Volume 5: Innovative Solutions for Energy Transitions: Part IV

Comparison of Biochar Enhancements for Ammonia (NH4-N) Sorption from Concentrated Wastewater Applications Aubrey Beckinghausen, Jonathan Reynders, Ryan Merckel, Yun-Wen Wu, Sebastian Schwede

Abstract

NH4-N-loaded steam-activated biochar (BC) is found to be a suitable candidate for soil amendment and fertilization. Compared with four other char-based sorbents, H2O-activated BC adsorbed the highest amount of NH4-N (1440 mgNH4−N. kgBC −1) sourced from a high nitrogen wastewater sample, and showed a limited desorption of 19.6 % under acidic conditions. In comparison, neat BC and activated carbon (AC) achieved lower adsorption capabilities, with theoretical maxima of 1028 mgNH4−N. kgBC −1 and 733 mgNH4−N. kgAC −1, respectively. While neat AC obtained a lower desorption of 19.5 %, neat BC showed similar desorption capabilities to that of the H2O-activated BC. Oxidative treatment using 10 % H2O2 reduced adsorption for BC (520 mgNH4−N. kgBC −1) and AC (545 mgNH4−N. kgAC −1) and increased desorption to 47.9 % and 41.9 %, respectively. From these results, H2O-activated biochar clearly is the most suitable for soil amendment that is resistant to leaching, is environmentally-friendly, and is an energyefficient nitrogen adjunct. A simplified version of an adsorption process simulated in AspenTech predicts that NH4-N may be recovered at an energy cost lower than that of the Haber-Bosch process for AC yields of below 19.5 %. A more in-depth investigation still needs to be completed to evaluate the techno-economic feasibility for this class of loaded sorbents, and whether this means of nitrogen capture from wastewater is a suitable replacement of the costly Haber Bosch process.

Keywords Nitrogen recovery, biochar, Haber-Bosch