Different types of biochar products for agronomic applications as soil improver and innovative fertilizer.
Author: Edward Someus (biochar S&T senior engineer, Terra Humana Ltd. www.3Ragrocarbon.com
Biochar is plant and/or animal biomass by-product based stabile carboniferous substance for conservation agriculture. The biochar must be well defined and controlled quality, that is processed under full reductive thermal conditions (pyrolysis), and applied to improve the soil physical, chemical and/or biological properties or the soil activity. All in order to achieve biochar feed material sustainability; the feed materials should not compete with human food, animal feed and plant nutrition production and supply.
The following materials are not biochar products: charcoal; energetic carbon; labile carbon materials; carbon products made from not recently living biogenic origin; materials with no legal producer/user permits and/or materials with no validated Extended Producer Responsibility certificate that is specific for biochar “fit for purpose” of use.
Biochar production and application in agriculture is to be mandatorily permitted according to the EU/MS regulations. The first biochar application Authority permit under EU regulations of an EU Member State has been issued in 2009 for Terra Humana Ltd (permit number 02.516717120). There is no one fit for all biochar production process and/or product type. However, there are two main and important aspects that are critically impacting all biochar product performances, such as the feed material character and the pyrolysis processing design condition. The input feed material character is reflected into the output biochar product characteristics, while the pyrolysis processing quality is reflected into the biochar product quality and safety. The thermal processing conditions for the traditional and low end pyrolysis technologies (designed and applied for energetic carbon processing) are usually not qualified for safe biochar production and to meet modern expectations towards zero emission operational performance. In this context the modern and economically industrial scale biochar processing require comprehensive installation. Plant derived biochar with high carbon content can serve as soil improver and/or growing media, but having no direct fertilizer value with economical importance; it has rather a high water holding and nutrient retention capacity besides a high C sequestration potential. Animal Bone bioChar (ABC) produced from food grade animal bones, having far lower carbon content but high recovered nutrient value with 30% P2O5 and 38-42% CaO content which increases the innovative fertilizer value of these products substantially.
The recommended dose for plant derived biochar is 3-20 t/ha (usually ~10 t/ha) while ABC could be efficiently applied at far less dose with 0.1-1 t/ha (usually ~0.3 t/ha). In the case of all types of biochar the Polycyclic Aromatic Hydrocarbons (PAHs) are priority hazardous substances and key performance indicators both for the production process and product quality as well. The occurrence of PAHs in biochar derives from obsolete, low grade and inefficient pyrolysis conditions. The plant derived biochar material may contribute high levels of PAHs to soil when the total PAHs concentration in the biochar product is high and/or when high application doses are applied to achieve the desired effect requirements. Certain Potentially Toxic Elements (PTEs); most importantly Cadmium, Nickel, Lead and Mercury; are also included in the list of priority substances. The higher the organic matter content in feedstock, the less the yield of biochar, thus PTE high accumulation occurs especially in plant derived biochar. The Potential Toxic Elements (PTE) and organic pollutant threshold values, safety and labelling of biochar with comprehensive aspects with “fit for purpose” of use are EU policy support recommended for the Commission by the REFERTIL project to be considered at EC Fertilizers Regulation revision.