Biochar – What can if offer beyond the hype?

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

mailto:[email protected]

http://www.biochar.org.uk/

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”.

Pyrolysed Wood Pellets

Biomass Conversion

Pyrolysis

Biomass

Bio-liquids

Gases

Solid – biochar

1/3

1/3

1/3

Why Biochar?

Charcoal production: ancient but still common …….

Small and Large Pyrolysis in Japan

Use of rice husks in Ankur gasifier for syngas production with rice husk char by-product

UKBRC Farm-scale pryolysis unit, East Lothian

UKBRC Pyrolysis Kiln (30kg/hr feed)

Carbon neutral versus carbon negative

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?

Biochar Images

Photo: Shackley & Cook, UKBRC

200 m

Integrating biochar into top soil

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



Pyrolysis





Soil Effects





Pyrolysis





Soil Effects





Soil Effects



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)







Miscanthus (large)




Wheat 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)







Miscanthus (large)




Wheat 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.

The Costs of Pyrolysis-Biochar Systems

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.

Biochar – What can if offer beyond the hype?

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