Effects of hydrothermal pre-treatments on Giant reed (Arundo donax) methane yield

Abstract

Twelve hydrothermal pre-treatment combinations of temperature (150 and 180 °C), time (10 and 20 min) and acid catalyst (no catalyst; H2SO4 at 2% w/w immediately before steam cooking or in 24-h pre-soaking) were tested to assess their effects on methane yield of Giant reed biomass vs. untreated control. A batch anaerobic digestion was conducted with 4 g VS l(-1) at 53 °C for 39 days. Untreated biomass exhibited a potential CH4 yield of 273 ml g(-1) VS; the four pre-treatments without acid catalyst achieved a 10%, 7%, 23% and 4% yield gain in the respective temperature/time combinations 150 °C/10 min, 150 °C/20 min, 180 °C/10 min and 180 °C/20 min. Conversely, the eight pre-treatments with H2SO4 catalyst incurred a methanogenic inhibition in association with high SO4(2-) concentration in the hydrolysate, known to enhance sulphate reducing bacteria. Furfurals were also detected in the hydrolysate of five strong pre-treatments with H2SO4 catalyst.

Keywords: 5-hydroxymethyl furfural; AD; AIL; ANOVA; Anaerobic digestion; B(0, th); BD; Biodegradability; Biomass pre-treatments; COD; FID; GC; GHG; HMF; HPLC; Potential methane yield; RID; SRB; STP; Steam cooking; TKN; TOC; TS; VFA; VS; acid insoluble lignin; anaerobic digestion; analysis of variance; biodegradability; chemical oxygen demand; flame ionisation detector; gas chromatographer; greenhouse gas; high performance liquid chromatography; refractive index detector; standard temperature and pressure; sulphate reducing bacteria; theoretical methane potential; total kjeldahl nitrogen; total organic carbon; total solids; volatile fatty acid(s); volatile solids.