Pyrolysis temperature affects phosphorus transformation in biochar: Chemical fractionation and 31P NMR analysis

Abstract

Phosphorus (P) recycling or reuse by pyrolyzing crop residue has recently elicited increased research interest. However, the effects of feedstock and pyrolysis conditions on P species have not been fully understood. Such knowledge is important in identifying the agronomic and environmental uses of biochar. Residues of three main Chinese agricultural crops and the biochars (produced at 300°C-600°C) derived from these crops were used to determine P transformations during pyrolysis. Hedley sequential fractionation and 31 P NMR analyses were used in the investigation. Our results showed that P transformation in biochar was significantly affected by pyrolysis temperature regardless of feedstock (Wheat straw, maize straw and peanut husk). Pyrolysis treatment transformed water soluble P into a labile (NaHCO 3 -P i ) or semi-labile pool (NaOH-P i ) and into a stable pool (Dil. HCl P and residual-P). At the same time, organic P was transformed into inorganic P fractions which was identified by the rapid decomposition of organic P detected with solution 31 P NMR. The P transformation during pyrolysis process suggested more stable P was formed at a higher pyrolysis temperature. This result was also evidenced by the presence of less soluble or stable P species, such as such as poly-P, crandallite (CaAl 3 Contents lists available at ScienceDirectScience of the Total Environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v P forms at higher pyrolysis temperature although their solubility or stability requires further investigation. Results suggested that a relatively lower pyrolysis temperature retains P availability regardless of feedstock during pyrolysis process.

Nonadditive effects of biochar amendments on soil phosphorus fractions in two contrasting soils

“…Washed and dried fresh wheat straw was selected as the raw material and charred using a muffle furnace in the absence of oxygen for 4 hr. The temperature was set to 300°C, 400°C, 500°C, and 600°C, respectively (Xu, Zhang, Shao, & Sun, ). After being charred, the samples were allowed to cool to room temperature, passed through a 2‐mm sieve, and packaged in bags for future use.…”

“…Details of the forms of P in the biochars are given in previous literature (Xu, Zhang, Shao, & Sun, ). The pH was determined with a glass electrode with 1:2.5 (1:20 for biochar) soil to water ratio.…”

Integration into plant biology and soil science has provided insights into the total environment

“…Plant biology is extremely interdisciplinary, reaching from agricultural science to paleobotany to soil science and molecular physiology to ecology. It uses the latest developments in computer science, optics, molecular biology, and genomics to address challenges in model systems, agricultural crops, and ecosystems; and explores the form, function, development, diversity, reproduction, evolution, and uses of both higher and lower plants, as well as their interactions with other organisms throughout the biosphere Sytar et al, 2016;Mao et al, 2016;Li et al, 2016aLi et al, , 2016bXu et al, 2016aXu et al, , 2016bXu et al, , 2016cZhang et al, 2016) (Fig. 1).…”

“…The following is to summarize the main results and their implications for the 20 accepted articles in the special topic. Xu et al (2016aXu et al ( , 2016bXu et al ( , 2016c and Sun et al (2016aSun et al ( , 2016b P NMR technique to analyze P transformation under different pyrolysis temperatures and further compared effects of biochar and P fertilizers on P availability and plant biomass, providing good reference for utilizing biochar amendment into salt-soil. Long et al (2016aLong et al ( , 2016b) discussed about the current status of developing coastal mudflat areas in China by taking Yancheng, Jiangsu as an example and basing on their practical work for more than 20 years.…”

“…Lu et al (2016a, b) reported the methodology of high-efficient use P, avoiding P loss and pollution in coastal zone by constructing periphyton technique. Zhang et al (2016)and Xu et al (2016aXu et al ( , 2016bXu et al ( , 2016c) applied molecular techniques to investigate related gene expression of important coastal crops and vegetables, providing insights into molecular breeding for salt-soil agriculture and sustainable use of salt-soil. Bai et al (2016)reported the latest result by using sewage sludge as an initial fertility driver for rapid improvement of mudflat salt-soil, starting a new way for raising salt-soil fertility on large-scale with low cost.…”