Effects of co-pyrolysis of heavy metal contaminated biomass with magnesium carbonate on heavy metal deportment and pyrolytic product properties

•Magnesium carbonate was mixed with heavy metal rich biomass to perform co-pyrolysis.•The elemental recovery of ten heavy metals in pyrolytic products were studied.•Co-pyrolysis effectively retained most heavy metals in biochars up to 700 °C.•Co-pyrolysis decreased the leaching potential of heavy metals in biochars.