two trials were carried out with Dunaliella salina using power plant exhaust gas as the carbon source. Second trial was run for three weeks with improved operating conditions compared to the first trail, which was only run for two weeks. Inlet and outlet CO 2 and O 2 concentrations were measured by FTIR. The difference between red curves shows CO 2 uptake while the difference between blue curves shows O 2 stripping rate. Supra-exponential growth

18. Chemical & Biological Engineering ‘Engineering from Molecules’ Probing operation

19. Chemical & Biological Engineering ‘Engineering from Molecules’ Pseudosteady operation

20. Chemical & Biological Engineering ‘Engineering from Molecules’ Next Steps Installing microbubble generators in algal bioreactor company’s pilot plants and other types of bioreactors. Catalyzing the next generation pilot plant to produce co- products and biofuels by assembling leading edge unit operations such as artificial lighting (AAT), dewatering (UoS), ultrasonic milking (NPL), microwave pyrolysis (York) and esterification intensification (CSL). When could it become commercially viable? Biofuels still need a large cost reduction. Nutraceuticals? NOW

21. Chemical & Biological Engineering ‘Engineering from Molecules’ Features From the other experiments, Microbubbles formed from fluidic oscillation draw 18% less electricity than the same flow rate of steady flow forming larger bubbles. 1.5-2 bar gauge pressure needed. 3-4 fold better aeration rates with ~300-500 micron bubbles, up to 50 fold larger with 20 micron sized bubbles Very low shear mixing is possible at low injection rates (rise rate 10 -4 m/s ) From the air-lift loop bioreactor performance, Microbubbles dissolve CO 2 faster and therefore increase algal growth. Microbubbles extract the inhibitor O 2 produced by the algae from the liquid so that the growth curve is wholly exponential. Algal culture with the fluidic oscillator generated bubbles had ~30% higher yield than conventionally produced bubbles with only dosing of one hour per day over a two week trial period. Bioenergy could become a more attractive option in the recycling of the high concentration of CO 2 emissions from stack gases (ongoing field trials).

22. Chemical & Biological Engineering ‘Engineering from Molecules’ Ozone Kills and mineralizes! Ozone dissolves in water to produce hydroxyl radicals Hydroxyl radical attacks bacterial cell wall, damages it by ionisation, lyses the cell (death) and finally mineralises the contents. One ozone molecule kills one bacterium in water!

23. Chemical & Biological Engineering ‘Engineering from Molecules’ Microfluidic onchip ozone generation Our new chip design and associated electronics produce ozone from O 2 with key features: 1. Low power. Our estimates are a ten-fold reduction over conventional ozone generators. 2. High conversion. The selectivity is double that of conventional reactors (30% rather than 15% single pass). 3.Recently discovered strong irradiation in UV “killing zone” of ~300 nm. 4.Operation at atmospheric pressure, at room temperature, and at low voltage (170V, can be mains powered).

24. Chemical & Biological Engineering ‘Engineering from Molecules’ Plasma discs 25 plasma reactors each with treble throughput over first microchip

25. Chemical & Biological Engineering ‘Engineering from Molecules’ Dosing lance assembly Axial view of the old lance With 8 or 16 microdisc reactors New lance = 70 microdisc reactors Quartz for UV irradiation

26. Chemical & Biological Engineering ‘Engineering from Molecules’

27. Chemical & Biological Engineering ‘Engineering from Molecules’ Consequences Our low power ozone plasma microreactor can be inserted into the microporous diffusers to arrange for ozone dosing on demand in an ALB, for sterilization or other uses. One potential use is providing a non-equilibrium driving force for biochemical reaction / biomass growth by breaking down extracellular metabolites secreted by microorganisms to minerals (CO2, H2O, nitrates, phosphates etc.) by UV-ozone providing a strong oxidizing environment in situ.

28. Chemical & Biological Engineering ‘Engineering from Molecules’ More Acknowledgements Corus: Bruce Adderley, Mohammad Zandi and many more. Suprafilt: Graeme Fielden, Jonathan Lord, and Hannah Nolan Micropore Technologies: Mike Stillwell HP Technical Ceramics: Tim Wang AECOM DB: Brenda Franklin, Ben Courtis, Hadi Tai Yorkshire Water: Martin Tillotson, Ilyas Dawood UoS: Jim Gilmour, Raman Vaidyanathan, Simon Butler, Graeme Hitchen, Adrian Lumby, Stuart Richards, Clifton Wray, Andy Patrick Yorkshire Forward, TSB, EPSRC, SUEL