Research Trends in the Recovery of By-Products from Organic Waste Treated by Anaerobic Digestion: A 30-Year Bibliometric Analysis

The prevailing extractive economic model is unsustainable due to the finite nature of resources, thereby necessitating the development of alternative models and policies. The anaerobic digestion (AD) process is key to achieving this objective, as it facilitates the conversion of organic waste into biogas and nutrient-rich digestate. This approach is aligned with the principles of a circular economy and contributes to a reduction in carbon emissions. This study aims to conduct a comprehensive bibliometric analysis of the literature published over the past three decades (1993-2023). The analysis will be based on data drawn from the Scopus database and then analysed using the VOSviewer software, which allows for the interconnection of the revised bibliography through a series of selected keywords. The results demonstrated the existence of four clusters: (i) the beneficial valorisation of waste; (ii) volatile fatty acids and biohydrogen as added value by-products resulting from AD; (iii) lignocellulosic substrates and their by-products; and iv) the main products of AD, biogas and digestate. The bibliometric analysis demonstrates a growing interest in AD within the biorefinery concept in recent years, showcasing its potential for effective waste management and integration into the production chain through the principles of the circular economy.