Production and characterization of biochar from organic waste and its application for bioremediation in diesel contaminated soils

Abstract

The pollution of the soil and water due to accidental/anthropogenic release of complex hydrocarbons has been a serious environmental problem all over the world. Current study focused on preparation of biochar from fruit and vegetable waste and sewage sludge and its application for bioremediation of diesel polluted soil. Biochar prepared was physio chemically characterized by pH, CEC, FTIR, SEM, EDX, XRD, surface area and pore analysis, proximate analysis, elemental analysis, nutrient analysis and thermogravimetric analysis. Study was conducted at pilot scale. Both types of biochar was applied in diesel polluted soil in a pot experiment in combination with cow dung to evaluate their relative efficacy in bioremediation. Two set ups were run in parallel. In one set up amendments were applied on naturally contaminated soils while in second setup artificially contaminated soil was used. The diesel degradation was estimated by standard curve, FTIR and Gas chromatography. Physicochemical parameters like pH, EC, total carbon, total nitrogen, phosphorous, potassium in soil were analyzed during treatment. Microbiological analysis was performed by CFU count and dehydrogenase activity. Soil microbial diversity was analyzed by Illumina 16S RNA sequencing. Analytical characterization of biochar depicted its crystalline nature with presence of carbon nanotubes and circular pores. Both types of biochar were aromatic, nutrient rich and thermostable materials. Higher percentage yield and ash content was obtained for sludge biochar while high fraction of fixed carbon was recorded in fruit/vegetable waste biochar. Fruit/vegetable waste biochar exhibited larger BET surface area of 52.50m2/g as compared to sludge biochar having surface area of 46.85m2/g. Results of diesel bioremediation studies showed that soil amended with biochar not only increased the soil pH, EC, nutrients and carbon content but also promoted the degradation of hydrocarbons. In Set up 1 diesel oil degradation efficiency recorded was up to 72.27±0.50% for fruit/vegetable waste biochar and 75.63±0.351% for sludge biochar. Highest removal efficiency was for SDN treatment with 82.86±0.60% following VDN treatment with removal capacity of 78.51±0.38%. In Set up 2 having artificially contaminated soil removal efficiency was recorded higher in both VDA and SDA with 76.23±0.42% and 73.24±0.21% while in treatments VA and SA it was 65.28±0.44% and 68.89±0.63% respectively. Highest microbial count and dehydrogenase activity was recorded in treatments having sludge biochar along with cow dung in both Set up 1 and in Set up 2. Microbial study of SDN treatment showing highest bioremediation efficiency indicated the presence of 27 different phyla with predominance of Proteobacteria and Actinobacteria contributing 29% and 19% to total bacterial community. Biochar amendment into soil to degrade hydrocarbons is very important consideration for research purposes and land applications as well. Another study was conducted with application of biochar for soil fertility and crop productivity purposes. In modern agriculture practices, application of biochar for improving soil fertility, plant growth and agriculture output is gaining great deal of attention. Both fruit/vegetable waste biochar and sludge biochar were applied separately and in combination to analyze their effect on wheat growth. Results proved that wheat growth and biomass production was highest at 0.5% concentration of biochar mixture while highest microbial count was observed with 1% sludge biochar. Promising wheat growth and shift in relative abundance of microbial community could be resulted from improvement in soil parameters such EC, total nitrogen and carbon along with phosphorous and potassium content. Our results conclude that the biochar amendment in soil at optimum level improve soil properties and stimulate soil microflora which in turn improves the agricultural performance of soil.