Effect of the dietary oregano (Origanum vulgare) on Cu and Zn balance in weaned piglets

Chemical speciation and risk assessment of Cu and Zn in biochars derived from co-pyrolysis of pig manure with rice straw

Pig manure has been utilized as a good feedstock to produce biochar. However, the pig manure-derived biochar from intensive pig cultivation contains high levels of total and bioavailable heavy metals. In this study, the co-pyrolysis of pig manure with other biomass (e.g. rice straw) at 300-700 °C was investigated to solve the above-mentioned topic. The ammonium acetate (CH₃COONH₄), Tessier sequential extraction procedure and hydrogen peroxide were adopted to evaluate the bioavailability, chemical speciation, and potential risk of Cu and Zn in the biochars. Results showed that the addition of rice straw significantly reduced the concentrations of total, exchangeable and carbonate-associated Cu and Zn in the biochars compared to the single pig manure biochars. Co-pyrolysis of pig manure with rice straw at a mass ratio of 1:3 and at 600 °C could be most effective to reduce the concentrations of CH₃COONH₄-extractable and potential released Cu and Zn in the biochars. In conclusion, the co-pyrolysis process is a feasible management for the safe disposal of metal-polluted pig manure in an attempt to reduce the bioavailability and potential risk of heavy metals at relatively high pyrolysis temperatures.

Contrasting effects of composting and pyrolysis on bioavailability and speciation of Cu and Zn in pig manure

The intensive and unregulated application of feed additives to commercial pig foods has resulted in high levels of Cu and Zn in pig manure. The aim of this study was to assess the impacts of composting and pyrolysis processes on the bioavailability and chemical speciation of Cu and Zn in pig manure products by single and sequential extractions, and to compare metal bioavailability in composts and biochar-amended soils in incubation experiments. Composting and pyrolysis processes can convert exchangeable and carbonate-bound Cu and Zn to organic matter and residual fractions, and significantly reduce the potential availability of metals in composts and biochars. The DTPA-Cu and Zn concentrations in soils amended with biochar BC700 were lower than in composts and soils amended with biochar BC400. It is suggested that 700 °C is the preferred pyrolysis temperature for the conversion of pig manure contaminated with heavy metals to biochar, in order to minimize environmental pollution.