Recycling slaughterhouse waste into fertilizer: how do pyrolysis temperature and biomass additions affect phosphorus availability and chemistry?
2015
Zwetsloot, Marie J | Lehmann, Johannes | Solomon, Dawit
BACKGROUND: Pyrolysis of slaughterhouse waste could promote more sustainable phosphorus (P) usage through the development of alternative P fertilizers. This study investigated how pyrolysis temperature (220, 350, 550 and 750 °C), rendering before pyrolysis, and wood or corn biomass additions affect P chemistry in bone char, plant availability, and its potential as P fertilizer. RESULTS: Linear combination fitting of synchrotron‐based X‐ray absorption near edge structure spectra demonstrated that higher pyrolysis temperatures decreased the fit with organic P references, but increased the fit with a hydroxyapatite (HA) reference, used as an indicator of high calcium phosphate (CaP) crystallinity. The fit to the HA reference increased from 0% to 69% in bone with meat residue and from 20% to 95% in rendered bone. Biomass additions to the bone with meat residue reduced the fit to the HA reference by 83% for wood and 95% for corn, and additions to rendered bone by 37% for wood. No detectable aromatic P forms were generated by pyrolysis. High CaP crystallinity was correlated with low water‐extractable P, but high formic acid‐extractable P indicative of high plant availability. Bone char supplied available P which was only 24% lower than Triple Superphosphate fertilizer and two‐ to five‐fold higher than rock phosphate. CONCLUSION: Pyrolysis temperature and biomass additions can be used to design P fertilizer characteristics of bone char through changing CaP crystallinity that optimize P availability to plants. © 2014 Society of Chemical Industry
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