Phosphorus speciation in a prairie soil amended with MBM and DDG ash: Sequential chemical extraction and synchrotron-based XANES spectroscopy investigations.

Sequential chemical extraction and synchrotron-based XANES spectroscopy techniques were used to identify P species in two ashes before and after addition to a prairie soil. The used ashes were: meat and bone meal ash (MBMA) and dried distillers grains ash (DDGA) plus mineral P fertilizer (MP) for comparison. Soil treated with MP contained higher content of resin-Pi and NaHCO3-Pi followed by DDGA and MBMA. The MBMA amended soil had the highest (47%) proportion of the soil P contained in recalcitrant HCl extractable fraction, reflecting more Ca-bound P present and being formed in soil after application. Analysis of both ashes with XANES spectroscopy before application to soil revealed that MBMA had strong spectral features consistent with hydroxyapatite (Ca5(PO4)3(OH)). DDGA exhibited spectral features consistent with a mixture of several Mg and K phosphate salts rather than a single mineral species. The distinctive features in the XANES spectra of both ashes largely disappeared after amendment to the soil, suggesting transformation to different P forms in the soil after application. It is also possible that the added amount of P to the studied soil via DDGS or MBMA was small enough so that P speciation is not different from the background P level.

Phosphorus recovery and reuse by pyrolysis: Applications for agriculture and environment.

Phosphorus ore extraction for soil fertilization supports the demand of modern agriculture, but extractable resource limitations, due to scarcity, impose a P reuse and recycling research agenda. Here we propose to integrate biochar production (pyrogenic carbon) with municipal and agricultural waste management systems, to recover and reuse phosphorous that would otherwise be lost from the ecological food web. A meta-analysis and available data on total P in biochar indicated that P-enriched feedstocks include animal manure, human excreta, and plant-biomass collected from P-polluted sites. Phosphorus in biochar could participate in P equilibriums in soils and is expected to supply P. The release, sorption and desorption of P by biochar will codetermine the potential of P replenishment by biochar and P loss from biochar-amended soils. Abiotic and biotic factors are expected to affect sorption/desorption of P between biochar and soil aggregates, and P acquisition by plants. Chemical extraction, using acid or alkaline solutions, is considered as a means for P retrieval from high P biochar, especially for biochar with high heavy metal contents. To bridge the gap between academia and practice, this paper proposes future development for phosphorus acclamation by pyrolysis: 1) identification of high-P bio-waste for pyrolysis; 2) retrieval of P by using biochar as soil amendment or by chemical leaching; 3) biochar modification by inorganic nutrients, P solubilizing microorganisms and other organic matter; and 4) compatible pyrolysis equipment fit to the current waste management context, such as households, and waste water treatment plants.