Zinc oxide nanoparticle impact on solid waste anaerobic digestion and biogas production

Abstract

Engineered nanoparticles incorporated into consumer products can enter the environment during the manufacture, use of the product and waste disposal. The effect of zinc oxide (ZnO) nanoparticle on anaerobic digestion was assessed using 250 mL batch digesters, fed with a blend of municipal solid waste and cow dung, spiked with 15 to 60 mg kg⁻ˡ shock dose of ZnO nanoparticle for 60 days at 35 ± 2 °C. The mean volatile fatty acid composition was 0.9 to 2.8 times higher in relation to the control. The difference was significant (p = 0.05) and suggests that the microbial community were unable to effectively use the available substrate although low ZnO concentration (15 mg kg⁻ˡ) exerted no pronounced adverse effect on the digestion process. Based on Archaea-specific phospholipid etherlipid (PLEL) derived saturated and monounsaturated isoprenoids, hydrogenotrophic and methylotrophic biomarkers were dominant with 1.0 to 2.3 times lower concentration in the ZnO nanoparticle spiked digester. The biogas produced was concentration-dependent and ranged from 1.1 to 4.3 times lower in the ZnO nanoparticle spiked digestate relative to the control. The results provide evidence on the inhibitory effect of ZnO nanoparticle on the performance, microbial richness and evenness during anaerobic digestion of municipal solid waste.

Keywords: ZnO nanoparticle, municipal solid waste, anaerobic digestion, biogas, inhibitory effect