Biogas Production from Dairy Cattle Residues: Definition of the Pretreatment Approach Through a Bibliometric Analysis of Publications and Patents

The use of bedding in livestock, such as wood shavings, is a technique that brings economic advantages, as it reduces the demand for water to clean the facilities and provides better animal welfare. On the other hand, the material used as litter is a lignocellulosic material which requires a pretreatment strategy for successful anaerobic digestion to produce biogas. This work examines the advances in science (articles) and technology (patents) to delimit pretreatment technology routes for lignocellulosic residues using a bibliometric approach. To identify the main articles and patents, search strategies were defined in such a way that all relevant documents were grouped and organized into four pretreatment routes (physical, biological, chemical, and combined). The number of published articles (2941) was 35% higher than patents (1923), and 70% of all the documents have been published in the last 10 years. The bibliometric analysis revealed that the chemical technological route has a higher technological maturity, as well as more research and development (R&D) effort applied. Articles using sodium hydroxide (NaOH) as an alkaline catalyst were analyzed and compared to judge its suitability. The work concludes that the combination of physical and alkaline pretreatment could provide degradation of cattle dairy residue and the costs and time in new R&D investigations can be reduced through the analysis of the technological maturity stage.