3. Doktoritööd
Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/7081
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Sirvi 3. Doktoritööd Autor "Da Rocha Meneses, Lisandra Marina" järgi
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Kirje Second-generation bioethanol production: strategies for sidestreams valorisation in a sustainable circular economy(Eesti Maaülikool, 2020) Da Rocha Meneses, Lisandra Marina; Kikas, Timo; Orupõld, Kaja; Gilroyed, Brandon Harvey (opponent)Due to the increase of the energy production mainly from non–renewable energy sources, there is a need for alternative sources of energy. Second–generation biofuel production, using lignocellulosic biomass as a feedstock, is emerging as an important liquid biofuel for the transportation sector. However, its production is still very costly, and inefficient mainly due to the large quantity of sidestreams that are generated. Sidestreams from bioethanol production process bring environmental, economic and energetic constraints. a. Environment From the environmental point of view, sidestreams from bioethanol production are highly pollutant. There are several handling options for these residues and it includes: discharge; marine outfall; agricultural fields; sewage treatment; lagoon treatment; anaerobic digestion; incineration; and drying. From all these solutions, anaerobic digestion can be used to reduce the pollution potential of the production waste, and to reduce CO2 and other greenhouse gas (GHG) emissions. b. Economics From the economic point of view, the high costs of bioethanol production require additional valorisation of its stillage to create new revenue streams. Pretreatment and enzymatic hydrolysis are the two most costly parts of the production process. Anaerobic digestion of bioethanol stillage is a prospective solution to offset the costs of bioethanol production and add value to the production chain. c. Energetics Finally, stillage has a high energetic value and can be used to produce energy in the form of methane. Its utilization can give higher net energy outputs and improve the efficiency of the production chain. In addition, ethanol from biomass has an energy return on energy invested (ERoEI) lower than for fossil fuels. Thus, stillage and bioethanol sidestreams can be used for processing energy, through anaerobic digestion to add value to the production chain and improve the energy balance. To sum up, there is a continuous search for strategies that make use of the high energy content of bioethanol sidestreams. Anaerobic digestion to produce energy in the form of methane has been reported as an effective strategy to increase the energy output from the biomass, help to balance the costs of bioethanol production and as an environmental solution to this highly pollutant residues.