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Bioenergy from Agricultural WastesBioenergy from Agricultural Wastes
World Energy Prospects
60% 63-160%
Increase in
Population Energy demand
Source: • CIA's The World Factbook
Other concerns
Pollution Climate change Resource depletion
Overview
Bioenergy history Ag wastes and other biomassBiomass to Bioenergy
Conversion processesPros & Cons
ApplicationsBiofuelsBioheatBioelectricity
World bioenergy history facts
1850s: Ethanol used for lighting (http://www.eia.doe.gov/ kids/energyfacts/sources/renewable/ethanol.html#motorfuel)
1860s-1906: Ethanol tax enacted (making it no longer competitive with kerosene for lights)
1896: 1st ethanol-fueled automobile, the Ford Quadricycle (http://www.nesea.org/greencarclub/factsheets_ethanol.pdf)
Bioenergy is not new!
More bioenergy history
1908: 1st flex-fuel car, the Ford Model T1919-1933: Prohibition banned ethanol unless mixed with
petroleum WWI and WWII: Ethanol used due to high oil costsEarly 1960s: Acetone-Butanol-Ethanol industrial
fermentation discontinued in USToday, about 110 new U.S. ethanol refineries in operation
and 75 more planned
(photo from http://www.modelt.org/gallery/picz.asp?iPic=129)
IN
Ag wastes and other biomass
Waste BiomassCrop and forestry residues, animal manure, food processing waste,
yard waste, municipal and C&D solid wastes, sewage, industrial waste
New Biomass: (Terrestrial & Aquatic)Solar energy and CO2 converted via photosynthesis to organic
compoundsConventionally harvested for food, feed, fiber, & construction
materials
Agricultural and Forestry Wastes
Crop residues Animal manures Food / feed processing residues Logging residues (harvesting and clearing) Wood processing mill residues Paper & pulping waste slurries
Municipal garbage & other landfilled wastes
Municipal Solid Waste Landfill gas-to-energy
Pre- and post-consumer residues Urban wood residues
Construction & Demolition wastesTree trimmingsYard wastePackagingDiscarded furniture
Village datacrop residue
animal manure
forest residue
MSW, C&D
Category
Crop residues
Animal manures
Forest residues
Landfill wastes
%
Biomass to BioenergyBiomass: renewable energy sources coming from
biological material such as plants, animals,
microorganisms and municipal wastes
Bioenergy ProcessesBiofuels
LiquidsMethanol, Ethanol, Butanol, Biodiesel
GasesMethane, Hydrogen
BioheatWood burning
BioelectricityCombustion in Boiler to TurbineMicrobial Fuel Cells (MFCs)
Conversion Processes
Biological conversionFermentation (methanol, ethanol,
butanol)Anaerobic digestion (methane)Anaerobic respiration (bio-
battery)Chemical conversion
Transesterification (biodiesel)Thermal conversion
CombustionGasificationPyrolysis
Wet biomass(organic waste, manure)
Solid biomass(wood, straw)
Sugar and starch plants(sugar-cane, cereals)
Oil crops and algae(sunflower, soybean)
Biomass
Biomass-to-Bioenergy RoutesBiomass-to-Bioenergy Routes
EthanolButanol
Methyl ester(biodiesel)
Pyrolytic oil
BiogasH2, CH4
Fuel gas
Sugar
Pure Oil
Conversion processes
Ele
ctric
ityH
eat
Ele
ctric
al d
evic
esH
eatin
g
Liqu
id b
iofu
els
Tra
nspo
rt
Biofuels and Bioenergy Application
Anaerobic
fermentation
Gasification
Combustion
Pyrolysis
Hydrolysis
Hydrolysis
Extraction
Crushing
Refining
fermentation
Transesterification
Photosynthesis
6CO
2 +
6H
2O
C
6H
12O
6 +
6O
2
co2
Advantages of Biomass
Widespread availability in many parts of the world Contribution to the security of energy supplies Generally low fuel cost compared with fossil fuels Biomass as a resource can be stored in large amounts, and
bioenergy produced on demand Creation of stable jobs, especially in rural areas Developing technologies and knowledge base offers
opportunities for technology exports Carbon dioxide mitigation and other emission reductions
(SOx, etc.)
Environmental Benefits
Drawbacks of Biomass
Generally low energy content Competition for the resource with food, feed, and material applications
like particle board or paper Generally higher investment costs for conversion into final energy in
comparison with fossil alternatives
Applications
Biofuel Applications: Liquids
Ethanol and Butanol: can be used in gasoline engines either at low blends (up to 10%), in high blends in Flexible Fuel Vehicles or in pure form in adapted engines
Biodiesel: can be used, both blended with fossil diesel and in pure form. Its acceptance by car manufacturers is growing
Process for cellulosic bioethanol
http://www1.eere.energy.gov/biomass/abcs_biofuels.html
Why Butanol?
More similar to gasoline than ethanol Butanol can:
Be transported via existing pipelines (ethanol cannot)Fuel engines designed for use with gasoline without modification
(ethanol cannot) Produced from biomass (biobutanol) as well as petroleum
(petrobutanol) Toxicity issues (no worse than gasoline)
Biodiesel from triglyceride oils
Triglyceride consists of glycerol backbone + 3 fatty acid tails The OH- from the NaOH (or KOH) catalyst facilitates the breaking of the
bonds between fatty acids and glycerol Methanol then binds to the free end of the fatty acid to produce a methyl
ester (aka biodiesel) Multi-step reaction mechanism: Triglyceride→Diglyceride
→Monoglyceride →Methyl esters+ glycerine
GlycerineMethyl Ester
Triglyceride
Methoxide
Biodiesel Production
Biodiesel, glycerin
Fuel GradeBiodiesel
Fertilizer K3PO3
water
Catalyst Mixing
Methanol
Neutralization
Acid (phosphoric)
Biodiesel,impurities
Methanol Recovery
Crude Glycerine
Recoveredmethanol
Wash water
Phase Separationgravity or centrifuge
Purification(washing)
Catalyst NaOH
Crude Biodiesel (methyl ester)Crude glycerinExcess methanolCatalyst KOH
Raw Oil
Transesterification Reaction
Biofuel Applications: Gases
Hydrogen: can be used in fuel cells for generating electricity
Methane: can be combusted directly or converted to ethanol
Bioheat ApplicationsSmall-scale heating systems for
households typically use firewood or pellets
Medium-scale users typically burn wood chips in grate boilers
Large-scale boilers are able to burn a larger variety of fuels, including wood waste and refuse-derived fuel
Biomass Boiler
(for more info: Dr. Harold M. Keener, OSU Wooster, E-mail [email protected])
Bioelectricity Applications
Co-generation: Combustion followed by a water vapor cycle driven turbine engine is the main technology at present
Microbial Fuel Cells (MFCs): Direct conversion of biomass to electricity
Microbial fuel cells (MFCs)
Electrons flow from an anode through a resistor to a cathode where electron acceptors are reduced. Protons flow across a proton exchange membrane (PEM) to complete the circuit.
PE
M
Bio-electro-chemical devices Bacteria as biocatalysts convert the biomass “fuel” directly to
electricity Oxidation-Reduction reaction switches from normal electron
acceptor (e.g., O2, nitrate, sulfate) to a solid electron acceptor: Graphite anode
Bio-electro-chemical devices Bacteria as biocatalysts convert the biomass “fuel” directly to
electricity Oxidation-Reduction reaction switches from normal electron
acceptor (e.g., O2, nitrate, sulfate) to a solid electron acceptor: Graphite anode
It’s all about REDOX CHEMISTRY!
Microbial fuel cells in the lab Microbial fuel cells in the lab • Two-compartment MFC • Proton exchange membrane:
Nafion 117 or Ultrex• Electrodes: Graphite plate
84 cm2
• Working volume: 400 ml
ANODE CATHODE
Membrane
Anode
Cathode
Ano
de
Proton ExchangeMembrane
Cat
hod
e
Anodecompartment
Cathodecompartment
Cellulose
β-Glucan(n≤7)
β-Glucan (n ≤7)
Glucose
Cellodextrin
β- Glucan (n-1)
n≥2
n=1
6CO2 + 24e- + 24H+
Butyrate
4CO2 + 18e- + 18H+
Propionate
Acetate
3CO2 + 28e- + 28H+
2CO2 + 8e- + 8H+
O2
H2O
e-
e-
Not to Scale
Bacteria Cell
BacteriaCell Wall
H+ e-
H+ e-
H+
e-
e-
H+