An Introduction to Biochar With an Emphasis on Its Properties

An Intro Introduc ductio tion n to Bioch Biochar ar with an an Emphasis on its Properties and Potential for Climate Change Mitigation Jim Amonette Pacific Northwest National Laboratory Richland, WA 99352 USA PNW Biochar Biochar Initiative Initiative Meeting Meeting 21 May 2009

PNNL-SA-66736

Outline What is Biochar? How is it Made? Pyrolysis and Hydrothermal Carbonization Processes Feedstocks Yields

What are its Properties? Physical Chemical

How can it be Used? Energy Soil Fertility Carbon Sequestration

Where does it fit in the Environmental Technology Landscape? Summary

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What is Biochar? “Biochar “Biochar is a fine-graine fine-grained d charcoal charcoal high in organ organic ic carbon  carbon  and largely resistant to decomposition. It is produced  from pyrolys pyrolysis is of plant plant and waste waste feedstoc feedstocks. ks. As a soil  soil  amendmen amendment, t, biochar biochar creates creates a recalcitrant recalcitrant soil soil carbon  carbon  pool that is carbon-negative, serving as a net  withdrawal of atmospheric carbon dioxide stored in  highly recalcitrant soil carbon stocks. The enhanced  nutrient retention capacity of biochar-amended biochar-amended soil not  only reduces the total fertilizer requirements, but also  the climate and environmental impact of croplands.”  (Internatio (International nal Biochar Biochar Initiative Initiative Scientific Scientific Adviso Advisory  ry  Committee)

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What is Biochar? Product Solid product resulting from advanced thermal degradation of biomass

Technology Biofuel   —process heat, bio-oil, and gases (steam, volatile HCs) Soil Amendment   —sorbent  —sorbent for for cations cations and organics, organics, liming liming agent, agent, inoculation carrier Climate Change Mitigation   —highly recalcitrant pool for C, avoidance of N2O and CH4 emissions, carbon negative energy, increased net primary productivity (NPP)

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How Ho w is Bi Bioc ocha harr Ma Made de? ? Major Techniques: Slow Pyrolysis traditional (dirty, low char yields) and modern (clean, high char yields) Flash Pyrolysis modern, high pressure, higher char yields Fast Pyrolysis modern, maximizes bio-oil production, low char yields Gasification modern, maximizes bio-gas production, minimizes bio-oil production, low char yields but highly recalcitrant Hydrothermal Carbonization under development, wet feedstock, high pressure, highest “char” yield but quite different composition and probably not as recalcitrant as pyrol pyrolyti ytic c carbon carbons s

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Slow Pyrolysis—Continuous Pyrolysis—Continuous Auger Feed Exhaust gas and heat Generator

Gas turbine Air

Electricity

Lignocellulosic feedstock

Gas cleaner and separator

Mill

Hopper

Flue gas

Steam

Motor

Pyrolysis gases

Pyrolysis

Dryer

reactor

Feeder

Cyclone

Combustor

Char

Heat Air Biochar storage

courtesy Robert Brown JE Amonette 24Apr2009

Fastt Pyrolys Fas Pyrolysis is Fl Fluid uidize ized d Bed React Reactor or Lignocellulosic feedstock

Pyrolysis gases Vapor, gas,

Mill

Flue

char

gas

products

Cyclone Quencher

Hopper

Pyrolysis reactor Motor

Biochar storage

Feeder

Fluidizing gas

Combustor

Air Brown (2009)

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Bio-oil storage

Char

Bio-oil

Pyrolysis Competition between three processes as biomass is heated: Biocha Biocharr and gas gas forma formatio tion n Liquid and tar formation Gasification and carbonization

Relative rates for these processes depend on: Highest treatment temperature (HTT) Heating rate Volatile removal rate Feedstock residence time

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Competit Comp etition ion Amon Among g Pyro Pyrolysi lysis s Proc Processes esses Factors favoring bioc biocha harr form format atio ion n Lower temperature Slower heating rates Slower volatilization rates Longer feedstock residence times

In general, process is more important than feedstock in determining products of pyrolysis

Spruce Wood, Slow Pyrolysis, Vacuum (Demirbas, 2001) 90 80 70

Char Gas Tar+Liquid

60

   %    t   w50  ,    d    l 40   e    i    Y 30

20 10 0 200

300

400

500

600

700

800

900

800

900

High Heating Temperature, C

Eastern Red Maple Wood, Fast Pyrolysis, High Purge Rate (Scott et al., 1988) 90 80 70

Char Gas Liquid

60

   %    t   w50  ,    d    l 40   e    i    Y

30 20 10

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0 200

300

400

500

600

High Heating Heating Tempe rature, C

700

Wood Char Yields from Pyrolysis

Figure from Amonette Amonette and Joseph (2009) (2009) showing data data of Figueiredo Figueiredo et al. (1989), (1989), Demirbas (2001), Antal et al. (2000), (2000), Scott et al. (1988), (1988), and Schenkel Schenkel (1999) (1999) as presented presented by Antal and Gronli Gronli (2003),. (2003),.

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Feedstocks Essentially all forms of biomass can be converted to biochar Preferable forms include: forest thinnings, crop residues (e.g., corn stover, alfalfa stems, grain husks), yard waste, paper sludge, manures, bone meal Trace element (Si, K, Ca, P) and lignin contents vary Lignin content can affect char yields

Lignin Lignin Content, Temperature, T emperature, and Char Yield Slow Pyrolysis, Vacuum (Demirbas, 2001) 50

y = 0.39x + 26.76

45

R2 = 0.99

40

Husks, Shells, Kernels

   %    t 35   w  , 30    d    l   e    i 25    Y   r 20   a    h 15    C

Corn Cob Wood

y = 0.33x + 15.29 R2 = 0.96

Char (277 C) Char (877 C)

10 5 0 0

10

20

30

40

Biomass Lignin Content, wt%

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50

60

What are the Properties of Biochar? Pine Wood Char

Oak Wood Char

Corn Cob Char

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Physical Properties

    w     o       l       S      t     s     a       F     s     a       G

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Physical Properties Change with HTT a )

b )

Downie et al., al., 2009 2009

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Kercher Kercher and Nagle, Nagle, 2003

Physical Structure and Chemical Properties Depend on Carbon Bonding Network

Radovic Radovic et al., al., 2001 13C

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CP-MAS NMR Amonette et al., 2008

X-ray Diffraction Analysis

Gasification and Fast Fast Pyroly Pyrolysis sis Chars Chars

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Slow Pyrolys Pyrolysis is and Hydrother Hydrothermal mal Chars Chars (steam present) Combustion Char (high mineral content)

Chemical Properties

    w     o       l       S      t     s     a       F     s     a       G

Slow Pyrolysis chars produced in presence of steam at 475° 475°C tend to be acidic (carboxylic acid groups activated) Fast Pyrolysis chars produced in absence of steam at 500°C 500°C tend to be slightly basic Gasification Gasificat ion chars produced p roduced in i n presence presence of steam at 700° 700 °C tend to be very basic and make good liming agents JE Amonette 24Apr2009

Surface Chemistry 1200

NaOH Analyte

Slow Pyrolysis (steam)

Na2CO3 Analyte

1000

NaHCO3 Analyte Fast Pyrolysis (no steam)

HCl Analyte

800 80 0

Gasification (steam)

600 60 0

400 40 0

200 20 0

0 OK EB

‐200 20 0

PBEB

PCEB

PCN

OAK

PNNL‐M PNN PNNL‐P

PNNL‐S

HW

O K (CSA)

WS

CSB

pH-Dependentt Exchange Capacities pH-Dependen Oak Feedstock 1000 Slow Slow Pyrolysis yr olysis (s team), team), 475°C

OKEB 800

  g    k    /   q 600   e   m  ,   y 400    t    i   c   a   p   a 200    C   n   o 0    i    t   p 0   r   o    S -200   n   o    I

OAK OK (CSA)

Fast Pyrolys Pyrolys is, 500°C Gasification (steam), 700°C

2

4

6

8

-400

-600

pH

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10

12

14

How can can Bioch Biochar ar Te Techn chnol olog ogy y be Used? Used? Generate Carbon-Negative Energy Soil Amendment Carbon Sequestration

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Compariso Comp arison n of of Bioch Biochar ar Prod Productio uction n Metho Methods ds Carbonization Method

Products

Net Energy Released, GJ/t C

Fossil C (Coal) Offset Efficiency

Solid C Production Efficiency

Fast Pyrolysis

CH4, CO2, BioOils, H2O, Char

22.0

0.65

0.15

Slow Pyrolysis

Char, tars, CH4, CO2, H2O

17.7

0.53

0.5

“lignite”, H2O

5.5

0.16

1.0

CO2, H2O

38.4

0.97

0.01?

Hydrothermal Conversion

Combustion

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The Bi Biofuel N2O Problem Recent work (Crutzen (Crutzen et al., 2007, Atmos.Chem. Atmos.Chem. Phys. Phys. Disc. 7:11191; Del Grosso, 2008, Eos 89:529) suggests that globally, N2O product production ion averag averages es at 4% 4% (+/(+/- 1%) of of N that is fixed IPCC reports have accounted only for field measurements of N2O emitted, which show values close to 1%, but ignore other indicators indicators discussed discussed by by Crutzen Crutzen et al. al. If 4% is correct, correct, then then combustion combustion of biofuels biofuels except for high cellulose (low-N) fuels will actually increase global warming relative to petroleum due to large global warming potential of N2O Biocha Biocharr avoids avoids thi this s issue issue Ties up reactive N in a stable pool Eliminates potential N2O emissions from manures and other biomass sources converted to biochar Decreases N2O emissions in field by improving im proving N-fertilizer use efficiency and increasing air-filled porosity JE Amonette 24Apr2009

Soil Amendment Biochar Biochar typically typically increases increases cation cation exchange exchange capacity, capacity, and hence + + 2+ 2+ retention of NH4 , K , Ca , Mg N from original biomass, however, may not be readily available P, on the other hand, is generally retained and available Liming agent Enhanced sorption of organics (herbicides, pesticides, enzymes) (Good? Bad?) Some evidence evidence for increased increased mycorrhizal mycorrhizal populations populations,, rhizobial infection rates Used as carrier for microbially-based environmental remediation Lowers bulk density

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Identificatio Identific ation n of best bioc biochar har type for soil application Criteria Near-neutral pH High ion exchange capacities (CEC and AEC) Moderate Moderate hydropho hydrophobicity bicity to retain retain organics organics High stability to oxidation Low volatile content Pre-treated with NH 4+ to avoid induced N deficiency

Recommendation Steam-activated Carbonized (i.e., treated to higher temperature to remove volatiles) Slow pyrolysis pyrolysis probably probably better

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Carbon Sequestration Why? Decrease atmospheric GHG levels Stop acidification of oceans by CO2 absorption We only have one Earth

Atmosphere 597 + 211

7. 2

Vegetation, Soil, and Detritus 2477 - 34

How? Create stable C pool using biochar Use energy to offset fossil-C emissions Avoid emissions of N 2O and CH4 Increase net primary productivity (NPP) JE Amonette 24Apr2009

Fossil Fuels 3700 - 319

Surface Ocean 900 + 22

Intermediate and Deep Ocean 37100 + 120

Pre-industrial values (1750) Anthropogenic changes (2005)

Adapted from IPCC AR4 WGI with updated inventory and flux data

Observed and Projected Global Warming

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IPCC (2007) WG1-AR4, SPM, p. 6, 14 14

Factors Affecting Global Warming (100-year timeframe)

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IPCC (2007) WG1-AR4, p. 136

Properties of Key Greenhouse Gases Atmos. Half-life, yr

Relative Radiative Efficiency

Global Warming Potential (20-yr)

Global Warming Potential (100-yr)

Global Warming Potential (500-yr)

CO2

30-325*

1

1

1

1

CH4

8.3

26

72

25

7.6

N2O

79

214

289

298

153

CFC12

69

23000

11000

10900

5200

H2O

~0.011

~0.4

Due to its short half-life (precipitation!), H2O is a feedback gas, rather than forcing warming

*Decay rate has several several pathways with different rates. About 22% of the CO2 is very long lived. The first two half-lives half-lives are 30 yr and 325 yr. IPCC (2007) WG1-AR4, SPM, p. 3 JE Amonette 24Apr2009

Projected Atmospheric Carbon Levels and Associated Global Warming    )    C    t 2500    G    ( Atmospheric concentration   e   r of CO2, ppm   e    h 2000       0   p       5   s       2   o       1   m    t    A 1500   n    i    C   c    i       0   n 1000       5       8   e   g   o   p   o       0   r 500       0    h       6    t   n    A       9       0   e       7       8       3       2   v    i 0    t   a    l    t   1   2    B    5  0   u   1    B   A   a  n    7    t   A   0   0   1   s   0   0   m   0   0   o  n   u   2  1   2  1   C   2  1    C    5   0

Irreversible warming threshold?

  2  0

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IPCC (2007) WG1-AR4, SPM, p. 14, modified to show show zone where irreversible warming of Greenland ice sheet is projected to occur (ibid., p. 17)

What to do . . . Eliminate the C-positive, accentuate the C-negative! Minimize fossil fuel inputs Improve energy efficiency Point-source capture/sequestration of CO 2 Replace with biofuels, biofuels, nuclear (???$$$)

Maximize terrestrial sink (diffuse capture/sequestration) Afforestation Low-input and perennial cropping systems

Implement C-negative energy technologies Biomass combustion with CO 2 sequestration Biomas Bio mass s pyrol pyrolysi ysis s wit with h biocha biocharr pro produc ductio tion/C n/CO O 2 sequestration JE Amonette 24Apr2009

Creating a Stable Carbon Pool with Biochar

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Human-Appropriated Human-Appro priated Net Primary Productivity 29% of all C fixed by photosynthesis aboveground (ca. 10.2 GtC/yr) is currently used by humans! Of this 1.5 GtC/yr is unused crop residues, manures, etc. An additional 1.8 GtC/yr) is not fixed due to prior human activities (e.g., land degradation) and current land use Current fossil-C emissions are ca. 8 GtC/yr Increased productivity and expanded use of residues residues from biochar biochar production production could could have a significant impact on global C budget

Haberl et al., PNAS 2007 2007 JE Amonette 24Apr2009

Carbon Sequestration using Biochar Slow Slow pyro pyroly lysi sis s bioc biocha hars rs are are highl highly y recalcitrant in soils with half-lives of 100-900 years Sensitivity analysis suggests that half lives of 80 years or more are sufficient to provide a credible C sink Recent evidence using 14C-labeled biocha biocharr shows shows no evide evidence nce for for enhanced enhanced rates rates of soil humic carbon degradation in agricultural soils (Kuzya (Kuzyakov kov et al., al., 2009 2009)) No evidence for polyaromatic hydrocarbon (PAH) contamination has been seen Down-side risks seem very small JE Amonette 24Apr2009

Estimates of Half-life in Soils (Slow Pyrolysis Biochars) 1400 Cheng et al. (2008) 1200 Kuzyakov et al. (2009)

1000   s   r   a   e   y  ,   e   m    i    T

800 600 400 200 0 5

10

15

20

25

Mean Annual Temp, C

30

35

IBI Estim Estimate ates s of Global Global Bioch Biochar ar Imp Impact act

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The last resort ? To balance the C cycle, annual human harvest of fixed biomass would have to double from about 8.2 Gt C curr current ently ly (Haber (Haberll et al., al., 2008) to more than 15 Gt C. This would amount to harvesting about 40% of above-ground biomass C, and is comparable to levels of biomass C appropriation seen in India today (Haberl (Haberl et al., al., 2008). 2008). The annual diversion of 11.3% of global global biomass biomass carbon carbon (7 Gt Gt C, roughly one-fifth of all above-ground biomass C produced) to a pyrolysis industry would have a profound impact on the global ecology and would be considered a last resort. JE Amonette 24Apr2009

See James Lovelock Interview http://www.guardian.co.uk/science/video/2009/  apr/22/james-lovelock-gaia-space-biochar

Methane and Traditional Methods Traditional methods without energy recovery generate methane Some decrease in mitigation potential results Difference in biochar yield is far more important These methods still yield a positive result

Woody Biomass No Energy Recovery 36% Biochar Yield 30% Biochar Yield

600

20% Biochar Yield 10% Biochar Yield

500

 ,    l   a    i    t   n   s   e   s    t   o   a 400    P   m   o   n   i   o   b    i   a   r   y   g    i    t    i    d 300   g    M   /    k   g   q   n   e    i     m   C   r    2   a   O200    W    C    l   g   a    b   o    l    G 100

Modern Slow Pyrolysis

Traditional kilns w/ no energy recovery

0 0. 0

0.5

1.0

1. 5

2.0

CH4 Emissions (Percent of all C Emissions)

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2.5

3.0

Impact of Energy Recovery Recovery of energy released during pyroly pyrolysis sis improv improves es mitigation potential significantly Modern pyrolysis methods should be implemented wherever possible Economic decision

All Sustainable Biomass 70% Pyrolysis Energy Recovery Efficiency 600

500  ,    l   a    i    t   n   s   e   s    t   o   a    P   m400   o   n   i   o   b    i   a   y   g   r    i    t    i    d   g 300    M   /    k   g   q   n   e    i     m   C   r    2   a   O200    W    C    l   g   a    b   o    l    G 100

Modern Slow Pyrolysis

36% Biochar Yield 30% Biochar Yield 20% Biochar Yield 10% Biochar Yield

Traditional kilns w/ no energy recovery

0 0. 0

0.5

1. 0

1. 5

2.0

CH4 Emissions (Percent of all C Emissions)

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2.5

3.0

Wher Wh ere e does does Bio Bioch char ar Fi Fit? t? Offers a flexible flexible blend of biofuel biofuel energy, energy, soil fertility fertility enhancemen enhancement, t, and climate change mitigation Limited by biomass availability and, eventually, land disposal area How much biomass biomass can can be made available available for biochar biochar production production vs. other uses? Crop-derived Crop-derived biofuels biofuels cannot cannot supply all the world’s world’s energy needs Maximum estimates suggest 50% of current, 33% of future Biodiversity (HANPP)? N2O?

Perhaps Perhaps best use of harvested harvested biomass biomass is to make make biochar biochar to draw down atmospheric C levels and enhance soil productivity, with energy production as a bonus (but not the driving force). This will require government incentives (C credits/taxes?) and a change in the way we value cropped biofuels

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Further Information and Acknowledgmen Acknowledgments ts Internat Internationa ionall Biocha Biocharr Initiati Initiative ve (www.biochar-international.org)

Biochar for Enviro Environmen nmental tal Manag Managemen ement:  t:  New book: Biochar Science and Technology, Earthscan, 2009 (in press) North North American American Bioch Biochar ar Conferen Conference ce 2009 University of Colorado at Boulder, August 9-12, 2009 Research supported by USDOE Office of Fossil Energy through the National Energy Technology Laboratory USDOE Office of Biological and Environmental Research (OBER) through the Carbon Sequestration in Terrestrial Ecosystems (CSiTE) project. Research was performed at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility at the Pacific Northwest National Laboratory (PNNL) sponsored by the USDOE-OBER. PNNL is operated for the USDOE by Battelle Memorial Institute under contract DE AC06 76RL01830. JE Amonette 24Apr2009

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