the case for biochar · amazonian terra preta source: terra preta (dark earth) soils high plant...
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Amazonian Terra preta
Source: www.biochar-international.org
Terra preta (dark earth) soils High plant productivity High organic carbon – stable char (black carbon)
Recreate Terra preta?
Pyrolysed biomass as a soil amendment
Source: Adriana Downie Pacific Pyrolysis
Adriana Downie – June 2012
EEA Continuous Flow System - scrap tyres
Splainex – Waste Pyrolysis
Dynamotive - fast-pyrolysis
Pacific Pyrolysis
Terrestrial Carbon Cycle
Substrate C litter & roots
Microbial Biomass C
Humified Organic carbon
Humification
-
Assimilation
Death
Fire
Charcoal
Photosynthesis
Particulate carbon
Labile carbon: Microbial biomass, Soluble C
Humification
Fire
Charcoal
After J. Skjemstad, CRC Greenhouse Accounting
Humified carbon
Atmosphere
Respiration
CO2 Mineral- isation
Cumulative per cent of biochar-C decomposed
0 20 40 60 260 520 780 1040 1300 1560 1820
Cum
ulat
ive
% o
f add
ed b
ioch
ar-C
min
eral
ized
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4.0
6.0
8.0
10.0
Duration of incubation (days)0 20 40 60 260 520 780 1040 1300 1560 1820
Cum
ulat
ive
% o
f add
ed b
ioch
ar-C
min
eral
ized
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4.0
6.0
8.0
10.0
Poultry litter
Low-temperature (400 oC) biochars High-temperature (550 oC) biochars
Cow manure
Eucalyptus leaf
Eucalyptus wood
Papermill sludge
Poultry litter
Cow manure
Eucalyptus leaf
Eucalyptus wood
0.5% to 8.9% of biochar C mineralized over 5 years.
BP Singh et al. 2012 (EST)
Biochar stability - a function of feedstock and pyrolysis conditions
Least stable(~100 years)
Most stable(~2000 years)
Fuse
d ar
omat
ic ri
ngs
Mineral nutrient content
Pyrolysis temperature
550°C wood (A or NA)
400°C manures (poultry, cow) (NA)
400°C wood (A or NA)
550°C leaf (A)
550°C paper sludge (A)??
Car
bon
cont
ent
400°C leaf (A)
550°C poultry (A)550°C cow (A)
Synthesis: “after E. Krull”
BP Singh et al. 2012 (EST)
Biochar can reduce soil N2O emissions
0
5000
10000
15000
20000
25000
30000
35000
4-Aug 9-Aug 14-Aug 19-Aug 24-Aug 29-Aug
The day of gas sampling
0
2000
4000
6000
8000
10000
12000
4-Aug 9-Aug 14-Aug 19-Aug 24-Aug 29-Aug
The day of gas sampling
Alfisol Vertisol Control
Poultry manure_400
Poultry manure_550
Wood_400
Wood_550
14-73% reduction in N2O 23-52% reduction in N2O
Cum
ulat
ive
N2O
em
issi
ons
µg /m
2
BP Singh et al. 2010 (JEQ)
N2O emissions
09 Dec 23 Dec 06 Jan 20 Jan 03 Feb
0.000
0.002
0.004
0.006
0.008
0.010
N 2O(k
g.ha
1.h
r1)
Biochar+Urea
Urea
Poultry
0
50
100
Rai
n (m
m)
010203040
Tem
pC
standard error = 1.0 least significant difference (5% critical value) = 2.5
Van Zwieten et al (2013) Science of the Total Environment.
N2O-N (kg.ha-1)
Calculated Emission
Factor
Biochar+ Urea 1.5 1.3
Urea 1.2 1.0
Poultry litter 4.9 8.4
0 40 80 120 260 520 780 1040130015601820
Cum
ulat
ive
prim
ed s
oil C
O2-
C (m
g g-
1 so
il C
)
-10
0
10
20
30
40
Wood550Leaf550APL550ACM550AYWood450_2%LOMYWood550_4%LOM
Duration of incubation (days)
0 40 80 120 260 520 780 1040130015601820
Cum
ulat
ive
prim
ed s
oil C
O2-
C (m
g g-
1 so
il C
)
-10
0
10
20
30
40
Wood400Leaf400APL400CM400YWood450_2%LOMYWood450_4%LOM
(c) (d)
Cumulative priming of soil C by biochar 400 °C biochars 550 °C biochars
Singh & Cowie (Unpublished)
Biochar initially enhanced mineralisation of native soil C Native soil C was stabilised as biochar aged
GHG mitigation benefits of biochar
Delayed decomposition of biomass
Reduced nitrous oxide emissions from soil
Increased soil organic matter
Avoided fossil fuel emissions due to use of syngas as renewable energy
Increased plant growth, plant health
Avoided emissions from N fertiliser manufacture
Reduced fuel use in cultivation, irrigation
Avoided methane and nitrous oxide emissions due to avoided decay of residues
Transport
Soil amendment
Pyrolysis to biochar and
syngas
Distribution of biochar
Distribution of energy carrier
Energy service (heat, electricity)
Biomass residue
Biochar system
Transport
Biomass residue
Fossil energy/carbon
source
Extraction
Conversion to energy carrier
Distribution of energy carrier
Energy service (heat, electricity)
Soil amendment
Fertiliser manufacture
Transport
Composting
Reference system
Distribution of compost
Distribution of fertiliser
Greenwaste biochar applied to canola
Poultry litter biochar applied to broccoli
Factors contributing to mitigation
Potential mitigation through biochar - global
Woolf et al 2010 Total mitigation predicted: 6 Gt CO2-e pa =12% current emissions
Sustainability issues for biochar – direct (1)
Biomass procurement Residues:
Soil erosion Soil compaction Nutrient depletion Soil carbon loss (GHG, productivity
impact) Purpose grown:
Water use Biomass and/or soil carbon decline GHG balance - N2O emissions
Biochar production GHG emissions particulate emissions
Biochar application dust contamination (if feedstock contaminated)
Whole system: net mitigation benefit (incl transport, plant
construction) Compared with reference use
Sustainability issues for biochar – direct (2)
Indirect land use change – Deforestation GHG emissions: loss of biomass carbon, soil carbon Biodiversity Air pollution Water quality
Social – community displacement, food security
Economic – competing uses of biomass
Sustainability issues for biochar – indirect
How can we encourage sustainability?
Sustainability framework approach:
Institutional systems: Regulation Incentives Standards
Guidelines Certification
Monitoring, assessment and reporting Criteria and Indicators
Adaptive management
What do we know about biochar? Biochar can increase plant yield
But not all plants / all soils
Biochar is resistant to decomposition But some biochars are more resistant than others
Biochar can reduce nitrous oxide emissions But not from nitrification
Biochar can deliver net greenhouse gas mitigation Other options may give greater mitigation; each situation must be
assessed separately
Biochar could contaminate soil But only if made from contaminated feedstock
Some unintended consequences Biochar can reduce efficacy of herbicides
Biochar can…
Contribute significantly to climate change mitigation
Enhance agricultural productivity
Restore degraded soils
BUT ONLY IF
produced in a facility that controls emissions and harnesses heat for efficient beneficial use
applied with care, to responsive soil type / crop
made from sustainably harvested and renewable biomass resources
More information:
International Biochar Initiative http://www.biochar-international.org/