Characterization of Biochars Produced from Cornstovers for Soil Amendment

Abstract

Through cation exchange capacity assay, nitrogen adsorption−desorption surface area measurements, scanning electron microscopic imaging, infrared spectra and elemental analyses, we characterized biochar materials produced from cornstover under two different pyrolysis conditions, fast pyrolysis at 450 °C and gasification at 700 °C. Our experimental results showed that the cation exchange capacity (CEC) of the fastpyrolytic char is about twice as high as that of the gasification char as well as that of a standard soil sample. The CEC values correlate well with the increase in the ratios of the oxygen atoms to the carbon atoms (O:C ratios) in the biochar materials. The higher O:C ratio was consistent with the presence of more hydroxyl, carboxylate, and carbonyl groups in the fast pyrolysis char. These results show how control of biomass pyrolysis conditions can improve biochar properties for soil amendment and carbon sequestration. Since the CEC of the fastpyrolytic cornstover char can be about double that of a standard soil sample, this type of biochar products would be suitable for improvement of soil properties such as CEC, and at the same time, can serve as a carbon sequestration agent. Through cation exchange capacity assay, nitrogen adsorption-desorption surface area measurements, scanning electron microscopic imaging, infrared spectra and elemental analyses, we characterized biochar materials produced from cornstover under two different pyrolysis conditions, fast pyrolysis at 450°C and gasification at 700°C. Our experimental results showed that the cation exchange capacity (CEC) of the fastpyrolytic char is about twice as high as that of the gasification char as well as that of a standard soil sample. The CEC values correlate well with the increase in the ratios of the oxygen atoms to the carbon atoms (O:C ratios) in the biochar materials. The higher O:C ratio was consistent with the presence of more hydroxyl, carboxylate, and carbonyl groups in the fast pyrolysis char. These results show how control of biomass pyrolysis conditions can improve biochar properties for soil amendment and carbon sequestration. Since the CEC of the fastpyrolytic cornstover char can be about double that of a standard soil sample, this type of biochar products would be suitable for improvement of soil properties such as CEC, and at the same time, can serve as a carbon sequestration agent.

Characterization of energy carriers obtained from the pyrolysis of white ash, switchgrass and corn stover — Biochar, syngas and bio-oil

“…That is because the biomass material consists of cellulose, hemicellulose and lignin which have a large amount of C, H and O [24]. It can also be seen that the strength of all chemical bonds was enhanced with the decrease of the temperature, which was also confirmed by Lee et al [28]. Secondary decomposition of the biochar took place at higher temperatures, which led to the strength of all chemical bonds being weaker.…”

“…FT-IR is primarily used for the structural determination of organic (carbonbased) molecules. FT-IR has also been used to describe characteristic bonds of biochar [28]. FT-IR spectra of biochar: (a) white ash, (b) switch grass and (c) corn stover are shown in Fig.…”

Crop response to soils amended with biochar: expected benefits and unintended risks

“…Physico-chemical Effect/changes due to PT parameters Spokas (2010), Budai et al (2014) BC yield Decreases with increase in PT Lehman (2007), Ippolito et al (2015) C recovery Decreases with increase in PT due to volatilisation of C at high PT Cantrell et al (2012), Subedi et al (2016b) N recovery Decreases with increase in PT due to volatilisation of N at high PT Singh et al (2010, Wang et al (2012b) P recovery Increases with increase in PT due to increased recovery of P in the ash fraction Cantrell et al (2012), Subedi et al (2016b) S recovery Decreases with increase in PT due to volatilisation of S at high PT Singh et al (2010), Budai et al (2014) Ash content Increases with increase in PT due to enhanced burning of organic matter at high PT Lehman (2007), Budai et al (2014) pH Increases with increase in PT due to increase in ash content Singh et al (2010), Mukome et al (2013), Subedi et al (2016b) Surface acidity Decreases with increase in PT due to loss of acidic functional groups at high PT Spokas et al (2011), Subedi et al (2016b VM Decreases with increase in PT Lehman (2007), Budai et al (2014), Mukome et al (2013) CEC Increases up to 500°C followed by decrease (>500°C) due to loss of acidic functional groups Lee et al (2010), Fuertes et al (2010), Chia et al (2015) Porosity Increases up to 600°C (anti-clogging of pore space) followed by decrease (>600°C) due to collapse of pore and surface structures Lehman (2007), Lee et al (2010), Budai et al (2014) SA Increases up to 600°C followed by decrease (>600°C) due to collapse of pore structure Singh et al (2010), Cantrell et al (2012), Subedi et al (2016b) Cations (Ca, Mg, K, Na) Increases with increase in PT due to increased recovery of cations in ash fraction Camps-Arbestain et al (2015), Domene et al (2015) Heavy metals Increases with increase in PT due to increase in ash content PT, pyrolysis temperature; BC, biochar; C, carbon; N, nitrogen; P, phosphorus; S, Sulphur; VM, volatile matter; CEC, cation exch...…”

Mitigating heavy metal accumulation into rice (Oryza sativa L.) using biochar amendment — a field experiment in Hunan, China

“…The cation exchange capacity (CEC) was determined referring to modified barium chloride compulsive exchange method (Lee et al 2010). Total carbon (TC) and nitrogen (TN) analyses of soil and biochar were conducted on a solid TC/ TN analyzer (Vario EL III, Elementar Analysen systeme, Germany).…”