Biofuels

1. UEET 603 Energy Engineering Biofuels Presented By Pradip Majumdar Professor Department of Mechanical Engineering Northern Illinois University DeKalb, IL 60115

2. What is Biofuel? • Biofuels are solid, liquid, gas fuels derived from recently dead biological materials. • Distinguished from the fossil fuels, which are formed from long dead biological materials over a long period of time. • Biofuels can be produced theoretically from any biological or organic carbon-source materials: - Most common being the photosynthetic plant - other plant-derived materials such woodchips, trash etc. • They essentially recycle existing carbon in the atmosphere rather than releasing any new carbon from fossil fuels. - because plants used in the production of the fuel removed carbon dioxide from the atmosphere. • In theory they are endlessly renewable

3. Common Bio-fuel Production • There are two common strategies for bio-fuel production: 1. Grow crops high in starch (Corn and maize) or grow crops high in sugar (sugar cane, sugar beet and sweet sorgum) and then use yeast fermentation to produce Ethyl Alcohol or Ethanol. - The most common bio-fuels are in the form of ethanol.

4. Grow plants that contain high amount of vegetable oil such as oil palm, soy bean, algae. - when these oils are heated, their viscosity is reduced and they can be burned directly in a diesel engine. or - they can be chemically processed to produce fuels such as biodiesel. • Wood and its byproducts can also be converted into biofuels such as wood gas, methanol and ethanol fuel.

5. Problems with Ethanol-Biofuel • Currently, ethanol is produced primarily from food grade materials such as such corn and soy bean. • Need considerable amount of energy using fossil fuel. • Study shows that USA can not produce enough ethanol from corn to meet its demand. • Current rush to produce ethanol from food grade material lead to global food shortage and increased food price.

6. Alternate Technology to Produce Ethanol New research is focused on to develop more efficient processes to make ethanol from wider range of non-food grade biomass. The key elements of a biomass is the cellulose that gives plant cells their strong walls. The process involves converting cellulose into sugar and then sugar into ethanol: Ethanol Cellulose Sugar

7. Conversion Process • One of the recent effort is to turn any carbon-rich organic material into a gas and then into liquid fuel. • Potential source for this carbon-rich organic biomass - Pine tress - Wood Chips - Trash (Municipal solid waste - Farming residues (cornstalks) - timber residues (unusable parts of logged trees) • Challenge is to cheaply transport these leftovers to the ethanol plants. • How about leaves, small limbs, waste woods (forest leftovers)?

8. Conversion Process Conventional Approach Gas Biomass Problem removing Nitrogen Nitrogen (If air is used) Oxygen (Expensive) or Air • Syngas is a mixture of mostly Carbon monoxide and hydrogen • Syngas is generally converted into liquid fuel ethanol by means of a catalyst (Range Fuels) • Newer approach involves no use of catalyst and but use bacteria to ferment the syngas into ethanol. New Approach (By Range Fuels and Coskata) Biomass Syngas Ethanol Steam

9. The amount of ethanol produced in processes with chemical catalyst is around 70-80 gallons per ton. • Bacteria-based process may produce 100 gallon per ton - this process makes more ethanol rather than other products such as butanols, propanol, hexanol, octanol and other alcohols.

10. Some Practical Issues Main challenge is to design a system that gives steady supply of ethanol from any biomass. Sorting out trash is a major huddle – practical issues - Plastic and bald tires are ideal use. Range Fuels system is currently designed for wood chips. - pretty uniform in size - no need for sorting process (taking out bad stuffs such as batteries) Use of garbage is quite challenging and may be risky for initial trials. - There may not be enough of it ( ???) - Municipal solid waste is less than 10 % of all the available biomass. - Is sorting process worthwhile?

11. Prospects of Biofuels • Need to develop more efficient ethanol production process from non-food grade biomass. • Need to develop infrastructures for packaging and transporting biomass waste to ethanol plant in a economical manner. • Estimated current cost of ethanol is $2.10 per gallon. • Projected cost is $1.33 per gallon by 2012 with in- progress in technologies. • Can we reach $1.00 per gallon (Target) ? • Future for biofuel cars – May be!

12. Some National and International Issues • Mitigation of carbon emission levels • Oil prices • Food vs. fuel • Deforestation and soil erosion • Impact on water resources • Energy balance and eficiency

13. Energy Animations • Biomass Program EERE: Biomass Program Home Page EERE: Biomass Program Home Page • BP www.bp.com

14. Energy Forms Total energy content of a system is classified into three basic categories: 1. Kinetic energy, - Associated with the translation velocity of the system 2. Potential energy, - Associated with the elevation the system from some reference level 3. Internal energy - Include all energy forms associated with the atomic and molecular structures and orientations.

15. Conversion of Kinetic Energy • Conversion of kinetic energy to mechanical energy and then into electrical energy - Wind Energy Generation using wind turbine - Tidal Energy Generation - Wave Energy Generation - Jet Propulsion Thrust

16. Conversion of Potential Energy • Conversion of potential energy to mechanical energy and then into electrical energy -Hydroelectric power generation using water – impact turbine

17. Internal Energy Forms Includes translation, rotation and vibrational motion of atoms and energy associated with the atoms, molecules and subatomic particles.

18. Internal Energy forms Internal energy is also classified in different forms: Latent energy associated with the phase of the substance; Chemical energy associated with the atomic bonds in a molecular structure. Nuclear energyassociated with the binding force within the nucleus of the atom.

19. Conversion Internal Energy to Thermal Heat Energy by Chemical Reaction • In a chemical reaction the bond structure of the reactants are modified to form new bond structure and in the process electronic configuration within the atoms are changed and chemical energy is released. • Amount of chemical energy released is the difference between the internal energy content of the original molecular structure of the reactants and the internal energy content of the molecular structures of the products.

20. Combustion • Combustion process is chemical reaction in which a fuel is oxidized and a large quantity of chemical energy is released. • In the combustion of hydrocarbon fuel, carbon, hydrogen and any other constituents in the fuel that are capable of being oxidized reacts with oxygen. In this reaction, one-kmol (32 kg) of Oxygen reacts with one-kmol (12 kg) of Carbon and forms one-kmol (44 kg) of Carbon dioxide – Mass Balance

21. Combustion with Air • Oxygen often supplied as air rather than in a pure form as it is free and available in abundance. • Even though air is composed number of different gases such as oxygen, nitrogen, argon , it is assumed primarily composed of 79% nitrogen and 21 % oxygen by volume for analysis purposes, i.e. for each k-mole of oxygen there are 79/21= 3.76 k-mole of nitrogen. The reaction methane with air is then written as

22. In this reaction nitrogen is assumed as inert and does not undergo any chemical reaction. • Nitrogen thus appears on both sides of the equation and simply effects the product temperature by absorbing part of the released chemical energy and raising its own internal energy. • In some high temperature and pressure reactions, nitrogen may undergo reaction and form air pollutants such as nitrogen oxide, or nitrogen dioxide, or nitric oxide,.

23. Incomplete Combustion • In general, air is supplied as 100% theoretical air or stoichiometric air that supplies sufficient amount of oxygen for complete combustion of all elements. • In a complete combustion, all carbon oxidizes to form , all hydrogen oxidizes to from and sulfur oxidizes to form . • In an incomplete combustion reaction the product may contain some fuel as unburnt fuel, some carbon in the form of CO and even as carbon particles.

24. Incomplete combustion is caused by insufficient supply of oxygen as well as inadequate mixing of fuel and air in the mixture. • In a real reaction process, air is supplied in excess to achieve complete combustion. • A combustion reaction with 50 % excess air, i.e. 150% theoretical air or stoichiometric air is represented as follows:

25. Conventional Power Generation Conventional power generations are based on heat engine principals developed based on Kelvin-Planck’s statement of second law of thermodynamics: High Temperature Source Heat Addition High Temperature Machine Work, W Heat Addition Heat Rejection Work, W Machine Low Temperature Sink Impossible Possible

26. Carnot Engine-Maximum Possible Performance Consist of Four Ideal Processes - Reversible isothermal heat addition, Qh - Reversible adiabatic Expansion (Work), W - Reversible Isothermal heat rejection, Qc - Reversible adiabatic compression Qh Thermal Efficiency, W Qc

27. The maximum thermal efficiency of reversible heat engine is given as For a reversible heat engine operating on a Carnot cycle: • The lower temperature reservoir in heat engine • power cycle is limited by the ambient condition. • The high temperature is limited by the • temperature of vapor in the boiler in a vapor • power cycle or the temperature of the product of • combustion in the internal combustion engine.

28. Vapor Power Systems • Vapor power cycles uses working fluids that alternately vaporized and condensed. • In a vapor power system the combustion takes place out the system in a furnace

29. Standard Vapor Power System Turbine Exhaust Vapor or Steam Heat Rejection Boiler Condenser Cooling Tower Furnace Feed Water Heaters Heat Addition 16 Cooling Water Pumps

30. Air- Gas Power System • This gas power systems includes gas turbine, jet propulsion and internal combustion engines of the spark ignition and compression-ignition types. • All these systems are internal combustion types with combustion taking place inside the system in contrast to vapor power systems where combustion takes place out the system.

31. Reciprocating Internal Combustion Systems • Two principal types of reciprocating internal combustion engines are the spark-ignition engine and the compression-ignition engine. • In a spark ignition engine, a mixture of fuel and air is ignited by a spark plug. • In a compression-ignition engine, air is compressed to a high enough pressure and temperature that combustion occurs spontaneously when fuel is injected.

32. Ideal Cycle for Spark Ignition Internal Combustion Four Processes: • 1-2: Isentropic compression as the piston moves from the crank-end dead center to head-end dead center. • 2-3: Heat addition at constant volume when piston is momentarily at rest at head-end dead center. • 3-4: Isentropic expansion as piston moves from head-end dead center to crank-end dead center (Work output). • 4-1: Rejection of heat when piston is at the crank- end dead center.

34. Why Alternative Energy? • High cost and higher risk of un-interrupted supply imported oil. • Increased demands for energy and fossil fuels due to continuing economic growth in countries such as China and India. • Global warming caused by emission of carbon or other greenhouses gases from consumption of fossil fuels such as coal and oil used in power generations and transportations. • Cleaner forms of energy are essential to reduce carbon and greenhouse gas emissions. • Increased concern over climate change and increased effort to use low-carbon energy to reduce greenhouse gas emission.

35. Alternative Energy Sources and Power generation Alternative energy sources that emit little or no carbon and greenhouse gasses are - Solar Power - Tidal power - Wind Power - Hydrogen Power - Geothermal - Hydroelectric - Fuel Cell