BGU’s Prof. Haim Kalman and the University of Florida’s Profs. Pratap Pullammanappallil, and Jennifer Curtis have just been awarded a BARD (United States-Israel Binational Agricultural Research and Development Fund) grant to improve the production of biogas through improving the capabilities of anaerobic digesters.
Farm based biogas systems (or anaerobic digesters) have traditionally treated animal manure, and the biogas produced has been used on site for supplying the energy needs of the farm. Manure by its very nature is a poor feedstock for anaerobic digestion. Recently, due to attractive renewable energy credits on offer in some countries, there has been a tremendous growth in the number of digesters that co-digest manure with other co-feedstocks (for example corn silage). Addition of co-feedstocks enhances the volumetric biogas productivity from the digester, leading to increased revenues for the farm.
Unagitated, high-solids, leach-bed anaerobic digesters have several advantages over other anaerobic digestion systems as they (1) do not require addition of large quantities of water as the digestion is carried out at 35% solids content, (2) do not involve pumping of solids/slurry during digestion, and (3) do not require agitation of digester contents which contrary to conventional wisdom guarantees rapid and stable start-up and operation of anaerobic digestion.
However, an operational issue with high-solids digestion is the removal of digested residue as it tends to pack at the bottom of the vessel. Also the solids compact within the digester inhibiting decomposition reactions. These problems arise due to the fact that the design of these systems does not account for the flow properties of the three-phase system (gas, liquid, biomass particles) within the digester.
In this research project, they will investigate the multiphase behavior specific to the particles and flow associated with this new technology for continuous, high-solids, leach-bed anaerobic digestion. This objective will be accomplished through a combined effort involving both simulation and experimentation. The simulations, to take place at the University of Florida, include both particle-level and bulk flow simulations. The particle-level simulations will be the first of their kind to describe the flow of wet and dry, fibrous, flexible particles characteristic of biomass. The validated models, validation to take place at BGU, will then be employed to describe the multiphase flow behavior within the new digester technology.
A broad outcome of the project will be the formulation of general design guidelines for continuous, high-solids, anaerobic digesters treating a wide variety of biomass feedstock. Such digester designs will eliminate operational problems and enhance the possibility of utilizing a wide range of on farm nutrient rich feedstocks for digestion, thereby increasing the farm revenues.
Prof. Kalman of the Department of Mechanical Engineering is a world leader in solids handling and particle transport and possesses the unique expertise and facilities to conduct these experiments. Professor Kalman has served as the International Scientific Chair of the International Conference of Conveying and Handling of Particulate Solids for over ten years now and chaired the international conference on this topic in Tel Aviv in May 2015.
Prof. Curtis’ research group is the only group in the world capable of simulating wet or dry, flexible, elongated fibrous materials. Prof. Pullammanappallil brings unique expertise and experimental facilities relevant to the anaerobic digestion process.
