Optimizing Algaeculture for the Production of Biofuels Presented by: Tim C. Keener, Ph.D. Department of Biomedical, Chemical, and Environmental Engineering University of Cincinnati Cincinnati, Ohio 45221, USA tim.keener@uc.edu Presented at the 3rd Bangkok International Conference on Engineering and Applied Science February 27, 2015 Bangkok, Thailand

Acknowledgement Drew McAvoya, N.M. Lakshminarasimmana, I would like to acknowledge the involvement of my co-authors for this work who include the following individuals: Worrarat Thiansathita, Drew McAvoya, N.M. Lakshminarasimmana, Thunyalux Ratpukdib, and Patcharee Hovichitrb aDepartment of Biomedical, Chemical, and Environmental Engineering University of Cincinnati Cincinnati, Ohio 45221, USA   bDepartment of Environmental Engineering Khon Kaen University 123 Mitraphab Road.  Khon Kaen, 40002, Thailand

Background Food waste is the single largest category of municipal solid waste (MSW) being landfilled comprising > 15% of total MSW in the U.S.; In the United States, many places are now banning food waste from going into landfills; Food waste is the world’s third-largest emitter of greenhouse gases, behind only China and the United States*; Only about 2.5% of food waste is currently recycled and the principal technology is composting; While composting provides an alternative to landfilling food waste, it requires large land area, produces smog precursor VOCs, emits greenhouse gases to the atmosphere and consumes energy; Anaerobic digestion is the best alternative to landfilling of food waste because it provides beneficial end products, i.e., biogas (a gaseous mixture of methane and carbon dioxide) and soil conditioning fertilizer. *http://www.weather.com/news/science/environment/wasted-food-makes-climate-change-much-worse-20130917

A New Approach Major innovation of coupling anaerobic digestion with algae cultivation utilizing the CO2 from biogas as the algae carbon source; Advantages include; Provides a major source of methane that can be used as a clean fuel; Utilizes waste carbon dioxide in a manner that produces more biofuels; Reduces climate change by preventing the release of large amounts of greenhouse gases (methane and carbon dioxide) into the atmosphere; Reduces the potential for groundwater and surface water contamination from landfills; Can be applied to almost all organic wastes including industrial wastes.

Anaerobic Digestion Many waste streams including animal manures and food wastes are excellent candidates for anaerobic digestion due to their high organic and moisture content; Anaerobic digestion is the biological degradation of organic matter in the absence of oxygen yielding biogas and digestate; Biogas is comprised of 60-70% methane, and 30-40% carbon dioxide; Biogas is capable of operating most devices intended for natural gas, although the carbon dioxide reduces the heat available from the gas; The carbon dioxide can be utilized to grow algae.

Algaeculture

The Technical Advantages of this Approach Includes: • Closed tanks with no open access for the dissolved CO2 to escape to the atmosphere – almost complete carbon utilization; • Use of continuously cleaned, closed top CFSTRs instead of more expensive and difficult to operate and clean plug flow reactors (PFRs); • The land space requirement for using CFSTRs compared to raceway systems will be reduced by 94%; • Use for carbon dioxide from biogas which has the largest concentration of CO2 gas to grow algae for the production of solid fuels, biodiesel, food products, and other products; • Biogas contains little or no acid gas components, thus no pretreatment is needed to prevent significant pH drops from the absorption of SOx, NOx or HCl as from using combustion flue gases; • Biogas contains trace amounts of NH3 and H2S which are both nutrients and generally offset each other in terms of pH in solution;

Technical Information Delivered waste feedstock would require preprocessing via mechanical systems; Digestion results in two products: biogas and digestate; AD technologies consists of wet (3-10% solids) or dry (> 15% solids); Water would need to be added for wet digestion, but dry digestion would need only minor amounts of additional water for processing food waste.; Advantage of dry systems is that they can be built to scale-up (batch/modular units) as more waste becomes available, and they require less space and time for digestion than wet systems.

Technical Information, con’t, A novel algae reactor system developed and tested by the faculty with an extremely small footprint (~94% smaller than traditional raceway designs) is being used; This reactor system utilizes closed, opaque polypropylene tanks which minimizes the overall cost, and allows for easy expansion in capacity by simply adding new tanks in service; CO2 scrubbing is accomplished with a unique bubble gas separation system developed by the faculty; Scrubbed effluent gas consists of methane and some water vapor and has the characteristics of pipeline natural gas; Algae is harvested continuously for further processing; Unique agglomerates are being tested and developed for enhanced algae dewatering and separation; Research is be conducted on the best uses of the dried algae.

Pilot Plant Design Criteria To process 25 kg-wet/d of food waste is equivalent to 7.50 kg-TS/d. Hydraulic residence time of 15 days, organic loading rates of 4.49 kg-VS/m3-d, VS 86% of TS, 1 kg-wet is equal to 0.3 kg-TS dry, biogas yield of 0.415 m3-CH4/kg-TS, and a heat value for CH4 =of 37.67 MJ/m3. Volume of AD = (7.5 kg-TS/d)/[(4.49 kg-VS)/(0.86 VS/TS)] = 1.4 m3 (2 tanks of 0.75 m3 each) Volume of CH4 produced = (7.5 kg-TS/d)(0.415 m3-CH4/kg-TS) = 3.1 m3-CH4/d Heat value of CH4 produced = 37.67 MJ/m3)(3.1 m3-CH4/d) = 116.8 MJ/d Assume biogas is 65% CH4 and 35% CO2 CO2 produced per day = 1.68 m3-CO2/d = 0.80 kg-c/d Algae reactor volume of 700 - 800 L will suffice. Amount of algae produced (2 kg-a/kg-c) = 1.60 kg-a/d Potential biodiesel production (assume algae is 30% lipid, and 85% conversion of lipid to biodiesel) = ~0.3 L/d (~10.4 MJ/d).

Why Is Thailand Best? Thailand offers significant advantages for the development of this technology; Meteorological advantages; Agricultural advantages; Technical advantages; Cultural advantages. We anticipate demonstrating the concept at UC with our pilot plant over the next 6 months (and longer), and that it will work in a manner in which is has been designed; We then seek the ability to take the pilot plant results and move forward to a larger, more important demonstration of the concept, hopefully in Thailand where it’s probability of success will be greatly enhanced.. This will require; Industrial support; Government support. We encourage all who are interested in our activities come to Cincinnati for a tour and discussions.

Biogas and Methane Storage Bags with Biogas Scrubber in Background

Biogas Scrubber

Algae Reactors

Algae Settling Tank and Hydroclone Concentrator

Algae in Settling Tank

Let’s Think Green! Let’s Think Smart!

Anaerobic Digester Reactor

Food Shredder

Food Shredder at work

Gas-Liquid Mixing in Biogas Scrubber