UCLA Chemical & Biomolecular Engineering Department
Waste Conversion Technologies
101
James Liao and Vasilios Manousiouthakis
UCLA Chemical & Biomolecular Engineering
Department
&
Hydrogen Engineering Research Consortium
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
UCLA Hydrogen Engineering
Research Consortium (HERC)
Hercules cleaning up the stables
of Augeas, following Athena’s
suggestion on where to dig, so
as to let the water clean the
accumulated dirt
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Solid Waste Generation and
Management
Trends in municipal solid-waste generation and
management in the United States, 1960-2010 (Source: NAE 2000).
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Material Classes in the Waste Stream
*1999 California Statewide
http://www.ciwmb.ca.gov/
WasteChar/Study1999
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UCLA Chemical & Biomolecular Engineering Department
Municipal Solid-Waste composition
by weight
*Source: NAE 2000
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UCLA Chemical & Biomolecular Engineering Department
*R. B. Williams et al. 2003
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UCLA Chemical & Biomolecular Engineering Department
Cellulosic Waste
Biomass components of MSW:
Paper/Cardboards
Food
Leaves and Grass
Other Organics
30.2%
15.7%
7.9%
7.0%
C&D Lumber
Prunings, Trimmings
4.9%
2.4%
68.1%
Estimated Cellulosic Components: 40-50%
MSW: 40 M tons.
Cellulosic components: 15-20 M tons.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Conversion Technologies
•
Biochemical:
Anaerobic Digestion
Aerobic conversion
Fermentation
• Thermochemical:
Pyrolysis
Gasification
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UCLA Chemical & Biomolecular Engineering Department
Biochemical - Anaerobic digestion
• A fermentation technique typically employed in waste water
treatment facilities but also the principal process occurring in
landfills.
• Produces fuel gas called biogas containing mostly methane and
carbon dioxide but frequently carrying impurities such as
moisture, H2S, siloxane.
•Anaerobic digestion requires attention to the nutritional
demands of methanogenic bacteria degrading the waste
substrates (C/N ratio is important.)
•Biogas can be used as fuel for engines, gas turbines, fuel cells,
boilers, industrial heaters, other processes, and the
manufacturing of chemicals.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Biochemical - Aerobic Conversion
• Aerobic conversion uses air or oxygen to support the
metabolism of the aerobic microorganisms degrading the
substrate. Nutritional considerations are also important to
the proper functioning of aerobic processes.
•Aerobic processes operate at much higher rates than
anaerobic processes, but generally
do not produce useful fuel gases.
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UCLA Chemical & Biomolecular Engineering Department
Biochemical - Fermentation
• Fermentation generally used industrially to produce fuel
liquids such as ethanol and other chemicals. Also operates
without oxygen.
• Cellulosic feedstocks including the majority of the organic
fraction of MSW, need pretreatment (acid, enzymatic, or
hydrothermal hydrolysis) to depolymerize cellulose and
hemicellulose to monomers used by the yeast and bacteria
employed in the process.
• Lignin in biomass is refractory to fermentation and as a
byproduct is typically considered for use as boiler fuel or as a
feedstock for thermochemical conversion to other fuels and
products.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Converting Cellulose to Ethanol
20 M tons of cellulosic wastes (in CA)  1-2 Billion gal Ethanol.
~ 300 billion gal gasoline/yr used in US.
•Currently, the cost of producing ethanol from cellulose is
estimated to be between $1.15 and $1.43 per gallon in 1998
dollars.
•The cost of producing ethanol could be reduced by as
much as 60 cents per gallon by 2015.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Industrial Process For Fuel Ethanol
Milo
Corn
Wheat
Rye
Barley Water
Tapioca
Thermo-Stable
Alpha Amylase
Glucoamylase
Liquefaction
Saccharification
*
GRINDING
Yeast
Fermentation
Alcohol
Recovery
Distillation &
Dehydration
JET COOKER
>100° C
5–8 MIN
STORAGE
TANK
60° C
8–10 HRS
(optional)
SLURRY
TANK
SECONDARY
LIQUEFACTION
95° C
~90 MIN
*
DDGS
*
pH adjustment steps are not shown
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Cellulosic Material Pre-treatment
•
•
40–50% cellulose, a glucose polymer
25–35% hemicellulose, a sugar
heteropolymer
• 15–20% lignin, a non-fermentable phenylpropene unit;
desirable
Remove, destruct
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Methods of Pretreatment
Dilute Acid, Ammonia, or Lime
Wyman, et al, Bioresource Technology (2005) 1959–1966
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Conceptual Process for Cellulosic
Ethanol Production
Cellulosic Waste
Size reduction
Pretreatment
to remove or destruct
hemicellulose and lignin
Ethanol distillation
Yeast Fermentation
Enzyme digestion to
Release glucose
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Current Bio-Ethanol
Current EtOH Production
= 3.4 billion gal/year (1.3% of gasoline energy)
Incentives for Bio-ethanol production
• $0.51 tax credit per gal
• Energy Policy Act (EPACT) mandate: up to 7.5 billion
gallons of Bio renewable fuel to be used in gasoline by
2012.
Current agriculture waste stockpile (corn stover) will give
7-12 b gallons of EtOH.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Corn EthanolCorn
Production cost: $1.18/gal, Selling price: $1.35-2.6/gal
$1.00
$0.47
$0.80
$0.60
$0.40
$0.57
$0.00
($0.20)
$2.22/Bushel
(=56lb)
DDGS
energy,
amino acids,
and
phosphorus
Energy for
milling,
cooking,
distilling,
and drying
1/3 CO2
1/3 Animal
feed
$0.04/gal
$1.20
$0.20
1/3 EtOH
DDGS
Depreciation
Enzyme, etc
Labor
Utilities
Net corn
From G. Chotani,
$0.23
($0.40)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Cellulosic Ethanol
Current enzyme cost: $0.45/gal
Potential enzyme cost: $0.10/gal
Currently, the cost of producing ethanol from cellulose is
estimated to be between $1.15 and $1.43 per gallon in 1998
dollars.
The cost of producing ethanol could be reduced by as much as 60
cents per gallon by 2015.
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Thermochemical - Pyrolysis
• Similar to gasification except generally optimized for the
production of fuel liquids (pyrolysis oils).
•Usually, processes that thermally degrade material without the
addition of any air or oxygen are considered pyrolysis.
• Direct pyrolysis liquids may be toxic, corrosive, oxidatively
unstable, and difficult to handle.
•Catalytic cracking employs catalysts in the reaction to accelerate
the breakdown of high molecular weight compounds into smaller
products.
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UCLA Chemical & Biomolecular Engineering Department
Thermochemical - Gasification
•Conversion via partial oxidation using substoichiometric air or
oxygen or by indirect heating
• Produce fuel gases (synthesis gas), principally CO, H2,
methane, and lighter hydrocarbons in association with CO2 and
N2.
• Gasification products can be used to produce methanol,
Fischer-Tropsch (FT) liquids11, and other liquid and gaseous
fuels and chemicals.
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UCLA Chemical & Biomolecular Engineering Department
Gasifier Types
Reactant contacting patterns
Operating temperatures
A) Moving bed (nonslagging,
countercurrent)
B) Fluidized bed
C) Entrained flow
D) Molten bath
HERC Hydrogen Engineering Research Consortium UCLA
Types of gasification reactor representing different methods of contacting reactants and operating
UCLA Chemical & Biomolecular Engineering Department
Waste Gasification Technologies
Advantages of moving-bed gasifiers
(1) The technology is mature with many commercial designs available.
(2) A large variety fuels can be used.
(3) The gasifier may be operated for long periods.
(4) The carbon conversion efficiency is high.
(5) The thermal efficiency is high because of countercurrent flow.
Disadvantages of moving-bed gasifiers
(1) Internal moving parts with some mechanical complexity are employed
(2) Gasifier capacity is limited by gas flow rates
(3) Feedstock fines must be handled separately (e.g., via agglomeration)
(4) Excess steam for temperature control leads to thermal losses
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Waste Gasification Technologies
Advantages of fluidized-bed gasifiers
(1) Commercial designs are available
(2) The technology does not involve moving parts
(3) The large fuel inventory provides safety, reliability, and stability
(4) A large variety of fuels can be handled
(5) The amount of tar and phenol formation is low
(6) Product composition is steady due to uniform conditions in the bed
(7) Moderate gasification temperatures can be used
Disadvantages of fluidized bed-gasifiers
(1) Capacity flexibility is limited by entrainment at high gas velocities
(2) Caking wastes may require pretreatment
(4) Difficult to handle feeds with conflicting temperature requirements
(5) Loss of carbon in ash occurs due to uniform solids composition of the bed
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Waste Gasification Technologies
Advantages of Entrained-Flow Gasifiers
(1) Commercial designs are available
(2) The gasifier has no moving parts and a simpler geometry than a fluidized bed
(3) The gasifier has the highest capacity per unit volume
(4) Any type of waste may be used without pretreatment
(5) No fines are rejected
(6) The product gas is free of tar and phenols
(6) The slagged ash produced is inert and has a low carbon content
Disadvantages of entrained-flow gasifiers
(1) Nozzles and heat recovery in the presence of molten slag are critical design areas
(2) Advanced control techniques required to ensure safe, reliable operation
(3) Pulverizing and drying of surface moisture are required
(4) The high gasification temperatures causes thermal losses
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Waste Gasification Technologies
Advantages of molten-bath gasifiers
(1) The large heat inventory provides safety, reliability, and stability
(2) The high-temperature bath ensures safe gasification
(3) Wide variety of feedstocks can be used without pretreatment
(4) Products contains no sulfur, halogens, tar, phenols (retained in molten bath)
Disadvantages of molten-bath gasifiers
(1) Cleanup of molten media is complicated
(2) Capacity is limited by melt entrainment at high flow rates
(3) Ash is removed as liquid slag, leading to loss of sensible heat
(4) The melt is highly corrosive to refractory at the gasifier temperatures
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Gasification Process Flow Diagram
Source: Orr D., Maxwell D., “A Comparison of Gasification and Incineration of Hazardous
Wastes”, Radian International LLC Report for DOE, 2000
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Toxic Contaminants in Gasifier gas
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UCLA Chemical & Biomolecular Engineering Department
Toxic Metals in Gasifier ash
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UCLA Chemical & Biomolecular Engineering Department
HERC Vision for MSW Management
• Embrace Zero Waste Principles
• Develop Source Reduction/Recycling strategies
• Develop Material Substitution strategies based on
sustainability concepts
• Convert material that reaches “waste” status to
hydrogen, electricity, and usable/recyclable products, in
facilities featuring only oxygen and nitrogen air
emissions, and carbon sequestration
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
A Zero-Waste Conversion Plant
Recyclable
Light Metals
Recyclable
Heavy Metals
Waste
Volatile Metal
Separation
Subsystem
Gasification
Subsystem
Chemical
Manufacturing
Subsystem
Chemicals
(HCL,HF,S,..)
Impurities
Shift
Subsystem
Oxygen
Air
Oxygen
Production
Subsystem
Nitrogen
Oxygen
Hydrogen
Purification
Subsystem
Nitrogen, Oxygen
Hydrogen
Energy and Possible Water Flows Among Subsystems Not Shown
Carbon
Sequestration
Subsystem
HERC Hydrogen Engineering Research Consortium UCLA
Carbon
(Dioxide
or other
chemical
form)
UCLA Chemical & Biomolecular Engineering Department
Elements by Boiling Point
Atomic #
2
1
10
7
9
18
8
36
54
86
17
35
53
15
80
85
16
33
55
87
34
37
19
48
11
Name
BP (°C)
helium
-269
hydrogen
-253
neon
-246
nitrogen
-196
fluorine
-188
argon
-186
oxygen
-183
krypton
-152
xenon
-107
radon
-62
chlorine
-34
bromine
59
iodine
184
white phosphorus
280
mercury
357
astatine
370
sulfur
445
arsenic
613
caesium
671
francium
677
selenium
685
rubidium
688
potassium
754
cadmium
767
sodium
890
Atomic #
30
84
52
12
3
51
38
81
20
83
56
88
82
49
25
47
50
14
32
31
4
5
29
24
13
Name
BP (°C)
zinc
907
polonium
962
tellurium
990
magnesium
1105
lithium
1317
antimony
1380
strontium
1384
thallium
1457
calcium
1487
bismuth
1560
barium
1640
radium
1737
lead
1744
indium
2000
manganese
2041
silver
2212
tin
2270
silicon
2355
germanium
2355
gallium
2403
beryllium
2487
boron
2550
copper
2582
chromium
2642
aluminium
2647
Atomic #
21
28
27
26
46
79
22
39
23
45
78
6
44
77
40
72
41
6
43
76
73
42
75
74
Name
BP (°C)
scandium
2831
nickel
2837
cobalt
2877
iron
2887
palladium
2970
gold
3080
titanium
3277
yttrium
3338
vanadium
3377
rhodium
3727
platinum
3827
Graphite (carbon)
3900
ruthenium
3900
iridium
4130
zirconium
4377
hafnium
4602
niobium
4742
Diamond (carbon)
4827
technetium
4877
osmium
5297
tantalum
5427
molybdenum
5560
rhenium
5627
tungsten
5660
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Dioxin Vapor Pressure
Data taken from Rordorf et al.,
Chemosphere Vol. 15, #9 – 12;
p. 2073 – 2076 (1986)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Natural Gas to Hydrogen:
Steam reforming and CO2 sequestration
H2O
298 K
H2O
H2O
Removal
SMR
Reactor
1
atm
CH4 + 2H2O = CO2 + 4H2
Unit
CO2 178 K 98.5%
Removal
CO
Unit
CH4
CH4 1 atm Liquefact.
298 K
Unit
CO
Removal
CH4
Removal
Unit
Unit A
CH4
Removal
H2
Compress.
Unit B
Unit
1 atm
2
Dry ice
298 K
99.9999%
300 atm
H2
Source: Posada A, Manousiouthakis V. “Hydrogen and dry ice production through phase equilibrium
separation and methane reforming”, J. Power Sources (2005)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Natural Gas to Hydrogen:
Steam reforming
feed
CH4
heat
electricity
H2
(300 atm)
CH4 + 2H2O = CO2 + 4H2
feed
H2O
ΔHo: 164.9 kJ/mol CH4
CO2
Cooling
Process
kgCH4/kgH2 kgCO2/kgH2 $/kg H2
Stoichiometric
1.99
5.45
0.68
Conventional (C)
3.30
8.99
1.17
C + Integrated (I)
2.84
7.71
0.97
C + I + CO2 sequest.
3.72
0
1.31
Natural gas cost: 0.33 $/kg (Jul 2005)
CO2 sequest. cost: 13 $/ton CO2
Source: Posada A, Manousiouthakis V. “Hydrogen and dry ice production through phase equilibrium
separation and methane reforming”, J. Power Sources (2005)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Biomass to Hydrogen
Gasification
Steam
Reformer
Biomass
WGS
PSA
Reactor(s)
H2
99.999+%
Steam
Condensed
Waste Gas (Fuel)
Water
Process
kg Biomass (bone dry)
/ kgH2
$ / kg H2
13.65
1.92
Battelle/FERCO 13.80
1.68
Pyrolysis
1.08
IGT
23.83
Source: Spath PL, Mann MK,
Amos WA. “Update of Hydrogen
from Biomass-Determination of
the Delivered Cost of Hydrogen”,
NREL (2003)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
DaimlerChrysler-UCLA H2 Vehicle
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Hydrogen Vehicle
Vehicle Type
Mercedes-Benz A-Class (extended)
Fuel cell system
PEM, 72 kW (97 hp)
Drive
Electric motor
Power
65 kW (87 hp)
Maximum torque
210 Newton-meters (156 foot-pounds)
Fuel
Hydrogen (350 bar / 5000 psi)
Range
160 km (100 miles)
Maximum Speed
140 km / h (87 mph)
Battery
NiMh, air cooled
Peak Power
15 kW (20 hp) / 20 kW (27 hp)
Capacity
6.5 Ah; 1.4 kWh (4800 BTU)
Source: “F-Cell Quick Reference Card”, Daimler Chrysler
HERC Hydrogen Engineering Research Consortium UCLA
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PEM Fuel Cell Mechanism
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UCLA Chemical & Biomolecular Engineering Department
Well-to-Wheels (WTW) Analysis
Fuel
Primary Source
Vehicle Powertrain
WTW Green House
Gas Emission*
( gCO2 eq. / 100 km )
WTW Energy Use*
MJ fuel / 100 km )
(
Fuel L. Heating Value
Fuel Cost
WTW Energy Cost
US$ / 100 km )
(
Gasoline
Hydrogen
Oil
Natural gas
Internal Combust.
Fuel Cell
197
93
254
161
117.92 MJ/gal
119.93 MJ/kg
3.10 $/gal
4.55 $/kg (DOE)
5.00 $/kg
6.68
6.11
6.71
* Source: “Well-to-Wheels analysis of future automotive fuels and powertrains in the European
context” (2004). Vehicle comparable to a Volkswagen Golf (33.8 mi/gal gasoline)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Hydrogen Safety
Hydrogen
Methane
Gasoline
Ignition Temp.
585 oC
540 oC
230 - 480 oC
Flammability
Limits
4 – 75 % by vol. †
5.3 – 15 % by vol. † 1 – 7.6 % by vol. †
Explosion Limits 15 – 59 % by vol. † 5.3 – 15 % by vol. † 1 – 7.6 % by vol. †
Energy content
120.1 MJ / kg*
50.5 MJ / kg
121.3 MJ / gallon*
Ignition Energy
0.02 mJ
≈ 0.2 mJ
≈ 0.2 mJ
†Source: “Hydrogen Fuel Cell Engines and Related Technologies Course Manual”, College of the Desert Energy
Technology Training Center - © 2001 National Academies Press (module 1, pages 25 and 26)
*Source: “The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs”, National Research Council
and National Academy of Engineering - © 2004 National Academies Press (page 240)
HERC Hydrogen Engineering Research Consortium UCLA
UCLA Chemical & Biomolecular Engineering Department
Hydrogen v. Gasoline Vehicles
*Source: Dr. Michael R. Swain, University of Miami, Coral Gables
Gasoline Leak: 1/16 in diameter hole in fuel line; 70,000 BTU energy released; one failure needed; flame visible
Hydrogen Leak: Tank Pressure Release Device; 175,000 BTU energy released; four failures needed; flame visibility
due to Na containing particulate matter
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Hydrogen v. Gasoline Vehicles
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UCLA Chemical & Biomolecular Engineering Department
Hydrogen v. Gasoline Vehicles
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UCLA Chemical & Biomolecular Engineering Department
Hydrogen v. Gasoline Vehicles
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