Abstract

The recovery of phosphorus (P) from milk processing flotation sludges (MFS) using pyrolysis can contribute to a sustainable reuse of P by converting waste to fertiliser. The objectives of this study were to quantify the recovery and transformation of P following MFS pyrolysis and compare the efficacy of raw and pyrolysed MFS as organic P fertilisers. Phosphorus retention in biochars was high (98 ± 0.73% yield), leading to the enrichment of P relative to the raw MFS by a factor of 4.3–4.5. Pyrolysis of the MFS at 450 °C led to a 3-fold increase in the proportion of P in the HCl-extractable fraction (65 ± 0.32%), a 2-fold reduction in NaOH-P (30 ± 2.1%), and negligible amounts of P in the H2O-P and NaHCO3-P fractions. The bioavailability of P in raw MFS and 450 °C biochar was compared to a soluble P fertiliser in P-limiting plant bioassays. In the short-term (70 day) trial where ryegrass was grown on three soil types (Arenosol, Vertisol or Ferralsol), biochar MFS showed higher efficacy as a P fertiliser than raw MFS in the acidic Ferralsol, whereas the opposite response was observed in the near-neutral Arenosol. In the Vertisol, neither the raw MFS nor biochar produced more cumulative biomass or P uptake than any of the nil P controls. Over a longer 200-day period, raw MFS and biochar applied to the Arenosol were about 20% as efficient at providing P to ryegrass plants as the water-soluble K2PO4, suggesting that higher application rates of MFS or biochar would be required to match synthetic fertilisers in the short term.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call