Integrating biochar and bacteria for sustainable remediation of metal-contaminated soils

Due to anthropogenic activities,heavy metal(HM)pollution in soils has increased,resulting in severe ecological problems and posing a constant threat to human health.Among various remediation methods,bacterial remediation is a relatively clean,efficient,and minimally negative approach.However,bacterial agents face multiple environmental stresses,making them challenging to achieve long-lasting and stable restoration effects.To address this issue,supportive organic substances such as biochar can be added to the soil with bacteria.According to bibliometric studies,integrating biochar and bacteria is extensively researched and widely used for HM-contaminated soil remediation.By integrating biochar and bacteria,heavy metals in the soil can be remediated,and soil conditions can be improved over time.Bacteria can also better promote plant growth or contribute effectively to phytoremediation processes when assisted by biochar.However,the remediation agents integrating biochar and bacteria are still some distance away from large-scale use because of their high cost and possible environmental problems.Therefore,further discussion on the interaction between biochar and bacteria and the integration approach,along with their remediation efficiency and environmental friendliness,is needed to achieve sustainable remediation of HM-contaminated soils by integrating biochar and bacteria.This paper discusses the potential mechanisms of biochar-bacteria-metal interactions,current advancements in biochar-bacteria combinations for HM-contaminated soil treatment,and their application in sustainable remediation,analyzes the interaction between biochar and bacteria and compares the remediation effect of different ways and feedstocks to integrate biochar and bacteria.Finally,future directions of biochar-bacteria combinations are presented,along with evidence and strategies for improving their commercialization and implementation.

Biochars produced from coconut palm biomass residues can aid regenerative agriculture by improving soil properties and plant yield in humid tropics

Lignin-rich recalcitrant biomass residues of coconut palms viz.(i)mature coconut husk,(ii)tender(immature or green)coconut husk(iii)coconut leaf petiole and(iv)coir-pith were successfully pyrolysed using a simple charring kiln into carbon-rich,black,light weight and porous biochars.High alkalinity and good ash content made them fit for remediating acid soils.High potassium content in these biochars could help reduce the use of inorganic K.Thermogravimetric analysis showed the mass loss phases of husk and coconut leaf petiole biochars to be similar.However,all four biochars gave smooth curves indicating thermal stability of the product.Positive seed germination and earthworm avoidance tests proved their potential as soil amendment.Soil incubation studies with coconut biochars in graded doses,alone or in combination with coconut leaf vermicompost,increased the pH,organic carbon and potassium contents,and promoted plant-beneficial microbiota and enzyme activities.Pot studies with tender coconut husk biochar and coconut leaf vermicompost enhanced the dry weight of cowpea plants accompanied with increased arbuscular mycorrhizal sporulation and root colonization,and root nodule dry weight.A field trial resulted in higher chilli yields with tender coconut husk biochar+coconut leaf vermicompost addition.The results from our studies highlight the potential of pyrolysis as an innovative technology for quick recycling of highly recalcitrant coconut palm biomass residues to biochars as a local source of soil amendment to aid regenerative agriculture in humid tropics.