A bibliometric analysis on potential uses of brewer's spent grains in a biorefinery for the circular economy transition of the beer industry

This comprehensive review aims to elucidate the state of the art related to research trends regarding the use of brewer's spent grains (BSG), the main solid by-product generated in breweries. Its status, future opportunities, and emerging trends were evaluated by bibliometric analysis, which contributed to clarifying the knowledge and perspectives in the field. In total, 510 documents were obtained from the Web of Science© database in a timespan from 1900 to 2020. VosViewer software and R-bibliometrix package were used to investigate and map the most frequently cited papers, international collaborative networks, keywords, and the main countries and journals associated with this research. The results showed that, globally, 65 countries have been engaged in research related to BSG, and Brazil has been the most productive country, with up to 70 publications. Keyword analysis revealed that the studies on BSG are divided into four main knowledge areas: (i) pretreatment; (ii) nutritional quality; (iii) bioactive compounds, and (iv) pyrolysis. It was also found that a biorefinery can be designed for the complete utilization of BSG to obtain several valuable compounds. In this sense, different technological routes can be applied to produce arabinoxylans, proteins, ferulic acid, xylitol, xylose, lactic acid, butanol, biogas, fertilizer, and ethanol. In conclusion, BSG is a cost-effective and feasible raw material for the sustainable production of bio-based products and bioenergy and its valorization in a biorefinery is a powerful strategy to promote the circular economy transition of the beer industry.