U.S.-FocUSed Biochar report - BioEnergy Lists

costs, then the cost of the thermal energy will be decreased relative to the “no biochar” baseline. Conversely, if thebiochar is worth less than the incremental cost of production, then the fuel must underwrite the cost of biocharproduction. This later situation is unlikely to persist on a commercial scale, unless there is an external economicbenefit, such as a government subsidy or creation of a carbon trading credit of defined market value.Valuing Biochar in the SoilBiochar is more than a fuel and its role in soils goes well beyond anything associated with the energy releasedupon oxidation. In fact, since biochar’s most unique property is its ability to persist in the soil, the least relevantaspect of biochar is its fuel value.Acknowledging that the science of biochar is just now exploring the interactions that occur between biochar andunique growing environments, biochar seems to have one property that distinguishes it from virtually all othersoil materials. That property is porosity, the measure of the void spaces in a material. Porosity is the ratio of thevolume of non-solid material to the total volume. The significance in soils is that the non-solid volume can be occupiedby either air or water, or a combination of both to varying degrees under varying conditions. Furthermore,biochar is made up of thermally-modified biomass, which forms graphitic-like structures that exhibit adsorptioncapacity at the molecular scale. Thus, the porosity in biochar extends from large open voids to molecular-scalecrevices. While there is a lower limit of the porosity of high quality biochars, it is at the molecular level and theporosity can conceptually be viewed as having “fractal” geometries extending from the scale of the entire particleto the scale of adsorbed molecules as small as water, methane and nitrous oxide. Because of this property, biocharcan accurately be called “Mother Nature’s Nanotechnology”.Typical biochars have bulk densities of around 250 kg/cubic meter, with some biochars having bulk densities aslow at 150 kg/cubic meter. Biochar is principally composed of amorphous graphite that has a density of about2000 kg/cubic meter (specific gravity of 2.00 or 2.00 grams per cubic centimeter). Thus, the porosity of biocharis in the range of 0.875 to 0.925. Even discounting the voids between the particles, biochars are essentially “rigidopen space”.The ability to form molecular scale crevices that exhibit adsorption capacity over a range of elevated adsorptionenergies is highly unusual and is one of the determining metrics for distinguishing biochar quality. Notably, thisadsorption capacity phenomenon is not intrinsic in all biochars and develops under fairly narrow conditions.Figure 1 shows the char yield and adsorption capacity for a series of chars made by the same experimental procedureexcept for the highest “Heat treatment temperature” reached during the thermal conversion of the biomassinto biochar.Two trends are depicted in Figure 1; the rapidly decreasing char yield between 250 and 350 degrees Centigrade(C), and the development of adsorption capacity between 500C and 700C. Notably, the char appears jet blackeverywhere above 300C, but does not develop maximum adsorption capacity until 550-600 C, only to have thatproperty fade and almost disappear by 900C.20U.S.-Focused Biochar Report:Assessment of Biochar’s Benefits for the United States of America