Carbon remaining (%)

Ca

rbo

n r

em

ain

ing

(%

)

100

1 2 3 4 5Years

Biochar

Uncharred Biomass

Centuries?Millennia?

CompostCompost500+°C

Dr. Johannes LehmanDr. Johannes Lehman

– – and and hydrophobichydrophobic – it repels water – it repels waterwith no biological activity with no biological activity –– no microbes no microbesFresh from a burner, biochar is sterile,Fresh from a burner, biochar is sterile,

Biochar isn’t consumed by soil lifeBiochar isn’t consumed by soil life

not affected by weathering, oxidation & digestionnot affected by weathering, oxidation & digestion– – not in months, but decades, even centuriesnot in months, but decades, even centuries

In soil, charcoal breaks down very slowlyIn soil, charcoal breaks down very slowly

: Habitat and housing for microbes: Habitat and housing for microbes

SubstrateSubstrate: Adsorp nutrient ions (C.E.C. & A.E.C.): Adsorp nutrient ions (C.E.C. & A.E.C.)StorehouseStorehouse

: Absorb, hold & conserve soil water: Absorb, hold & conserve soil waterSpongeSpongeBiochar supplies three important soil services:Biochar supplies three important soil services:

Adding only raw charcoal to soilAdding only raw charcoal to soil

Fertilizers must be added with charcoalFertilizers must be added with charcoalretards plant growth 1 or 2 yearsretards plant growth 1 or 2 years

is biochar a fertilizer?is biochar a fertilizer?is biochar a nutrient?is biochar a nutrient?Biochar PropertiesBiochar Properties

50

PyrolysisPyrolysis

10 Humus

Particle sizeParticle size Surface areaSurface area Residence TimeResidence Time Structural densityStructural density Micropore densityMicropore density Moisture contentMoisture content Water AbsorptionWater Absorption Ion AdsorptionIon Adsorption CECCEC pHpH Microbial ActivityMicrobial Activity

Physical PropertiesPhysical Properties

& & AECAEC

Biochar PropertiesBiochar Properties

Particle sizeParticle size

Micropore densityMicropore density

Water AbsorptionWater Absorption

CECCEC & & AECAEC

Microbial ActivityMicrobial Activity

PHOTO: Bob Cirino, University of DelawarePHOTO: Bob Cirino, University of Delaware

Surface areaSurface areaExternal:External: square inches vs. square milessquare inches vs. square milesInternal: Internal: microporesmicropores

Varied sizesVaried sizes varied purposes: varied purposes: broadcast, seed drill, potting mix, hydroponicsbroadcast, seed drill, potting mix, hydroponicsGravelGravelRice grainRice grainPowder & DustPowder & DustWater soluble: Water soluble: lowest molecular weightlowest molecular weight

Micronize:Micronize: Nature’s nanotechnology Nature’s nanotechnologyBrittle:Brittle: easy to crush easy to crushDusty:Dusty: easily blows away easily blows awayVariable:Variable: with feedstock with feedstockWoody vs. WeedyWoody vs. WeedyScreen:Screen: separate sizes separate sizesIntimate mix:Intimate mix: at cellular and molecular scales at cellular and molecular scales

Particle Conversion ChartParticle Size Diameter

(microns)Mesh

(screen size)

Fine Sand 250 - 100 50 - 125Very Fine Sand 100 - 50 125 - 250

Silt 50 - 2 250 - 6000Clay 2 or less 6000 or more

Particle SizeParticle SizeBiochar PropertiesBiochar Properties

RecalcitrantRecalcitrantResists chemical & weathering actionResists chemical & weathering action

Resists microbial digestion & decayResists microbial digestion & decay

Sequestration = at least 100 yearsSequestration = at least 100 years

Dr. David Laird, USDA Tilth Lab: 1600 year half-lifeDr. David Laird, USDA Tilth Lab: 1600 year half-life1 to 5% loss1 to 5% lossTar & Resins Residues Tar & Resins Residues (VOC & PAH)(VOC & PAH)

HydrophobicHydrophobic (oily hydrocarbons) (oily hydrocarbons)

Vary with production processVary with production processTemperature: 500-700°CTemperature: 500-700°C (energy only: up to 1500°C) (energy only: up to 1500°C)

Pressure, Length of Time, SteamPressure, Length of Time, Steam

Gasification vs. Pyrolysis Gasification vs. Pyrolysis (burning vs. baking) (burning vs. baking)

Torrefication, Fast Pyrolysis, Flash Pyrolysis, MicrowaveTorrefication, Fast Pyrolysis, Flash Pyrolysis, Microwave

Residence TimeResidence TimeBiochar PropertiesBiochar Properties

Ca

rbo

n r

em

ain

ing

(%

)

51 2 3 4Years

50

10

100

PyrolysisPyrolysis

Composted Biomass

Humus

Biochar1−5%

10−15%

35−50%