Recycling slaughterhouse waste into fertilizer: how do pyrolysis temperature and biomass additions affect phosphorus availability and chemistry?
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.


CONCLUSIONS
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.
Department of Crop and Soil Sciences, Cornell University, NY 14853, USA.
Marie J
MJ
Zwetsloot
Johannes
J
Lehmann
Dawit
D
Solomon
D000003:Abattoirs; D000818:Animals; D001682:Biological Availability; D018533:Biomass; D001842:Bone and Bones / Q000737:chemistry*; D002130:Calcium Phosphates / Q000032:analysis; D002606:Charcoal; D005308:Fertilizers / Q000032:analysis*; D005561:Formates; D007220:Industrial Waste; D010758:Phosphorus / Q000032:analysis*; D010944:Plants / Q000737:chemistry*; D059027:Recycling; D013696:Temperature; D014934:Wood; D003313:Zea mays
D002130:Calcium Phosphates; D005308:Fertilizers; D005561:Formates; D007220:Industrial Waste; C030544:formic acid; D002606:Charcoal; D010758:Phosphorus; C020243:calcium phosphate
XANES spectroscopy; biochar; bone char; phosphorus; pyrolysis