1. Overview of Biofuels: System Approach and Analysis Prof. Steven G. Buckley MAE 118b February 21, 2007 (Slides 14-23 from presentation by Melanie Zauscher)

2. Taking a systems approach to biofuels

3. Biofuels in perspective Total world power draw ≈ 15 TW Total world solar flux ≈ 120,000 TW  So this should be easy, right? Earth intercepts 8000 times more power than we use.

4. Going green – the reality 29.2% of earth is land 18.8% of the land is arable (CIA World Factbook) Photosynthesis is ~ 6% efficient at best, 1% is reasonable average given ground coverage, etc. So far: 8000 * 0.292 * 0.188 * 0.01  we still have 4.3 times as much energy as we consume! (but this is if we take 100% of the arable land)

5. “Problem” of food production 11% of land area is in cropland (Worldwatch) Assuming this is all “arable land”  7.8% of land remains 23% of land area is in pastureland (assume that much of this is “non-arable,” but some of this is arable) Sobering fact: 1960, 0.5 hectare of cropland per person, considered adequate for healthy diverse omnivorous diet 2000, 0.23 hectare of cropland per person –Declining quality and quantity

6. Conversion efficiency to fuel Energy stored in plants is recovered at what rate? –Direct combustion – best biomass combustion plant efficiency ≈ 20% conversion into electricity –Production of biofuel – this is an open question! Currently ~ 10 billion gallons of both ethanol and ~ 1 billion gallons of biodiesel are produced annually, worldwide (various sources) –Gasoline consumption, worldwide ≈ 300 billion gallons –Diesel consumption, worldwide ≈ ? 30 billion gallons of diesel in the U.S., annually

7. Biodiesel yield for some common crops Cropkg oil/halitres oil/halbs oil/acreUS gal/acre corn (maize)14517212918 oats18321716323 cotton27332524435 hemp30536327239 soybean37544633548 rice69682862288 cocoa (cacao)8631026771110 peanuts8901059795113 macadamia nuts188722461685240 Brazil nuts201023921795255 avocado221726381980282 coconut226026892018287 oil palm500059504465635 Algae7983295,00010,000 From Wikipedia / biodiesel, reference: http://www.globalpetroleumclub.com/

8. Questions to ask What are the resource inputs? –Fertilizer, pesticides –Transportation –Harvesting –Processing What is being displaced / used? –Food crops –Water –Forest, other land uses

9. As always, defining system boundaries is crucial! Example: how do you define the energy return on energy invested for biofuels? –DOE, 2006: Corn-based ethanol – 1.36 today Biodiesel – 3.2 today –Institute for Local Self-Reliance Best corn-based ethanol – 2.09 Best cellulosic bioethanol – 2.62 Biggest academic critics: Prof. David Pimentel (Cornell), Prof. Tad Patzak (U.C. Berkeley)

10. Critics point to flaws in analyses of biofuel energy balances and “net carbon” efficiency Most fertilizers (e.g. urea, CO(NH 2 ) 2 have a common ammonia (NH 3 ) feedstock –Tremendous amounts of energy are used in fertilizer manufacture –Some amount of this potent greenhouse gas escapes during manufacture, and nitrogenous fertilizers convert to greenhouse gases  converting into more greenhouse gas equivalents than simply burning an equivalent energy content of gasoline

11. Reading … H. Shapouri et al. “THE 2001 NET ENERGY BALANCE OF CORN-ETHANOL” –www.ethanolrfa.org/objects/pdf/net_energy_balance_2 004.pdf David Pimentel and Tad Patzek, "Ethanol Production Using Corn, Switchgrass and Wood", Natural Resources Research (March 2005), pp 65-76 –http://petroleum.berkeley.edu/papers/Biofuels/NRRetha nol.2005.pdf Conclusion: this is a close call!

12. Why bother with biofuels? Critical need for liquid transportation fuels –Peak oil –Geopolitics –Climate change threat

13. Ethanol and Biodiesel are oxygenated fuels derived from plant sources Oxygen on-board the fuel molecule –Reduces incomplete combustion Promotes CO  CO 2 and oxidation of soot particles –The bonded O does not add to thermodynamic energy content Less energy per unit mass or unit volume of fuel Production processes are plant-specific

14. Gallons of Gasoline Equivalents http://www.nafa.org/Content/NavigationMenu/Resource_Center/Alternative_Fuels/ Energy_Equivalents/Energy_Equivalents.htm

15. Biodiesel Made from vegetable oil or animal fat and methanol or ethanol Locally produced, renewable, simple to make and use Can use same infrastructure as petrodiesel including engines Sold as B2, B5, B20, B99 & B100

16. Trans-esterification Reaction This is most common way to reduce oil viscosity

17. Biodiesel Production Facilities From the National Biodiesel Board

18. Biodiesel Retailers From the National Biodiesel Board

19. Issues with Biodiesel Material compatibility: –Biodiesel can dissolve neoprene rubber hoses and o-rings in fuel lines of older vehicles –Same problem with ULSD, so new cars are compatible already Cold temperature problem –Tendency to cloud and stop flowing in cold climates Shelf life –No more than 6 months Pahl 2005

20. Ethanol Made from sugar, starch or biomass Locally produced, renewable Can use limited gasoline infrastructure, and only small blends on most gasoline engines Sold as octane enhancer, E10, E25, E85 and E100

21. Issues with Ethanol Can't transport it in pipelines –Absorbs water –More expensive to ship As E-85, has reduced MPG, so fuel costs more even when ethanol is cheaper than gasoline Hard to find E-85 –A 2002 DOT/DOE study found ~1% of all flex-fuel cars use E-85, but automakers still get credit for CAFE standards http://www.nhtsa.dot.gov/cars/rules/rulings/CAFE/alternativefuels/analysis.htm

22. Ethanol in California Current annual demand of ethanol is estimated ~950 million gallons Demand about ¼ of national supply Demand mostly to replace MTBE with (5.7%) ethanol Current CA annual production is ~25 million gallons 95% of ethanol delivered to CA is transported via rail cars ~1 million barrels of foreign ethanol were imported in 2004- 2005 Perez 2005

23. Only one public ethanol (E-85) station in California and that is in San Diego!

24. What is the future of biofuels? Not only are we carbon-constrained, we are land- constrained! How does peak oil influence the problem? Is the energy balance > 1 or < 1? Please read the Pimentel and Patzek paper for Friday –http://petroleum.berkeley.edu/papers/Biofuels/NRRetha nol.2005.pdf