4- bio system (bioethanol-methane-compost-algae)

The aim of this project is to perform and validate a new integrated system of 4 biological processes transforming biomass into: boiethanol, methane (thermal and electric energy), compost and algal biomass. The integrated biological system proposed in this process includes four different industrial microbial processes: 1. fermentation (bioethanol production), 2. anaerobic respiration (methane production), 3. aerobic respiration (compost production), 4. photosynthesis (algae production -biodiesel and proteins). A computerized system will connect the 4 industrial system in order to control in real time all the processes, starting material, transformation pathway and by products, giving the quantity and the quality of these parameters. All the parameters that affect the rate of the process and the quality of the end-products will be controlled and optimized by the same computer program.

The starting material for these process can be cellulose, starch and sugar crops or by-products. Cellulose crops are firstly enzymatically hydrolyzed to sugar; starch also by α-amylase is converted to sugar. The fermentation of glucose to ethanol is operated by selected strains of Saccharomyces cerevisiae in a single stage continuously stirred reactor, with simple Monod kinetics, using a plot of steady-state concentration. The main parameters to be controlled are: flow rate, temperature, yeast concentration, nutrient concentration, catabolite concentration, recycling operation, pH, oxygen level, C/N ratio. A computer simulation for the ethanol fermentation with cell recycling is used. Ethanol is then extracted from the medium by fractional destillation at atmospheric pressure. Further purification of ethanol requires a dehydration step to reach 99.99% purity.

The by-products from bioethanol production (exhausted pulps, stillage, lingo-cellulosic residues, etc.) are used to feed Anaerobic Digestion process. This process is carried out in thermophilic conditions, in two separate reactors: in the first hydrolysis and acidification occur with a retention time of about 17 days; in the second the methanogenesis occurs with a retention time of 7 days.

The methane produced undergoes to a treatment of purification to remove H2S, water and CO2. The purified biogas will feed a turbine system to produce electric and theral energy. Thermal energy is completely recycled inside the plant to dry the starting material, for fermentation and distillation and for thermophilic anaerobic digestion. Electric energy is recycled inside the plant only 20-25%. The remaining energy is sold. Sludge from anaerobic digestion mixed with other agricultural residdues is composted in order to produce an organic fertilizer suppressive top lant pathogens, to be used int he fields where the crops for starting material are produced.

The composting process is carried out inside an industrial building with a continuous air change. The aspirated air from the building is purified by passing through a water basin with algae. The composting process is performed in horizontal reactors (channels) periodically turned with an automatic mechanical system and ventilated from the bottom. Air coming from ventilation is also purified by algae. Parameters like temperature, oxygen leveli n the mass and moisture are continuously monitored and the values transmitted to a computer which manages the feed back control of the process. After 30 day retention time, the material is automatically removed and proceeded to the final refinery process by screening: the smaller parts are mature compost and the bigger will be recycled in a new composting process.

All exhausted air coming from the three processes (bioethanol, methane and compost) is treated biologically by algae avoiding any CO2 emission in atmosphere.

This integrated plant producing bioethanol, methane and compost, is completely self-sufficient both for thermal and electric energy, because they are produced in a huge quantity by itself. It produces biethanol, energy and compost from renewable sources with sustainable process, in accord with Kyoto protocol, reducing the emission of CO2 (carbon credits). No waste production: 100% of the raw materials and by-products of the processed are recycled and converted in energy. No air, water and soil pollution. The cost of bioethanol production is lower than with other processes owing to the huge quantity of energy recovered. It preserves the biological fertility of the soils where the crops for starting materials are produced; moreover, compost utilization reduces the use of chemical fertilizers and pesticides, both products that are produced with petrol energy.



Copyright: © European Compost Network ECN e.V.
Quelle: Orbit 2014 (Juni 2014)
Seiten: 0
Preis: € 0,00
Autor: Prof. Marco de Bertoldi
Dr. Ulrike de Bertoldi - Schnappinger
 
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