PRODUCING GREEN ENERGY FROM POST- CONSUMER SOLID FOOD WASTES AT A

WASTEWATER TREATMENT PLANT USING AN INNOVATIVE NEW PROCESS

Presented by: Donald Gray

Innovative Energy Management Workshop December 16, 2008

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Number of Landfills in the United States 1988-2005

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

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Municipal Solid Waste Generation Rates 1960-2005

0

50

100

150

200

250

300

1960 1970 1980 1990 2000 2005

Tota

l MSW

Gen

erat

ed (

mill

ion

tons

)

0

1

2

3

4

5

6

7

8

9

10

Per C

apita

Gen

erat

ed (l

bs/p

erso

n/da

y)

MSW

MSW/cap

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Municipal Solid Waste Recycling Rates 1960-2005

0

5

10

15

20

25

30

35

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

% o

f MSW

Rec

ycle

d

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Total 2006 MSW Generation Before Recycling

PAPER33.9%

YARD12.9%FOOD

12.4%

PLASTICS11.7%

METALS7.6%

TEXTILES7.3%

WOOD5.5%

GLASS5.3%

OTHER3.3%

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Generation and Recovery of Materials in MSW 2006

MaterialWeight

Generated (million tons)

Recovery as a Percent of Generation

Paper and Paperboard 85.2 51.6%

Yard Trimmings 32.4 62.0%

Food Scraps 31.1 2.4%

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EBMUD’s Food Waste Program

Background• Excess digester capacity• Energy Crisis—grant funding

Food waste program development:• Contacted local haulers• MOA with one hauler 2002• Contract with hauler 2003• Completed facility and accepted food waste 2004• Developed new process and filed patent 2006• New production facility in operation and patent issued

2008

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Food Waste Challenges

Contaminants

Processing technology

Permitting

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EBMUD Facility 2004

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Food Waste Delivery

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Delivered Food Waste

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From Food Waste Moyno Pump

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EBMUD-patented Food Waste Recycling Process

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Pulp and Pomace

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Food Waste Pulp Volatile Solids Reduction

0

10

20

30

40

50

60

70

80

90

100

11/25/06 12/9/06 12/23/06 1/6/07 1/20/07 2/3/07 2/17/07 3/3/07 3/17/07

Date

VSD

(%) Thermo

MesoTypical Avg: 55% (1)

10d MCRT 5d MCRT 15d MCRT

NOTES:1. Average values from previous EBMUD municipal sludge digestion studies.

EPA 503 Regulations Minimum 38%EPA 503 Regulations Minimum 38%

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Food Waste Pulp Percent Volatile/Total Solids

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

11/25/06 12/9/06 12/23/06 1/6/07 1/20/07 2/3/07 2/17/07 3/3/07 3/17/07

Date

VS/T

S (%

)

FeedThermoMeso

10d MCRT 5d MCRT 15d MCRT

NOTES:1. Average values from a previous EBMUD municipal sludge digestion study.

Typical Feed Avg 77% (1)

Typical Digested Sludge Average 65% (1)

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Food Waste Pulp Volatile Solids Loading Rate

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

11/25/2006 12/9/2006 12/23/2006 1/6/2007 1/20/2007 2/3/2007 2/17/2007 3/3/2007 3/17/2007

Date

VS L

oadi

ng R

ate

(lb/c

f-day

)

Thermo Test

Meso Test

Recommended Maximum

*Based on WEF MOP 8, pg. 22-27.

10d MCRT 5d MCRT 15d MCRT

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Food Waste Pulp COD Loading Rate

0.0

0.5

1.0

1.5

2.0

2.5

3.0

11/25/2006 12/9/2006 12/23/2006 1/6/2007 1/20/2007 2/3/2007 2/17/2007 3/3/2007 3/17/2007

Date

CO

D L

oadi

ng R

ate

(lb/c

f-day

)

ThermoMeso

Typical: 0.06 to 0.3 lb COD/cf-day*

*Based on M&E 4th Ed. pg 998.

10d MCRT 5d MCRT 15d MCRT

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Food Waste Pulp Total Solids

0

2

4

6

8

10

12

14

16

11/25/06 12/9/06 12/23/06 1/6/07 1/20/07 2/3/07 2/17/07 3/3/07 3/17/07

Date

Tota

l Sol

ids

(%)

FeedThermoMeso

Typical Digester Avg: 2 %(1)

Typical Feed Avg: 4 %(1)

10d MCRT 5d MCRT 15d MCRT

NOTES:1. Average values from previous EBMUD municipal sludge digestion studies.

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Food Waste Pulp Percent Methane in Digester Gas

0

10

20

30

40

50

60

70

80

90

100

11/25/06 12/9/06 12/23/06 1/6/07 1/20/07 2/3/07 2/17/07 3/3/07 3/17/07

Date

% C

H4

ThermoMesoTypical Avg: 63 % (1)

10d MCRT 5d MCRT 15d MCRT

NOTES:1. Average values from a previous EBMUD municipal sludge digestion study.

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Food Waste Pulp Digested Sludge Total Alkalinity

2,000

4,000

6,000

8,000

10,000

12,000

14,000

11/25/06 12/9/06 12/23/06 1/6/07 1/20/07 2/3/07 2/17/07 3/3/07 3/17/07

Date

Tota

l Alk

alin

ity (m

g C

aCO

3/L)

ThermoMeso

Typical Avg: 9,000 mg/L(1)

10d MCRT 5d MCRT 15d MCRT

NOTES:1. Average values from a previous EBMUD municipal sludge digestion study.

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Food Waste vs. Wastewater SolidsParameter Food Waste

PulpWastewater

Solids% VS in Feed 85-90 70-80VS Loading (lbs/ft3-day) 0.60 + 0.20 maxCOD Loading (lbs/ft3-day) 1.25 + 0.06-0.30%TS Fed 10+ 4VSD (%) 80 56Minimum MCRT (days) 10 15Gas Produced (l/l digester vol.) 58 17Biosolids Produced (lbs/lbs fed)

0.28 0.55

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Benefits ObservedFood Waste vs. Wastewater Solids Digestion• Requires about half the digester volume• Produces about half the biosolids/lbs fed• Produces about 3.5 X methane/digester volume

Provides New Renewable Energy SourceDiverts Food Wastes From LandfillsSignificantly Reduces Green House GasesWastewater Treatment Plant Permit compliance should not be impacted

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Challenges ObservedLevel of Food Waste Contaminants Determines Throughput and Costs• Processing time can vary between 1 ½ hrs to 8+ hrs per

load (10-24 tons/load)Labor requirementsProcessing capacity

• Rejects can vary from < 10% to 70+% wet weight• Reject handling at higher % difficult, costly• Accumulation of contaminants in slurry tanks• Equipment appears reliable, but long-term is unknown

Contaminants always present• Requires EBMUD Process or Similar• Pre-Grinding Necessary• Still Some Art Involved

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Conclusions

Exciting opportunity to bring post- consumer food wastes to wastewater treatment plantsMany uncertainties remain to determine long-term feasibility

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