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

PPPParticle size SSSSurface area RRRResidence Time SSSStructural density MMMMicropore density MMMMoisture content WWWWater Absorption IIIIon Adsorption CCCCEC ppppH MMMMicrobial Activity Physical Properties & AEC Biochar Properties PPPParticle size MMMMicropore density WWWWater Absorption CCCCEC & AEC MMMMicrobial Activity

PHOTO: Bob Cirino, University of Delaware 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: Nature’s 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 SizeDiameter (microns) Mesh (screen size) Fine Sand Very Fine Sand Silt Clay 2 or less 6000 or more Particle Size Biochar Properties

RRRRecalcitrant Resists chemical & weathering action Resists microbial digestion & decay Sequestration = at least 100 years Dr. David Laird, USDA Tilth Lab: 1600 year half-life  1 to 5% loss Tar & Resins Residues (VOC & PAH) Hydrophobic (oily hydrocarbons)  Vary with production process Temperature: °C (energy only: up to 1500°C) Pressure, Length of Time, Steam Gasification vs. Pyrolysis (burning vs. baking) Torrefication, Fast Pyrolysis, Flash Pyrolysis, Microwave Residence Time Biochar Properties Carbon remaining (%) Years Pyrolysis Composted Biomass Humus Biochar 1−5% 10−15% 35−50%