The update of anaerobic digestion and the environment impact assessments research

An increasing number of studies on biogas as a renewable energy including the industrial implementation have been published. The important issues dealing with anaerobic digestion (AD) includes integration of the evidence into patterns, capable of illustrating the current research trend and gaps. Although AD is widely perceived as a clean technology, the assessing and reporting of its environmental impacts remain an important research scope. This work attempts to highlight the recent AD development through a systematic reviewing approach. The criteria for searching are year, type of search engine, keywords and for the selection according to the relevance of the available sources. The presented review covers a case study, mixed mode, by experiment and review. The environmental impact analysis in AD life cycle assessment is also discussed. This facilitates the future studies in improving the environmental impact of AD system. The digestate management and application were suggested as the hotspot of AD system that needs to be improved as the first priority. The AD overview that has been presented statistically proposes the other potential research direction through the interpretation of the type, amount and characteristics of available research. The key future research area is a feasibility study of AD with the consideration to optimise the energy efficiency, economic and environmental aspects which would attract the investors as well as convince the policy makers