Biochar is pyrolyzed biomass that is roughly 70% stable, aromatic carbon. Mixed into soil under tree rows, its porous structure holds water and nutrient cations while the tree canopy shades the surface, cutting evaporative loss. Only a small "labile" fraction of biochar carbon decomposes; the rest persists for centuries, so cumulative carbon storage rises with application rate while decay approaches a plateau.
C_stored(t) = R · f_C · [ f_stable + f_labile · e^(-k·t) ]
WHC(t) = WHC0 + a · R · (1 − 0.35·shade)
CEC(t) = CEC0 + b · R · (1 + 0.2·shade)
R = application rate (t/ha), f_C = 0.7 carbon fraction
f_stable = 0.82, f_labile = 0.18, k = 0.35 /yr
shade = canopy cover fraction, a,b = empirical soil response coefficients
- Biochar rate — sets particle density mixed into the soil block, driving CEC and water-holding gains.
- Tree canopy cover — sets number of trees/roots and the shading factor that slows evaporation.
- Time scale — advances simulated years, decaying the labile carbon pool and accumulating stable carbon storage.
- Water flow / Nutrient cycle — switches the animated particles between soil moisture movement and root–biochar nutrient exchange.
Agroforestry cooperatives pair this soil chemistry with tree rows that supply the feedstock (prunings) for biochar kilns on-site, closing a local carbon-negative loop between farming and forestry.