Opportunities for Energy Production from Solid Waste in the

Mexicali/Imperial Valley Region

Kevin WhittyChristina Smith

The University of UtahSalt Lake City, Utah

Margarito QuinteroSara Ojeda Benitez

Universidad Autónoma de Baja CaliforniaMexicali, Mexico

SCERP Project HW-06-3

SCERP Annual Technical ConferenceSCERP Annual Technical ConferenceDecember 5-6, 2008December 5-6, 2008

Tempe, ArizonaTempe, Arizona

2

Outline

Background / Motivation

Project Objectives

Approach

Sampling and Analysis

Key Findings

Conclusions

3

Mexicali and the Imperial Valley

MexicaliMexicali

4

The Imperial Valley Region

5

Mexicali / Imperial Valley Region

Imperial Valley• Area 28,000 km2 • Population: 1.16 million

Mexicali Municipality• Area: 12,000 km2 • Population (2008): 1,000,010• Population expected to double by 2035

Approx. 700 tons solid waste produced per day

Approx. 100 to 400 MW power consumed• Varies by season• Primarily natural gas based

6

Yearly Electricity Consumption

50,000

100,000

150,000

200,000

250,000

300,000

1988 1990 1992 1994 1996 1998 2000 2002 2004

February

August

0

Co

nsu

mp

tion

, MW

h

Year

Total Monthly Consumption – Mexicali Residential Sector

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Monthly Electricity Consumption

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

50,000

100,000

150,000

200,000

250,000

0

Co

nsu

mp

tion

, MW

h

Year 2000 – Residential Sector

8

Waste Management Scheme

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Project Objectives

Assess potential for converting non-hazardous solid waste to electrical power• Consider entire Imperial Valley region• Consider residential, commercial, industrial waste

Evaluate waste production• Quantity of waste• Quality of waste from a fuel perspective

Consider several possible technologies• Incineration• Gasification• Landfill methane capture

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Approach / Methodology

Task 1: Survey of solid waste

Task 2: Characterization of solid waste• Gross characterization

• Chemical characterization

• Thermochemical characterization

Task 3: Evaluation of energy production technologies• Technical feasibility (feedstock quantity, quality)

• Maturity of the technology

• Cost

11

Task 1: Waste Survey

Split into three demographic groups• Low• Medium• High

Consider all four seasons of the year

Challenges…• Lack of cooperation from private contractors

responsible for commercial and industrial waste• Lack of cooperation from U.S. side of the border

Focus primarily on residential waste

12

Location of Sampling Colonies

13

Waste Sampling

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

21 22 23 24 25 1m

1m

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Result of Waste Survey

Roughly 678 tons of solid waste per year available for energy production

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Task 2: Characterization of Waste

Gross characterization (metal, plastic, paper, etc.)• Effort to obtain representative samples• Three socioeconomic strata over 4 seasons

Chemical characterization• Homogenization of sample• Analysis performed by external lab• Proximate, ultimate, energy value analysis

Thermochemical characterization• Determine volatility of sample versus temperature

Challenge to obtain representative, homogeneous samples

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Waste Classification Categories

Cotton

Cardboard

Fine waste

Cardboard packaging

Synthetic fiber

Bone

Rubber

Aluminum cans

China and ceramic

Wood

Building and demolition material

Iron material

Tin cans (Iron material)

Non iron metals

Paper

Disposable diapers

Sanitary waste

Plastic film

Rigid plastic

PET

Polyurethane

Extended polystyrene

Polyethylene foam

Food waste

Yard trimmings

Fabrics

Colored glass

Clear glass

Electric batteries

Others

17

Spring Waste Classification

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Classification of Waste Samples

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

High Med Low High Med Low High Med Low High Med Low

Com

posi

tion

(wei

ght%

)

Autumn Winter Spring Summer

Paper, cardboard, natural fibers

Wood, yard waste

Plastics

Other wastes

Non-combustible(metal, glass, etc.)

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Proximate Analysis

Volatile matter

Fixed carbon

Ash

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

High Med Low High Med Low High Med Low High Med Low

Wei

ght%

Autumn Winter Spring Summer

20

Ultimate Analysis

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

High Med Low High Med Low High Med Low High Med Low

Com

posi

tion

(wei

ght%

)

Autumn Winter Spring Summer

Nitrogen (N)

Sulfur (S)

Oxygen (O, diff)

Hydrogen (H)

Carbon (C)

Chlorine (Cl)

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Energy Value of Waste

0

2,000

4,000

6,000

8,000

10,000

12,000

High Med Low High Med Low High Med Low High Med Low

Hea

ting

valu

e (B

tu/lb

dry

)

Autumn Winter Spring Summer

Dry Basis

Average: 5,860 Btu/lb

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Thermochemical Characterization

Thermogravimetric analysis to track mass loss as a function of temperature

Indication of volatility (reactivity) of fuel

Required that samples were homogenized to a fine powder

23

Weight Loss vs. TemperatureLow Socioeconomic Stratum

0%

20%

40%

60%

80%

100%

0 200 400 600 800 1000Temperature, °C

We

igh

t, p

erc

en

t of i

niti

al

Winter

Autumn

Summer

Spring

24

Weight Loss vs. TemperatureMedium Socioeconomic Stratum

0%

20%

40%

60%

80%

100%

0 200 400 600 800 1000Temperature, °C

We

igh

t, p

erc

en

t of i

niti

al

Winter

Autumn

Summer

25

Weight Loss vs. TemperatureHigh Socioeconomic Stratum

0%

20%

40%

60%

80%

100%

0 200 400 600 800 1000Temperature, °C

We

igh

t, p

erc

en

t of i

niti

al

Autumn

Winter

Spring

Summer

26

Task 3: Energy Production Evaluation

Total thermal energy input (fuel input) approx. 77 MWth on continuous basis

Corresponding electrical output approx. 23 MWel on continuous basis

Actual output can be adjusted for time of day and season to correspond to demand

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Energy Production Alternatives

Incineration• Sufficient waste production to support at least one

incinerator• Best technology option

– Mature technology– Costs are reasonable at this scale

• Consider removal of non-combustible components to produce higher energy value "refuse-derived fuel" (RDF)

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Energy Production Alternatives (cont.)

Gasification• Fluidized bed gasification best approach• Amount of available waste too little to justify cost and

complexity• Technology not currently mature enough to

recommend

Landfill methane capture• Requires waste in existing landfill• Relatively little electricity generation (< 5 MW)• New landfill recently opened• Possibly use on old landfill

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Conclusions

Approx. 680 tons solid waste/year available for energy production in Mexicali region

Waste composition and quality varies significantly with season and source

Average energy content approx. 6,000 Btu/lb

Sufficient waste to support one incineration-based system

Potential to dramatically reduce quantity of waste sent to landfill

Additional study recommended

30

Acknowledgements

Co-authors

SCERP

Department of Chemical Engineering

Institute for Clean and Secure Energy