Lecture 7 - Biofuels PDF

Renewable Fuel Standard: U.S Federal Renewable Fuel Standard https://afdc.energy.gov/laws/RFS.html Alternative Fuel Data Center https://afdc.energy.gov/  Biofuels ME 4180 – Energy Systems and Sustainability Prof. Mario Medina Department of Mechanical Engineering...

Renewable Fuel Standard: U.S Federal Renewable Fuel Standard https://afdc.energy.gov/laws/RFS.html Alternative Fuel Data Center https://afdc.energy.gov/  Biofuels ME 4180 – Energy Systems and Sustainability Prof. Mario Medina Department of Mechanical Engineering Sept. 23, 2020 Agenda Agenda Definitions and categories Pathways for biofuel Generation I biofuels Ethanol Biodiesel Generation II-IV biofuels Biobutanol Algae Methanol Biofuels and Biomass Biofuels are made from biomass What is biomass? Young carbon Biomass can be used to describe: Natural vegetation  wood! Energy tree plantations Specific energy crops Waste Water-based biomass Feedstocks and biofuels Biomass is quickly replenished, compared with fossil fuels Biomass is derived from recently living organisms Feedstocks vary by geographic location, utilizing fast growing, native species where available United States: corn, soybeans Europe: rapeseed, wheat, sugar beet Brazil: sugar cane India: jatropha S.E. Asia: palm oil Each source plant can result in different processing needs and potentially different fuel composition (bulk and impurities) Ethanol from corn, sugar cane, sugar beet Oils from other crops listed above Unsaturated (60-80%), and saturated Methyl and ethyl esters Containing 12+ carbon atoms Categories of biofuels Generation I biofuels: any fuel derived from a food crop, typically produced using fermentation (ethanol), typically low energy return on energy invested (EROI) ~10-1, at best carbon neutral or weakly carbon fixing (more carbon in than out of the cycle) followgreenliving.com Generation II-IV biofuels: any fuel derived from a non-food crop, can include non- food portions of a food crop, e.g. stems, leaves, stover, etc.; Gen IV biofuels would be net carbon fixing, capturing more carbon than is released in the fuel cycle Pathways for biofuel production There are many feed stocks and many conversion pathways, including thermal, chemical, and biological processes. Magnitude of biomass resources “An estimate of the world solid biomass standing in forests in 1979 was 1.8x 1022 J. At that time this figure was comparable with the world’s proven natural gas and oil reserves” (Shepherd and Shepherd, Energy Studies, 2003) In 2001, Global primary energy consumption was 418EJ. Net biomass production on the global land surface is estimated to be 2280 EJ/yr Bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ/yr (Smeets et al., PECS, 2007) There is a lot of energy content in biomass!! But the resources are distributed geographically and the feed stocks are diverse. Biofuel demand is driven by Federal policy The renewable fuel standard (RFS) is a requirement that a certain percentage of petroleum transportation fuels be displaced by renewable fuels. (2.78% of the gasoline consumed in the U.S. by 2006 had to be a renewable fuel). RFS1 started with the Energy Policy Act of 2005 Congress updated the standard in the Energy Security and Independency Act of 2007 (EISA). This new renewable fuel standard is known as RFS2. RFS2 is a renewable fuel standard for biofuels only that requires obligated parties to sell a certain amount of biofuels per year through 2022. RFS2 contains a four-part mandate for lifecycle greenhouse gas emissions levels relative to a 2005 baseline of petroleum: for renewable fuel, advanced biofuel, biomass-based diesel, and cellulosic biofuel. Center for Climate and Energy Solutions (www.c2es.org) History of biofuels in transportation Historic use of biofuel in engines Rudolf Diesel designed his engine to run on peanut oil (1892) Ford Model T designed to run on ethanol (1908) Low cost of petroleum fuels quickly displaced biofuels WWII Germany blended alcohol from potatoes WWII Britain blended grain alcohol Recent use of biofuel in engines Brazil started wide use of ethanol in the 1980’s (federally mandated) U.S. blends 10% ethanol in all gasoline; many vehicles advertised capable of 85% blends Biodiesel widely used in up to 20% blends Gen I: Ethanol Ethanol’s attractive features Ethanol leads to larger charge cooling compared to gasoline due to the higher enthalpy of vaporization Ethanol can reduce in-cylinder particulate formation Ethanol has a higher octane rating than gasoline, so can use higher compression ratios compared to gasoline Fuel FuelProperty PropertyComparison Comparisonfor forGasoline Gasolineand and Ethanol Ethanol[1,2] [1,2] Property Gasoline Ethanol MW 111.19 46.06 O2 (wt%) 0.00 0.35 LHV (MJ/L) 30-33 21.40 Specific gravity at 20°C 0.72-0.78 0.79 Viscosity at 15°C (x10-3 Pa-s) 0.37-0.44 1.19 Boiling Point (°C) 27-225 78 ΔHvap (kJ/kg) ~351 1168 Thermal Effects Specific heat at 15°C 2.01 2.39 ↓ RON 88-98 109 MON 80-88 90 Chemistry Flamability limits at 15°C (vol%) 1.4-7.6 4.3-19 Effects Barraza, Cesar B., 2017 Ethanol’s not so attractive features Large scale use of agricultural crop for ethanol production requires vast land resources. Competitive with food crops, impacting the agricultural economy in complex and not always positive manner. Ethanol is often energy neutral or weakly energy positive (energy into raising crops = energy content of fuel) when made from fermentation. Ethanol is corrosive and requires upgrades to the fuel tank and fuel handling system in a vehicle. Ethanol cannot be transported using the pipeline. Have to use tanker trucks Fueleconomy.gov The Business Journal, 2015 Production volume 10.2 millions of barrels per day (MBD) of gasoline used by cars and light trucks (2019) 1.06 millions of barrels per day of ethanol produced in 2018 (from 40% of the corn crop) 1.5% of the annual need in the U.S. was met using ethanol derived from corn starch. Copyright 2010 Crago, Khanna, Barton, Giuliani and Amaral U.S and Brazil ethanol production Many factors make ethanol more beneficial (financially, energetically, agriculturally, etc.) for Brazil compared with the U.S. Hofstrand, Iowa State University, http://www.extension.iastate. edu/agdm/articles/hof/hofjan0 9.html Gen I: Biodiesel Biodiesel features Biodiesel consists of long chain methl and ethyl esters that can be produced from renewable plant or animal feed stocks. Biodiesel is non-toxic with properties similar to petroleum-based diesel fuel. Considered an energy positive fuel (~3* more energy out than energy in). Currently can be distributed by tanker truck. May be able to use the pipeline. Cloud point is a concern, i.e. at low temperatures biodiesel can congeal. Biodiesel production has been increasing every year, and predictions for potential target 0.204 MBDOE by 2015 U.S. Environmental Protection Agency, A Comprehensive *U.S. DOE Energy Efficiency and Renewable Energy Analysis of Biodiesel Impacts on Exhaust Emissions Scales and capacities Biodiesel and Transesterification Easy technology – transesterification, can be done in your bathtub (3:1) But, must be done well or you will fail your engine Biodiesel ~25 million gallons produced in 2004 ~75 million gallons produced in 2005 ~225 million gallons produced in 2006 ~1.1 billion gallons produced in 2011 But, we used 48 billion gallons of diesel fuel in 2006 for on-road vehicles Biodiesel chemistry Conforth, 2007 DEER Conference Biodiesel engine studies Oxygenated additives/biofuel blends Generally increases NOx emission Increased oxygen concentration increases thermal NOx Exhaust emissions (Song et al. 2002) Lower NOx when Tad is significantly lowered Exhaust emissions (Miyamoto et al. 1998) Generally decreases PM emissions Suppression of soot precursors (Song et al. 2002) Certain oxygenates have greater reductions Structural properties effect PM emissions Imaging (Mueller et al. 2002) Exhaust emissions (Gonzales et al. 2001) Affects combustion phasing (and therefore power and efficiency) compared to neat fuels Generally have different octane/cetane numbers Affects operable engine limits If phasing is shifted to early, engine knock If phasing is shifted too late, dramatic increases in UHC (Xingcai et al. 2006) Gen II – IV Biofuels Biofuels: cellulosic Making cellulosic ethanol – or how to make a better termite Cellulosic ethanol is produced from waste materials like woodchips, sawdust, switchgrass, corn stover, etc., so it does not compete with food crops; most abundant material on planet Process uses complex enzymes (like cellulases) to convert plant feed stocks (made of cellulose, hemicellulose and lignan) to ethanol Process includes 3 general steps: 1. thermochemical treatment to make the enzymes used in step 2 more efficient, 2. application of enzymes to create sugars, 3. fermentation (using yeasts or bacteria) to convert sugars to ethanol Lots of research on identifying the best enzymes for the job and genetically engineering the best, highest yield plants Switchgrass generally does not compete with food crops and is a year-round crop (thus you get year-round carbon dioxide uptake, unlike corn, etc.) Genome Management Information System, Oak Ridge National Laboratory Converting land from forests to crops changes the albedo of the planet, as well as the CO2 uptake properties. More complex than making ethanol from corn. Potentially dual benefit of reducing land fill costs and space by using waste material. Energy positive process, but not financially competitive yet. It is not economical to ship waste materials very far. Can produce MUCH larger quantities of fuel compared to corn, soybeans, etc. As of 2/07, 6 biorefineries are expected to produce 130 million gallons of cellulosic ethanol per year. Research supported by the U.S. DOE Energy content of the biomass is high. Could use the waste feed stock as a direct source of fuel, as opposed to a source for solid-to-liquid (STL) conversion. Biobutanol Biobutanol = new biofuel developed by cooperative effort between BP and DuPont Butanol (C4H10O) derived from biomaterial feed stock Can be created using fermentation and distillation from same biomass feed stocks as ethanol. This is currently a low production rate (butanol dilute in water), energy intensive process Can be created using algae (more on this later) Can be transported by pipeline (as opposed to ethanol which requires tanker transport) Higher energy content than ethanol, less corrosive than ethanol, less hygroscopic (water absorbing) than ethanol Could be a direct substitute for gasoline in an ICE (i.e. without engine modification)  maybe Approximately the same octane rating as gasoline, so no compression ratio benefit Algae Algae can be used to produce high yields of oil (projected at over 10 times the yields of energy or food crops), using land unsuitable for food or other energy crops. Project to be able to meet the annual U.S. diesel fuel needs Methods have been studied for several decades (see the Aquatic Species Program, initiated by U.S. President Jimmy Carter in 1978; killed by U.S. President Bill Clinton in 1996) Research is currently sponsored by the private sector Can be used to create butanol, biodiesel, kerosene (jet fuel), hydrogen, gasoline, etc Does not require potable water Algae fuel conversion by Solazyme, Conversion process and product depends on the algae. Solazyme uses sugars to feed San Francisco, CA the algae. Others use sunlight, etc Need a robust algae strain The case for algae 21 billion gallons per year of “advanced biofuels” ≈ 10% of U.S. liquid on-road fuel usage ≈ how much cultivation area? 21 billion gallons per year of soy biodiesel (≈ Alaska) 21 billion gallons per year of algae biodiesel (≈ Connecticut) Marchese, ASME ICE, 2011 From algae to fuel Lipid co-products, Omega-3 Fatty Acids (FAME) (alkanes) Methane, Renewable Diesel, SPK Hydrothermal Liquefaction Alcohols, methane Marchese, ASME ICE, 2011 Algae fuel in flight Holmgren, USDA ERRC, 2009 Methanol Methanol is not currently produced from biomass (although it could be) Methanol is created by steam reforming natural gas or coal Methanol is inexpensive to produce Methanol has a higher octane rating than gasoline, so can we derive a compression ratio benefit Methanol can also be used as a carrier for hydrogen CH3OH