Table 9.

Impact of biochar addition to anaerobic digestion on heavy metals stabilisation

Digested feedstock	Biochar condition	Fermentation temperature	Main effect	References
Sewage sludge	Pyrolysis, 600 °C Potassium permanganate-biochar	35 °C	Chromium, cadmium, nickel, zinc and copper, were reduced to 4.8%, 8.8%, 15.5%, 7.6%, and 9.7%, respectively	Li et al. (2019c)
Sewage sludge	Pyrolysis, 600 °C Manganese iron oxide-biochar	35 °C	Carbonate-bound chromium, cadmium, and nickel were reduced by 49.8%, 49.5%, and 49.8%, respectively	Zhang and Wang (2020)
Pig manure	Particle size less than 0.425 mm	25 °C	Exchangeable nickel, lead, arsenic, manganese, and chromium decreased by 6.5%, 12.3%, 12.9%, 3.1%, and 22.1%, respectively	Wang et al. (2021f)
Organic Municipal Solid Waste	Pyrolysis-gasification process	51–53 °C	Lead, mercury, copper, nickel, chromium, and zinc content in the slurry was reduced	Bona et al. (2020)

Digested feedstocks such as sewage sludge, pig manure, organic municipal solid waste were investigated, and the impact of biochar preparation conditions along fermentation temperature was provided