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Summary of Waste Conversion Technologies

Prepared for NEWMOA

Bryan Staley, PhD, PEPresident 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 WasteConversion?• 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? Recycling

Landfill

- No to partial

conversion (e.g. CH4)

• 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-short-history-of-anaerobic-digestion

Historical Background

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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 WasteConversion 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

Paper/Cardboard Maybe Yes Yes

Plastic Yes Yes

Yard Waste Yes Yes

Food Waste Yes Maybe

Other Organics Maybe Yes

Metal Yes

Glass Yes

Electronics Yes

Bulky Items

% of Generated MSW 15 – 30 % 50 – 60 % 60 – 75 %

Organic waste

‐ Yard Waste (non‐

woody)

‐ Food Waste

‐ Other organics  

(wet)Sorted mixed solid waste

Dry combustibles 

‐ Paper

‐ Plastic

‐ Other organics (dry)

‐ Yard waste (woody)

Waste Conversion Inputs byTechnology & Composition

Conversion Process:

Ideal Inputs:

WTEGasification

Pyrolysis

Anaerobic DigestionFermentation

Hydrothermal CarbonizationHybrid

Processes

-Thermal-Biological

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Types ofWaste 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 ConversionOverview

• 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 ConversionInputs and PreprocessingInputs

• 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 DigestionSchematic

Digester

Biogas (55 ‐

95% methane)

Source separated 

organic waste

Municipal 

wastewater/ 

sewage sludge 

Sale to local 

utility/industry

Electricity

Combustion Engine 

or Gas Turbine

Mixing 

tank

Boiler

Steam Turbine

Biogas cleanup/compression

Solid Digestate 

and Wastewater

(May be 

combined)

Anaerobic Digestion

Sale to grid 

Disposal or soil amendmentRecycle stream

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Biological ConversionComparison

Anaerobic Digestion

• 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

Fermentation

• 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-trash-into-renewable-energy-treasure

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Waste to EnergyInputs & 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 CraneMixing

https://www.asme.org/events/asme-energy-forum/turning-trash-into-renewable-energy-treasure

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Waste to EnergySchematic

Bottom ash, inerts, 

metal for recycling

Flue 

Gas

Heat from Flue Gas

Fly ash and pollutants

Steam

Stack

Electricity

Turbine Generator

Flue Gas 

Cleanup 

Heat 

Recovery 

Boiler (heated 

water tubes)

Combustion Chamber

Incineration 

Grate

Waste Bunker

Waste to EnergyOutputs

• 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 & GasificationIntroduction

• 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 IncinerationGasification

No oxidation Complete oxidationPartial oxidation

750-1650°F 880 to 2200°F1450-3000°F

Endothermic ExothermicEndothermic/Exothermic

Lack of oxygen Excess oxygenControlled oxygen level

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PyrolysisOverview

• 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

GasificationOverview

• Thermochemical transformation of carbon-based feedstock into synthetic natural gas (syngas) using an injected gasification agent– Air

– Oxygen

– Air enriched with oxygen

– Steam

• Two types:– Conventional: occurs at 1,450 – 3,000°F

– Plasma Arc: 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

http://www.waste-management-world.com/content/dam/etc/medialib/new-lib/wmw/online-articles/2012/05/80275.res/_jcr_content/renditions/original

• Currently used for destroying medical waste, chlorine-containing materials, asbestos, and printed circuit boards

• Energy intensive

Pyrolysis & GasificationInputs 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 & GasificationOutputs

Pyrolysis

• Completely carbonized solid “char” or “biochar”

• Heating-oil like liquid “pyrolysis oil”

• Some Syngas

• Composition of outputs vary according to process conditions

Gasification

• Syngas (composition varies based on gasifying agents used)

• Ash and/or slag

http://www.transitiontowns.org.nz/node/1968

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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

43.17

21.2

15.83

13.46

5.85

Steam‐blown

Carbon monoxide

Hydrogen

Methane

Carbon dioxide

Other Hydrocarbons

8.8

8.6

6.5

15.65

4.9

45.8

9.5

Air‐blown

Carbon monoxide

Hydrogen

Methane

Carbon dioxide

Other Hydrocarbons

Nitrogen

Water

Syngas Composition by Gasification Agent

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GasificationSchematic

Ash, slag, and inerts for 

disposal/building materials

Steam

Combustion Engine or 

Gas Turbine

Product Syngas

Fischer‐Tropsch or Other Process

Gasification chamber

Syngas cleanup

Boiler/Heat 

Recovery

Waste pre‐processing 

(drying, sorting etc.)

Turbine

Electricity

Gas

Sale to local 

utility/industry

Waste Heat

Solid waste

Gasif. agent

Liquid fuels and other chemicals

Aldehydes & 

Alcohols

Mixed Alcohols

Methyl Acetate

Acetic Acid

Formaldehyde

Diesel Waxes

Gasoline OlefinsFischer –

Tropsch 

Process

Ethanol

Gasoline Olefins

Hydrogen AmmoniaSyngas (CO + H₂)

Methanol (CH₃OH)

Dimethyl Ether 

(CH₃OCH₃)

Syngas Conversion

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Gasification & PyrolysisComparison

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 CarbonizationOverview

• 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 CarbonizationInputs & 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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http://www.rewmag.com/FileUploads/image/conversion-technology-pathways.jpg

Conversion TechnologyProduct Summary

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)

45

LCA Results: Electricity and Fuel Production

FT Product

No RecyclingCurbside Recycling

lb/ton MSW

gal/ton MSW

lb/ton MSW

gal/ton MSW

Diesel 96 14 70 10Gasoline 184 30 135 22LiquifiedPetroleum Gas (LPG) 12 3 8 2Kerosene 40 6 29 4Residual Fuel Oil 21 3 16 2Refinery Gas 20 14Bitumen 16 12Petroleum Coke 26 19Petroleum Refining Coproduct 22 16Total 437 320

46

579

-27

145

474

114

-100

0

100

200

300

400

500

600

700

LFGTE WTE GFT

Net

Ele

ctri

city

Pro

du

ctio

n (

kWh

/to

n) Case 1

Case 2

Case 1: No recycling.Case 2: Curbside recycling performed. Only non-recycled materials used for energy production

GASIFICATION

BIOFUEL PRODUCTION FROM GASIFICATION

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Results:Global Warming Potential

16

-77

-684-573 -577

-821

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100Landfill Gas-to-Energy Waste-to-Energy Gasification

Net

GW

P (

lb C

O2-

e/ t

on

)

Case 1

Case 2

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 PlannedConversion 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 DigestionProject Examples

• W2E Organic Power/Eisenmann: Columbia, SC– Technology: Wet anaerobic digestion

– Feedstock: Food, grease, waste produce, yard waste

– Pre-processing requirements: Shredding

– Throughput: 130 TPD

– Cost: $23 million

http://www.eisenmann.us.com/http://biomassmagazine.com/articles/5774/w2e-to-build-23-million-wte-facility-in-sc

http://www.zerowasteenergy.com/

• Zero Waste Energy LLC: San Jose, CA (shown)– Technology: Dry

anaerobic digestion

– Feedstock: Organic waste

– Throughput: 740 TPD

FermentationProject 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

GasificationProjects

• 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 dayhttp://www.covantaenergy.com/cleergas.aspx

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Covanta Cleergas™

Plasma GasificationProjects

• 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

– Cost: $4 millionhttp://www.agilyx.com/

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 biocoalfor 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/BiologicalProjects• 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

• 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/

http://fulcrum-bioenergy.com/index.html

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

Additional Projects By Company

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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 InformationBryan Staley, PhD, PE

bstaley@erefdn.org

(919) 861-6876

www.erefdn.org

www.erefcontinuingeducation.org