Nutrient management from biogas digester effluents: a bibliometric-based analysis of publications and patents

Abstract

Interest in organic waste(water) processing by anaerobic digestion to produce biogas as renewable energy source has increased significantly in recent years. The characteristics of the digested effluents vary depending on the feedstocks treated, and different handling alternatives are possible. This study reviews advances in science and technology in the specific field of nutrient (nitrogen and phosphorus) management from biogas digester effluents during the last two decades (from 1995 to 2014) using a bibliometric approach. Information concerning publications as representative of the outputs of scientific research, and concerning patents as representative of the outputs of technological development was retrieved from specialised databases and analysed systematically. The number of publications was twice the number of patents. Production followed a rising trend (in both cases, partial productivity in the last 5 years was >45%). The USA, China, and Japan were the three most prolific countries when considering the joint production of publications and patents. However, while the number of publications was higher than the number of patents for the USA, the opposite was true for China and Japan. The institutions which published more (and also the most cited items) were mainly European, whereas Asian countries were more active in filing for patents even though the patents from the USA were more frequently cited. Relative interest in particular nutrient management alternatives and their evolution were identified. Reducing the consumption of resources, implementing integral solutions, and circular economy approaches will be among key issues in future studies and development to promote sustainability.