Non-Peer ReviewedThe exploitation of phosphorus (P) ore for soil fertilization supports the high demand of modern
agriculture, but limitations of P sources encourage research in sustainable P use, recovery and reuse.
Here we propose the integration of pyrogenic carbon (i.e. biochar) production into waste management
systems for phosphorus (P) reuse and recovery by pyrolysis (PRP). A meta-analysis indicated animal
manure, human excreta, and plant-biomass collected from P polluted sites to be sources of P-enriched
biomass, all of which have been examined as feedstocks for biochar. As a soil amendment, biochar could
serve to both supply P and reduce P loss. 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. Factors
such as pH, metal content, colloidal-sized particles, and activities of soil biota (arbuscular mycorrhizal
fungi and phosphorous solubilizing microorganisms) are expected to affect sorption- desorption of P
between biochar and soil aggregates and P acquisition by plants. Phosphorus in biochar is expected to
participate in P equilibrium in soil. Chemical extraction, using acid or alkaline solutions, is considered as
a means for P retrieval from high P biochar, especially for biochars with high heavy metal contents.
To bridge the gap between academia and practice, this paper stresses key objectives for PRP: 1) identification of key biomass for pyrolysis; 2) retrieval of P from biochar in soils 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 waste water plants