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Bioenergy Fundamentals Biomass – solar energy stored in plant/animal tissue Chemical Composition 25% Lignin 75% Carbohydrates and Sugars Carbohydrate – many sugars bound together into long polymer chains Carbohydrates consist of cellulose/ hemicellulose - PowerPoint PPT Presentation
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Bioenergy FundamentalsBiomass – solar energy stored in plant/animal
tissueChemical Composition
25% Lignin75% Carbohydrates and Sugars
Carbohydrate – many sugars bound together into long polymer chains
Carbohydrates consist of cellulose/hemicelluloseLignin – a non-sugar polymer, like plant mortar
- Glue that holds cellulose fibers together
Lignin Molecular Structure
Carbohydrate/Cellulose Structure
Origins of Biomass
CO2 + H2O + Sunlight = Biomass + O2
Solar Radiation Chemical EnergyCyclic Process14% of worldwide energy consumption40-90% in developing world4% of U.S. electricity from biomass (9000 MW)Mass of total living matter = 2000 billion tons
or 300 tons per personNet Annual Production = 400,000 million tons
Energy Content of Biomass
Moisture content causes huge variation8-20% for wheat straw30-60% for wood75-90% for animal manure
Dry biomass - 17-20 GJ/ton (coal 20-30 GJ/ton)Biomass – less ash, toxic metals, sulfur, etc.Wide range of usesCyclic process that is potentially sustainable
Common Pathways
Developed, Widespread UseFirst Generation Biofuels – Ethanol,
BiodieselLandfill and Digester GasesIndustrial and Agricultural Wastes
(Sawmills…)
Future DevelopmentSecond Generation Biofuels – Range of feedstocks, conversion
processesAdvanced use of residential, industrial and
agricultural wastes, byproducts and crops
Ethanol
EthanolSubstitute for GasolineProduced by fermenting sugar cane or sugar beetProduced in large quantities in BrazilCan also be made from vegetable starches –
requires milling and treatment with acidsEnergy content = 30 GJ/tonEnergy content about 2/3 that of gasoline
C2H5OH
Ethanol
So, you pull up to the gas station in your flexible fuel vehicle and see that gasoline is selling for $3.00 per gallon and ethanol (100%) is selling for $2.12 per gallon. Which is a better deal?
Ethanol
Commonly blended with gasolineUp to 10% ethanol with gas, octane boost85% ethanol + 15% gasoline = E85
Octane rating – what is it…Octane rating of ethanol about 1135-10% blends boost octane rating 2-4 pointsBefore ethanol was used, MTBE
Ethanol
Methyl tert-butyl ether, C5H12OPollutes groundwater
- leaks from storage- leaks from fueling- leaks from industry
Also used as oxygenate- Winter fuel blends- Reduces CO emissions
Ethanol
Ethanol1. Corn stored at plant (7-10 day supply)2. Screened to remove debris, milled into flour3. Liquefaction (aka. Mashing)• Hot slurry (mixed with water, enzyme
added, heated for 30-45 minutes)• Time, heat and enzymes break down starch
into shorter chains4. Saccharification – Glucoamylase enzyme
breaks short chains into simple sugars5. Fermentation – Yeast converts sugar into
ethanol, 50-60 hours to 15% alcohol “beer”
Ethanol6. Distillation – Difference in boiling point of
alcohol and water, produces 95% alcohol7. Dehydration – Remaining water from 190
proof alcohol removed through molecular sieve (uses different sizes of molecules)
Byproducts- CO2 from fermentation- Spent grains – turned into cattle feed
Biodiesel
Diesel fuel from vegetable oil (or animal fat)Veg oils – fatty acids (triglycerides)Long chain alkyl (methyl, propyl, ethyl) estersAn ester group…
Glycerol
O O OMe Me Me
O = O =O =
HO
HO
HO
Biodiesel(Methyl Ester Alcohol)
3 ester alcohol + 1 glycerine
O =O O
O =O
O =
Triglyceride
1 triglyceride + 3 alcohol
3 MeOH
KOHCatalyst
catalyst
Transesterification Reaction
PROF. NAVEEN KUMAR, DELHI COLLEGE OF ENGINEERING, DELHI, INDIA
Fats and oils have quite big molecules with a spinal of glycerol on which are bond three fatty acid rests.
By the transesterification, the fatty acid rests are removed from the glycerol and each is bond with methanol.
The products are one mole glycerol and three mole of fatty acid methyl ester.
Molecular Structure
Biodiesel
Biodiesel
For every ton of biodiesel, 100 kg of glycerol Market for glycerol used to exist… not anymore
(everybody is making biodiesel)Companies are trying to find ways to use it
(Cargil, Dow, etc.)High water content, not cheap to separate
Market for free/cheap veg oil used to exist…(but everybody is making biodisel)
Biodiesel
What the ?!!?!?!
BiodieselSources
- Palm (41 million tons per year)- Soybean (38 million tons per year)- Rapeseed (aka Canola, 18 mil. tons per
year)- Sunflower, peanut, cottonseed, olive, etc.
Can be run 100% or any blendVolumetric heating value 10% less than dieselWater emulsifications a serious problem
Pyrolysis
Decomposition of solids- High temperatures- Absence of oxygen
Pyrolysis of biomass- Heated to 400-500oC for a few seconds- Yields a bio-oil- Not a fuel that can be burned directly
Currently in commercialization phase
Catalytic Reforming
Biogas transformed into liquid fuelTypically a CO and H2 blend to produce gasoline
or diesel substituteKey component is the catalyst
Transition metals (iron, cobalt, ruthenium)Most common method is called Fischer-Tropsch
Short course in catalysis…
Technical Skills for Liquid Biofuels
Combustion- Stoichiometry (proper A/F ratio, etc)- Heating value of a fuel or mixture (by vol)- Product gas composition- Assessing pollutant, GHG emissions
Otto, Diesel Cycle FundamentalsLife Cycle Analysis
- Quantification of energy, GHG, emissions- Does it make sense to do this?- Where should we focus to improve
process?
Stoichiometry Example
Calculate the following information for an E85 fuel assuming that the 15% is composed of C8H18
• Stoichiometric A/F Ratio• Lower heating value of the fuel in kJ/kg and
kJ/gallon• Mass of CO2 produced per kg of fuel burned• Mass of CO2 produced per MJ of energy
released
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