Energy recovery from agricultural waste by means of thermochemical conversion in fluidized bed reactors: Abstract

The current commercial supply of renewable energy from biomass and the legislative focus on cutting-edge cogeneration is predominantly based on the renewable resource wood. This is generating an exponentially increasing demand for wood as reserves are steadily being reduced by competition for material. Wood prices are therefore rising and the cost effectiveness of existing methods of use is diminishing. By 2030, Europe will face a deficit between supply and demand of 150 million tons of wood. This makes the development of unutilized biowaste with great potential for energy recovery imperative and particularly pertains to agricultural waste, which is largely precluded from direct use as material. Germany alone has a theoretically available supply of 20 million tons of culmiferous waste per year. Other agricultural waste includes rice husks (China alone produces 197 million tons of rice annually, olive pits and citrus fruit waste (from Italy and Spain), and sugar cane (Brazil produces 514 million tons annually). The objectives of the project are to ascertain both the hyperstoichiometric and hypostoichiometric thermochemical conversion characteristics of representative agricultural fuels with high relevance for Central European agriculture sector separately and in blends using laboratory and pilot-scale fluidized bed combustors, to identify the options for conditioning process products, and to assess the potential for optimization. Furthermore, potential uses of process products as material will be identified for the purpose of creating closed material cycles and measures will be taken to influence the quality of the process products positively. Combustion, gasification, pyrolysis and combinations of individual conversion paths will be the processes studied. The conversion characteristics of agricultural waste will be studied to underpin the process engineering of thermochemical conversion plants, specifically innovative concepts for distributed recovery of power and heat or cooling in the range of 1-10 MW of thermal output. This will contribute to the development of hitherto unutilized potentials of agricultural waste for energy recovery. Project deliverables will be reliable bases of data on conversion characteristics of agricultural wastes, thus facilitating the implementation of a system and/or concept in the agricultural sector in particular. Among others, potential users will be farms and farming collectives requiring heat, cooling and power and possibl