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How can plant biomass become fuel?

• Ethanol• Biodiesel• Burgeoning (expanding)

Technologies– DMF– Butanol– Fischer Tropsch

FUEL CHEMISTRIES• Methane (CH4), the primary constituent of liquefied or compressed natural

gas, and propane (C3H8), the primary constituent of liquified petroleum gas.

• Petroleum fuels are blends of lots of different chemical species; in general, the molecules of a liquid petroleum fuel are pretty big and complex.

•

Isooctane (C8H18), typically found in gasoline

Cetane (C16H34), typical of diesel fuel

COMBUSTION

• Hydrocarbons when burning completely – combine with hydrogen from water and O2 in the air to form CO2.

• Incomplete combustion of carbon combines with one oxygen yielding CO (toxic)

Non-Hydrocarbon Fuels

• METHANOL

• ETHANOL

• Oxygen promotes more complete combustion

• Hydrogen

Ethanol• Fermentation and distillation (nothing new)

Beer is 1000’s of years old

Distillation

Feedstock harvest/storage

Enzymes release sugars

Add yeast

Ethanol evaporates

cooler temps. allowing

separation

Add waterGermination releases enzymes

Yeast makes a low ethanol % liquid

Ethanol

• Fermentation and distillation– Modern ethanol plants (use starch or cellulose)

– Still combustion releases CO2 into the atmosphere

Feedstock harvest/storag

e

Add waterGermination releases enzymes

Enzymes release sugars

Add yeast

Yeast makes a

low ethanol % liquid

Ethanol evaporates cooler than

water allowing

separation

All images from a virtual tour www.Ethanol.org

Biodiesel

• Rudolf Diesel and his engine and its fuel– Early diesels ran on vegetable oil– 1920 crude oil distillates– 1990 Gulf war, increased energy price• EU was converting canola to biodiesel• US farms had excess of soybean

– Biodiesel from soybean continues to gain popularity

Biodiesel• Biodiesel production needs to remove glycerol

from fatty acids

Biodiesel

• Increasing biodiesel production capacity– 200 M gal sold in 2006– 1.37B gal production capacity when online

NBB 2005, 2007Schmidt 2007

Burgeoning Technologies - DMF• DiMethylFuran (DMF) synthesis

from sugars– Higher energy density (40%

greater than ethanol, making it comparable to gasoline)

– Chemically stable – Evaporating DMF during

production also requires ~ one third less energy than the evaporation of ethanol

– Not soluble in water (does not absorb moisture )

– Higher boiling point than ethanol (92 oC, compared to 78 oC for ethanol)

– Has the ability to efficiently and rapidly be produced from simple sugars which are readily available in nature

– Safety issues must be examined

Roman-Leshkov 2007

Burgeoning Technologies - Butanol

• Butanol– alcohol with 4 carbon atoms

compared to ethanol’s 2– stores more energy per L than

ethanol– less corrosive than ethanol to

pipelines– easily separated from water– can be blended into gasoline at

higher concentrations– Like Ethanol its fermented

• Clostridium acetobutylicum

www.lightparty.com

Burgeoning Technologies – Fischer Tropsch Process

• a collection of chemical reactions that converts a mixture of CO and H into liquid hydrocarbons

• produces synthetic lubrication oil and synthetic fuel, typically from coal, natural gas, or biomass

How can we change plants to get more fuel?

• Change efficiency of any step in process– More crop yield– More oil/sugar– Enzyme supplements– Better microbes– Better chemical

engineering

More Oil

• Oil crops already exist– US soybeans biggest oil crop– EU canola

• 44% of cars run on diesel

• Canola yield 40% oil vs. 20% for soybean

• Crop yields can be increased with both traditional breeding and transgenic resistance traits

100 years of breeding -Changing oil

More Sugar

• Access to carbon can be done with simple gene effects

• It is possible to knock out a gene in this pathway and shift carbon away from starch

http://www.hort.purdue.edu

Sh2 knock out

Normal field corn

Enzyme Supplements

Better Microbes

• Engineered microorganisms can break down sugars from biomass and convert them into biofuels such as alcohols, diesels, or jet fuels

• However, a major challenge

in microbial biofuel production is that biofuels are often toxic to cells

Future Directions

• Alternates to corn, soybean– Non-food– Low input– Grow on marginal land– Biomass rich (fast growing)

We Need Carbon Neutral Options

• Tilman’s group developed a scenario that is carbon negative

– The plants fix CO2 and store C in the roots.

– The shoot biomass is harvested for biofuel

– The planting is diverse and provides 16 crops

• Basically a low input scenario– Neither ethanol

or biodiesel are carbon

negative

Cellulosic Ethanol• There is 1.3 Billion tons (BT) of

non-food biomass out there (per year)

• It is possible to get 100gal/ton of biomass

• If can access and ferment all 1.3 BT biomass, can create 130B gal

• U.S. used 5.4B gallons of ethanol in 2006 (www.energyfuturecoalition.org)

• Fuel of the future?

Somerville 2006