Optimization of pyrolysis parameters for maximizing biochar production and enhancing soil fertility from maize cobs

Abstract

Uganda's agricultural sector, while being the backbone of the national economy, faces pressing challenges related to declining soil fertility and unsustainable agricultural waste management practices. Maize cobs, a predominant byproduct of Uganda’s maize farming, are often disposed of through environmentally harmful methods such as open burning and decomposition. These practices release greenhouse gases, degrade soil quality, and contribute to climate change. In response, this study explores pyrolysis as a sustainable solution for converting maize cobs into biochar, a carbon-rich byproduct with significant potential for improving soil health and agricultural productivity. The primary objective of the study is to optimize key pyrolysis parameters i.e. temperature, heating rate, and residence time in order to maximize both the yield and agronomic effectiveness of biochar derived from maize cobs. Laboratory-scale pyrolysis experiments were conducted at varying temperatures (300°C, 400°C, and 500°C), while maintaining a consistent heating rate of 10°C/min and a residence time of 30 minutes. The resulting biochar samples were evaluated for yield, pH, moisture content, ash content, volatile matter, bulk density, and fixed carbon content. Additionally, nutrient analyses for nitrogen, phosphorus, and potassium were performed to assess the suitability of the biochar as a soil amendment. Results indicate that pyrolysis temperature significantly influences both the physicochemical properties and nutrient composition of the resulting biochar. Higher temperatures (up to 500°C) yielded biochar with increased fixed carbon content and pH, but decreased overall yield and bulk density. Biochar produced at moderate temperatures (around 400°C) demonstrated a favorable balance of structural and nutrient characteristics, making it most effective for enhancing soil fertility. The study concludes that optimizing pyrolysis conditions can produce high-quality biochar that not only improves soil water retention and nutrient availability but also reduces environmental pollution by providing a sustainable alternative to conventional waste disposal methods.