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: