biochar – what can if offer beyond the hype? dr simon shackley [email protected] uk biochar...
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Biochar – What can if offer beyond the hype?
Dr Simon [email protected]
UK Biochar Research Centre, University of Edinburgh www.biochar.org.uk
Managing Sustainable Development Thursday 15th March 2012
Talk outline• Biochar as a potential win–win “wedge” in climate
change - storing carbon and doing something useful with it
…… but: • Does it add-up?
– Life-cycle assessment – techno-economic evaluation – agronomy
• Potential barriers / difficulties in implementation – regulatory issues and risks– Incentive mechanisms – state-of-knowledge
• Implications & Conclusions
What is Biochar?
….. think of charcoal ……..
“….. the porous carbonaceous solid produced by thermochemical conversion of organic materials in an oxygen depleted atmosphere which has physiochemical properties suitable for the safe and long-term storage of carbon in the environment and, potentially, soil improvement”.
Use of rice husks in Ankur gasifier for syngas production with rice husk char by-product
UKBRC Farm-scale pryolysis unit, East Lothian
Simple Carbon / Energy balance
x
Indicator Combustion Pyrolysis-biochar
Starting feedstock mass
1 tonne 1 tonne
Carbon content at start
0.45 tonne 0.45 tonne
Carbon content at end (stabilised)
0 0.25 tonne
Expressed as CO2 0 0.92 tonnes CO2
Calorific value of wood
16 GJ per tonne
Efficiency of conversion
35% 15%
Delivered energy 5.6 GJ per tonne 2.4 GJ per tonne
Carbon emission factor: 0.5 kg CO2 per kWh (2008 electricity mix)
Convert to kWh 1556 kWh 667 kWh
Avoided CO2
emissions
0.778 tonnes CO2 0.334 tonnes CO2
Total CO2 abatement
per tonne feedstock
0.778 tonnes CO2 1.25 tonnes CO2
Soils and Agronomy• Nutrient content
• pH (biochar typically alkaline)
• Cation exchange capacity (CEC)
• Water retention
• Micro-organisms
• Soil structure
• Pollution reduction (nitrates)
• Nitrous oxide and methane suppression?
Soil impacts
• Ash pH is also alkaline so same benefit may occur
• Alkalinity may also explain N2O suppression
• Biochar appears to break-up into small particles (<50 μm) from physical weathering and abrasion
• Properties likely to differ greatly from material incorporated at e.g. <2cm
• Evidence for mineral-char interaction which may guard against char degradation
Angus – May 2010Horticultural (carrots,
potatoes, beets): (not sig)
Fife – March 2010 spring barley (not sig)
East Lothian – 2009 - spring barley (sig)
2010 - oil seed rape (not sig)2011 – wheat (sig)
Nottinghamshire – April 2010 -
Spinach (no sig)
Midlothian
2011 – spring barley (significant)
Yield Results from Stonelaws Farm,
September, 2009 (barley) (all 10t/ha eqv) (courtesy of Jason Cook)
Plot Grain Yield in Kgs
56 5558
69 68
5457
60
68
75
6462
0
10
20
30
40
50
60
70
80
Block
Gra
in Y
ield
(K
g)
Overview of the Boghall trial
• Spring Barley, 2011-2012
• 5 N-fertilisation rates • 2 biochar application
rates• 3 replicates of each• Gases, soils, crops
sampled.
10m
N fertilisation rates
0% 60% 120% 180% 240%
0 kg/ha
72 kg/ha
144 kg/ha
216 kg/ha
288 kg/ha
courtesy of Jim Hammond
Crop YieldsAverage Grain Yield (September 2011)
0
2
4
6
8
10
12
14
0 60 120 180 240
N Fertiliser Treatment (%)
Gra
in Y
ield
(t/h
a)
0 t/ha10 t/ha30 t/ha
Life – Cycle Assessment
Feedstock Production
Transport to Pyrolysis
Pyrolysis
Electricity and Heat Generation
Transport of Char to Farm
Transport of Char to Fields
Application to Soils
Soil Effects
Char Carbon Soil Sequestration
Electricity and Heat offset
Life Cycle Stages
Feedstock Production
Transport to Pyrolysis
Pyrolysis
Electricity and Heat Generation
Transport of Char to Farm
Transport of Char to Fields
Application to Soils
Soil Effects
Char Carbon Soil Sequestration
Electricity and Heat offset
Feedstock Production
Transport to Pyrolysis
Pyrolysis
Electricity and Heat Generation
Transport of Char to Farm
Transport of Char to Fields
Application to Soils
Soil Effects
Char Carbon Soil Sequestration
Transport of Char to Farm
Transport of Char to Fields
Application to Soils
Soil Effects
Char Carbon Soil Sequestration
Electricity and Heat offset
Life Cycle Stages • ‘cradle – to - grave’ • ‘seed – to – seed’ • Measures environmental
impacts of all stages
• Here we focus on energy and CO2 (equivalent) emissions (including N20
and CH4)
Purpose grown feedstock
Collection of wastes
Preparation
Further drying
Pyrolysis
Syngas/Synoil
Biochar
Addition to soil
Transport to farm
Transport
Transport
Method of addition to soil
Land management type – tilled, no till, pasture, forestry etc.
Quantity of char added, how many times, what time period
Carbon sequestered in soil
Type of Soil
Effect on soil N20emissions
Crop to be grown
Change in NPP
Impact on N-fertiliser use
What feedstock?Growing method?Harvesting method?
What waste?Alternative use of waste?
What energy generation method is being offset?
Heat
Electricity
Transport to site
Labile fraction and decomposition rate of char
Quantity of char added, how many times, what time period
Changes in SOC
SourceSource of GHGsSource of GHGs
Sink of GHGsSink of GHGs
VariableVariableSinkKey:
Hammond, Shackley, Sohi & Brownsort (2011)
0 200 400 600 800 1000 1200 1400 1600
Wheat straw (small)
Barley straw (small)
Oil seed rape and other straw (small)
Short rotation coppice (small)
Arboricultural arisings (small)
Sawmill residues (large)
Forestry residue chips (large)
Miscanthus (large)
Short rotation coppice (large)
Short rotation forestry (large)
Canadian forestry residue chips (large)
Wheat straw (large)
Barley straw (large)
Oil seed rape and other straw (large)
kgCO₂eq t-1feedstock
PBS carbon abatement in kg of CO2 equivalent per oven dry tonne of feedstock: 1 to 1.4 tCO2 per odt feedstock
The percentage contribution to carbon abatement from different life-cycle stages for virgin biomass feedstocks
-200 0 200 400 600 800 1000 1200 1400 1600
Wheat straw (small)
Barley straw (small)
Oil seed rape and other straw (small)
Short rotation coppice (small)
Arboricultural arisings (small)
Sawmill residues (large)
Forestry residue chips (large)
Miscanthus (large)
Short rotation coppice (large)
Short rotation forestry (large)
Canadian forestry residue chips (large)
Wheat straw (large)
Barley straw (large)
Oil seed rape and other straw (large)
kgCO2 eq t-1 feedstock
Pyrolysis process Transport and spreading Electricity generation & offset
Heat generation and offset Soil sequestration Soil effects
0 5 10 15 20 25 30 35
Wheat straw (small)
Barley straw (small)
Oil seed rape and other straw (small)
Short rotation coppice (small)
Arboricultural arisings (small)
Sawmill residues (large)
Forestry residue chips (large)
Miscanthus (large)
Short rotation coppice (large)
Short rotation forestry (large)
Canadian forestry residue chips (large)
Wheat straw (large)
Barley straw (large)
Oil seed rape and other straw (large)
tCO₂eq ha-1 land used
Tonnes of CO2e abatement per hectare of land per year (assuming co-product allocation based on economic indicators)
Comparison with Other Bioenergy Options
Expressed as CO2 abatement per oven dry tonne (odt) feedstock:
Conventional bioenergy systems (combustion) inUK: emissions of 0.06 – 0.4 tCO2eq Per Odt
Expressed as CO2 abatement per hectare
Conventional bioenergy systems in UK: abatement of 1-7 tCO2eq per ha
Most productive system (Brazilian bioethanol from sugarcane: 16 tCO2eq per Ha
Pessimistic 3.590 0.980 1,019 0 1,019 416 703
Optimistic 15.915 4.340 2,547 1,934 3,514 1,434 2,423
Very optimistic 21.867 5.960 3,267 2,902 4,718 1,926 3,254
Biochar produced per annum ('000 t) Applied land area ('000 ha)Feedstock availability
CO2 C Virgin biomass
resources
Non- virgin biomass
resources
Total available for use on land
Scenario 30/1: 30t/ha in year one, then 1t/h
(20 year timeline)
Scenario 10/1: 10t/ha in year one, then 1t/h
(20 year timeline)
Abatement per annum
(106 t)
Preliminary and provisional estimate of UK production of biochar per annum and carbon equivalent abatement per annum under three feedstock scenarios and resulting land-use implications (using virgin biomass feedstock-derived biochar only)
Biochar C abatement & feedstock quantities
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Mt
CO
2 e
q ab
atem
ent
0.0
0.5
1.0
1.5
2.0
2.5
Mt
feed
stoc
k
Feedstock Input
How important is biochar?
• Biochar could provide 1.5 – 10% of emissions reductions required in the UK by 2020
• Current global potential production = 0.6 +/- 0.1 GtC per year
• If agri- and forestry wastes all used, this would constitute 1 to 1.8 GtC … probably achievable by 2050 - a carbon ‘wedge’
The role of biochar? • It is one of the very few technologies that can
actually remove CO2 from the atmosphere
• Carbon negative technologies needed because we are v. likely to exceed ‘safe’ concentration of CO2 in the atmosphere
• Other options are: Bioenergy-CCS (BECCS), direct air-capture, permanent reforestation, etc.
234
Saw
mill resid
ues
289
SR
C ch
ips (S
)
298
wh
eat straw b
ales med
ium
scale
344
Imp
orted
Can
adian
forestry (ch
ips)
Ø 118
0 2,000,000 4,000,000 6,000,000 8,000,000 10,000,000 12,000,000
volume (tCO2e)
-150
-100
-50
0
50
100
150
200
250
Co
st (
£)
pe
r to
nn
e o
f b
ioch
ar
Green
waste, d
om
estic foo
d (M
)
88
Waste w
oo
d (L
)
3625
Sew
age slu
dg
e (L)
389
-94
do
mestic o
rgan
ic waste (L
)
OS
R straw
(L)
135
Wh
eat straw b
ales (L)
Waste w
oo
d (M
)
216
Miscan
thu
s(chip
s)(L)
Barley S
traw b
ales (S)
-94
Co
mm
ercial org
anic w
aste (L)
-197
14,000,000
-200
300
350
400
S= small scale
M= Medium scale
L= Large scale
Co
mm
ercial org
anic w
aste (M)
168
277S
ho
rt Ro
tation
Fo
restry
Figure 7: Production cost curve for biochar from different feedstocks (cost in £ per ton versus quantity of CO2 abated).
Figure Six: Biochar Marginal Abatement Cost (£tCO₂e-1) for higher feedstock supply scenario
155
do
mestic o
rgan
ic waste (L
)
-86
Co
mm
ercial org
anic w
aste (L)
-144
Miscan
thu
s (chip
s) (L)
144
Wh
eat straw b
ales(L)
Co
st
(£)
pe
r to
nn
e o
f C
O2
e
250
200
4,000,000
150
100
50
0
-50B
arley straw b
ales (S)
-150
volume (tCO2e)
12,000,00010,000,0008,000,0006,000,0002,000,0000
Ø 57Im
po
rted C
anad
ian fo
restry (chip
s)
208
Saw
mill resid
ues
Fo
restry residu
e (chip
s)
184199
Sh
ort ro
tation
forestry (ch
ips)
90
156163
OR
S straw
(M)
SR
C (ch
ips) (L
)
8080
Arb
oricu
ltural arisin
gs
76
waste w
oo
d (L
)
Barley straw
bales (L
)
1918
Sew
age slu
dg
e (L)
-86-100
S= small scale
M= Medium scale
L= Large scale
OSR = Oil seed rape
SRC = Short rotation coppice
Values do not include indirect effects of biochars in soils on net CO₂equivalent abatement
Marginal Carbon Abatement Cost Curve for pyrolysis-biochar
Carbon Abatement Value • If biochar costs £100 per tonne, a carbon abatement
price of £30-40 per tCO2 would be required for the operation to break-even (assuming no agronomic value)
• ‘Front-runners’: Non-virgin resources:- where waste handling costs occur (gate fees, landfill tax) - e.g.
green waste wood wastefood waste sewage sludge
• Virgin resources: arboricultural arisingslow-cost straw (<£20 per t)
Valuing biochar in soil
• Added soil benefit + C abatement benefits must exceed cost– Long term effects
• soil structure and organic matter• nutrient use efficiency (CEC and soil solution)
– Short and medium term effects• soil pH (liming effect)• ash nutrient value (extended release)• water dynamics
– Aspects of cost• rate• frequency• method and timing
Potential Barriers: Regulation
• EU Waste Framework Directive (WFD): biochar would, in some cases, be classified as a waste
• Waste is: ‘any substance or object …which the holder discards or intends or is required to discard’.
• Waste applications to land require a licence which can be expensive and time consuming to obtain.
• There are waste categories that are exempted from the WFD but biochar is not one of these
• If biochar becomes an established product, with a recognised market, it could (under the WFD) cease to be classified as a waste.
Regulation • Pyrolysis is a regulated process under Pollution Prevention Control
(PPC) legislation
• Health and safety / environmental nuisance issues could arise from dust particles, etc.
• Wind and water erosion of biochar from application site
• Metal contaminants
• Polycyclic aromatic hydrocarbons (PAHs) – some are carcinogens, which may be produced during certain types of pyrolysis
• Others: dioxins, phenols?
• Nitrate vulnerable zones and N input controls (arising from N in the added biochar)
Incentive Mechanisms • Presently, there is no mechanism to obtain a carbon
value from biochar • EU Emissions Trading Scheme – now includes CCS, but
not carbon storage in soils • EU ETS only relevant to relatively large-scale power
generation (>20MW) • Many PBS will be below this – hence not market players
in the EU ETS in any case• Domestic market, Carbon Reduction Commitment (CRC)
Energy Efficiency Scheme. Recently established as domestic carbon trading scheme for companies + organisations not included in the EU ETS – but off-setting is not permitted
Incentive Mechanisms• Flexibility Mechanisms under Kyoto Protocol - Clean
Development Mechanism (CDM), Joint Implementation (JI)
• CDM: Biochar not yet included. It will be tough to develop a robust methodology for its inclusion given current scientific uncertainties.
• Voluntary Carbon Market (VCM): a biochar methodology has been submitted, but heavily criticised (for good reasons)
• Biochar more likely to be registered through VCM in first instance, though methodological hurdles to overcome first.
How will biochar be deployed? • Seems unlikely that biochar will attract a market value for carbon
abatement in the immediate future.
• Even if it did, the current market price of CO2 is low – under EU ETS, CDM or VCM ($10-15).
• Biochar deployment may, therefore, depend in the near future upon the agronomic value of biochar …...
• And/or as an element in the environmental stewardship schemes
• And upon the value of treating wastes through pyrolysis as opposed to alternative waste management (e.g. landfill, sewage sludge to land)
So can biochar add up?• What does it cost?
– Producing biochar is generally not cheap unless waste feedstocks are utilised!
– Front-runners are where feedstocks are low-cost or negative cost
• What is it worth?
– Biochar is valuable for carbon abatement, but no current mechanism for monetising this value
– Biochar has uncertain benefits for soils / agronomy
• Therefore, urgent need for including land-based carbon storage in C trading arrangements
• But key scientific uncertainties have to be addressed first.