Perspective Chapter: Agronomic Properties of Biochar from Slow Pyrolysis of Human Waste

Abstract

The treatment and safe disposal of sanitation waste is imperative to human health and the environment. In developed countries, the emphasis is on recovering phosphorus from municipal sewage sludge (SS) and the reduction of landfill. Whilst in developing countries, the focus is on long-term mechanisms to treat fecal sludge (FS) generated from non-sewered sanitation facilities. This chapter summarizes the thermal treatment of FS and SS via slow pyrolysis, and the resultant characterization of FS and SS-derived biochar with the aim of utilization by agriculture. In general, FS and SS biochars have high pH, ash content and macronutrient concentrations, with a low surface area and carbon content. The concentration of potentially toxic elements is a key difference between FS and SS biochars with FS biochars containing lower concentrations of these harmful metals. Assessing the properties of these biochars is challenging because of the different methods involved in the processing of raw sludge. The slow pyrolysis of FS and SS to produce biochar can play a pivotal role in a circular economy through the recovery and re-use of waste. Waste-derived biochar provides an opportunity to utilize an integrated systems-based approach to improve soil health, increase crop yield, and improve water retention.