How can plant biomass become fuel? Ethanol Biodiesel Burgeoning (expanding) Technologies – DMF – Butanol – Fischer Tropsch

FUEL CHEMISTRIES Methane (CH 4 ), the primary constituent of liquefied or compressed natural gas, and propane (C 3 H 8 ), 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 (C 8 H 18 ), typically found in gasoline Cetane (C 16 H 34 ), typical of diesel fuel

COMBUSTION Hydrocarbons when burning completely – combine with hydrogen from water and O 2 in the air to form CO 2. 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 water Germination releases enzymes Yeast makes a low ethanol % liquid

Ethanol Fermentation and distillation – Modern ethanol plants (use starch or cellulose) – Still combustion releases CO 2 into the atmosphere Feedstock harvest/storage Add water Germination 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

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, 2007 Schmidt 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 o C, compared to 78 o C 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

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 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 CO 2 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 ( Fuel of the future? Somerville 2006