Recovery of the Humic Substance from the Wastewater on the Biochar Produced from Waste Materials Using Sorption

In recent years, increasing attention has been paid to the possibility of converting waste materials, e.g. manure, bio-waste, green waste, waste from the water and sewage industries (e.g. post-fermentation sludge), and agri-food waste into biochars by pyrolysis. The growing interest in using biochar as a soil amendment results from its ability to improve soil health and fertility. The superiority of biochar over other organic soil amendments is mainly due to its high soil stability and excellent nutrient sorption properties. In addition, biochar can retain soil-relevant compounds, including humic substances (HSs). Since most of the resources used for the production of humic fertilisers are non-renewable, the effluents from anaerobic digestion of sewage sludge (RW), which contain high levels of HSs, are considered promising targets for their recovery. Herein the potential of ten biochars derived from pine, oak, straw, sunflower and digestate at different pyrolysis temperatures for the recovery of HSs from RW was evaluated. It was observed that the biochars produced from the same biomass at different pyrolysis temperatures have various sorption capacities of the HSs.