8/29/2013
Summary of
Waste Conversion Technologies
Prepared for NEWMOA
Bryan Staley, PhD, PE
President and CEO
Overview
•
•
•
•
Waste conversion defined/historical background
Diversion and conversion hierarchy
Waste composition and diversion/conversion
Types of waste conversion technologies
– Biological:
• Anaerobic digestion
• Fermentation
– Thermal:
• WTE
• Pyrolysis and Gasification
• Hydrothermal Carbonization
• Technology comparison using LCA
• Current state of practice
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What is Waste
Conversion?
• Rearrangement of majority of carbon atoms to a
valuable product
• Process that converts waste to:
– energy (heat, electricity)
– fuel (methane, gasoline)
– chemical products (alcohols, ammonia)
The Difference?
Landfill
- No to partial
conversion (e.g. CH4)
Recycling
Historical Background
• Pyrolysis as a chemical process has been around since
ancient times (ex. conversion of wood to charcoal)
• Achieved by covering burning wood with leaves and dirt.
Resulting product was used as a soil amendment.
• Coal was gasified in the mid 19th century to produce coal gas
or “town gas” used to light street lamps
• Anaerobic digestion first utilized to produce biogas around
the same time. First US plant began operation in 1939.
• Pyrolysis and gasification first seriously considered as a
commercial waste treatment methods in the 1970s oil crisis
http://extension.psu.edu/natural-resources/energy/waste-to-energy/resources/biogas/links/history-of-anaerobic-digestion/a-shorthistory-of-anaerobic-digestion
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Conversion and the Waste
Management Hierarchy
WTE
WTE
Conversion and the Waste
Management Hierarchy
2 Categories of Waste Conversion
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Types of Waste
Conversion Technology
• Biological
– Utilizes microbial processes to transform waste
– Restricted to biodegradable waste
– Primarily inputs include food and yard waste
• Thermal
– Applies external heat source to transform waste
– Restricted to combustible materials
– Primary inputs include paper, plastic waste, biomass
Conversion and the Waste
Management Hierarchy
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Waste Composition and
Diversion Options
Component
Composting
Recycling
Conversion
Maybe
Yes
Yes
Yes
Yes
Paper/Cardboard
Plastic
Yard Waste
Yes
Yes
Food Waste
Yes
Maybe
Maybe
Yes
Other Organics
Metal
Yes
Glass
Yes
Electronics
Yes
Bulky Items
% of Generated MSW
15 – 30 %
50 – 60 %
60 – 75 %
Waste Conversion Inputs by
Technology & Composition
Conversion Process:
-Thermal
-Biological
WTE
Gasification
Pyrolysis
Anaerobic Digestion
Fermentation
Hybrid
Processes Hydrothermal Carbonization
Ideal Inputs:
Dry combustibles Organic waste
‐ Paper
‐ Yard Waste (non‐
woody)
‐ Plastic
‐ Food Waste
‐ Other organics (dry)
‐ Yard waste (woody)
Sorted mixed solid waste
‐ Other organics (wet)
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Types of
Waste Conversion Technologies
Waste Conversion
Process Steps (general)
1. Mechanical pre-processing of the waste
•
•
•
•
Smaller particle size
More uniform
Removal of contaminants
Lower moisture content (for most thermal technologies)
2. Conversion process
• Thermal or biological
3. Treatment of process outputs
• Disposal of process waste products
• Post-conversion processing
Input
Processing
Primary
Process
Output
Processing
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Biological Conversion
Biological Conversion
Overview
• Anaerobic digestion (AD)
– Biological degradation of waste in an oxygen free
environment
– Produces biogas, which is mostly methane
– Historically used on wastewater sludge and animal
waste
– Two types: wet and dry
• Fermentation
– Similar to AD, but end product is typically an alcohol
(e.g. ethanol) rather than methane
– Can be used in conjunction with gasification
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Biological Conversion
Inputs and Preprocessing
Inputs
• Food and non-woody yard waste
• Lignocellulosic materials such as wood, paper,
and cardboard can be partially digested, but
are better suited for recycling and other
methods of disposal
Pre-processing Requirements
• Removal of glass, plastic, and metal
• Organic material is shredded for size reduction
• Process determines desired moisture content
Anaerobic Digestion
Schematic
Boiler
Biogas cleanup/compression
Anaerobic Digestion
Source separated organic waste
Sale to local utility/industry
Combustion Engine or Gas Turbine
Biogas (55 ‐
95% methane)
Steam Turbine
Digester
Mixing tank
Municipal wastewater/ sewage sludge Electricity
(May be combined)
Sale to grid Recycle stream
Solid Digestate and Wastewater
Disposal or soil amendment
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Biological Conversion
Comparison
Anaerobic Digestion
Fermentation
• Hydrolysis is initial step
• Final process step is methanogenesis
• Primary output product is biogas
• Currently utilized worldwide to treat MSW as well as other feedstocks
• Hydrolysis is initial step
• Final process step is distillation
• Primary output products are alcohols
• Currently, few facilities exist worldwide for MSW; facilities using other feedstocks do
Thermal Conversion
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Waste-to-Energy (WTE)
Waste to Energy (WTE)
Overview
• Also called “incineration with
energy recovery”
• Best known and most widely
used conversion method
• Referred to as “Mass Burn”
without preprocessing of waste
• Generally occurs at combustion
temperatures of 880 to 2200°F
https://www.asme.org/events/asme-energy-forum/turning-trashinto-renewable-energy-treasure
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Waste to Energy
Inputs & Pre-processing
Inputs
• All MSW
Pre-Processing Requirements
• Very little pre-processing required
– Removal/sorting for recyclables (typ. done away from
facility as part of a recycling program)
– Removal of:
• Bulky items and white goods
• Chlorinated plastics such as PVC
• Mixing for homogeneity (e.g. with feed crane)
Feed Crane
Mixing
https://www.asme.org/events/asme-energy-forum/turning-trash-into-renewable-energy-treasure
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Waste to Energy
Schematic
Heat from Flue Gas
Combustion Chamber
Waste Bunker
Incineration Grate
Boiler (heated water tubes)
Flue Gas
Stack
Heat Recovery Flue Gas Cleanup Fly ash and pollutants
Steam
Bottom ash, inerts, metal for recycling
Turbine Generator
Electricity
Waste to Energy
Outputs
• Energy in the form of electricity, steam or hot water
• Fly ash and air pollution control residue: contains
pollutants/toxins
• Bottom ash: relatively inert
• Ash makes up 5-15% of feedstock by mass
• Most of the initial feedstock goes up the stack as
water or carbon dioxide
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Pyrolysis & Gasification
Pyrolysis & Gasification
Introduction
• Two closely related processes
• Similar to incineration, both employ heated chambers
to transform waste to a simplified molecular state
• Differ in their chamber temperature and air, oxygen,
or steam inputs
Pyrolysis
Gasification
Incineration
Lack of oxygen
No oxidation
Endothermic
Controlled oxygen level
Partial oxidation
Endothermic/Exothermic
Excess oxygen
Complete oxidation
Exothermic
750-1650°F
1450-3000°F
880 to 2200°F
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Pyrolysis
Overview
• Endothermic thermal decomposition process in
sealed chamber sealed off to prevent air infiltration
• Feedstock is “baked” and transformed
• Generally occurs at 750-1650°F
• Outputs generally higher in liquids/solids content
than those of gasification
• Two forms: Slow and fast (“flash”). Slower pyrolysis
results in higher solids content of outputs
• Primarily used for waste destruction
Gasification
Overview
• Thermochemical transformation of carbon-based
feedstock into synthetic natural gas (syngas) using
an injected gasification agent
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–
–
–
Air
Oxygen
Air enriched with oxygen
Steam
• Two types:
– Conventional:
– Plasma Arc:
occurs at 1,450 – 3,000°F
occurs at 7,200 - 12,600°F
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Plasma Arc Gasification
• Uses plasma torch to gasify the feedstock
• Non-combustibles (glass, metal, etc.) end up as inert
vitrified slag - used to vitrify incineration ash.
• Theoretically more energy efficient than conventional
gasification
• Difficult to scale up
• Currently used for destroying
medical waste, chlorinecontaining materials, asbestos,
and printed circuit boards
• Energy intensive
http://www.waste-managementworld.com/content/dam/etc/medialib/new-lib/wmw/onlinearticles/2012/05/80275.res/_jcr_content/renditions/original
Pyrolysis & Gasification
Inputs and Pre-processing
• Mixed MSW with removal of glass, metal, inerts,
contaminants
– leaves paper, plastic, wood, other organics
• Consistent and uniform particle size
• homogeneous non-MSW feedstock also a viable option
for co-processing (dry wood, agricultural waste, etc.)
• Low moisture content
– Gasification: typ. <10%
– Pyrolysis:
typ. < 20%
– Achieved through removal of food waste or possibly
drying
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Refuse Derived Fuel
• Paper, plastic, waste wood, rubber and some
other materials are collected or sorted separately
• Material is then shredded into a fluff or pelletized
for homogeneity and easier handling
http://www.itrimpianti.com/public/userfiles/files/Foto%203(2).jpg
Pyrolysis & Gasification
Outputs
Pyrolysis
• Completely carbonized solid “char” or “biochar”
• Heating-oil like liquid “pyrolysis oil”
• Some Syngas
• Composition of outputs vary
according to process conditions
http://www.transitiontowns.org.nz/node/1968
Gasification
• Syngas (composition varies based on gasifying
agents used)
• Ash and/or slag
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Syngas
• Synthetic natural gas produced as a result of
gasification
• Composed primarily of carbon monoxide,
hydrogen, methane, and carbon dioxide
• Largest component is nitrogen when air is used as
gasification agent
• Cleanup and compression of syngas generally
follows the gasification process
• Can be chemically transformed through catalytic
processes (e.g. Fischer-Tropsch) into methanol,
ethanol etc.
Syngas Composition &
Gasifying Agents
• Primary gasification agents:
– Air: cheapest. Injected in stoichiometric ratio above that achieved by
an open chamber (WTE)
– Oxygen: only economically viable in large scale operations
– Steam: results in large amounts of hydrogen and carbon monoxide
Syngas Composition by Gasification Agent
Steam‐blown
Air‐blown
5.85
9.5
13.46
8.8
43.17
Carbon monoxide
8.6
Carbon monoxide
Hydrogen
Hydrogen
6.5
Methane
15.83
Carbon dioxide
Other Hydrocarbons
21.2
Methane
Carbon dioxide
15.65
45.8
Other Hydrocarbons
Nitrogen
4.9
Water
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Gasification
Schematic
Waste pre‐processing (drying, sorting etc.)
Gasification chamber
Gasif. agent
Waste Heat
Syngas cleanup
Gas
Ash, slag, and inerts for disposal/building materials
Product
Syngas
Turbine
Boiler/Heat Recovery
Steam
Solid waste
Sale to local utility/industry
Fischer‐Tropsch or Other Process
Combustion Engine or Gas Turbine
Electricity
Liquid fuels and other chemicals
Syngas Conversion
Aldehydes & Alcohols
Gasoline Olefins
Fischer –
Tropsch Process
Syngas (CO + H₂)
Hydrogen
Ammonia
Diesel Waxes
Mixed Alcohols
Ethanol
Methanol (CH₃OH)
Formaldehyde
Acetic Acid
Gasoline Olefins
Dimethyl Ether (CH₃OCH₃)
Methyl Acetate
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Gasification & Pyrolysis
Comparison
Gasification
• Partial and controlled oxygen input
• Temperatures range from 1450 ‐ 3000°F
• Results primarily in syngas
• Primarily designed for the production of syngas
• Can be combined with pyrolysis in a two stage process
• Faster than pyrolysis
Pyrolysis
• No oxygen input into process
• Temperatures range from 750 ‐ 2200°F • Results in char, pyrolysis oils, and some syngas
• Primarily designed for waste destruction
• Can be combined with gasification in a two stage process
Hydrothermal Carbonization
(emerging technology)
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Hydrothermal Carbonization
Overview
• Chemical acceleration of natural geothermal
processes using an acid catalyst
• Waste is heated in a “pressure cooker” for 4-24
hours
• Relatively low temperatures around 400°F
• Process requires wet waste
• Transforms feedstock material into coal-like product
called “hydrochar” (coalification)
• May be ideal for carbon sequestration
http://www.ava-co2.com/web/pages/en/products/ava-biochar.php
Hydrothermal Carbonization
Inputs & Pre-processing
Inputs
• Needs high moisture content (> 70%) compared to
other typical thermal treatment feedstocks
• Any organic material can be “coalified” including
lignocellulosic materials such as paper but food
waste ideal due to moisture content
• Acid catalyst such as citric acid is necessary
Pre-processing
• Inerts such as glass and metal should be removed
prior to carbonization
• Not yet done on a large scale, so relatively unknown
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Hydrothermal
Carbonization Outputs
• Solid hydrochar (lignite-grade coal)
– Can be used as coal alternative or soil amendment
– May be effective for carbon sequestration
• Liquids (with high COD)
• Gas
– Mainly carbon dioxide
– Some energy rich hydrocarbons
http://www.ava-co2.com/web/pages/de/downloads/foto-archiv/andere.php#
Thermal Conversion
Technology Overview
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Conversion Technology
Product Summary
http://www.rewmag.com/FileUploads/image/conversion-technology-pathways.jpg
Comparing Technologies
Using Life Cycle Assessment
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LCA Goals
To conduct a life-cycle assessment that
– accounts for all processes required to transform MSW to a
usable fuel
– estimates syngas yield, electricity generation, and fuel
production
– calculates the environmental impacts associated with fuel
production
To compare the environmental impacts of
– gasification to liquid fuels
– landfill gas-to-energy
– waste-to-energy (incineration with electricity generation)
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LCA Results: Electricity
and Fuel Production
BIOFUEL PRODUCTION FROM GASIFICATION
Net Electricity Production (kWh/ton)
700
No Recycling
Case 1
600
Case 2
500
400
300
579
474
200
100
0
145
114
46
-27
-100
LFGTE
WTE
GFT
GASIFICATION
lb/ton
FT Product
MSW
Diesel
96
Gasoline
184
Liquified
Petroleum Gas
(LPG)
12
Kerosene
40
Residual Fuel
Oil
21
Refinery Gas
20
Bitumen
16
Petroleum Coke 26
Petroleum
Refining
Coproduct
22
Total
437
Curbside
Recycling
gal/ton
MSW
14
30
lb/ton
MSW
70
135
gal/ton
MSW
10
22
3
6
8
29
2
4
3
16
14
12
19
2
16
320
Case 1: No recycling.
Case 2: Curbside recycling performed. Only non-recycled materials used for energy production
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Results:
Global Warming Potential
Landfill Gas-to-Energy
Waste-to-Energy
Gasification
100
0
16
-77
Net GWP (lb CO2-e/ ton)
-100
-200
-573
-300
-577
-684
-400
-821
-500
-600
-700
-800
Case 1
Case 2
-900
Case 1: No recycling.
Case 2: Curbside recycling performed. Only non-recycled materials used for energy production
State of Practice
Source: GBB Consulting, Inc. (www.gbbinc.com) & EREF internal research
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Current and Planned
Conversion Projects
• ~150 operating AD, gasification, pyrolysis or
hybrid companies worldwide handling MSW
• Breakdown of companies worldwide:
•
•
•
•
•
67 Anaerobic Digestion
48 Gasification
19 Plasma Gasification
16 Pyrolysis
1 Hydrothermal Carbonization
Biological Treatment
• Fermentation
– Only a few stand-alone facilities exist
– Typically used in conjunction with thermal treatment
• Anaerobic Digestion
– Stand alone facilities treating organic component of MSW
• 39 facilities identified in operation or under development
• 25 of these are in California
– Co-digestion facilities
• AD’s at domestic wastewater treatment plants primarily designed to
digest sludge
• On-Farm AD’s designed to digest manure/other ag. organics
• Accept food waste, green yard waste, FOG, industrial food wastes
(e.g., whey, milk by-products, etc.)
• 250+ facilities reported as doing or having capability for co-digestion
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Anaerobic Digestion
Project Examples
• W2E Organic Power/Eisenmann: Columbia, SC
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–
–
–
–
Technology: Wet anaerobic digestion
Feedstock: Food, grease, waste produce, yard waste
Pre-processing requirements: Shredding
Throughput: 130 TPD
Cost: $23 million
• Zero Waste Energy LLC:
San Jose, CA (shown)
– Technology: Dry
anaerobic digestion
– Feedstock: Organic waste
– Throughput: 740 TPD http://biomassmagazine.com/articles/5774/w2e-to-build-23-million-wte-facility-in-sc
http://www.eisenmann.us.com/
http://www.zerowasteenergy.com/
Fermentation
Project Example
• Fiberight: Various locations
– Technology: Ethanol fermentation, combustion of
plastic
– Feedstock: MSW
– Pre-processing requirements: Sorting and primary
pulping
– Throughput: ~350 TPD
– Cost: Around $50 million
http://fiberight.com/
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Thermal Conversion &
Hybrid Projects
• Approximately 17 facilities in operation,
under construction, or in final planning
stages in the U.S.
– 7 Gasification/plasma gasification
• Companies: Covanta, Enerkem, Plasco Energy
– 2 Pyrolysis
• Companies: Agilyx, RES Polyflow
– 8 Hybrid (gasification + fermentation)
• Fulcrum BioEnergy, INEOS Bio
Gasification
Projects
• Enerkem: Pontotoc, MS (under development)
–
–
–
–
–
Technology: Gasification with chemical ethanol production
Feedstock: Sorted MSW and wood residue
Pre-processing requirements: Sorting
Throughput: 10 million gallons of ethanol per year
Cost: At least $130 million
• Covanta Cleergas™: Tulsa, OK
–
–
–
–
Technology: Gasification with syngas combustion
Feedstock: Post-recycling waste
Pre-processing requirements: None
Throughput: 350 tons of waste per day
http://www.covantaenergy.com/cleergas.aspx
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Covanta Cleergas™
Plasma Gasification
Projects
• Plasco Energy: Ottawa, Canada
– Technology: Conventional gasification followed by plasma
refinement of syngas
– Feedstock: Post-recycled MSW
– Pre-processing requirements: Pre-sorting for recyclables
– Throughput: 300 TPD
– Cost: $270 million total investment in Plasco
– To be implemented by the Salinas Valley SWA, CA
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Pyrolysis Projects
• Agilyx: Tigard, OR (demo facility)
–
–
–
–
Technology: Pyrolysis of plastic into crude oil
Feedstock: “Hard-to-recycle” plastic
Pre-processing requirements: Sorting for plastic, shredding
Throughput: 50 TPD (“typical system”)
• RES Polyflow: Akron, OH (demo under development)
–
–
–
–
–
Technology: Pyrolysis of plastic into transportation fuels
Feedstock: Waste plastics, tires, carpets etc.
Pre-processing requirements: Sorting for plastic, shredding
Throughput: 52 TPD
http://www.agilyx.com/
Cost: $4 million
http://www.respolyflow.com/
Hydrothermal
Carbonization Projects
• AWA-CO2: Germany (2012 first plant worldwide)
– Technology: Hydrothermal
Carbonization
– Feedstock: Wet and dry
biomass “of all kinds” except
meat and some manures
– Products: CO2 neutral biocoal
for energy generation and CO2
negative biochar for soil
enrichment
http://www.ava-co2.com/web/pages/en/home.php
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Hybrid Thermal/Biological
Projects
• Fulcrum BioEnergy: McCarran, NV
– Technology: Gasification w/chemical synthesis or alcoholic
fermentation of syngas into ethanol and other final products
– Feedstock: Post-recycled MSW
– Pre-processing requirements: Recyclables and inerts removed
– Throughput: 10.5 million gallons of biofuel produced per year
– Cost: $175 million for construction
http://fulcrum-bioenergy.com/index.html
• INEOS Bio: Vero Beach, FL
– Technology: Gasification with fermentation
– Feedstock: Organic waste (some residual plastic left in feedstock)
– Pre-processing requirements: Drying and mechanical treatment
(i.e. shredding, densification)
– Throughput: Demo facility takes about 400 TPD
– Cost: $130 million total investment
http://www.ineos.com/en/businesses/INEOS-Bio/
Additional Projects
By Company
Gasification
•
InEnTec
•
•
•
•
Arlington, OR, MSW plasma gasifier
Midland, MI, industrial waste gasification facility
Richland, WA, testing center (processes some MSW)
Plasco Energy
•
Santa Barbara, CA, shortlisted
Hybrid
•
Fulcrum BioEnergy
•
•
Four additional facilities under development
INEOS Bio
•
•
Fayetteville, AK, pilot plant
Lake County, IN, on hold
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Parting Comments
• Use of thermal waste conversion technologies is
promising… but still speculative in the U.S.
• Key Hurdles:
1) Integration within existing solid waste management infrastructure
2) Scalability or Process Capacity
3) Economics/Cost-Benefit have yet to be proven or fully evaluated
• High capital expenditure
• Revenue from product sales alone may not be enough for economic viability
• Tipping fees may also not tip the scale favorably for some technologies
– $15 to $20/ton in Southwest
– $80-100+ per ton in the Northeast
• “Show me your data”
– Many companies out there are start-ups
– Data they may use may not be from their own facility and may not
even be based on anything ‘real’
THANK YOU
Contact Information
Bryan Staley, PhD, PE
[email protected]
(919) 861-6876
www.erefdn.org
www.erefcontinuingeducation.org
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