Impacts of biochar additions on soil microbial processes and nitrogen cycling

Kurt Spokas

USDA-ARS, Soil and Water Management Unit, St. Paul, MNAdjunct Professor University of Minnesota – Department of Soil, Water and Climate

HUMIC SCIENCE & TECHNOLOGY FOURTEENMarch 9-11, 2011 Boston, MA

Biochar: New purpose not a new material

Pyrolysis, carbonization, and coalification are well establish

conversion processes with long research histories

Except:

Prior emphasis:

Conversion of biomass to liquids (bio-oils) or

gaseous fuels and/or fuel intermediates

Solid byproduct (biochar) has long been

considered a “undesirable side product” (Titirici et al., 2007)

Used as fuel

(3000-4000 BC)

Cave Drawings

(>10,000 to 30,000 BC)

Water filtration

(2000 BC)

Charcoal production

(15th century)

Gas

(syngas)

Liquid

(bio-oil)

Solid

(black carbon)

Biochar: New purpose not a new material

Pyrolysis, carbonization, and coalification are well establish

conversion processes with long research histories

Except:

Prior emphasis:

Conversion of biomass to liquids (bio-oils) or

gaseous fuels and/or fuel intermediates

Solid byproduct (biochar) has long been

considered a “undesirable side product” (Titirici et al., 2007)

Used as fuel

(3000-4000 BC)

Cave Drawings

(>10,000 to 30,000 BC)

Water filtration

(2000 BC)

Charcoal production

(15th century)

Pyrolysis

Biomass

Pyrolysis, carbonization, and coalification are well establish

conversion processes with long research histories

Except:

Prior emphasis:

Conversion of biomass to liquids (bio-oils) or

gaseous fuels and/or fuel intermediates

Solid byproduct (biochar) has long been

considered an “undesirable side product” (Titirici et al., 2007)

What is new

The use (or purpose) for the creation of charred biomass:

Atmospheric C sequestration

Dates to 1980‟s and early 2000‟s(Goldberg 1985; Kuhlbusch and Crutzen, 1995; Lehmann, 2006)

Used as fuel

(3000-4000 BC)

Cave Drawings

(>10,000 to 30,000 BC)

Water filtration

(2000 BC)

Climate Change Mitigation

(1980‟s)

Charcoal production

(15th century)

Biochar: New purpose not a new material

Biochar: Black Carbon Continuum

Thermo-chemical conversion products

Graphite

0 0.25 0.5 0.75 1.0

Oxygen to carbon (O:C) molar ratio

Soot

Charcoal

Char

Combustion residuesCombustion condensates Combustion residues

Biomass

Complete new structure Retains relic forms of parent material

0.2 0.6

Biochar – Spans across multiple divisions in the Black C Continuum

However, biochar is NOT a new division…

Adapted from Hedges et al., 2000; Elmquist et al., 2006

Biochar

Biochar: Soil Application

• The assumed target for biochar has been soil application

• Focus has been on “creating” Terra Preta soils

Observations of increased soil fertility and productivity.

Postulated from „slash and burn‟ historic charcoal additions

• Biochar (BC) Hypothesized also involved in humic acid formation(Haumaier and Zech, 1995)

However, on the other side:

• Wood distillation plants [1800-1950‟s]

• Wood pyrolysis – source of chemicals and energy prior to petroleum

• Some historic plants on US-EPA Superfund site list

• Other charcoal sites

• Not always productive

• Reduced seed germination

• Reduced plant growth

Biochar: Soil Application

(BEGLINGER AND LOCKE, 1957)

Applications date back to the beginning of modern science [1800‟s]:

Soil Application… Long History

(LeFroy, 1883)

Applications date back to the beginning of modern science [1800‟s]:

Soil Application… Long History

And even earlier…

Fire pits built on soil…

Ancient Egyptians - pyroligneous acid

(bio-oil)

-used for embalming

• Recent compilation of historical and recent biochar applications:

Soil Application… Long History

• 50% positive,

• 30% no effect, and

• 20% negative impacts on growth and/or yield (Spokas et al., 2011)

• However, should not be used as a basis for

forecasting outcomes Publication bias(Møller and Jennions, 2001)

Proposed Biochar Mechanisms

1. Alteration of soil physical-chemical properties

pH, CEC, decreased bulk density, increased water holding capacity

2. Biochar provides improved microbial habitat

3. Sorption/desorption of soil GHG and nutrients

4. Indirect effects on mycorrhizae fungi through effects on other soil microbes

Mycorrhization helper bacteria produce furan/flavoids beneficial to germination of fungal spores

Warnock et al (2007)

Biochar impacts on Soil Microbes & N Cycling

70+ different biochars evaluated

Various biomass parent materials

Hardwood, softwood, corn stover, corn cob,

macadamia nut, peanut shell, sawdust, algae,

coconut shell, turkey manure, distillers grain,

chicken feathers, bamboo, coconut shell

Represents a cross-sectional sampling of available “biochars”

C content 1 to 84 %

N content 0.1 to 2.7 %

Production Temperatures 350 to 850 oC

Variety of pyrolysis processes

Fast, slow, hydrothermal, gasification,

and microwave assisted pyrolysis.

Laboratory Biochar Incubations

Soil incubations:

Serum bottle (soil + biochar)

5 g soil mixed with 0.5 g biochar

(10% w/w) [GHG production]

Field capacity and saturated

Oxygen & soil sterilization effects

Mason Jar (soil + biochar/isolated)

Looking at impact of biochar

without mixing with soil

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

CO

2 P

rod

uction

(mg C

O2

/gsoil/

da

y)

-0.8

-0.6

-0.4

-0.2

0.0

0.2

Biochar Amount (g)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

N2

O P

rodu

ction

(ng

N2

O/g

soil/

da

y)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

CH

4 P

rod

uctio

n

(ng

CH

4/g

so

il/d

ay)

-7

-6

-5

-4

-3

-2

-1

0

Influence of biochar addition on GHG Production

(Spokas et al., 2009)

Biochar isolated or mixed with soil

CH4 Oxidation

Soil Control Soil + BC (mixed) Soil + Beaker BC

CH

4 O

xid

atio

n r

ate

(g C

H4 g

soil-1

d-1

)

0

2

4

6

8

N2O Production

Soil Control Soil + BC (mixed) Soil + Beaker BC

N2O

Pro

du

ctio

n r

ate

(n

g N

2O

gsoil-1

d-1

)

0

5

10

15

20

25

EthyleneProduction

Rates

So

il

Activa

ted

Ch

arc

oa

l

BC

-1

BC

-2

BC

-3

BC

-4

BC

-5

BC

-6

BC

-7

BC

-8

BC

-9

BC

-10

BC

-11

BC

-12

Eth

yle

ne

Pro

du

ctio

n (

ng

C2

H4

0.5

gchar-1

d-1

)

0

10

20

30

40

Dry

Wet

So

il

Activa

ted

Ch

arc

oa

l

BC

-1

BC

-2

BC

-3

BC

-4

BC

-5

BC

-6

BC

-7

BC

-8

BC

-9

BC

-10

BC

-11

BC

-12

Eth

yle

ne

Pro

du

ctio

n (

ng

C2

H4

gsoil-1

d-1

)

0

5

10

15

20

25

30

Field Capacity

Saturated

Biochar Alone

Biochar + Soil

10% w/w

Wood

Mac n

ut

Wood

DD

GS

DD

GS

Co

b

Co

b

Wo

od

Wood

Pelle

ts

Wood

Peanut

Spokas et al. (2010)

Ethylene Impacts

Soil Microbial Impacts

Induces fungal spore germination

Inhibits/reduces rates of nitrification/denitrification

Inhibits CH4 oxidation (methanotrophs)

Involved in the flooded soil feedback

Both microbial and plant (adventitious root growth)

Ethylene Headspace Concentration ( L L-1

)

0 (control) 1 5 25 50 275

Am

moniu

m C

oncentr

ation (

g N

H4 g

so

il-1)

0

10

20

30

40

50

0 (control) 1 5 25 50 275

N2O

Pro

du

ctio

n (

ng

N2O

gsoil

-1 d

-1)

0

20

40

60

80

100

postN2O

Plot 1 Lower control line

Ethylene Headspace Concentration (0 to 275 ppmv) Ethylene Headspace Concentration (0 to 275 ppmv)

N2O Production NH4+ Production

, 24-Apr-2010 + 00:48:10NRC104

1.01 6.01 11.01 16.01 21.01 26.01 31.01Time5

100

%

5

100

%

5

100

%

5

100

%

5

100

%

5

100

%

RXI5_032210_001_126 Scan EI+ 45-2501.27e7

RXI5_032210_001_099 Scan EI+ TIC

1.27e75.19

5.96 29.198.62 12.9411.739.87 18.2913.65

16.44 22.9518.99

21.7623.78

RXI5_032210_001_092 Scan EI+ TIC

1.27e79.29

8.37

9.8918.3012.15 16.4713.6814.82

20.56 27.4129.00

RXI5_032210_001_091 Scan EI+ TIC

1.27e77.006.005.24

10.9113.68

15.08

18.6721.75

23.81 27.1025.1027.76 29.25

RXI5_032210_001_087 Scan EI+ TIC

1.27e78.64

7.005.68

11.76

11.5413.69

12.4116.21

18.84

17.2520.02

21.81

24.16 29.7126.2027.12

RXI5_032210_001_088 Scan EI+ TIC

1.27e712.0010.419.51

5.69 7.2229.9725.8523.9423.07

21.0420.0113.09 14.41

28.9527.08

To

luene

Be

nze

ne

(13.6

5)

xyle

nes

meth

anol

Naphth

ale

ne

1,2

-dic

hlo

robenzene

eth

ylb

enzene

Acetic A

cid

Wood Ash

Activated Charcoal

Wood pellet

BC

Macadamia

Shell BC

Hardwood

Sawdust

Oak

Hardwood

Bituminous

coal

nonanal

Aceto

ne

2-m

eth

ylb

uta

ne eth

anol

Biochar has a variety of sorbed volatiles = range of potential microbial inhibitors

Headspace Thermal Desorption GC/MS scans of biochars

Fu

rfura

l

(10.9

)

Closer look at N-

cycling(hardwood sawdust biochar)

0 1 2 3

Nitra

te (

pp

m)

0

20

40

60

80

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Nitrite

(p

pm

)

0.0

0.1

0.2

0.3

0.4

0.5

Biochar Amount (g)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

NH

4 (

pp

m)

0

1

2

3

4

5

0 1 2 3

0.0

0.5

1.0

0 1 2 3

0.0

0.5

1.0Biochar Alone

Biochar Alone

Putting the pieces together: Not quite a full picture yet…

Ammonium (NH4+)

Nitrite (NO2-)

Nitrogen Uptake (plants/microbes)

Nitric Oxide (NO)

Nitrogen Gas (N2)

Nitrous Oxide (N2O)

Nitrification

N2

Mineralization

Organic N

Nitrogen fixation

Em

itte

d to a

tmosphere

Nitrate (NO3-)

Denitrification

Increased amounts

Decreased amount

However – no consistent trends

Impact of Biochar Volatiles in Soils

• Sorbed BC volatiles could interfere with microbial signaling (communication): Releasing or sorb signaling compounds

• Volatile organic compounds can interfere with microbial processes

• Terpenoids – interfere with nitrification [Amaral et al., 1998; White 1994]

• Furfural + derivatives – inhibits microbial fermentation & nitrification (Couallier et al.,

2006; Datta et al. 2001)

• Benzene, Esters – Also inhibit microbial reactions

• Still ongoing and developing research area in the plant/microbe research area

• Alterations in VOC content could be sensitive indicators of soil conditions (Leff and Fierer, 2008)

Conclusions

Despite the long research history – No absolute “biochar” consistent trends

Highly variable material

– Production & post-production handling

Different responses to biochar Function of soil ecosystem (microbial linkage) & position on black

carbon continuum

Importance of fully documenting methods of creation,

handling, and properties – Allow future elucidation of factors

Several inter-related mechanisms

Biochar does act as a carbon sequestration agent As long as biochar has low O:C ratio (Spokas, 2010)

Conclusions

Economics caused the shift from biomass to fossil fuels in the early

1920‟s: We at the cusp where environmental stewardship is

returning the pendulum back to biomass as the source for human‟s

energy, chemical and agronomic needs

Research is needed to optimize both:

1. Advanced pyrolysis system development for

energy and chemical production

2. Subsequent utilization of biochar in a

sustainable and environmentally responsible

manner

"I have but one lamp by which my feet are guided, and that is the lamp of experience.

I know of no way of judging the future but by the past." (Patrick Henry, 1775)

AcknowledgementsI would like to acknowledge the cooperation:

Dynamotive Energy Systems

Fast pyrloysis char (CQuest™) through non-funded cooperative agreement (NFCA)

Best Energies

Slow pyrolysis char through a NFCA

Northern Tilth

Minnesota Biomass Exchange

NC Farm Center for Innovation and Sustainability

National Council for Air and Stream Improvement (NCASI)

Illinois Sustainable Technology Center (ISTC) [Univ. of Illinois]

Biochar Brokers

Chip Energy

AECOM

Avello Bioenergy

ICM , Inc.

Partial Funding:

Minnesota Corn Growers Association/Minnesota Corn Research Production Council

Minnesota Department of Agriculture Specialty Crop Block Grant Program

USDA-ARS Biochar and Pyrolysis Initiative

Technical Support : Martin duSaire, Tia Phan, Lindsey Watson, Lianne Endo,

Kia Yang, Eric Nooker, and Amanda Bidwell

USDA-ARS Biochar and Pyrolysis Initiative

GRACEnet Project (30 locations): Greenhouse Gas Reduction and Carbon Enhancement Network

REAP Project (24 locations): Renewable Energy Assessment Project

Biochar and Pyrolysis Initiative (15 locations)

Ongoing field plot trial (6 locations)

Multi-location USDA-ARS research efforts: