Lars Angenent, Ph.D.!Dept. of Biological & Environmental Engineering!!BEE 4870!
http://angenent.bee.cornell.edu!
Goal and outline of Bioenergy Chapter 14:!!1. Current or close-to-adaptable technology!2. Decision making process!
A. Policies!B. Net energy balance ratio and life cycle assessment!C. Productivity (cropland and time)!D. Environment, etc.!
3. Biomass!4. Bioenergy platforms!5. Ethanol – sugarcane vs. corn grain!6. Biodiesel!7. Methane and hydrogen!!
Vanek F. M., Albright L. D. and Angenent L. T. Energy Systems Engineering: Evaluation & Implementation, 2nd edition, McGraw Hill, New York, NY.!!
Policies!!• Laissez fair (but then subsidies for fossil fuels
should be disbanded)!
• Mandates: 36 billion gallons of ethanol equivalent fuel in 2020 (US Energy Independence and Security Act of 2007)!
• Feed-in Tarrifs: 20 cents per unit electricity (kWh) for 20 years for renewable energy.!
Life cycle assessment (LCA)!!• Environmental impact from cradle to grave!!!• Net energy balance (NEB) ratio:!
! ! Energy in fuel and other credits (animal feed)! = -------------------------------------------------------------------------------------------!
!All energy needed to produce fuel (growing, processing, transporting)!!!!= < 1 (more fossil fuel energy going in than biofuel energy out!= 10-20 = sustainable?!!But, oranges with oranges; and remain critical, but open minded!!!!!!!!
Biomass Sources:!!1. Plant materials:!
A. Starches/sugars/oils!B. Lignocellulose!
2. Algae!3. Organic wastes!
A. Agricultural (crop and animal waste)!B. Urban (food and wood waste)!
!
Sugarcane plantation in Brazil!
Energy density in source!
Lignocellulosic feedstock and hydrolysis (pretreatment)!
Pretreatment!1. Milling!2. Dilute-sulfuric acid – toxic byproducts = furfurals!3. Hot water!4. Alkaline!
Algae!!NEB ratio < 1 even with advanced reactors and extracting oil plus digestion rest of cells to methane!!
Biomass to bioenergy (biorefinery platforms) !Sugar platform!(enzymes-yeast)!
Syngas platform!(thermochemical)!
Carboxylate platform!(undefined mixed cultures)!
Acetate: CH3COOH!Propionate: CH3CH2COOH!Butyrate: CH3CH2CH2COOH!
Syngas: H2 + CO!
Bio-oil platform!(thermochemical)!
Syngas and bio-oil platforms:!!Gasification (anaerobic combustion) products:!!• Biochar!• Syngas (carbon monoxide, hydrogen)!• Bio-oil!
Gas Engine, MicroturbineFuel Cell!
Gasification unit!
Syngas!Biomass! Electrical Power!
Heat!Heat!
Methanation Unit!
Gasification unit!
Syngas!Biomass! Synthetic Natural Gas (SNG)!
Heat!Heat!
Syngas
Methane
Q Q
Utilization of syngas besides fermentation!
Ethanol!
Ethanol from sugar cane in Brazil (7 billion gallons)!
Ethanol from corn grain in US (14 billion gallons)!
20% of energy value in ethanol itself is used for distillation (recovery)* * Shapiro et al. (2010) evaluated several dry milling plants based on 2008 data gathering.
NEB ratio now around 2: biomass combustion/other fuel!
Biodiesel mostly from plant-derived oils (0.8 billion gallons)!
POLYMERS!proteins, polysaccharides, lipids!MONOMERS & OLIGOMERS!amino acids, sugars, fatty acids!
INTERMEDIATES!propionate, butyrate, alcohols!
CH!4! !+ CO!2!
H!2! + CO!2! ACETATE!
Fermenters!
Acetogens!
Hydrogen-utilizing!Methanogens!
Acetate-utilizing!Methanogens!
70%!30%!
Anaerobic food web!
Carboxylic acids!
Undefined mixed cultures!(1000s of different species)! • Who are they?!
• Improve function (stability)!
Thanks!
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