hugh mclaughlin, phd, pe director of biocarbon research alterna biocarbon inc....

Hugh McLaughlin, PhD, PE

Director of Biocarbon Research

Alterna Biocarbon Inc.

hmclaughlin@alternabiocarbon.com

All Biochars are Not Equal

Version 1 – November 13, 2009

Presented at the Northeast Biochar Symposium 2009, Amherst, MA

What is in that bag of Biochar?

What is in that bag of Biochar?

What is in that bag of Biochar?

• Moisture (as delivered)• Moisture is not a bad thing, but it is not

worth paying for ……• Moisture is added after char production,

usually to cool or passivate the char• Moisture in the bag does not mean the

char will have superior moisture retention in soil – it means moisture was added …

0

50

100

150

200

250

300

Weig

ht

perc

en

t o

f d

ry s

am

pleWater (gm/100 gms dry biochar)

Ash

Mobile Matter

Resident Matter

What is in that bag of Biochar?

• Moisture (as delivered)• Ash (as delivered and from what)

• Converting Biomass to Char removes the moisture and much of the organic portion, but very little of the ash constituents

• Ash levels are 3 to 4 x that of the dry pre-carbonization biomass

• Soluble Ash is the principal pH effect of biochar addition to soils – can act like lime

• Ash includes Nitrogen? – depends on test

0%

20%

40%

60%

80%

100%

Weig

ht

perc

en

t o

f d

ry s

am

ple

Resident Carbon Resident H & O Resident Nitrogen Mobile Carbon

Mobile H & O Mobile Nitrogen Ash (acid soluble) Ash (non-soluble)

What is in that bag of Biochar?

• Moisture (as delivered)• Ash (as delivered and from what)• Mobile Matter versus Resident Matter

• Mobile - can migrate out of the char• Resident - stays with the char & soil• Matter = Carbon and H&O portions• Carbon is measured for CO2 sequestration,

but plants care about soluble organics and plant nutrients available in the soil

0%

20%

40%

60%

80%

100%

Weig

ht

perc

en

t o

f d

ry s

am

ple

Resident Carbon Resident H & O Resident Nitrogen Mobile Carbon

Mobile H & O Mobile Nitrogen Ash (acid soluble) Ash (non-soluble)

What causes the variations in Mobile and Resident Matter?

What it was made from andthe way it was made.

D

drying (A)

ExtensiveDevolatilisation

and

carbonisation(E)

Limiteddevolatilisation

andcarbonisation (D)

depolymerisationand

recondensation(C)

A

E

D

C

E

A

D

C

glass transition/softening (B)

Hemicellulose Lignin Cellulose

100

150

200

250

300

Tem

pera

ture

(°C

)

Hemicellulose Lignin Cellulose100

150

200

250

300

Tem

pera

ture

(°C

)

TO

RR

EF

AC

TIO

N

Pyrolysis & Carbonization Reactions of Wood

- above 325C = Biochar, below = Torrefied Wood

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

200 250 300 350 400 450 500

Biomass Processing Temperature Celsius

Mas

s fra

ctio

n (%

)Carbon Hydrogen

Oxygen Fuel Yield

Fixed Carbon % Fixed Carbon Yield

What is in that bag of Biochar?

• Moisture (as delivered)• Ash Content (as delivered and from

what)• Mobile Matter versus Resident Matter

• Cation Exchange Capacity• ion exchange resin behavior

• Adsorption Capacity• activated carbon behavior

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.0010% of CEC in meq/100 grams

Adsorption Capacity (wt% @ 100C)

0

50

100

150

200

250

300

350

400

450

300 400 500 600 700 800 900 1000

Terminal pyrolysis temperature(C)

Spec

ific

surf

ace

area

(m2/

g)

What is in that bag of Biochar?• Moisture (as delivered)• Ash Content (as delivered and from

what)• Mobile Matter versus Resident Matter • Cation Exchange Capacity• Adsorption Capacity

And why do you CARE?• - well, you did pay for it, and• it is going to be part of your garden, and• it’s effects last pretty much forever…..

What is in that bag of Biocharand why do you CARE?

• Moisture (as delivered) – You don’t care• However, Moisture Dynamics in Soil are

pivotal to plant health and dictate survival• Biochar influences high moisture retention

and soil aeration properties• Moisture is adsorbed by Biochar and

released slowly in soil desiccation• Need soil tests to optimize biochar

properties and addition levels in soils

What is in that bag of Biocharand why do you CARE?

• Moisture (as delivered)• Ash Content – short term concern

• Soluble ash influences soil pH• Biochars have alkaline carbonates and

hydroxides – weak and strong bases• Biochar can make pH better or worse• Biochar also has phosphorus,

potassium and nitrogen in various forms – depending in the char process

What is in that bag of Biocharand why do you CARE?

• Moisture (as delivered)• Ash Content (as delivered and from

what)• Mobile Matter versus Resident Matter

• Mobile Matter is going to stimulate soil microbial populations

• Resident Matter is the long-term biochar phenomena

• Resident carbon is not the only goal

What is in that bag of Biocharand why do you CARE?

• Moisture (as delivered)• Ash Content (as delivered and from

what)• Mobile Matter versus Resident Matter • Cation Exchange Capacity – pivotal in

nutrient retention in soils• May be due to oxidation of resident

matter or adsorption of oxygenated Dissolved Organic Matter

• May develop over time in soil

What is in that bag of Biocharand why do you CARE?

• Moisture (as delivered)• Ash Content (as delivered and from what)• Mobile Matter versus Resident Matter • Cation Exchange Capacity• Adsorption Capacity - formed during char

production and, hence, does not improve • Responsible for trace moisture retention in

soils may prolong growing season• Responsible for adsorption/desorption of

DOM, stimulates microbial populations

Pivotal Biochar properties:

Short-term Effects• Ash Content – due to pH impact• Mobile Matter – due to stimulating soil

microbes, which complete for nitrogen

Long-term Effects• Resident Matter – because it contains the

• Cation Exchange Capacity• Adsorption Capacity