Bio-oil and biochar production from halophyte biomass: effects of pre-treatment and temperature on Salicornia bigelovii pyrolysis

Abstract

Salicornia bigelovii (SB) is a strategically important plant in many regions owing to its ability to grow in arid climates and saline water. This study evaluates the effects of halophyte biomass pre-treatment on the production of bio-oil and biochar via pyrolysis of SB. The pyrolysis experiments were performed in a quartz tube reactor at 600, 700, and 800 °C to understand the effect of the temperature on the products obtained from untreated SB (USB) and pre-treated SB (PSB). USB and PSB samples were characterized to determine their thermal stability, elemental composition, mineral composition, and functional group identification. Pre-treatment of SB reduced the ash and Na content by 71% and 45%, respectively. Ash removal favored the pyrolysis-assisted extraction of carboxylic acids, and their selectivity in the bio-oil increased from 20.7% (USB) to 33.4% (PSB) at 600 °C. The selectivity to phenolics was observed to be the highest at 800 °C in the bio-oil from USB (10.4%) and PSB (13.4%). PSB pyrolysis increased the specific surface area of biochar by four times, whereas carbon nanostructures were observed in the biochar from USB. The formation pathways of the major compounds from the pyrolysis of various amino acids, cellulose, hemicellulose, fatty acids, and lignin present in SB were elucidated by proposing a plausible reaction scheme.