Current and prognostic overview of digestate management and processing practices, regulations and standards

Digestate is a byproduct of anaerobic digestion (AD) where organic waste is converted into biogas, a clean source of energy. The growing interest in renewable energy and waste management has increased the number of AD plants worldwide in recent years. Therefore, the appropriate digestate management has shifted towards the concept of waste to products and the realization of a circular economy to maximize the benefits of AD plants as well as digestate valorization. The various properties of digestate such as organic matter, nutrient composition, moisture content, and plausible pollutants, determine its suitability for further application. Proper management and handling are required to minimize environmental risks and enhance the value of the digestate valorization. Instead, its use in conventional ways, novel strategies for digestate utilization are emerging to properly benefit and practically realize the biorefinery of AD plants at a large scale. Moreover, the proper knowledge of regulations and standards concerning the proper digestate utilization is required. This article summarizes the digestate properties and their factor affecting, digestate treatment technologies. The current digestate valorization practices have been discussed along with the focus on the novel and emerging practices. Most importantly, the regulations and standards followed around the globe have been majorly focused upon so that the environmental concerns arising due to its utilization should be taken care of well. Further, the challenges and future perspectives of digestate management and valorization are discussed to be understood for attaining a full circular economic concept in the AD plants at an industrial scale.