Hugh McLaughlin, PhD, PE
Director of Biocarbon Research
Alterna Biocarbon Inc.
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
Top Related