Pyrolysis temperature and feedstock alter the functional groups and carbon sequestration potential of Phragmites australis‐ and Spartina alterniflora‐derived biochars

Abstract

Biochar produced by pyrolysis of biomass under oxygen‐limited conditions has recently attracted increasing attention. To investigate the effects of feedstock and pyrolysis temperature on biochar characteristics, Phragmites australis straw and Spartina alterniflora straw were used to produce biochars at different temperatures from 300 to 500°C with an increment of 50°C. The biochars were characterized by their yields, ash contents, elemental compositions (i.e., carbon [C], hydrogen [H], oxygen [O], and nitrogen [N]), functional groups, dissolved organic carbon (DOC) contents, carbon sequestration potential, higher heating values (HHVs), and production costs. The results illustrated that pyrolysis temperature negatively affected biochar yields, H and O contents. In contrast, biochar produced at high temperature showed high ash contents, C contents, HHVs, and stronger aromaticity with low H/C and O/C ratios. In addition, S. alterniflora‐derived biochar (SB) contained higher ash content but lower C/H/N/O contents and HHVs than P. australis‐derived biochar (PB; p < 0.05). In addition, DOC contents in both SB and PB declined as temperature increased, and SB exhibited higher DOC contents than PB. Fourier transform infrared spectroscopy showed that absorption intensities of –OH, C=O, –CH, and –C–O–C‐stretching vibration declined with increasing temperature. The stability of the biochars was enhanced at high temperatures, and the biochar derived from S. alterniflora at 500°C might have a better carbon sequestration potential according to thermogravimetric analysis. Additionally, cost analysis showed that the production cost of biochar with large‐scale reactor was lower than that with bench‐scale reactor, and SB had a higher cost than PB due to the price of feedstock and drying process for the former. Our results could offer effective information on resource utilization of P. australis and S. alterniflora straw and are valuable for optimizing pyrolysis temperature to tune P. australis and S. alterniflora biochar properties for specific environmental usage.

Effect of pyrolysis temperature on composition, carbon fraction and abiotic stability of straw biochars: correlation and quantitative analysis

“…This might due to the breakage of weaker chemical bonds in feedstock at low temperatures (Imam and Capareda 2012), leading to the depolymerization of lignocellulose. However, the R 50 exponentially increased as pyrolysis temperature increased from 300 to 500 °C, and reached the maximum value at 500 °C (Wang et al 2021b). Straw biochar derived at 500 and 600 °C had the similar R 50 value, which was consistent with the change rule of corrected TPO curves measured (Fig.…”

“…Biochar applied into soil will be affected by severval abiotic factors, such as rainfall (Wang et al 2022), temperature changes (Liu and Chen 2022), and environmental oxidation (Wang et al 2021a). For example, rainfall can cause biochar to release soluble organic matter or mineral components by dissolution (Wang et al 2021b). Dissolved organic carbon (DOC) is an important component of soluble organic matter, which will flow into the water environment through surface runoff (Jaffe et al 2013) or infiltrate into the soil and then be used by microorganisms (Quan et al 2020), decreasing the capacity of C sequestration.…”

Influence of pyrolysis temperature on the physicochemical properties of biochars obtained from herbaceous and woody plants

“…Previous studies demonstrated that biochar half-life is in related to the O/C molecular ratio, a longer than 1000 year half-life is expected when biochar with an O/C molecular ratio is lower than 0.2, a half-life range of 100 ~ 1000 years is expected when biochar with the O/C molecular ratio is between 0.2 and 0.6, and the half-life may shorter than 100 years when the O/C molecular ratio is higher than 0.6. Therefore, the low O/C in this study indicated that most of the as-prepared biochar had the possibility of carbon sequestration (Elmquist et al 2006 ; Wang et al 2021 ).

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Influence of Pyrolysis Temperature and Time on Biochar Properties and Its Potential for Climate Change Mitigation

“…Pyrolysis is the process by which a biomass substrate is thermochemically converted within a temperature range of 300 °C to 700 °C under oxygen-limited or oxygen-free conditions [4,5]. According to the meta-analysis literature, biochar is recognized as a potential material for achieving environmental sustainability due to its unique properties and diverse applications, which include agricultural applications that can reduce greenhouse gas emissions [6][7][8] and achieve carbon capture and storage [9,10], in addition to achieving increases in soil fertility and enhancing crop productivity [11,12]. Moreover, biochar has the potential to be applied as a catalyst [13], an adsorbent [14], and for energy storage [15].…”