Physicochemical characterization of pig manure and its carbonaceous derivatives: Climate and sustainability impacts

Summary Pig manure, a significant by-product of the swine industry, presents challenges and opportunities regarding management and environmental sustainability, especially in developing countries. The manure is composed of undigested feed remnants, including cellulose, proteins, minerals, and other excretory products, which makes it a nutrient-rich yet problematic resource. This review summarizes the state of knowledge up to the year 2024 by evaluating 201 relevant scientific articles on the physicochemical properties of pig manure and its biocarbon derivatives, highlighting their potential agricultural and environmental benefits. Understanding the factors influencing manure and biochar characteristics is critical in driving manure management and sustainability policies. Literature exploration showed that the carbon-rich products from carbonization have a higher pH (8–12), carbon (38%–75%), and ash (13%–72%) contents compared to the original manure, making them suitable for applications such as soil-crop improvement, renewable energy production, feed supplementation, and bioremediation. These biocarbon derivatives also exhibit enhanced surface area, porosity, and redox-active properties, fostering a beneficial soil or gut microbiome and overall environmental health improvements. The char characteristics are dependent on the manure quality and processing methods, with co-pyrolysis with other carbon-rich materials improving the char quality. However, the results from some of the selected studies on biochar properties and its production protocols were poorly characterized, which may be a major drawback for generalizing results. Overall, the thermal conversion of pig manure to biocarbon provides a sustainable solution to on-farm manure recycling, while mitigating pollution challenges in pig farming.