Microalgae Biofuels and Carbon Cycling

Transcription

1 Microalgae Biofuels and Carbon Cycling Prepared for the 2009 Annual Conference GA A&WMA Umakanta Jena & Nisha Vaidyanathan Biorefining and Carbon Cycling Program Department of Biological & Agricultural Engineering The University of Georgia

2 Why Biomass? Broad Problems: (1) Energy crisis and (2) global warming U.S energy consumption 97 quads (2001). 20 million bbl oil/ day, 55% imported, will increase to 68% by % of total energy (2.9 quads) comes from biomass. National Target: 30% energy from biomass by 2030, 35 billion gallons of biofuel by Need an increase in the biomass use for energy by five times. (USDA-DOE, 2005)

3 2. Global warming U.S. leads among the producers of emissions in the world green house gas (GHG)

4 Why Microalgae? Highest biomass productivity, 100 g/m 2 /day (365 tones/ha/yr against 70 tones/ha/yr for energy cane). No competition with food unlike other biofuels Uses waste water for growth (waste water treatment media) Net GHG reduction as it is carbon neutral ( g of CO 2 needed for biosynthesis of 1 g dry algal biomass).

5 Algae to biofuel: Major challenges Production of biomass Cultivation Harvesting Processing of biomass

6 Attributes of Algae Production Costs Water CO2 Other Electricity Major purchased equipment Labor Algae Production Costs Installation Fertilizers Infrastructure Building

7 (Chisti, 2008; Shen, 2009)

8 Present Algae Cultivation Systems -Open Ponds (suspended algae cultivation) (Shen, 2009)

9 Photobioreactors for suspended algae cultivation (Tredici, 1999)

10 Immobilized algae cultivation systems for Attached algae Enclosure methods :(a) cells in a polymer matrix sheet; (b) cells in a gel bead Non enclosure methods- Algal Turf Scrubber Technology developed for attached algae cultivation (Shen, 2009)

11 Dewatering or harvesting Low productivities Improper mixing of water Contamination Predation Highly technical and hence least economical

12 (Adey, 1980) A substrate material. Cells grow attached on this substrate. Initial attachment by bacteria. Algae starts dominating the substrate with the help of bacteria. Mature biomat formation with highest dominance by algae.

13 To develop an advanced cultivation system for algal biomat production using high strength industrial wastewater for bioremediation, carbon cycling and bioenergy applications.

14 Standard reactor configuration

15 Attached algae cultivation systems at UGA Bioconversion laboratory

16 Preliminary experimental details Substrates- Geotextile and polymer materials Growth media- Tap water and industrial wastewater. Months: April-July 2009 ph of water- 7.5 Span of each experiment- 21 days

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23 g/m²/day Results and discussion Tap Water Biomass Productivity Dalton Utilities Raw Water S1 S2 S1 S2 S1 S2 S1 S2 Mixed culture A Ulothrix Mixed culture B Harvest1 Harvest2 Harvest3 S1-Substrate 1 (Polymer material) S2-Substrate 2 (Geotextile material)

24 VARIABLES TAP WATER GROWTH MEDIA INDUSTRIAL WASTEWATER 1.Microbial consortia Chlamydomonas, Diatoms, Thin filaments, Bacteria Oscillatoria, Diatoms, Ulothrix, Chlamydomonas, Nostoc, Characium sp., Anabaena, Thin filaments, Bacteria 2.Productivity (g/m 2 /day) Structural Compositions (%) Carbohydrates Proteins Lipids

25 Algae grown with tap water Algae grown with industrial wastewater Carbon (%) Hydrogen (%) Nitrogen (%) Sulphur (%) Other (%)

26 %removal %removal %removal Nutrient removal potential %Nitrogen removal %Ammonia removal %removal %removal Time (days) Time (days) %Phosphate removal %removal - Efficient wastewater treatment with 83% nitrogen, 47% ammonia and 76% phosphate removals. - Low water evaporation losses from reservoir. Time (days)

27 Future work Improve the reactor configuration to an advanced and robust system. Experiment different optimizing conditions for best biomat productivity. Assess the cost economics of the improved bioreactors in comparison open pond cultivation systems

28 Next step?? Processing of Microalgae into fuels

29 Biomass Energy Conversion Routes Biomass Biochemical Conversion Direct Combustion Thermochemical conversion Extraction of Hydrocarbons Fermentation Anaerobic Digestion Thermo Chemical Liquefaction Pyrolysis Gasification Biodiesel & Value added products Ethanol, Acetone, Butanol Methane, Hydrogen Heat & power Bio-oil Oil and Charcoal Fuel Gas

30 What is pyrolysis Heating of biomass in absence of oxygen

31 (Matsumura et al, 2006) Thermochemical Liquefaction Hydrothermal conversion under high pressure Tarry material is the precursor to biocrude or biooil Solubility, density, ionic properties, chemical potential, reactivity of water change drastically as it approaches towards critical point

32 Our research goal Investigate the production of bio-oil (biocrude) from microalgae by two thermochemical conversion processes

33 Reaction mixture Separation Statistical Analysis Experimental Methodology Compositional Analysis Ultimate analysis Biocrude Proximate Analysis Solid residue Bomb Calorimeter Analysis Microalgae GC-MS Aqueous phase HPLC Analysis Gas TCC Process GC Analysis

34 Experimental Set up for Batch Pyrolysis N 2 gas cylinder, 2. Flow meter, 3. Heating furnace, 4. Reactor, 5. Thermocouple, 6. Data logger, 7. Sample, 8. Condenser set up, 9. Ice bath, 10. Gas vent

35 Experimental set up for TCL 7 8 rpm 6 10 P 4 3 Power supply Gas sample Water in 11 1-Reactor, 2-Heater unit 3-Power relay 4-Pressure sensor 5-Thermocouple, 6- Stirrer assembly, 7- Controllers, 8- Computer, 9-Condenser for liquid sampling, 10-Valves 11- N 2 gas cylinder

36 Product separation Separation of condensate into three phases using a separatory funnel.

37 Results: Feedstock composition Composition Algae feedstock Proximate analysis (%) Moisture 6.04±0.02 Volatiles 80.70±0.05 Ashes 6.60±0.05 Fixed carbon 15.25±0.06 Ultimate analysis (%) C 45.16±0.19 H 7.14±0.20 N 10.56±0.04 S 0.74±0.01 Higher heating value, (HHV) in MJ/kg 20.52±0.23 * Biochemical composition, (%) Protein 68.64±0.26 Lipids 13.30

38 Results: Product distribution % Others, Solid, Others, Solid, 4.67 Gas, 23.6 Biooil, Gas, 19.2 Pyrolysis process Biooil, Thermochemical Liquefaction Others are the products dissolved in aqueous phase

39 Results: Biocrude Vs petroleum crude oil Biocrude from Pyrolysis Biocrude from TCL Petrocrude (Matar and Hatch, 2001) Elemental analysis Carbon, wt% Hydrogen, wt% Nitrogen, wt% Sulfur, wt% Oxygen, wt% Viscosity, Cp Heating value, MJ/kg

40 Viscosity, cp Storage properties of algal bio oil Pyrolysis biooil TCL biooil Time, Days Change in viscosity during storage (measured at 60 o C)

41 Results: Analysis of biocrude A b u n d a n c e T im e --> Pentanones Furan Benzenamine T I C : J 1 N C D \ d a t a. m s Phenols Indoles Cyclohexanol Pentadecence Alkanes Hexadecanoic acid Pentadecanoic acid Carboxylic acids Styrene Majority of the compounds of bio-crude (Phenol, furan, styrene, indole, alkanes, benzene, cyclohexane) are basic components of the petroleum crude oil.

42 Yield, g/kg of algae % Results: Other co-products Gas analysis CO 2 is the major product. H 2, CH 4 and C 2 H 5 are high energy value gases and can be used as fuel gas Spirulina Mixed algae 0 Carbon dioxide Carbon monoxide Hydrogen Methane Methyl acetylene Ethanol Formate Succinate Sp/Cat5/30 min Sp/Cat5/60 min SP/NC/60 min MA/NC/60 min Treatments Aqueous phase analysis Ethanol, formate and succinates are the major products, can be used as fuels/ chemicals

43 Major conclusions Microalgae have potential for biofuel in the form of biocrude that has similar fuel properties as the petroleum crude oil. About 25-30% and 36-48% biocrude could be produced from spirulina platensis via pyrolysis and TCL respectively.

44 Benefits: Conceptual microalgae biorefineries CO 2 Algae cultivation and harvesting Industrial Waste water Combustion for maintaining temperature and CO 2 level Microalgae TCC Processing Recycled water Syngas Biocrude Solid/ char Aqueous phase Upgrading Upgrading Transesterification Upgrading Transport fuel Biodiesel Land use (Fertilizer) Carbon catalysts Chemicals

45 Is the concept sustainable?? Environment (GHG reduction, water quality) Social (Biofuels, new jobs, science & technology) Economic (New business Opportunities)

46 Acknowledgements United States Department of Energy Dalton Utilities, GA UGA Biorefining and Carbon Cycling Program Dr K C Das Dr Senthil Chinnasamy Dr Ashish Bhatnagar Joby Miller

47 THANK YOU!!! QUESTIONS?

48 Liquefaction Methodology: Product Separation Microalgae Reaction mixture Washing with water and filtration Water soluble Water insoluble Washing with acetone and filtration Acetone soluble Acetone insoluble Evaporation Drying Gas Aqueous phase Bio-crude Solid residue

49 Methodology: response terms Biocrude yield (%) Weight of biocrude Weight of starting biomass 100 Gas yield (%) Weight of gas Weight of starting biomass 100 Solid yield (%) Weight of solid residue Weight of starting biomass 100 Others yield (%) 100 % yield of (bio crude gas solid) Carbon conversion efficiency (CCE) CCE (%) Weight of starting biomass Heat value Weight of solid residue Weight of starting biomass Heat value Heat value 100

50 Batch Pyrolysis Experimental Set up 1 Vent (1) Computer connected to thermocouples, (2) Carrier gas cylinder, (3) Mass flow controller (4) Oven, (5) Pyrolysis reactor, (6) Thermocouples, (7) Condensing traps

51 Bio-crude yield, % Bio-crude yield, % Results: Effect of time and temperature Biocrude yield was 48% maximum. The yield increased with 1) Increase in reaction time 2) Decrease in organic solid concentration % organic concentration 20% organic concentraion Non-catalytic Na2CO3 NiO Treatments min reaction time 60 min reaction time Biocrude yield was the lowest for NiO used as catalyst Na 2 CO 3 has shown higher yield than other treatments 0 Non-catalytic Treatm ents Na2CO3

52 Heating Biomass in absence of oxygen Pyrolysis Process Bio-oil Gaseous products Char as Soil conditioner