NOVELTY - Producing a biochar core comprises: providing a biomass to a pyrolysis unit; pyrolyzing the biomass in the pyrolysis unit to produce a stable biochar core that is resistant to degradation, where the stable biochar core has a rate of degradation that is less than 2.5% per year, and the biomass is pyrolyzed under (i) a heating rate of 0.1 degrees C/second and 50 degrees C/second, (ii) a temperature of greater than 250 degrees C and (iii) a heating time of greater than 0.01 days; and optionally combining the biochar core with a supplement to produce a functionalized biochar.    USE - The biochar core is as a soil amendment, potting mix, a substitute in a growing media (including peat and/or compost media), a horticultural media, a carbon sequestration agent, a fertilizing agent, a turf grass establishment, a bioremediation agent, a delivery agent for a fungi or bacterial population, and a synthetic terra preta (or equivalent material). The biochar core is useful for: carbon sequestration by fixing of carbon in the soil in a recalcitrant form; mitigation of soil greenhouse gas emissions; reducing emission of methane or nitrogen containing gases, such nitrous oxide; on-demand release of chemicals or other materials, where the chemicals can be fertilizers, nutrients, or other materials that are depleted over time at a particular site; enhancing agricultural output, horticultural qualities, or turf grass; improving the yield of an agricultural crop and/or improving the resistance of the crop to detrimental environmental effects including harmful organisms e.g. harmful fungi or insects, diseases, drought, low water, heat, wind, cold, frost, pollution, saline-containing water, and polluted water; improving water retention, drainage, aeration, or the effects of compaction; improving crop quality or nutritional value; reducing pollution in water run-off streams; improving retention of water; removing phosphorus and nitrogen compounds from water streams or from other sources; and protecting ground water and other water bodies from undesired effects. No biological data given.    ADVANTAGE - The biochar core is stable, inert and/or exhibits reduced degradation over time. The biochar core can lead to increased crop yield, lower use of water or irrigation, less nutrient run-off, reduced fertilizer use and cost, reversed soil degradation, and elimination, reduction, and avoidance of greenhouse gas emissions from soil. The biochar can be designed to absorb toxic chemicals or has organisms that can convert the toxic chemicals to less harmful chemicals.    DESCRIPTION OF DRAWING(S) - The figure shows a flow chart of a process for producing a functionalized biochar.