In recent years, researchers have utilized interdisciplinary approaches to achieve the objectives laid out by the Sustainable Development Goals (SDGs). This can be accomplished through the strategic incorporation of environmental pillars such as life cycle assessment, waste reduction, and waste to wealth strategies. Anaerobic digestion (AD) and composting are at the forefront of the circular economy as valuable nutrients are reincorporated back into environmental systems.

AD and composting are both biological techniques that have proven to be efficient solutions in combating the huge amounts of organic wastes produced by humans, such as food waste, agricultural waste, or sewage sludge. They are useful techniques with regards to long-term waste management and nutrient recycling solutions that provide renewable energy and organic fertilizer while reducing greenhouse gas emissions. Technological advances in anaerobic digestion and composting enhance the continuous flow of resources within the ecosystem. AD and composting are green engineering techniques that are economically viable while also reducing environmental and health threats as well as reducing pollutant contaminations.

This Special Issue aims to provide insight into recent advances in the field of anaerobic digestion and composting We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Design modifications, operational parameters, and stability of AD and composting
• Optimisation of AD and composting technologies
• Formulation of feedstock, process reactions, and safety measures in AD and composting
• Processing of compost leachates and digestates
• Phytotoxicity assessment of compost and by-productss
• Production of new microbes and biocatalysts
• Molecular transformation processes of organic matter
• Community succession of microbial structure and function
• Production and processing of vermicompost, vermifiltration and vermitea
• Production and processing of larvae based composting
• City and campus organic composting and farming
• Social and techno-economic studies on AD and composting processes