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

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

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

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:

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

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 Breakdown of US renewables in

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

Life cycle of traditional biofuels Important consideration: life cycle greenhouse gas emissions SC Opinion on Greenhouse Gas Accounting in Relation to Bioenergy: committee/sc-opinions/opinions-on-scientific-issues/ Image: 10

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

Photosynthesis: Overview 13 Image: Oxidation/reduction (Redox) reactions – CO 2 gets reduced to glucose – H 2 O gets oxidized to O 2

Photosynthesis: Inside a Chloroplast 14 Image:

Photosystems convert light energy into reducing equivalents 15 Image:

The Calvin Cycle uses those reducing equivalents to turn CO 2 into sugar 16 Image:

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Typical efficiency of photosynthesis 18 Figure based on statistics listed here: 100% Sunlight 47% Non-Bioavailable Photons 53% (in 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

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

Feedstocks 20 Image: 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 Image: 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

Drawbacks of Corn as a Feedstock 22 Image: Used for food Grows slowly Grows only on arable land Provides low energy per acre Is an annual crop

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Can grow up to 8 feet in 6 weeks 24 Image:

25 Source: “Biodiesel from microalgae.” Energy yield per acre does not favor corn ?

Bioreactors/ponds used to grow algae 26 Images: ; Bioreactors required to cultivate high cell densities

27 Images: both from -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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Cellulose 29

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

Cellulosic biofuel – a reality? 32

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

Pathway to ethanol 34 Glycolysis (~10 enzymatic reactions) Image: Pyruvate decarboxylase Alcohol dehydrogenase Under anaerobic conditions (no O 2 ):

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 The E10 “Blend Wall”

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:

39 Images: (Left) time/Weber/Microbiology%20Majors/Chpater5/chapter5sub/figure_05_30_labeled.jpg

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

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

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

Thank you for listening! 43 Questions?