Optimization of pyrolysis parameters for enhanced biochar production from agricultural biomass: A study on energy efficiency and carbon sequestration potential.

Biomass pyrolysis presents an attractive opportunity for sustainable energy generation while also sequestering carbon, but efforts to systematically optimize it in consideration of feedstock variability, process parameters, and energy efficiency are still in their infancy. This research assesses the pyrolysis characteristics of five types of agricultural wastes, including rice husk, corn stalk, palm kernel shell, coconut shell, and wheat straw, at a fixed-bed reactor, with temperature (300 to 700 °C), heating rate (5-20 °C/min), and residence time (30 to 120 min). All biomass materials underwent proximate, elemental, and BET analyses, and bio-oil and emissions characterization were performed using gas chromatography. The optimization procedure has been performed on the basis of response surface methodology. Our research on the measurement of biochar and bio-oil products obtained through the pyrolysis process of biomass feedstocks revealed the trend that yields of biochar rise with an increase in pyrolysis temperature, with a correlation degree of 51.3 and 52.5 % at 400 °C in rice husk and corn stalk, respectively. The bio-oil yield showed a shift, relative to the composition at the lower pyrolysis temperatures, towards higher concentrations of ketones (7.8 %) and esters (5.1 %) as pyrolysis temperature was raised, with a reduction in phenolic content from 15.2 to 13.0 %. Energy efficiency was greatest for palm kernel shell (≈44 %) and coconut shell (≈43 %), suggesting these two feedstocks are best for utilizing heat recovery during the pyrolysis process. The findings for both rice husk and corn stalk suggested the high levels of fixed‑carbon content would have significant potential for carbon sequestration in soils. The findings present an integrated roadmap for different types of biochar production from pyrolysis while enhancing the potential to derive renewable energy and climate mitigation.