Anaerobic digestion is a biological process converting organic matter into a methane-rich gas (biogas). It is mostly used for municipal and agricultural organic wastes, which constitute a valuable resource: the European production of biogas was equivalent to 6 million tons of oil in 2010. Biogas is a well-known energy source that can be used for common applications. In Sweden, 800 buses, 4500 cars and… one train are using this renewable fuel! Most systems used for municipal wastes today are called dry digestion processes: they are more efficient and less water-consuming than classical systems, but the mechanical structure of the digestion medium is still ill-defined and difficult to control at the industrial scale. The essence of the ANAMIX project is to answer to specific questions associated to dry digestion, using new techniques and new approaches for the description of dense and pasty media. Our project is guided by a double expectation: first, to improve our knowledge of basic mechanisms that take place in dry digestion systems; Second, to provide the tools for making the future industrial systems easier to design and to operate. 2 kinds of waste have been studied: residual municipal solid waste, and biowaste.
The aim of ANAMIX project is to address questions associated to dry digestion by developing new and specific investigation methods for the description of dense and pasty media. The concepts of process engineering (rheology, mass and momentum transfer) and life science (microbial kinetics and microbial ecology) have been used to study the complex interactions in the process. The key factor for process design and operation is the moisture content since it influences both the mechanical and the biochemical processes. The nature and origin of the waste are also important parameters. This project provides a specific model for process simulation. Above all, our project is guided by a double expectation: first, to improve our knowledge of basic mechanisms that take place in dry digestion systems; Second, to provide the tools for making the future industrial systems easier to design and to operate.
ANAMIX is the first collaborative project on high solid (dry) digestion. It has permitted to i) better understand the nature of the waste and their influence on the process, ii) determine the influence of the moisture content on the mechanical and biochemical properties depending on the nature of the waste, iii) develop new techniques for rheological measurements and residence time distribution analysis and iv) to identify lower and upper values for optimizing the moisture content. It opens perspectives concerning the role of mass transfer as limiting factor at low moisture content, and technical bottleneck for process intensification.
To date, ANAMIX gave way to 6 articles published on the project results. 2 deal with waste characterization (Waste Management IF 2,66 and Chemical Engineering Journal IF 3,17), 4 with the influence of the water content on the kinetics and its modeling (Biochemical Engineering Journal, IF 2,9 ; Bioresource Technology IF 4,9 ; Journal of Chemical Technology and Biotechnology IF 1,8). 4 are co-signed by at least 2 partners. 2 PhD thesis have been defended at the end of the project. Nevertheless, an important part of the results have not been published yet (8 papers in preparation). The project also gave way to 9 oral communications in 5 international conferences, and 3 communications at the French Society for Process Engineering (SFGP) congress in 2011.
Monsieur Pierre BUFFIERE (Autre établissement d’enseignement supérieur)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Help of the ANR 528,841 euros
Beginning and duration of the scientific project: - 36 Months