Slow pyrolyzed biochars from crop residues for soil metal(loid) immobilization and microbial community abundance in contaminated agricultural soils

Abstract

This study evaluated the feasibility of using biochars produced from three types of crop residues for immobilizing Pb and As and their effects on the abundance of microbial community in contaminated lowland paddy (P-soil) and upland (U-soil) agricultural soils. Biochars were produced from umbrella tree [Maesopsis eminii] wood bark [WB], cocopeat [CP], and palm kernel shell [PKS] at 500 °C by slow pyrolysis at a heating rate of 10 °C min. Soils were incubated with 5% (w w) biochars at 25 °C and 70% water holding capacity for 45 d. The biochar effects on metal immobilization were evaluated by sequential extraction of the treated soil, and the microbial community was determined by microbial fatty acid profiles and dehydrogenase activity. The addition of WB caused the largest decrease in Pb in the exchangeable fraction (P-soil: 77.7%, U-soil: 91.5%), followed by CP (P-soil: 67.1%, U-soil: 81.1%) and PKS (P-soil: 9.1%, U-soil: 20.0%) compared to that by the control. In contrast, the additions of WB and CP increased the exchangeable As in U-soil by 84.6% and 14.8%, respectively. Alkalinity and high phosphorous content of biochars might be attributed to the Pb immobilization and As mobilization, respectively. The silicon content in biochars is also an influencing factor in increasing the As mobility. However, no considerable effects of biochars on the microbial community abundance and dehydrogenase activity were found in both soils.

Response of microbial communities to biochar-amended soils: a critical review

“…In contrast, Igalavithana et al (2017b) reported that the application of umbrella tree (Maesopsis eminii)-derived biochar to a heavy-metalcontaminated soil had no effect on microbial abundance determined by FAME analysis and dehydrogenase activity in a short term. The low surface area and low volatile matter content of the resultant biochars reduced the microbial community and the activity in the soils amended with biochars (Igalavithana et al 2017b). Elevated metal concentrations in soils can disrupt microbial functions, resulting in adverse effects on the ecosystem.…”

“…Application of vegetable waste biochar produced at 200 °C improved the soil quality of heavy-metal-contaminated soils, through increasing soil microbial abundance and associated microbial activities which were proven by dehydrogenase activity and fatty acid methyl ester (FAME) analysis (Igalavithana et al 2017a;Meier et al 2017b). In contrast, Igalavithana et al (2017b) reported that the application of umbrella tree (Maesopsis eminii)-derived biochar to a heavy-metalcontaminated soil had no effect on microbial abundance determined by FAME analysis and dehydrogenase activity in a short term. The low surface area and low volatile matter content of the resultant biochars reduced the microbial community and the activity in the soils amended with biochars (Igalavithana et al 2017b).…”

Phytostabilization of arsenic and manganese in mine tailings using Pennisetum purpureum cv. Mott supplemented with cow manure and acacia wood-derived biochar

“…Even so, acidic conditions can make heavy metals less stable and able to be taken up by plants despite a high OM content in the soil. Furthermore, manure will decompose over time, releasing various elements ( Igalavithana et al., 2017 ). After 120 d of culture, P. purpureum had increased As and Mn uptake, in accordance with a previous report ( Elouear et al., 2016 ), where sheep manure-derived biochar and potassium chloride fertilizer (KCl)-supplemented soil with 970 mg kg −1 Pb, 9,641 mg kg −1 Zn, and 53 mg kg −1 Cd was used to grow alfalfa grass ( Medicago sativa L.).…”

Comparison of Fuel Yield of Biomaterials Between Fast Pyrolysis and Gasification

“…Pyrolysis is a viable method of converting bio-waste or otherwise unusable organic matter into solid, liquid and gaseous, high carbon, biofuels [1,5,6]. There is an obvious need for cleaner, more cost effective energy sources in the world and while environmental benefits and socio-economics are not the focus of this Meta study they are still worth mentioning.…”

“…Organic vapours can be condensed into bio-oils and acid extract [1,2,6]. Through pyrolysis, the chemical decomposition of carbon-carbon bonds occur that then form carbon-oxygen bonds, to form a range of different molecules such as aldehydes, carboxylic acids, phenols, etc.…”