Examination of Three Different Organic Waste Biochars as Soil Amendment for Metal-Contaminated Agricultural Soils

Abstract

The efficiency of biochars (BCs) derived from paper mill sludge (PM-BC), distillery sludge (DS-BC), and pruned branches from roadside trees (PB-BC) for immobilization of selected heavy metals (Cd and Zn) in agricultural soils was examined in the current study. This examination was conducted in order to elucidate whether the recycling of organic wastes could be used as a management option for metal-contaminated agricultural soils. Biochars were applied to contaminated upland soil exceeding the guideline values for Cd (4 mg kg −1 ) and Zn (300 mg kg −1 ) in Korea. Both the incubation study and the pot trial with lettuce cultivation were carried out using soil-BCs mixtures at 0, 1, 2, and 5 % (w/w). From the incubation study, it appears that BCs incorporated into the soil induces an increasing soil pH and a significant decline (Cd 36~100 %; Zn 54~100 %) in the phytoavailable metal pool examined by 1 M NH 4 NO 3 extraction. The PM-BC was most effective in the reduction of Cd and Zn phytoavailability, due to a significantly higher pH and surface area than the DS-BC and PB-BC. Similar results were observed in the pot trial, where the uptake of heavy metals by lettuce greatly declined with PM-BC incorporation (Cd 26~71 %; Zn 28~45 %). PM-BC enhanced the lettuce growth performance evidenced by the highest yield of lettuce being observed with PM-BC-treated soils at 5 %. This was attributed to retardation of the metal toxic effect induced by a decrease in Cd accumulation, while the increased nutrient elements originated from PM-BC. This present study indicates that paper mill sludge is a great candidate for biochar production that can be utilized as a soil amendment for metalcontaminated agricultural soils.

Inherent organic compounds in biochar–Their content, composition and potential toxic effects

“…Where biochar has been applied to soil, it decreased the availability and plant uptake of various potentially toxic elements (PTEs) such as Cd, Pb, Cu, Ni and Zn (Beesley et al, 2011;Buss et al, 2012;Karer et al, 2015;Kim, 2015;Kloss et al, 2014a;Méndez et al, 2012;Park et al, 2011;Puga et al, 2015;Uchimiya et al, 2011). The mechanisms responsible for the immobilisation can be separated into: (I) direct mechanisms, e.g.…”

“…Finally, biochar can also contain contaminants which are supplied to soil with biochar. Rosa et al, 2014;Uzoma et al, 2011) locking up of N (Deenik et al, 2010;Nelissen et al, 2014;Prommer et al, 2014;Rondon et al, 2007;Shenbagavalli and Mahimairaja, 2012) binding and immobilisation of organic compounds reduced toxicity of contaminants (Beesley et al, 2011;Buss et al, 2012;Karer et al, 2015;Kim, 2015) reduced efficacy of pesticides (Cabrera et al, 2014;Graber et al, 2012;Jones et al, 2011;Kuppusamy et al, 2016;Yu et al, 2009) increase in soil pH reduced availability and toxicity of several PTEs and increased P availability (Butnan et al, 2015;Deal et al, 2012;Jeffery et al, 2015a;Kloss et al, 2014b) potential germination and plant growth inhibition when pH raised into alkaline range (Jeffery et al, 2015a;Shoemaker et al, 1990;Singh et al, 1975) supply of ash to soil provision of plant nutrients (Hossain et al, 2011;Ippolito et al, 2015) nutrient imbalances and salinity-related issues (Butnan et al, 2015;Domene et al, 2015;Gell et al, 2011;Rajkovich et al, 2012)…”

“…This method was selected as it has been used to establish German soil legislation threshold values for available PTEs to protect crop growth (German Federal Soil Protection and Contaminated Sites Ordinance, 1999) and has been used for extraction of cationic nutrients in soil (Schöning and Brümmer, 2008;Stuanes et al, 1984) and PTEs and nutrients in biochars (Alling et al, 2014;Karer et al, 2015;Kim, 2015;Kloss et al, 2014b;Park et al, 2011).…”

“…BS ISO 19730:2008(2008 , 1999). In addition to extraction of PTEs in soil, the method has also been tested and recommended for extractable cationic nutrients (Schöning and Brümmer, 2008;Stuanes et al, 1984) and for extracting PTEs and nutrients in biochar/biochar-amended soils (Alling et al, 2014;Karer et al, 2015;Kim, 2015;Kloss et al, 2014b;Park et al, 2011). The proportion recovered by such extractants has been described in various ways, e.g.…”

Adsorption–desorption behavior of carbendazim by sewage sludge-derived biochar and its possible mechanism

“…However, a greater proportion of research on pyrolysis of sewage sludge have focused on energy and fuel quality. 12,13 Although several studies have considered the effects of sludge-derived biochar on environmental behavior (e.g., bioavailability) of inorganic (e.g., arsenic, cadmium, chromium, cobalt, copper, nickel, lead and zinc) and organic pollutants in soil, [14][15][16][17] to our knowledge few studies have been conducted to ascertain the effect of sewage sludge derived biochar on pesticides applied to agricultural soils and the mechanism was largely unknown.…”