PYROLYSIS OF ANIMAL AND VEGETAL BIOMASS RESIDUES FOR FERTILIZER AND ENERGY PRODUCTION

Aim of the work is to produce organic mineral fertilizer (OMF) and energy by feeding organic (animal or vegetal) wastes to a pyrolysis plant and to convert the raw material into bio-products: solid stabilized organic matter and syngas. The solid product (biochar) must be as rich as possible in nutrients, to be used in the production of OMF in dedicated facilities, where the stabilized organic matter is mixed and balanced with inorganic fertilizers. Actually fertilizer production Companies are producing OMF through composting plants, but the process is very time consuming and expensive and the final product is not completely stabilized. The pyrolysis process can be applied to different types of feedstocks (preferably residuals) to obtain different by-products (gaseous, liquid or solid) to be used for different final applications. The project applies slow pyrolysis, to maximize the char production (biochar by vegetal or animal residues) and the nutrients contained, managing the temperature and residence time in the reactor, so to address the char to fertilizers production. Available organic wastes taken into consideration are: chicken litter, filtration cake from sugar cane industry, sludge from slaughterhouse, chicken manure, chicken hatchery waste and several others. The wastes input composition is in average: moisture (up to 75 % w/w); nitrogen (from 1 to 6,5 % w/w dry base); P2O5 (from 0,3 to 3.5%); K2O (from 0,2 to 3%) and the organic matter content can range between 30 to 90% on dry base. To avoid high energy consumption and losses of nutrients, the raw materials are charged into the pyrolyser once dried by means of heat recovered from the process (low temperature): in these conditions, the char will maintain most part of etheroatoms contained in the raw materials (nitrogen, phosphor, potassium, etc.). The raw materials are blended, after being dried up to a 10% water content: this will help having a final by-product (biochar) with constant characteristics: the Lower Heating Value (LHV) of the dried organic fraction is about 4.350 Kcal/Kg. The rotating pyrolysis drum is here operated at about 450 degrees C (skin temperature), in order not to completely eliminate volatile and nutrients contents in the biochar. The other pyrolysis by-products (syngas and/or fuel oil) can be used for electric or thermal energy production: depending on the specific needs. The authors suggest to use only gaseous by products (so to minimize gas cooling and tar separation) in order to increase plant's reliability, burning directly the hot syngas produced in a single combustion chamber. The high temperature exhausts will be used at for the production of electricity through an Organic Ranking Cycle (high reliability, very low maintenance and operating costs, but low efficiency), and downstream for the drying of raw materials. The rather low efficiency will be compensated by heat recovery for drying purposes (about 80 degrees C). The results obtained are so interesting that the Project are under application at different farmers in South America, where energy needs and waste elimination problems can be transformed in a great opportunity.