Algal Biomass Conversion To Low Carbon Energy Agamemnon Koutsospyros, Ph.D. Professor and Graduate Coordinator of Environmental Engineering, University of New Haven
Christos Christodoulatos, Ph.D. Professor and Director of Center for Environmental Systems, Stevens Institute of Technology
Presentation Outline • • • • • • • • •
NetZero Energy, Water, Waste Systems View of an Energetics Production Facility Sustainability of Energetics Production Facilities Nutrient and Energy Recovery Integration Options for Anaerobic Digestion and Algal Biomass Production Processes Algae vs. Other Biofuel Feedstocks Anaerobic Digestion of Algal Biomass Research Tasks Examples of • Physical‐chemical treatment experiments • Algal growth experiments
• Conclusions 2
Net Zero Energy, Water, Waste • Net Zero Energy • A facility that generates as much energy on site as it consumes
• Net Zero Water • A facility that does not deplete groundwater and surface water resources in quantity and quality by: • Limiting the consumption of freshwater resources • Returning water back to the original watershed
• Net Zero Waste • A facility that reduces, reuses, and recovers waste streams, converting them to resource values with zero landfill demand
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Systems View of an Energetics Production Facility
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Typical Analysis of an Energetics Production Facility Type I Ecology
• Raw and other materials • • • • •
Organic precursors Acetic and Nitric acid Various amines Various organic solvents Water
• Energy • Electricity • Heat
• Energetic Materials • Waste streams • Biosolids • Treated wastewater • NH3 nitrates
Currently material flows in munitions production facilities follow a linear Type I Ecology Model 5
Typical Energetic Materials • Nitro‐substituted organics (nitramines, nitoaromatics, etc.) • RDX (Research Department eXplosive ) • HMX (High Melting eXplosive ) • NTO (Nitrotriazolone) • DNAN (2,4‐ Dinitroanisole) • NQ (Nitroguanidine)
• Degradation of these compounds yields high amounts of nitrates
RDX
HMX
NTO
DNAN
NQ 6
Net Zero Goal and Objectives
Goal
• To aid energetic production facilities attain NetZero energy, water, and waste
Objectives
• To devise physical‐chemical treatment schemes that mineralize organic carbon to CO2 and liberate nitrogen nutrients (ammonia, nitrates) • To design algal bioreactors that utilize the released products of physical‐chemical treatment processes • To derive biofuels and/or biogas from algal biomass
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Net Zero Vision • NetZero can be attained by converting energetic production facilities from a current linear material flow of Type I ecology to a quasi‐cyclic material flow in Type II ecology.
Linear Type I Ecology
Quasi‐cyclic Type II Ecology 8
Systems View of a NetZero Facility
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Nutrient and Energy Recovery • Nutrient recovery processes • Physical‐chemical treatment processes to recover nutrients and reuse them to cultivate algal biomass
• Energy recovery • Algal biomass cultivation • Algal biomass pre‐treatment to optimize biofuel production • Anaerobic digestion integration (three options) 1. Concentrated algal biomass 2. Disrupted algal biomass 3. Lipid extracted biomass
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Conceptual Integration Options for Anaerobic Digestion (AD) and Algal Biomass (AB) Production Processes
Nutrient Recovery
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Algae vs. Other Biofuel Feedstocks • Higher photosynthetic efficiency • Higher lipid content • Higher growth rates • Higher biofuel yields (2,000‐ 5,000 gal/acre/yr) • Lower land requirements • Lower environmental impact • No need for soil • Non‐competitive to agriculture • Can be used for fuel, feed and food • Can be used in the production of many useful products (plastics, chemical feedstocks, lubricants, fertilizers, and even cosmetics)
http://oakhavenpc.org/cultivating_algae.htm
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Anaerobic Digestion Fundamentals • A complex reductive environment where diverse consortia of hydrolytic, fermentative, and methanogenic bacteria convert organic matter to biogas (60% CH4, 40% CO2) • Methanogenic conversion is the rate limiting step • Methanogens are slow growers with strict environmental and nutritional requirements
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Methane Yield of Algal Biomass*
Theoretical Yield calculated by the stoichiometric equation:
Where a, b, c, d = elemental molar content of C, H, N, O Vm = molar volume of methane = 22.14 L/mol (0 oC, 1 atm) 14
AD of Algal Biomass Challenges Difficult to attain recommended AD loadings (2.4‐8.0 kg VS/m3d) without concentrating harvested microalgae Certain algal species possess cell walls resistant to anaerobic degradation without cell disruption pretreatment (Cell disruption pretreatment maybe cost excessive) C/N ratio of most species is well below AD recommended minimum (C/Nmin 20) to avoid ammonia and volatile acid toxicity. Saline algal species may cause salinity inhibitory effects High sulfate contents may cause hydrogen sulfide inhibitory effects (COD/SO4 90% 20
Typical Batch Algal Growth Experiments • Experiments performed in 100 mL flasks • Culturing 4 different species • 2 marine algae: • •
Tetraselmis sp. Dunaliella tertiolecta
• 2 freshwater algae: • •
Scencedesmus obliquus Chlorella vulgaris
• Conditions: • • • •
Commercial media: ATCC #5, BG‐11 and F2 ‐ 25 ºC ‐ 14:10 h light: dark cycle, ~3700 lux ‐ 120 rpm
• Commercial media used: • F2 in seawater (no C source) • ATCC #5 (organic C source) • BG‐11 (inorganic C source)
• Evaluate algal growth using absorbance, fluorescence and cell counting on a daily basis
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Tetraselmis sp. (40x OM)
Growth Rate and Doubling Time
Microalgae (Growth medium) Scenedesmus obliquus (ATCC#5) Scendesmus obliquus (BG-11) Dunaliella tertiolecta (F2) Tetraselmis sp. (F2)
Growth rate (μ), day-1 0.53 0.30 0.22 0.16
doubling time (dt), day 1.3 2.3 3.2 4.3
* Experiment still in progress
Growth rate S (ATCC#5) > S (BG‐11) > D > T
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Exponential phase up to: 7 days So far, 13 days* 9 days 11 days
Toxicity Assessment of Untreated Waste and Treated (UV/H2O2) Streams • IMX1
• Protocol • Adjust pH= 7.00 • Incubation at 25*C, 3700 lux and 14:10 h light: dark cycle ~ 3 days • Monitor fluorescence, absorbance, and color changes Initial test Extended test
24‐well microplate 23
Toxicity Assessment of Untreated EC1 Wastewater Streams on S. obliquus
Growth inhibition effect at all wastewater levels No growth – no color development 24
Toxicity Assessment of CE1 Treated (UV/Peroxide, 9h) Streams on S. obliquus
Growth enhancement up to 60 % wastewater compared to 0% 25
Conclusions • NetZero can be attained by converting munitions production facilities from a current linear material flow of Type I ecology to a quasi‐cyclic material flow in Type II ecology • Physical‐chemical treatment processes can be used for nutrient recovery from waste streams that are converted into feed for algal biomass cultivation • Anaerobic digestion integrated algal biomass production may offer alternatives for energy recovery in the form of biofuel and or biogas • Up‐to‐date experimental results are encouraging.
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