HHMI Teachers Workshop:

Transcription

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

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

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

4 What is BioEnergy According to the InternaFonal Energy Agency (IEA): Material which is directly or indirectly produced by photosynthesis and which is uflized as a feedstock in the manufacture of fuels and subsftutes for petrochemical and other energy intensive products. IEA Bioenergy: hvp:// 4

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

6 Some advantages of bioenergy compared to other renewables The only renewable source that can replace fossil fuels in all energy markets in the producfon 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 % 5% 13% 35% Hydropower Biomass Wood Biomass Biofuels Biomass Waste 21% Wind Other 22% hvp:// 8

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

10 Life cycle of tradiional biofuels Important considerafon: life cycle greenhouse gas emissions SC Opinion on Greenhouse Gas AccounFng in RelaFon to Bioenergy: hvp:// us/governance/scienffic- commivee/sc- opinions/opinions- on- scienffic- issues/ Image: hvp:// 10

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

13 Photosynthesis: Overview OxidaFon/reducFon (Redox) reacfons CO 2 gets reduced to glucose H 2 O gets oxidized to O 2 Image: hvp:// 13

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

15 Photosystems convert light energy into reducing equivalents Image: hvp:// 15

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

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

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

20 Feedstocks Two categories of photosynthefc organisms: 1) Those that capture light energy into non- fuel biomass - Chemical conversion sfll required 2) Those that capture light energy and produce a fuel - Only physical separafon required Image: hvp://www1.eere.energy.gov/biomass/images/feedstock1.jpg 20

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

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

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

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

26 Bioreactors/ponds used to grow algae Bioreactors required to culfvate high cell densifes Images: hvp:// Bio- reactor- V2/main.jpg hvp://assets.inhabitat.com/files/bioreactor1.jpg ; 26

27 Bioreactors/ponds used to grow algae - Algal cells make up very small fracfon of pond - Dewatering and processing is cost- prohibifve Images: both from hvp:// and- ua- team- arid- raceway- algae- test- bed 27

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29 Cellulose 29

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

32 Cellulosic biofuel a reality? 32

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

34 Pathway to ethanol Under anaerobic condifons (no O 2 ): Glycolysis (~10 enzymaic reacions) Pyruvate decarboxylase Alcohol dehydrogenase Image: hvp:// 34

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

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37 The E10 Blend Wall 37

38 AlternaIve fuel opions Longer, branched alcohols Biodiesel Methane Methanogens CO 2 + 4H 2 à CH 4 + 2H 2 O Important for waste- to- energy Image: hvp://canola.ab.ca/image.axd/images/uploads/news/bio_pump_200x250.jpg?m=crop&w=200 38

39 Images: (Les) hvp://www2.raritanval.edu/departments/science/full- Fme/Weber/Microbiology%20Majors/Chpater5/chapter5sub/ figure_05_30_labeled.jpg 39

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

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

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

43 Thank you for listening! QuesFons? 43