Effect of pretreatment and biomass blending on bio-oil and biochar quality from two-step slow pyrolysis of rice straw. (1st February 2022)

• Record Type: Journal Article
• Authors: Bhatnagar, Anubhuti; Singhal, Abhishek; Tolvanen, Henrik; Valtonen, Kati; Joronen, Tero; Konttinen, Jukka
• Is Part Of: Waste management. Volume 138(2022)
• Page Start: 298
• Page End: 307
• Publication Date: 2022-02-01
• Subjects: TGA -- Kinetic coefficients -- Levoglucosan -- Ash elements -- Washing -- Co-pyrolysis; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2021.12.013
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Rice straw was co-pyrolyzed with two crop residues before and after washing. The removal efficiency was > 73% Na and > 42 % K after washing rice straw. Co-pyrolysis of 60 min washed rice, and wheat straw (1:1 w/w) doubled levoglucosan. Biochar samples obtained were potential fuel-source and soil amendment additives. Abstract: This study investigated biomass blending and water washing to improve product quality from two-step pyrolysis of rice straw. Rice straw (RS) was mixed with groundnut shells (GNS) and wheat straw (WS) in different weight ratios. Blending RS with GNS/WS in a 1:1 ratio increased the total bio-oil yields by 7–9% and reduced the pyrolysis gas and char yields by 5–7% and < 2%, respectively. RS was washed with water separately to examine the effect of removing water-soluble ash elements. The optimum washing duration was 60 min; the ash removal efficiency was then 26%. The bio-oil yields from washed straw increased by 4% over unwashed straw, and pyrolysis gas yields decreased. Combining the washing and blending processes increased the levoglucosan yield by 1.6–2.1 times compared to unwashed RS, and the water content in bio-oil was reduced by ∼ 10%. Moreover, the biochar samples obtained after pyrolysis of washed biomass blends had potential fuel applications owing to low fouling or slagging propensity. They also had possible use in the soil for adsorption of soil contaminants and increasing acidic soil pH, with likely stability of ∼ 1000 years in the ground. These results provide a promising alternative for efficiently converting rice straw to multiple value-added products.