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)
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
• 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
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