Re-routing lignocellulosic biomass for the generation of bioenergy and other commodity fractionation in a (Bio)electrochemical system to treat sewage wastewater

Abstract

Biomass extracted molecules such as cellulose, hemicellulose (HC), and lignin have been extensively considered to generate functional materials for wider applications. Biochar, preparation is inspiring for the treatment and disposal of agricultural solid waste. However, a major fraction of biochar is lost as pyrolytic vapours depending on preparation conditions. Moreover, a huge quantity of degraded compounds, including process inhibitors are generated in liquor hydrolysate during the biomass pre-treatment process to produce biofuels. Considering these limitations, this study processed the lignocellulosic biomass into adsorbents (HC, an inhibitor generator), and biochar from the solid residual of the electrochemical pre-treatment, and hydrogen production from the hydrolysate. The HC and biochar showed the highest adsorption capacity of 102.37±5.20 mg/g and 5.51±0.014 mg/g for NH₄⁺ and PO₄^3- respectively. The replacement of Ca²⁺/Ce⁴⁺ bound to functional groups resulted in adsorption of heavy metals from the wastewater. A hydrogen enrichment of up to 87.39 % was observed in the hydrolysate recovered during the modification of HCs. The NH₄⁺ adsorption cost of 1.59, 0.59, 21.13, and 8.72 US$/g by HCs, Biochar, Ce-HC, and Ca-HC respectively in BES treated sewage wastewaters, fall within very cheap to the intended use of maximum uptake of chemical species. Hydrogen production cost of 0.73, 1.11, and 0.83 US$/kg of HCs, Ce-HC, and Ca-HC respective hydrolysate are also sustainably below green hydrogen production cost.The low cost HCs and Biochar with high adsorption capacity can be utilised as a more economic and effective adsorbents for NH₄⁺ recovery. Therefore, to develop a sustainable agricultural waste management process, present study demonstrates the electrochemically extracted HC utilization for nutrient recovery from sewage wastewater, a novel application that has rarely been reported. Additionally, remaining residues of solid and liquid were employed in the preparation of biochar and hydrogen production respectively to a closed loop system circularity.