The effect of different pyrolysis temperatures on the speciation and availability in soil of P in biochar produced from the solid fraction of manure

Abstract

Biochar application to agricultural land has been proposed as a means for improving phosphorus (P) availability in soil. The purpose of the current study was to understand how pyrolysis temperature affects P speciation in biochar and how this affects availability of P in the amended soil. Biochar was produced at different temperatures from digestate solids. The primary species of P in digestate solids were simple calcium phosphates. However, a high co-occurrence of magnesium (Mg) and P, indicated that struvite or other magnesium phosphates may also be important species. At low temperatures, pyrolysis had little effect on P speciation; however, as the temperature increased above 600 °C, the P gradually became more thermodynamically stable in species such as apatite. At very high temperatures above 1000 °C, there were indications of reduced forms of P. Biochar production decreased the immediate availability of P in comparison with the original digestate solids. However, for biochar produced at low temperatures, availability quickly increased to the same levels as in the digestate solids. For biochar produced at higher temperatures, availability remained depressed for much longer. The low availability of P in the biochar produced at high temperatures can probably be explained by the formation of less soluble P species in the biochar. In contrast, the transient decrease of availability of the P in the biochar produced at low temperatures can be explained by mechanisms, such as sorption on biochar, which gradually decreases because of oxidation of the biochar surfaces or changes in pH around the biochar particles.

Phosphorus bioavailability of sewage sludge‐based recycled fertilizers in an organically managed field experiment

“…() reported a high P efficiency of pyrolysis coals produced at 500°C tested at soil pH 6.1. Decreased P availability of the Pyrolysis coal in our experiment might thus be caused by the higher production temperature of 650°C ( Bruun et al, ).…”

Effects of Maize Residue Biochar Amendments on Soil Properties and Soil Loss on Acidic Hutton Soil

“…According to [16], approximately 2.2 Mton year −1 of SOC can potentially be sequestered through biochar use. Researchers generally agree that C derived from biochar can be retained in soils for approximately 1300-4000 years, which is longer than that of uncharred organic material [21,[36][37][38]. Furthermore, about 50% of the initial C can potentially be sequestered when biomass is converted to biochar as opposed to the low amounts retained after burning (3%) and biological decomposition (less than 10-20% after 5-10 years) [39].…”

“…Furthermore, there are very few studies on the influences of biochar on the physical properties of soil and soil loss in an acidic soil. Biochar used in most studies was made using advanced pyrolysis methods (muffle furnaces or gasifiers) [10,36,37] while the biochar used in this study was made from locally-made oil drum kilns, a process that can be done by smallholder farmers. Moreover, given the high variability in biochar's physicochemical properties and its response to different types of soils and climates; estimates from other studies are, therefore, not universal to all locations and types of biochar [15,16,42,43].…”

Influencia del biocarbón aplicado al suelo sobre atributos de rendimiento y calidad de avena forrajera

“…El BC es el subproducto sólido del proceso de pirólisis (Jung et al, 2016), un proceso de conversión termoquímica de la biomasa (Bruun et al, 2017), el cual, se lleva a cabo en condiciones limitadas o en ausencia de oxígeno (Ahmed et al, 2016). La temperatura para elaborar BC puede variar de 300 a 1000 °C Tripathi et al, 2016).…”