How Green can Biodiesel Be?

Ruminations by Thatcher Root

Department of Chemical & Biological Engineering

University of Wisconsin - Madison

Biodiesel Production

• Conversion of vegetable oil to motor fuel • Triglycerides from corn, soy, canola, …• Transesterify with alcohol (methanol or ethanol)• Catalyze with base or acid

TG + 3 ROH Methyl Esters + Glycerol

• Focus on heterogeneous base catalyst• Simplify separations• Eliminate neutralization requirement, water wash• Production of clean glycerine phase

History of diesel engines

• Invented in 1893 by Rudolf Diesel

• Ran on peanut oil at 1900 World’s Fair

• Switched to cheaper petroleum distillate

• Fuel must ignite from compression alone

Diesel’s first engine

http://www.deutsches-museum.de/sammlungen/ausgewaehlte-objekte/meisterwerke-ii/dieselmotor/dieselmotor-grossansicht/

Petroleum Consumption in the United StatesEstimated total petroleum use by sector

4.1 million barrels diesel fuel consumed per day!

2/3 of petroleum consumedgoes for transportation!

Estimated petroleum product use

OilOil Methyl alcoholMethyl alcohol(wood alcohol)

BiodieselBiodiesel GlycerinGlycerin

Waste forest products (wood, paper, pulp)

Cosmetics

Food

Pharmaceuticals

InksHeating oil

Passenger cars

Lye, potashLye, potash

What is biodiesel?What is biodiesel?+ +

Waste fryer oilVegetable oil

Production of biodiesel

oil

methanol

lye+

biodiesel

glycerin

biodiesel

water

Water wash3-4 times

Glycerin drained, purified,sold

Reacts for 3 hours at 140°FSettles for 24 hours

Water drained, discarded

Catalyst and alcoholpremixed

Pump

What’s the real deal with biodiesel emissions?

Type of emission

B100 B2

Total unburned hydrocarbons

- 67% - 20%

Carbon monoxide - 48% - 12%

Particulate matter - 47% - 12%

Nitrogen oxides + 10% +2% to -2%

Emission reduction measured as compared to 100% petrodiesel.http://www.biodiesel.org/pdf_files/fuelfactsheets/emissions.pdf.

Potential feedstocks

• Soybean oil, canola oil• Inedible oils

– Jatropha

• Palm oil – Only in tropics

• Used fryer oil– Needs pretreatment

• Beef tallow– Edible and inedible

• Algae– 10,000 gal/acre

CanolaSoybean

Jatropha

Comparison of annual oil yields

Crop Average oil yield (gal/acre)

Crop Average oil yield (gal/acre)

Corn 18 Rapeseed (canola)

127

Soybean 48 Oil palm 635

Sunflower 102 Algae 10,000

http://www.biodiesel.org/buyingbiodiesel/producers_marketers/ProducersMap-Existing.pdfBQ-9000 is a voluntary accreditation program through the National Biodiesel Board

Estimated US production capacity: 580.5 million gallons

Biodiesel Production in the United StatesBiodiesel Production in the United States

Current Wisconsin Biodiesel Production

• Wisconsin biodiesel production, 2005: 1 million gallons

• Estimated current production: 2 million gallons

• Current Wisconsin biodiesel plants: – Renewable Alternatives, Manitowoc– Great Lakes Biofuels, Madison – WE BE Bio, Mauston– WRR Environmental Services, Eau Claire

Future Wisconsin Biodiesel Production

• Expected Wisconsin production, 2007: 100 million gallons

• Under construction:– North Prairie Productions, LLC, Evansville

• 45 million gallons/year

– Anamax Energy Services, DeForest• December 2006• 20 million gallons/year

– Two plants proposed for Jefferson and Clinton

Production of biodiesel

oil

methanol

lye+

biodiesel

glycerin

biodiesel

water

Water wash3-4 times

Glycerin drained, purified,sold

Reacts for 3 hours at 140°FSettles for 24 hours

Water drained, discarded

Catalyst and alcoholpremixed

Pump

Biodiesel Production - Scale

• “Home Brew” system• Use waste fryer fat from restaurants• Cook in small batches• Waste disposal in city sewers

• Commercial Scale production - 5 M gal/year• Market value of glycerine co-product

• $1.60/lb - 0.30/lb - 0.10/lb• Variation with purity

• Wash water consumption - permit issues• Soap production

• Separation• Disposal

Biodiesel Seasonal Variations

• Cold Flow Filter Plugging test• ASTM standard for flow through wire mesh• FAME “wax” crystal formation

• Variation with fat/oil origin and FAME production• Chain length• Saturation• Alcohol used for ester

• “Dewaxing” treatment

• Variation in oil source with seasonal temperature

NExBTL Biodiesel

• Alternative process from Finland

• Vegetable oil + hydrogen -> alkanes + water

• Higher energy content (and input)

• Propane byproduct

• Higher capital cost, production cost

• More conventional petro-diesel-like properties

• Conventional petro-diesel distribution, processing

Biodiesel Chemistry

100 lbs 10 lbs 100 lbs 10 lbs

Biodiesel Reaction Initiation

CH3OH + NaOH → CH3O-Na + H2O

• Methoxide is active intermediate• Form from any basic catalyst or feed

• Water byproduct leads to soap byproduct• Loss of fatty acid chains• Difficulty in separation in settling tank

• Avoid water by using sodium methoxide at start• Cost, hazard to handle• Water levels in alcohol, oil feedstock?

Biodiesel Product Workup

•Reactor product has methanol in biodiesel•ASTM standard regulates level•Affects volatility (vapor pressure)

•Glycerine byproduct contains excess alcohol, catalyst•Use of acid to neutralize

•Mineral acid (HCl, H2SO4, H3PO4, …)•Organic acid (acetic acid, …)

•Water wash removes methanol, all polar species•Efficiency of wash process affects consumption•Huge impact on permit requirements

Glycerine Byproduct Use

•Glycerine byproduct from soap - cosmetic use

•Price plunging as production surges

•Minimal value - as fuel, or feedstock for another process•Impact of salt content

•Ash content prevents use in boilers•Affects value for other processes

Biodiesel Catalyst Goal

Ideal catalyst creates methoxide without water formation or salt waste product

Solid base catalyst:

MgO + CH3OH -> MgOH+ + CH3O-

Catalyst remains in reactor for further useNo acid neutralization, new base needHigh quality glycerine byproduct

Research on solid base catalysts now underway

Resources

• National Biodiesel Board: www.biodiesel.org

• Energy Information Administration: www.eia.doe.gov

• Biodiesel America: www.biodieselamerica.org

12 Principles of Green Chemistry1. Prevent waste2. Design safer chemicals and products3. Design less hazardous chemical syntheses4. Use renewable feedstocks5. Use catalysts, not stoichiometric reagents6. Avoid chemical derivatives7. Maximize atom economy8. Use safer solvents and reaction conditions9. Increase energy efficiency10.Design chemicals and products to degrade after use11.Analyze in real time to prevent pollution12.Minimize the potential for accidents