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
PresentationOutline
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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
NetZeroEnergy,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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SystemsViewofanEnergeticsProduction
Facility
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TypicalAnalysisofanEnergeticsProduction
Facility
Type I Ecology
• Raw and other materials
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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
TypicalEnergetic
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
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NetZeroGoalandObjectives
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 7
NetZeroVision
• 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
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SystemsViewofaNetZeroFacility
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NutrientandEnergyRecovery
• 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 10
ConceptualIntegrationOptionsforAnaerobicDigestion
(AD)andAlgalBiomass(AB)ProductionProcesses
Nutrient Recovery
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Algaevs.OtherBiofuelFeedstocks
• 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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AnaerobicDigestionFundamentals
• 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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MethaneYieldofAlgalBiomass*
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)
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ADofAlgalBiomassChallenges
Difficult to attain recommended AD loadings (2.4‐8.0 kg VS/m3d) 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 < 1.7‐
2.7)
Some of these challenges maybe addressed by mixing algal biomass with other waste streams (e.g. wastewater residuals) 15
TypicalProcessesforBiomassProduction
fromEnergeticsWastewaterStreams
Physical‐chemical treatment processes
• UV/H2O2 degradation of energetic waste streams • Bimetal Mg‐Cu reductive degradation of energetic waste streams
• Kinetic experiments
• Factors affecting conversion
• Identification of by‐products
• Reactor design
Algal growth experiments
• Screening and identification of algal species to be studied
• Toxicity experiments
• Reactor design and operation
• Biofuel extraction experiments
Anaerobic digestion and biogas production experiments 16
Example:Physical‐ChemicalTreatmentofan
EnergeticCompound(EC1)
EC1 UV/H2O2 experiments
• Kinetics of EC1 UV/H2O2 kinetic experiments – effect of H2O2
dose
• Kinetics of EC1 degradation – effect of initial pH
• pH evolution during EC1 degradation experiments
• Evolution of total nitrogen
• Evidence of EC1 degradation
Bimetal reduction of EC1 experiments
• Screening bimetal pair experiments
• Effect of initial pH 17
EffectofPeroxideDoseandpHonthe
DegradationofEC1
Complete EC1 degradation in 3.5 hours at 8 ml H2O2
The higher the initial pH, the faster the EC1 degradation rate
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Nitrogen&CarbonEvolutioninEC1Degradation
Total‐N remains constant and equal to the stoichiometric; No gaseous N species are produced
NO3‐ is the main end‐product, with traces of other substances
TC and TOC are identical and decrease to very low levels upon reaction completion.
Evidence of organic carbon mineralization to gaseous CO2
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EC1BimetalReduction
BimetalPairSelectionMg/M
%EC1 Removal in Mg/Ni, Mg/Cu, Mg/Zn, ZVMg
Mg/Cu outperforms all Mg/M pairs and ZVMg when initial pH is not adjusted;
For initial pH  3.3 Mg/Zn, ZVMg and Mg/Cu produce EC1 removals > 90% 20
TypicalBatchAlgalGrowthExperiments
• Experiments performed in 100 mL flasks
• Culturing 4 different species
• 2 marine algae: •
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Tetraselmis sp. Dunaliella tertiolecta
• 2 freshwater algae: •
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Scencedesmus obliquus Chlorella vulgaris
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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)
GrowthRateandDoublingTime
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
ToxicityAssessmentofUntreatedWaste
andTreated(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
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ToxicityAssessmentofUntreatedEC1
WastewaterStreamsonS.obliquus
Growth inhibition effect at all wastewater levels No growth – no color development
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ToxicityAssessmentofCE1Treated(UV/Peroxide,
9h)StreamsonS.obliquus
Growth enhancement up to 60 % wastewater compared to 0%
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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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