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HHMI Teachers’ Workshop:Biofuels – More Than Ethanol From Corn Starch

Aditya Kunjapur, Ph.D. Candidate, MITJuly 20, 2014

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Outline

• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

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• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

Outline

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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.”

IEA Bioenergy: http://www.ieabioenergy.com/IEABioenergy.aspx

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Overview of BioEnergy

Energy

Photosynthesis

Chemosynthesis

Photons

Inorganic Molecules

- Plants- Algae- Cyanobacteria

- Chemolithotrophs (in deep oceans, isolated caves, etc)

Fuelsor

Chemicals

Biomass+ CO2

Enzymatic - Same organism- Different organism

Thermochemical - Pyrolysis- Gasification

- Ethanol- Biodiesel- Jet Fuel- Methane

Energy Capture Chemical Conversion

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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 CO2 is consumed

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Breakdown of US renewables in 2011

35%

22%

21%

5%

13%

4%

HydropowerBiomass WoodBiomass BiofuelsBiomass WasteWindOther

http://www.eia.gov/totalenergy/data/monthly/pdf/sec10_3.pdf

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Percentage of the world’s energy• 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

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Life cycle of traditional biofuels

Important consideration: life cycle greenhouse gas emissionsSC 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

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• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

Outline

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Photosynthesis: Overview

Image: http://www.phschool.com/science/biology_place/biocoach/images/photosynth/photo1.gif

• Oxidation/reduction (Redox) reactions– CO2 gets reduced to glucose

– H2O gets oxidized to O2

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Photosynthesis: Inside a Chloroplast

Image: http://hyperphysics.phy-astr.gsu.edu/hbase/organic/imgorg/rubc3.gif

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Photosystems convert light energy into reducing equivalents

Image: http://www.biologycorner.com/resources/photosystem.jpg

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The Calvin Cycle uses those reducing equivalents to turn CO2 into sugar

Image: https://benchprep.com/blog/wp-content/uploads/2012/08/Calvin_cycle.jpg

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Typical efficiency of photosynthesis

18Figure 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

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• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

Outline

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Feedstocks

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

21Image: http://ericpetersautos.com/wp-content/uploads/2012/12/corn-1.gifSource of facts: EIA – Biofuel Trends and Issues – Oct 2012

Estimated corn use for ethanol production (2011):4.9 billion bushels or 279 billion pounds

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Drawbacks of Corn as a Feedstock

Image: http://media.treehugger.com/assets/images/2011/10/bushcorn-jj-001.jpghttp://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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Can grow up to 8 feet in 6 weeks

Image: http://newswire.uark.edu/images/miscanthus.JPG

25Source: “Biodiesel from microalgae.” http://www.sciencedirect.com/science/article/pii/S0734975007000262#

Energy yield per acre does not favor corn

?

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Bioreactors/ponds used to grow algae

Images: http://www.inventgeek.com/Projects/Photo-Bio-reactor-V2/main.jpghttp://assets.inhabitat.com/files/bioreactor1.jpg ;

Bioreactors required to cultivate high cell densities

27Images: 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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Cellulose

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

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Cellulosic biofuel – a reality?

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• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

Outline

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Pathway to ethanol

Glycolysis(~10 enzymatic reactions)

Image: http://www.emc.maricopa.edu/faculty/farabee/biobk/alcferm.gif

Pyruvate decarboxylase

Alcohol dehydrogenase

Under anaerobic conditions (no O2):

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Drawbacks of ethanol• 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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The E10 “Blend Wall”

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Alternative fuel options

• Longer, branched alcohols

• Biodiesel

• Methane

– Methanogens

– CO2 + 4H2 CH4 + 2H2O

– Important for waste-to-energy

Image: http://canola.ab.ca/image.axd/images/uploads/news/bio_pump_200x250.jpg?m=Crop&w=200

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

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• Context for biofuels and key facts

• Photosynthesis and carbon fixation

• Feedstocks

• Fuels

• Recap

Outline

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Overview of BioEnergy

Energy

Photosynthesis

Chemosynthesis

Photons

Inorganic Molecules

- Plants- Algae- Cyanobacteria

- Chemolithotrophs (in deep oceans, isolated caves, etc)

Fuelsor

Chemicals

Biomass+ CO2

Enzymatic - Same organism- Different organism

Thermochemical - Pyrolysis- Gasification

- Ethanol- Biodiesel- Jet Fuel- Methane

Energy Capture Chemical Conversion

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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!)

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Thank you for listening!

Questions?