Biochar Systems as Options for Carbon Dioxide Removal

Johannes Lehmann and Dominic Woolf

Cornell University, USA

Climate Mitigation: Harnessing Big Fluxes

Lehmann, 2007

Entry Points: A: Soil CDR and emission

reduction through pyrolysis:

reduce CO2/N2O/CH4 return of

the charred OM

B: Soil CDR and emission

reduction through soil

application:

B1: reduce soil GHG

emissions (CO2/N2O/CH4)

B2: increase CO2 capture by

plants through photosynthesis

Pyrolysis-Biochar System

Lehmann, 2007, Frontiers in Ecol Env

© All Rights Reserved by kiwitonita

Climate Change Mitigation – Life Cycle

Woolf et al, 2010, Nature Communications 1, 56

Molecular Properties

Nguyen et al, 2010, EST 44, 3324–3331

McBeath et al, 2011, OG 42, 1194-1202

Mao et al, 2012, EST 46, 9571-9576

Corn-350-BC

Corn-600-BC

Low temperature

High temperature A (corn-350-BC) B (corn-600-BC)

5 nm 5 nm

5 nm5 nm

C (oak-350-BC) D (oak-600-BC)

“Small” cluster sizes:

18-40 C from oak wood and corn residues

at 350°C and 600°C

25 to 52 C from chestnut wood between

500°C and 700°C

20 or more C in Midwestern Mollisol and

an Amazonian Dark Earth

Persistence in Soil

Biochar with higher

condensation (=low

H/Corg ratios) have

greater persistence

Lehmann et al, 2015, Routledge

500

(Only experiments longer than

one year, 2-pool model, 10°C)

Priming of Existing Soil OC by Biochar

Wang et al., 2016 Global Change Biology 8, 512-523

Whitman et al, 2015, Routledge

Average reduction -3.8%

(95% CI = -8.1–0.8%)

Priming of Existing Soil OC by Biochar

Weng et al., 2017 Nature Climate Change 7, 371-376

Greater SOC while root biomass

unchanged

Negative priming of SOM by 6% and

increased recovery of root-derived C by

20%

Nine years after one-time biochar

application of 10 t ha-1

Cayuela et al. 2015, Agr. Ecosys. Env. 191, 5-16

Soil Nitrous Oxide Emissions with Biochar

(n=30 studies)

Average reduction 54%

Electron Flux through Biochar

Sun et al, 2017, Nature Communications 8, 14873

Life-Cycle Assessment: Energy Balance

GJ per Mg of dry, ash-free feedstock

example system based on slow pyrolysis

at 450°C followed by tar-cracking at

800°C (Woolf et al., 2014 ES&T)

Life-Cycle Assessment: Greenhouse Gases

0 2000 4000 6000

cons.

gen.

cons.

gen.

cons.

gen.

cons.

gen.

Energy (MJ t-1 dry feedstock)

agrochems

field ops

drying

shredding

biomass trans

plant constr

other

syngas heat

avoid fos fuel

avoid compost

Late

sto

ver

Early

sto

ver

Sw

itch

gra

ss

Yard

waste

Net = + 4116

Net = + 3044

Net = + 4899

Net = + 4043

0 300 600 900

emit.

reduct.

emit.

reduct.

emit.

reduct.

emit.

reduct.

emit.

reduct.

Greenhouse gases (kg CO2e t-1 dry feedstock)

LUC & fieldemiss.agrochems

field ops

other

stable C

avoid foss fuelgen. & comb.land-use seq.

reduced soilN2O emiss.avoid compost

Late

sto

ver

Ea

rly

sto

ver

Sw

itch

gra

ss B

Ya

rd

wa

ste

Net = - 864

Net = - 793

Net = - 442

Net = + 36

Net = - 885

Sw

itch

gra

ss A

(b)

(a)0 2000 4000 6000

cons.

gen.

cons.

gen.

cons.

gen.

cons.

gen.

Energy (MJ t-1 dry feedstock)

agrochems

field ops

drying

shredding

biomass trans

plant constr

other

syngas heat

avoid fos fuel

avoid compost

Late

sto

ver

Early

sto

ver

Sw

itch

gra

ss

Yard

waste

Net = + 4116

Net = + 3044

Net = + 4899

Net = + 4043

0 300 600 900

emit.

reduct.

emit.

reduct.

emit.

reduct.

emit.

reduct.

emit.

reduct.

Greenhouse gases (kg CO2e t-1 dry feedstock)

LUC & fieldemiss.agrochems

field ops

other

stable C

avoid foss fuelgen. & comb.land-use seq.

reduced soilN2O emiss.avoid compost

Late

sto

ver

Ea

rly

sto

ver

Sw

itch

gra

ss B

Ya

rd

wa

ste

Net = - 864

Net = - 793

Net = - 442

Net = + 36

Net = - 885

Sw

itch

gra

ss A

(b)

(a)

Roberts et al, 2010, Environmental Science and Technology 44, 827–833

Effects on crop growth

or soil GHG not included!

(kg CO2e t-1 DM biomass)

Pyrolysis+biochar: -864

Combustion: -987

Offsetting NG for heat

Assumes energy can be

utilized!

Cu

mu

lative

Avoid

ed

Em

issio

ns

(Pg

CO

2-C

e/1

00

yrs

)

Cu

mu

lativ

e A

void

ed

Em

issio

ns

(Pg

CO

2 -Ce

/10

0yrs

)

Bio

ch

ar

Co

mb

usti

on

CDR and Avoided Emissions: Global

Woolf et al, 2010, Nature Communications 1, 56

Cu

mu

lative

Avoid

ed

Em

issio

ns

(Pg

CO

2-C

e/1

00

yrs

)

Cu

mu

lativ

e A

void

ed

Em

issio

ns

(Pg

CO

2 -Ce

/10

0yrs

)

Bio

ch

ar

Co

mb

us

tio

n

0.9

5 P

g C

yr-

1

Cu

mu

lative

Avoid

ed

Em

issio

ns

(Pg

CO

2-C

e/1

00

yrs

)

Cu

mu

lativ

e A

void

ed

Em

issio

ns

(Pg

CO

2 -Ce

/10

0yrs

)

Bio

ch

ar

Co

mb

usti

on

CDR and Avoided Emissions: Landuse

Woolf et al, 2010, Nature Communications 1, 56

Cu

mu

lative

Avoid

ed

Em

issio

ns

(Pg

CO

2-C

e/1

00

yrs

)

Cu

mu

lativ

e A

void

ed

Em

issio

ns

(Pg

CO

2 -Ce

/10

0yrs

)

Bio

ch

ar

Co

mb

usti

on

Tg

C y

r-1

11

0

50

230

230

55

70

60

70

11

0

BECCS vs BEBCS?

Bioenergy-Biochar Systems

(BEBCS)

Nearly 50% of total energy generated

About 50% of carbon sequestered

Bioenergy with Carbon Capture and Storage

(BECCS)

Nearly 100% of total energy generated

About 100% of carbon stored

Energy

Ph

oto

syn

the

sis

En

erg

y+

Em

iss

ion

s

Bio

ch

ar

to S

oil

Energy

Ph

oto

syn

the

sis

Em

iss

ion

s

En

erg

y

Potential plant growth increases

non-CO2 GHG decreases

eventual (but slow) CO2 evolution

Potential

CO2 leakage

BECCS vs BEBCS?

BECCS:

o Large industrial investment and

technical capabilities (techno-

economic discussion)

o Failure on transport and storage

(risk discussion)

o Geostrategic decision how to

utilize photosynthetically fixed

organic carbon (societal

discussion)

BEBCS (and without bioenergy):

o Limited scalability for individual

boilers, materials handling

(techno-economic discussion)

o Distributed (adoption

discussion)

o Deviation to bioenergy (risk

discussion)

Relative Economic Viability

Earlier Adoption of Biochar Systems than BECCS at lower C prices

Woolf et al, 2016, Nature Communications 7, 13160

BEBCS: Bioenergy-Biochar Systems

BECCS: Bioenergy with Carbon Capture and Storage

BES: Bioenergy Systems

Biochar in Context: Soil Management

Paustian et al, 2016, Nature 532, 49-57

Biochar on upper end of

soil-based approaches

Highly distributed

Biochar in Context: Land Management

World Bank 2012, Report 67395-GLB

Abate

ment ra

tes (

t C

O2e h

a-1

yr-

1)

Combinations?

Exclusions?

Basic Research Needs on Soil

o Mechanisms of N2O reduction in the presence of biochar

(increases found with high biochar N) and how to maximize

these

o Mechanisms of CH4 changes in the presence of biochar

(both increase and decreases observed)

o Mechanisms of negative priming that can be leveraged to

decrease mineralization of native SOC and plant C input

(root and leaf litter, exudation)

o Mechanisms of biochar effects on soil microorganisms,

water, and metal biogeochemistry

Basic Research Needs on Biochar Systems

o Spatial modeling of distributed biomass potential

for pyrolysis and its alternative uses

o Spatially-explicit techno-economic modeling of

biochar systems and its alternatives

Applied Research + Developm. Needs (M&E)

o Industrial-scale bioenergy with biochar production

• Product consistency

• Energy budget

• Problematic wastes (animal manures; sewage sludge; pine bark

beetle kill; invasive species; fire reduction; etc.)

o Biochar product development for large-scale distribution (small/medium-scale distribution, such as garden stores and commercial

greenhouses is already happening)

• Materials handling through to soil application

• Fate of biochar at a landscape scale (mineralization, 3-way-

priming, leaching, wind and water erosion)

• Establishing persistence (mineralization) under different soil

environments (climate, soil mineralogy, texture, terrain)

Relative Economic Viability

Woolf et al, 2016, Nature Communications 7, 13160

Relative Net Present Value

BEBCS: Bioenergy-Biochar Systems

BECCS: Bioenergy with Carbon Capture and Storage

BES: Bioenergy Systems

Avoided Emissions and CDR: Sensitivity

Woolf et al, 2010, Nature Communications 1, 56

Soil Responsiveness to Biochar Intervention

Woolf et al, 2010, Nature Communications 1:56

Soil Benefits in GHG Balance

C Intensity of Offset Energy

Coal Oil Gas

Severity

of F

ert

ility

Constr

ain

ts

Soil Benefits

Essential! (in many systems)

Woolf et al, 2010, Nature Communications 1, 56

At 0: combustion = pyrolysis+biochar

Electron Flux through Biochar

Sun et al, 2017, Nature Communications 8, 14873

Electron Flux through Biochar

Sun et al, 2017, Nature Communications 8, 14873

Electron Flux – Microbial Growth E

lectr

on T

ransfe

r R

ate

(cm

s-1

)

Bacte

rial G

row

th R

ate

(m

A h

-1)

Sun et al, in prep

Microbial Signaling

Masiello et al, 2013 ES&T

acyl-homoserine lactone

E. coli

Microbial Signaling

Masiello et al, 2013 ES&T

acyl-homoserine lactone

E. coli

Biochar Persistence – How Much is Needed?

Lehmann et al, 2010, in: Imperial College Press

Years

0 100 200 300 400 500

Annual A

pplic

ation a

nd N

et S

equestr

ation

(fra

ction p

er

year)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Application

100

500

1000

10,000

50

200

50

10

5

0

20

Mean residence times

Proportion of labile C (MRT of 20 yrs) Long term

Biochar Persistence – How Much is Needed?

Life Cycle Assessment

of GHG emissions

Roberts et al, unpubl. data

20% mineralization

*

Biochar Persistence – How Much is Needed?

Sensitivity analyses

Table - Sensitivity analysis results.

Parameter Value

Net GHG

(kg CO2e

t-1 DM)

Change

from

baseline

(%)

Net

revenue

($ t-1

DM)

Change

from

baseline

(%)

biochar yield 20 -971 -10 28 -26

(%) 25 -1076 0 37 0

30 -1180 10 47 26

stable C 70 -1014 -6 36 -3

(%) 80 -1076 0 37 0

95 -1169 9 39 5

reduced soil 0 -1047 -3 37 -2

N2O emissions 1 -1076 0 37 0

(yrs) 5 -1193 11 40 6

Roberts et al, unpubl. data

$20 t-1 CO2e

5 t biochar ha-1