How Green can Biodiesel Be? Ruminations by Thatcher Root Department of Chemical & Biological Engineering University of Wisconsin - Madison
Dec 28, 2015
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 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