Significance and Challenges of Poultry Litter and Cattle Manure as Sustainable Fuels: A Review

Growing animal production results in a significant amount of waste, composed of manure, bedding, feed, feathers, etc., whose safe and cost-effective disposal becomes a troublesome challenge. The literature review points out that the higher heating value (HHV) of animal-origin waste reaches 19 MJ/kg (dry basis), which positions it as a promising renewable energy source. Various paths of energy recovery were investigated in the literature, but the thermal processes, particularly combustion and co-combustion, were indicated as the most effective from both technical and environmental points of view. The presented study reviews the fuel characteristics, possible combustion-related challenges, and ash disposal routes of the most popular animal-origin waste: poultry litter and cow (cattle) manure with a slight sight on piggery (swine) manure. When considering animal-origin feedstock as fuel, usually only animal species is given (poultry, cattle, etc.). However, according to the analyzed literature data, this is not sufficient information. Several more factors crucially influence the fuel and ash properties of animal waste and the most vital are: the housing system, type of bedding, and farming style. Animal litter is considered a “difficult” fuel, nevertheless, it does not always cause combustion-related problems. Some analyzed feedstock feature low chlorine concentrations and high ash melting temperatures, which makes them combustion-friendly.