1. HHMI Teachers’ Workshop: Biofuels – More Than Ethanol From Corn Starch Aditya Kunjapur, Ph.D. Candidate, MIT July 20, 2014 1

2. Outline Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 2

3. Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 3 Outline

4. What is “BioEnergy” According to the International Energy Agency (IEA): “Material which is directly or indirectly produced by photosynthesis and which is utilized as a feedstock in the manufacture of fuels and substitutes for petrochemical and other energy intensive products.” 4 IEA Bioenergy: http://www.ieabioenergy.com/IEABioenergy.aspx

5. Overview of BioEnergy 5 Energy Photosynthesis Chemosynthesis Photons Inorganic Molecules -Plants -Algae -Cyanobacteria -Chemolithotrophs (in deep oceans, isolated caves, etc) Fuels or Chemicals Biomass + CO 2 Enzymatic -Same organism -Different organism Thermochemical -Pyrolysis -Gasification -Ethanol -Biodiesel -Jet Fuel -Methane Energy Capture Chemical Conversion

6. Some advantages of bioenergy compared to other renewables The only renewable source that can replace fossil fuels in all energy markets – in the production of heat, electricity, and fuels for transport (IEA) The source of a variety of drop-in liquid fuels The source of petroleum in the first place The primary way by which atmospheric CO 2 is consumed 6

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8. 8 Breakdown of US renewables in 2011 http://www.eia.gov/totalenergy/data/monthly/pdf/sec10_3.pdf

9. Percentage of the world’s energy 9 Biomass-based energy accounted for ~10% of world total primary energy supply in 2009 – Includes cooking/heating in developing countries Global production of biofuels: – 2000: 16 billion liters – 2011: 100+ billion liters Total road transport fuel globally: 3% – Brazil: 23% Source: IEA

10. Life cycle of traditional biofuels Important consideration: life cycle greenhouse gas emissions SC Opinion on Greenhouse Gas Accounting in Relation to Bioenergy: http://www.eea.europa.eu/about-us/governance/scientific- committee/sc-opinions/opinions-on-scientific-issues/ Image: http://www.extension.org/sites/default/files/w/2/22/BiofuelLifeCycle.jpg 10

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12. Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 12 Outline

13. Photosynthesis: Overview 13 Image: http://www.phschool.com/science/biology_place/biocoach/images/photosynth/photo1.gif Oxidation/reduction (Redox) reactions – CO 2 gets reduced to glucose – H 2 O gets oxidized to O 2

14. Photosynthesis: Inside a Chloroplast 14 Image: http://hyperphysics.phy-astr.gsu.edu/hbase/organic/imgorg/rubc3.gif

15. Photosystems convert light energy into reducing equivalents 15 Image: http://www.biologycorner.com/resources/photosystem.jpg

16. The Calvin Cycle uses those reducing equivalents to turn CO 2 into sugar 16 Image: https://benchprep.com/blog/wp-content/uploads/2012/08/Calvin_cycle.jpg

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18. Typical efficiency of photosynthesis 18 Figure based on statistics listed here: http://en.wikipedia.org/wiki/Photosynthetic_efficiency 100% Sunlight 47% Non-Bioavailable Photons 53% (in 400-700 nm range) 30% Not Absorbed 37% (Absorbed Photon Energy) 24% Wavelength Mismatch 28% (Energy Captured in Chlorophyll) 68% Loss in Conversion of ATP and NADPH to glucose 9% (Collected as sugar) 40% Loss in Dark and Photo- Respiration ~5% Net Leaf Efficiency

19. Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 19 Outline

20. Feedstocks 20 Image: http://www1.eere.energy.gov/biomass/images/Feedstock1.jpg Two categories of photosynthetic organisms: 1)Those that capture light energy into non-fuel biomass - Chemical conversion still required 2)Those that capture light energy and produce a fuel - Only physical separation required

21. 21 Image: http://ericpetersautos.com/wp-content/uploads/2012/12/corn-1.gif Source of facts: EIA – Biofuel Trends and Issues – Oct 2012 Estimated corn use for ethanol production (2011): 4.9 billion bushels or 279 billion pounds

22. Drawbacks of Corn as a Feedstock 22 Image: http://media.treehugger.com/assets/images/2011/10/bushcorn-jj-001.jpg http://www.shirkebiofuels.com/images/biofuel-feedstock.gif Used for food Grows slowly Grows only on arable land Provides low energy per acre Is an annual crop

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24. Can grow up to 8 feet in 6 weeks 24 Image: http://newswire.uark.edu/images/miscanthus.JPG

25. 25 Source: “Biodiesel from microalgae.” http://www.sciencedirect.com/science/article/pii/S0734975007000262# Energy yield per acre does not favor corn ?

26. Bioreactors/ponds used to grow algae 26 Images: http://www.inventgeek.com/Projects/Photo-Bio-reactor-V2/main.jpg http://assets.inhabitat.com/files/bioreactor1.jpg ; Bioreactors required to cultivate high cell densities

27. 27 Images: both from http://www.asulightworks.com/blog/asu-and-ua-team-arid-raceway-algae-test-bed -Algal cells make up very small fraction of pond -Dewatering and processing is cost-prohibitive Bioreactors/ponds used to grow algae

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29. Cellulose 29

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31. 31 I Gelfand et al. Nature 000, 1-4 (2013) doi:10.1038/nature11811

32. Cellulosic biofuel – a reality? 32

33. Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 33 Outline

34. Pathway to ethanol 34 Glycolysis (~10 enzymatic reactions) Image: http://www.emc.maricopa.edu/faculty/farabee/biobk/alcferm.gif Pyruvate decarboxylase Alcohol dehydrogenase Under anaerobic conditions (no O 2 ):

35. Drawbacks of ethanol 35 Hygroscopic Miscible with water Low energy density Requires different distribution system than gasoline Limit to how much can be added to conventional engines

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37. 37 The E10 “Blend Wall”

38. Alternative fuel options Longer, branched alcohols Biodiesel Methane – Methanogens – CO 2 + 4H 2  CH 4 + 2H 2 O – Important for waste-to-energy 38 Image: http://canola.ab.ca/image.axd/images/uploads/news/bio_pump_200x250.jpg?m=Crop&w=200

39. 39 Images: (Left) http://www2.raritanval.edu/departments/Science/full- time/Weber/Microbiology%20Majors/Chpater5/chapter5sub/figure_05_30_labeled.jpg

40. Context for biofuels and key facts Photosynthesis and carbon fixation Feedstocks Fuels Recap 40 Outline

41. Overview of BioEnergy 41 Energy Photosynthesis Chemosynthesis Photons Inorganic Molecules -Plants -Algae -Cyanobacteria -Chemolithotrophs (in deep oceans, isolated caves, etc) Fuels or Chemicals Biomass + CO 2 Enzymatic -Same organism -Different organism Thermochemical -Pyrolysis -Gasification -Ethanol -Biodiesel -Jet Fuel -Methane Energy Capture Chemical Conversion

42. Recap and take home points Traditional biofuels have several drawbacks When evaluating a biofuel process, consider: – Carbon lifecycle – Food versus fuel – Land (or water) required – Feedstock transportation – Desired end fuel Research efforts directed toward production of advanced and cellulosic biofuels make most sense (just my opinion!) 42

43. Thank you for listening! 43 Questions?