Biomass & Biofuels

San Jose State University

FX RongèreApril 2008

Biomass 2nd Renewable in California

California Gross System Power for 2006 (GWh)

Fuel Type In-State NW Imports SW Imports GSP GSP PercentageCoal 17,573 5,467 23,195 46,235 15.70%Large Hydro 43,088 10,608 2,343 56,039 19.00%Natural Gas 106,968 2,051 13,207 122,226 41.50%Nuclear 31,959 556 5,635 38,150 12.90%Renewables 30,514 1,122 579 32,215 10.90%

Biomass 5,735 430 120 6,285 2.10%Geothermal 13,448 0 260 13,708 4.70%Small Hydro 5,788 448 0 6,236 2.10%

Solar 616 616 0.20%Wind 4,927 244 199 5,370 1.80%

TOTAL 230,102 19,804 44,959 294,865 100.00%

Source: CEC http://www.energy.ca.gov/electricity/gross_system_power.html

Bio-fuels: Clean and Renewable Energy?

Biomass stores energy and carbon

Source: Boyle, Renewable Energy, 2nd edition, 2004

Conversion efficiency

Typical solar energy in the Central Valley : 6 kWh/m2/day

6 KWh/ m2/ day

2,190 KWh/ m2/ year

Reaching the leaves 10% 219 KWh/ m2/ yearPart of spectrum contributing to Photosynthesis

50% 110 KWh/ m2/ year

Absorption coefficient of leaves 85% 93 KWh/ m2/ year

Converted to store energy 20% 19 KWh/ m2/ year

Non directly consumed 60% 11 KWh/ m2/ year0.5% 11 KWh/ m2/ year

402 GJ /ha/year154 MMBTU/acre/year

Average daily Solar Energy

Stored Energy

Annual Solar Energy

Biomass conversion and storage rate: 0.5%

Effective radiation on photosynthesis

So

lar

Sp

ectr

al I

rrad

ian

ce (

103 W

.m-2.μ

m)

No conversionConversion

min.. hh

λ (m)

Carbon Balance

Theoretically:

Biomass is carbon neutral

Actually: Additional CO2 emissions for:

Planting, Maintaining and Harvesting Water management Fertilizer Biofuel manufacturing

Avoided decomposition GHG emissions for residues

Life cycle analysis depending on the bio-fuel and technologies

CombustionEmittedExcessStoredspirationDesorbedesisPhotosynthAbsorbed

COOCCOCO 22Re

22

Global Warming Potential

GWP: Normalized index provided by the Intergovernmental Panel on Climate Change (IPCC)

IPCC was established in 1988 by two United Nations organizations: the World Meteorological Organization (WMO), the United Nations Environment Program

(UNEP),

to evaluate the risk of climate change caused by human activity.

IPCC shared the 2007 Nobel Peace Prize with former Vice President Al Gore.

GWP

By definition:

Time Horizon is very important because of the complex decay of the chemical components in the atmosphere

timetheduringxofionconcentrattheofVariationtx

xtodueabsorptionraredAdditionala

yearsHorizonTimeTH

componentchemicalx

dttCOa

dttxaxGWP

x

TH

CO

TH

x

:)(

inf:

)(:

:

).(.

).(.)(

0 2

0

2

GWP

Values provided by IPCC in 2001

20 years 100 years 500 years

Methane CH4 3.7x10-4 12 62 23 7

Nitrous oxide N2O 3.1x10-3 114 275 296 156

CFC-12 CCl2F2 0.32 100 10,200 10,600 5,200

HCFC-22 CHClF2 0.2 12 4,800 1,700 540

HFC-134a CH2FCF3 0.15 14 3,300 1,300 400

Time horizonGas

Chlorofluorocarbons

Hydrochlorofluorocarbons

Hydrofluorocarbons

Radiative efficiency

(Wm-2 ppb-1)

Lifetime (years)

Global Warming Potential

Source: IPCC Climate Change 2001 The Scientific Basishttp://www.grida.no/climate/ipcc_tar/wg1/index.htm

Net life cycle emissions from Electricity Generation

CO2 SO2 NOx

10 2.42 3.913 0.88 1.5529 0.11 1.95

364 2.54 3.3

4 1.13 2.0131 1.12 2.3849 0.34 2.6

14 0.06 0.4324 0.06 0.57

446 0 0.5955 11.8 4.3

Natural gas, CCGTCoal, best practice

Fossil fuels

Poultry litterStrawForestry residuesMunicipal Solid Waste (MSW)

Sewage gasAnimal slurryLandfill gas

Energy cropsForestry residues

Emissions in kg/ MWh

Combustion, steam turbine

Anaerobic digestion, gas engine

Gasification, BIGCC

Source: Boyle, Renewable Energy, 2nd edition, 2004

Net Life Cycle Greenhouse Gas Emissions

Taking the avoided decomposition methane emission into account forest residue direct combustion may have a negative GWP

Source: Margaret K. Mann and Pamela L. Spath LIFE CYCLE ASSESSMENT COMPARISONS OF ELECTRICITY FROM BIOMASS, COAL, AND NATURAL GAS, 2002 Annual Meeting of the American Institute of Chemical Engineers November 2002

Resource in the USA

Biofuels

Biofuels cover a broad range of technologies and applications:

Thermochemical Conversion

Direct Combustion

Direct Combustion

Gasification

Gasification

PyrolysisLiquefaction

PyrolysisLiquefaction

Biochemical Conversion

Anaerobic Digestion

Anaerobic Digestion

Fermentation

Fermentation

Extraction

Extraction

Heat Electricity Transportation

Steam Gas Oil Charcoal Bio-dieselBiogas Ethanol

Source: From Boyle, Renewable Energy, 2nd edition, 2004

Biomass for Power Generation in California (2005)

Wood

40%

Agricultural

waste

11%

Landfill gas

12%

Digesters

5%

Others

32%

Direct Combustion

Wood and straw residues are dominant About 600 MWe in California

Location of wood power plants in California

Number ofPlants

California 29 588Maine 7 184

Michigan 7 165Florida 5 151

Washington 3 83Virginia 2 80Vermont 2 70

New Hampshire 4 51Pennsylvania 3 50North Carolina 3 56TOTAL USA 65 1,478

Plants Operating in 2003State Sales

generation, MW

Wood combustion Wood has an energy content of 6 to 18

MJ/kg depending on its moisture Wood macro-molecules (cellulose polymers)

break-down starts at about 300oC (575oF) It generates inflammable gas (CnHm) which

burn with the air oxygen (Gaseous combustion releases about 85% of the energy content of dry wood)

The combustion requires about 5.5 kg of air per kg of dry wood

Remaining charcoal is directly oxidized at high temperature (600oC)

Straw-fired power plant

Source: Boyle, Renewable Energy, 2nd edition, 2004

Typical Wood Power Plant

Example of a 10 MWe industrial power plant in Denmark

Steam Cycle

Steam Cycle

0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

40004000

s [kJ/kg-K]

h [

kJ

/kg

] 90 bar

30 bar

0.055 bar

SteamNBS

turbineW

CondensorQ

Cycle conversion rate: η=35%

GeneratorSteamQ

pumpW

Tracy Power Plant

Wood Power Plant in Tracy: 20 MWe

1,000 ton per day of wood

Honey Lake Power Plant

Wood Honey Lake Power Plant: 36MW Wood processing: 1,300 tpd Condensate water pre-heating with

geothermal source

Gasification To obtain a better efficiency and a better control

of the combustion and pollution, pyrolysis, charcoal gasification and combustion are controlled separately.

Gasifier Types

Examples of technologies

Counter current Gasifier (Babcock&Wilcox)Fluid bed Gasifier (JFE)

Integrated Gas Combined Cycle

IGCC is the association of a gasifier, a gas turbine and a steam cycle

Biomass

Gas turbine generates electricity by direct combustion of syngas

Heat of the exhaust gas is recovered to run a steam cycle

Gas Turbine

CompressorTurbine

Combustion

5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.07.00

200

400

600

800

1000

1200

s [kJ/kg-K]

h [

kJ

/kg

]

1 bar

17 bar

Air

Conversion rate: 36%Brayton Cycle

IGCC

Steam Cycle

0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

40004000

s [kJ/kg-K]

h [

kJ

/kg

]

90 bar

30 bar

0.055 bar

SteamNBS

Conversion rate: 29%

IGCC

Conversion rate

Example:ηIGCC= 55%

TurbineGasCycleSteamTurbineGasIGCC 1.

Fluidized Bed Gasifier in Gussing Burgenland Austria operated on wood chips

Wood bio-mass potential in California

Forest biomass represents about 50% of the wood residue resource

The potential for the forestry residue is 27 MM BDT/year

Biomass wood source (2005)

Urban Wood

31%

Forest

46%

Agricultural

16%

Food

Processing

7%

Source: CEC An Assessment of Biomass Resources in California, 2006

(BDT = Bone Dry Ton)

Calculation of the Electricity Generation potential

Energy content: Ec=18 MJ/kg Conversion rate: η=25% Capacity factor: CF=85%

GW

CF

EPower

yTWhETontonBDTE

year

Cyearyear

1.48760.

/30...

This potential represents about 10% of the electricity consumption in California and about 15 times what is currently in operation

Municipal Solid Waste

Source: Boyle, Renewable Energy, 2nd edition, 2004