How to make biochar

1
Biochar Properties
is biochar a nutrient?
is biochar a fertilizer?
In soil, charcoal breaks down very slowly
not in months, but decades, even centuries
Compost
Pyrolysis
not affected by weathering, oxidation digestion
500C
100
Biochar isnt consumed by soil life
Fresh from a burner, biochar is sterile,
with no biological activity no microbes
and hydrophobic it repels water
Adding only raw charcoal to soil
Dr. Johannes Lehman
?
50
retards plant growth 1 or 2 years
Centuries?
Carbon remaining ()
Biochar
Fertilizers must be added with charcoal
Millennia?
Biochar supplies three important soil services
Uncharred Biomass
Habitat and housing for microbes
Sponge
Absorb, hold conserve soil water
10
Humus
Storehouse
Adsorp nutrient ions (C.E.C. A.E.C.)
Substrate
Years
2
Physical Properties
Biochar Properties

• Particle size
• Surface area
• Residence Time
• Structural density
• Micropore density
• Moisture content
• Water Absorption
• Ion Adsorption
• CEC
• pH
• Microbial Activity

• Particle size

• Micropore density

• Water Absorption

AEC
AEC

• CEC

• Microbial Activity

3
Biochar Properties
Particle Size

• Surface area
• External square inches vs. square miles
• Internal micropores
• Varied sizes
• varied purposes broadcast, seed drill, potting
  mix, hydroponics
• Gravel
• Rice grain
• Powder Dust
• Water soluble lowest molecular weight
• Micronize Natures nanotechnology
• Brittle easy to crush
• Dusty easily blows away
• Variable with feedstock
• Woody vs. Weedy
• Screen separate sizes
• Intimate mix at cellular and molecular scales

Particle Conversion Chart Particle Conversion Chart Particle Conversion Chart
Particle Size Diameter (microns) Mesh (screen size)
Fine Sand 250 - 100 50 - 125
Very Fine Sand 100 - 50 125 - 250
Silt 50 - 2 250 - 6000
Clay 2 or less 6000 or more
PHOTO Bob Cirino, University of Delaware
S4700 3.0kV 11.9mm x 300 SEM 12/2/13
4
Residence Time
Biochar Properties

• Recalcitrant

Pyrolysis
Resists chemical weathering action Resists
microbial digestion decay Sequestration at
least 100 years Dr. David Laird, USDA Tilth Lab
1600 year half-life
100

• 1 to 5 loss

Tar Resins Residues (VOC PAH) Hydrophobic
(oily hydrocarbons)
50
1-5
Carbon remaining ()
Biochar
35-50

• Vary with production process

Temperature 500-700C (energy only up to
1500C) Pressure, Length of Time,
Steam Gasification vs. Pyrolysis (burning vs.
baking) Torrefication, Fast Pyrolysis, Flash
Pyrolysis, Microwave
Composted Biomass
10
Humus
10-15
Years