Transcript Document

All Biochars are Not Equal
Version 1 – November 13, 2009
Presented at the Northeast Biochar Symposium 2009, Amherst, MA
Hugh McLaughlin, PhD, PE
Director of Biocarbon Research
Alterna Biocarbon Inc.
[email protected]
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 …
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Weight percent of dry sample
300
250
Water (gm/100 gms dry biochar)
Ash
Mobile Matter
Resident Matter
200
150
100
50
0
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 precarbonization biomass
• Soluble Ash is the principal pH effect of
biochar addition to soils – can act like lime
• Ash includes Nitrogen? – depends on test
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Weight percent of dry sample
100%
80%
60%
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20%
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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
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Weight percent of dry sample
100%
80%
60%
40%
20%
0%
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 and
the way it was made.
Pyrolysis & Carbonization Reactions of Wood
- above 325C = Biochar, below = Torrefied Wood
Lignin
Cellulose
Extensive
Devolatilisation
and
E
E
carbonisation
(E)
D
D
D
Limited
devolatilisation
and
carbonisation (D)
250
C
200
200
C
150
depolymerisation
and
recondensation
(C)
150
glass transition/
softening (B)
drying (A)
A
A
100
100
Hemicellulose
Lignin
Cellulose
Temperature (°C)
Temperature (°C)
250
300
TORREFACTION
300
Hemicellulose
100%
Carbon
Hydrogen
Oxygen
Fuel Yield
Fixed Carbon %
Fixed Carbon Yield
90%
Mass fraction (%)
80%
70%
60%
50%
40%
30%
20%
10%
0%
200
250
300
350
400
Biomass Processing Temperature Celsius
450
500
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
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10% of CEC in meq/100 grams
9.00
Adsorption Capacity (wt% @ 100C)
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
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Specific surface area (m2/g)
450
400
350
300
250
200
150
100
50
0
300
400
500
600
700
800
T erm inalpyrolysis tem perature(C )
900
1000
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 Biochar
and 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 Biochar
and 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 Biochar
and 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 Biochar
and 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 Biochar
and 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