Characteristics of biochars from crop residues: Potential for carbon sequestration and soil amendment

Biochar has potential to sequester carbon in soils and simultaneously improve soil quality and plant growth. More understanding of biochar variation is needed to optimise these potential benefits. Slow pyrolysis at 600°C was undertaken to determine how yields and characteristics of biochars differ when produced from eight different agricultural residues. Biochar properties such as carbon content, surface area, pH, ultimate and proximate analysis, nutrient and metal content and the R50 recalcitrance index were determined. Significant variations seen in biochar characteristics were attributed to feedstock variation since pyrolysis conditions were constant. Biochar yields varied from 28% to 39%. Average carbon content was 51%. Ash content of both feedstocks and biochars were correlated with biochar carbon content. Macronutrients were concentrated during pyrolysis, but biochar macronutrient content was low in comparison to biochars produced from more nutrient rich feedstocks. Most biochars were slightly alkaline, ranging from pH 6.1 to pH 11.6. pH was correlated with biochar K content. Aromaticity was increased with pyrolysis, shown by a reduction in biochar H/C and O/C ratios relative to feedstock values. The R50 recalcitrance index showed biochars to be either class 2 or class 3. Biochar carbon sequestration potential was 21.3%-32.5%. The R50 recalcitrance index is influenced by the presence of alkali metals in the biochar which may lead to an under-estimation of biochar stability. The residues assessed here, at current global availability, could produce 373Mt of biochar. This quantity of biochar has the potential to sequester 0.55PgCO2yr-1 in soils over long time periods

Thermogravimetric pyrolysis for neem char using novel agricultural waste: a study of process optimization and statistical modeling

Agricultural biomasses are the underutilized sources that have extraordinary potential to synthesize green and cost-effective chemicals. This research focuses on the utilization of novel agricultural residue, i.e., waste neem cake, to produce highly efficient, cost-effective, and environment-friendly fuel, i.e., neem char (NC), through thermogravimetric pyrolysis. To study the effects of process variable on char yield and higher heating value (HHV), statistical modeling was applied by central composite design of response surface methodology. Furthermore, chemical and structural characterization of neem cake and char were carried out by using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The reaction temperature was the most prominent variable found from the ANOVA (analysis of variances) to affect char yield and its HHV. The optimal result was achieved with 21.46% char yield and HHV value of 6371 kcal/kg at 600 °C, 60 min, and 3 mm. The heating value of char was highly improved indicating the potential application of char as a high-energy renewable fuel. Further, the carbon content and fixed carbon values increased, whereas hydrogen, oxygen, volatile matters, and moisture content decreased in char after the pyrolysis process

Role of Biochar in Carbon Sequestration and Greenhouse Gas Mitigation

Not AvailableGlobal warming and associated climate change are becoming a threat to almost all the ecosystems on the earth. According to the intergovernmental panel on climate change (IPCC) special report 2019, the global mean surface (land and ocean) temperature has been increased by 0.87 °C while mean of land surface air temperature has increased by 1.53 °C since 1850–2015. Climate change is affecting food security and human life due to warming, changing precipitation patterns, and the greater frequency of some extreme events. The main cause of global warming is the continuous increase in the atmospheric concentration of greenhouse gases (GHGs) like CO2, CH4, N2O and fluorinated gases due to several anthropogenic activities. Therefore, reducing the increasing concentration of GHG is necessary to slow down global warming and climate change. Among several options of greenhouse mitigation, application of biochar into the soil is gaining popularity due to several advantages over other options. Biochar is a highly stable form of carbon derived from pyrolysis of biomass at relatively low temperatures. Application of biochar into the soil has been reported to provide multiple benefits like increase in crop yield, nutrient and water use efficiency and several environmental benefits. Recalcitrant nature, relatively higher carbon content and easily available feedstock make biochar a highly sustainable and quick option for carbon sequestration into the soil. Biochar application into the soil not only helps in carbon sequestration but also provides a better option for managing agricultural residues. The application of biochar has also reported for reducing a considerable amount of methane and nitrous oxide emission from the agricultural field due to its priming effect on the soil. Biochar yield, physical properties, and carbon content varies with the type of feedstock and pyrolysis condition. Therefore, the rate of carbon sequestration and mitigation of greenhouse gas is also highly variable, however, the biochar application ultimately leads to a positive contribution towards climate change mitigation. However, most of the reported benefits are confined to laboratory and field trial at institute level, widespread adoption of biochar on farmer’s field is still lacking. In the present chapter, all the aspects of biochar towards carbon sequestration and greenhouse mitigation have been well discussed.Not Availabl