Bioenergy from
Agricultural Wastes
Ann D. Christy, Ph.D., P.E.
Associate Professor
Dept of Food, Agricultural, and
Biological Engineering
USAIN April 2008
World Energy Prospects
World's Population
12 10
10 6.7
Population
8
(billion)
6
4 Increase in
2
Population Energy demand
0
2008 2050
63-
Year
60%
160%
Source:
•CIA's The World Factbook
• World POPClock Projection, U.S. Census Bureau
• Energy Sources, 26:1119-1129,2004
Other concerns
³Pollution
³Climate change
³Resource depletion
Renewable energy sources
Summary of energy resources consumption in United States, 2004
•By 2030, bio-energy, 15-20% energy consumption
Source:
USDA-DOE, 2005, http://www.eere.energy.gov/biomass/publications.html.
Overview
³Bioenergy history
³Ag wastes and other biomass
³Biomass to Bioenergy
³Conversion processes
³Pros & Cons
³Applications
³Biofuels
³Bioheat
³Bioelectricity
Some U.S.
bioenergy history
Bioenergy is not new!
³1850s: Ethanol used for lighting
(http://www.eia.doe.gov/
kids/energyfacts/sources/renewable/ethanol.html#motorfuel)
³1860s-1906: Ethanol tax enacted (making it
no longer competitive with kerosene for lights)
³1896: 1st ethanol-fueled automobile, the
Ford Quadricycle
(http://www.nesea.org/greencarclub/factsheets_ethanol.pdf)
More bioenergy
history
(photo from http://www.modelt.org/gallery/picz.asp?iPic=129)
³1908: 1st flex-fuel car, the Ford Model T
³1919-1933: Prohibition banned ethanol unless
mixed with petroleum
³WWI and WWII: Ethanol used due to high oil costs
³Early 1960s: Acetone-Butanol-Ethanol industrial
fermentation discontinued in US
³Today, about 110 new U.S. ethanol refineries in
operation and 75 more planned
Ag wastes and
other biomass
³Waste Biomass
³Crop and forestry residues, animal
manure, food processing waste, yard
waste, municipal and C&D solid wastes,
sewage, industrial waste
³New Biomass: (Terrestrial & Aquatic)
³Solar energy and CO2 converted via
photosynthesis to organic compounds
³Conventionally harvested for food, feed,
fiber, & construction materials
Agricultural and Forestry Wastes
³Crop residues
³Animal manures
³Food / feed processing residues
³Logging residues (harvesting
and clearing)
³Wood processing mill residues
³Paper & pulping waste slurries
Municipal garbage & other
landfilled wastes
³Municipal Solid Waste
³Landfill gas-to-energy
³Pre- and post-consumer residues
³Urban wood residues
³Construction & Demolition wastes
³Tree trimmings
³Yard waste
³Packaging
³Discarded furniture
% U.S. Data
crop residue
animal manure
forest residue
MSW, C&D
Category Millions of U.S. (%)
dry tons/yr
Crop 218.9 43
(modified from residues
Perlack et al., 2005)
Animal 35.1 7
manures
Forest 178.8 35
residues
Landfill 78 15
wastes
%
crop residue
Ohio data
animal manure
forest residue
(modified from Jeanty
MSW, C&D et al., 2004)
Category Billions of Ohio (%)
BTUs
Crop residues 53,717 18
Animal 2,393 1
manures
Forest residues 33,988 12
Landfill wastes 199,707 69
Biomass to Bioenergy
³Biomass: renewable energy sources coming
from biological material such as plants, animals,
microorganisms and municipal wastes
Bioenergy Types
³Biofuels
³Liquids
³Methanol, Ethanol, Butanol, Biodiesel
³Gases
³Methane, Hydrogen
³Bioheat
³Wood burning
³Bioelectricity
³Combustion in Boiler to Turbine
³Microbial Fuel Cells (MFCs)
Conversion Processes
³Biological conversion
³Fermentation (methanol,
ethanol, butanol)
³Anaerobic digestion
(methane)
³Anaerobic respiration (bio-
battery)
³Chemical conversion
³Transesterification
(biodiesel)
³Thermal conversion
³Combustion
³Gasification
³Pyrolysis
Biomass-to-Bioenergy Routes
Conversion
Photosynthesis Biomass processes Biofuels and Bioenergy Application
Heating
Heat
Wet biomass Anaerobic Biogas
(organic waste, manure) H2, CH4
C6H12O6 + 6O2
fermentation
Electrical devices
Electricity
Gasification
Fuel gas
Solid biomass Combustion
(wood, straw)
Pyrolysis
Pyrolytic oil
Hydrolysis
co2
Sugar and starch plants Hydrolysis Ethanol
Sugar Butanol
6CO2 + 6H2O
(sugar-cane, cereals)
Liquid biofuels
Extraction
fermentation
Transport
Oil crops and algae Crushing
Methyl ester
(sunflower, soybean) Pure Oil
Refining (biodiesel)
Transesterification
Advantages of Biomass
³ Widespread availability in many parts of the world
³ Contribution to the security of energy supplies
³ Generally low fuel cost compared with fossil fuels
³ Biomass as a resource can be stored in large
amounts, and bioenergy produced on demand
³ Creation of stable jobs, especially in rural areas
³ Developing technologies and knowledge base offers
opportunities for technology exports
³ Carbon dioxide mitigation and other emission
reductions (SOx, etc.)
Environmental Benefits
Drawbacks of Biomass
³Generally low energy content
³Competition for the resource with food,
feed, and material applications like
particle board or paper
³Generally higher investment costs for
conversion into final energy in
comparison with fossil alternatives
Applications
Biofuel Applications: Liquids
³Ethanol 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
³Biodiesel: can be used, both
blended with fossil diesel and in
pure form. Its acceptance by car
manufacturers is growing
Process for cellulosic bioethanol
³ http://www1.eere.energy.gov/biomass/abcs_biofuels.html
Why Butanol?
³More similar to gasoline than ethanol
³Butanol can:
³ Be transported via existing pipelines
(ethanol cannot)
³Fuel engines designed for use with gasoline
without modification (ethanol cannot)
³Produced from biomass (biobutanol) as
well as petroleum (petrobutanol)
³Toxicity issues (no worse than gasoline)
Biodiesel from triglyceride oils
Methoxide
Methyl Ester
Triglyceride Glycerine
³ Triglyceride consists of glycerol backbone + 3 fatty acid tails
³ The OH- from the NaOH (or KOH) catalyst facilitates the breaking
of the bonds between fatty acids and glycerol
³ Methanol then binds to the free end of the fatty acid to produce a
methyl ester (aka biodiesel)
³ Multi-step reaction mechanism: Triglyceride→Diglyceride
→Monoglyceride →Methyl esters+ glycerine
Biodiesel Production
Methanol Raw Oil
Catalyst NaOH
Crude Biodiesel (methyl ester)
Crude glycerin Acid (phosphoric)
Excess methanol
Catalyst KOH
Catalyst Mixing Transesterification
Reaction Neutralization
Methanol Recovery
Recovered
methanol
Biodiesel,
glycerin
Phase Separation
gravity or centrifuge Crude Glycerine
Biodiesel,
impurities
Purification Wash water
(washing)
water
Fertilizer Fuel Grade
K3PO3 Biodiesel
Biofuel Applications: Gases
³Hydrogen: can be used in
fuel cells for generating
electricity
³Methane: can be
combusted directly or converted
to ethanol
Bioheat Applications
³Small-scale heating systems
for households typically use
firewood or pellets
³Medium-scale users typically
burn wood chips in grate
boilers
³Large-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 keener.3@osu.edu)
Bioelectricity Applications
³Co-generation:
Combustion followed by a
water vapor cycle driven
turbine engine is the main
technology at present
³Microbial Fuel Cells
(MFCs): Direct conversion
of biomass to electricity
Microbial fuel cells (MFCs)
PEM
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.
³Bio-electro-chemical devices
³Bacteria as biocatalysts convert the
biomass “fuel” directly to electricity
³Oxidation-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
•Two-compartment MFC
• Proton exchange membrane:
Nafion 117 or Ultrex Membrane
• Electrodes: Graphite plate
84 cm2 Cathode
• Working volume: 400 ml
ANODE CATHODE
Anode
Not to Scale
6CO2 + 24e- + 24H+ e-
e-
2CO2 + 8e- + 8H+
Cellulose
Cathode
Acetate
H+
e-
H+
n=1 e- e-
Glucose
e-
β-Glucan β-Glucan (n ≤7)
(n≤7) H+ O2
H+
n≥2
Propionate
Anode
Cellodextrin
Bacteria
Cell Wall
3CO2 + 28e- + 28H+
H2 O
Proton Exchange
β- Glucan (n-1) Membrane
Butyrate
Anode Bacteria Cell 4CO2 + 18e- + 18H+ Cathode
compartment compartment
My own MFC story
³Undergraduate in-class presentation, 2003
³ Bond, D.R. Holmes, D.E., Tender L.M., Lovley D.R. 2002. Electrode-
reducing microorganisms that harvest energy from marine sediments.
Science 295: 483–485.
³Extra-curricular student team project, 2004-2005
³USEPA - P3 first round winner 2005
³#1 in ASABE’s Gunlogson National Competition 2005
³Research program, 2005 to present
³3 Ph.D. students, 2 undergrad honors theses, 4 faculty
³Over $200,000 in grant funding
³High school science class project online resource
http://digitalunion.osu.edu/r2/summer07/nskrinak/index.html
References
³ Ezeji, T., N. Qureshi, H.P. Blaschek. 2007. Butanol production from agricultural residues: Impact of
degradation products on Clostridum beijerinckii growth and butanol fermentation. Biotechnol.
Bioeng. 97, 1460-1469.
³ Jeanty, P.W., D. Warren, and F. Hitzhusen. 2004. Assessing Ohio’s biomass resources for energy
potential using GIS. OSU Dept of Ag, Env., and Development Economics, for Ohio Dept of
Development.
http://www.puc.state.oh.us/emplibrary/files/media/biomass/bioenergyresourceassessment.pdf
³ Klass, Donald L. 1998. Biomass for Renewable Energy, Fuels, and Chemicals. Academic Press.
ISBN: 9780124109506.
³ Perlack et al. 2005. Biomass as feedstock for a bioenergy and bioproducts industry: The technical
feasibility of a billion-ton annual supply. USDOE-USDA.
http://www.puc.state.oh.us/emplibrary/files/media/biomass/BiomassFeedstock.pdf
³ Rabaey, K., Verstraete, W. 2005. Microbial fuel cells: Novel biotechnology for energy generation.
Trends. Biotechnol. 23:291-298.
³ Rismani-Yazdi, H., Christy, A. D., Dehority, B.A., Morrison, M., Yu, Z. and Tuovinen, O. H. 2007.
Electricity generation from cellulose by rumen microorganisms in microbial fuel cells. Biotechnol.
Bioeng. 97, 1398-1407.
³ Skrinak, N. 2007. OSU Microbial Fuel Cell Learning Center
<http://digitalunion.osu.edu/r2/summer07/nskrinak/index.html>
³ USDOE Biomass Program. ABCs of Biofuels
<http://www1.eere.energy.gov/biomass/abcs_biofuels.html>. Accessed April 2008.
For more info
(or to request reference list)
Ann D. Christy, Ph.D., P.E.
Associate Professor
Dept of Food, Agricultural, and
Biological Engineering
614-292-3171
Email: christy.14@osu.edu
