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

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Ele

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evic

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Liqu

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Tra

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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  keener.3@osu.edu)

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+