Скачать или смотреть Integrated 1G2G Ethanol and Electricity Industrial Production Model

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The perspective of a world-wide increased demand for transportation energy puts a lot of pressure on scientists and engineers to develop efficient, robust and competitive industrial processes for the large scale production of biofuels, among which bioethanol is probably the most important one. Major sustainability issues have already been raised and relate mainly to the overall energy balance and soil depletion due to intensive farming, in addition to impacts on food prices. Second generation ethanol produced by saccharifying lingo-cellulosic biomass obtained from specific crops (eucalyptus, miscanthus, etc.) or from agricultural or industrial wastes (corncobs, straw, etc.) constitutes a very promising conversion route since it can literally coexist without competing with food crops. For example, there are interesting research work on intercropping corn with different species of Brachiaria with an increased overall photosynthetic efficiency, the first being a source of food starch, the second constituting the primary source of cellulose for conversion into biofuel.
Sugarcane has one of the highest photosynthetic efficiencies in the plant kingdom, being able to convert around 1% of incident solar energy into biomass with a high sucrose content, which is very easily fermented and converted into bioethanol. Its large scale cultivation is a well established agro-industrial business in Brazil, particularly after the development of flex-fuel technologies, which freed the consumers from their captive condition by enabling the choice of any proportion of gasoline/ethanol depending on market prices. Also contributed to this picture a combination of simultaneous favorable conditions, such as a good incidence of sunlight, amenable temperatures, regular and adequate rain pattern, availability of arable land, fertile soils, long term research efforts to develop hybrids adapted to specific conditions, etc. Despite a highly favorable overall energy balance when compared with other biomass feedstock, there is still a lot to be done to improve conversion efficiency, to minimize GHG emissions, to preserve soil fertility, aquatic resources and so forth. It is also necessary to increase processing flow rates beyond 1000 tsc/h to enable benefits from economies of scale. An integrated agro-industrial model for the sustainable production and conversion of biomass into biofuels and added value products has been proposed. The instantiation of this model to a typical (reference) sugarcane industrial plant reveals several obstacles and bottlenecks to its implementation, mainly due to lack of scientific knowledge and absence of robust and cost-competitive large scale processing technologies related to 2nd generation ethanol and high concentrations microalgae cultivation.
To overcome these difficulties a large spectrum of expertise needs to be articulated, going from genetics, biomolecular sciences and cell biology to engineering design and optimization, industrial processing and sustainability assessing. Specific research topics and actions are: 1) understanding the structure and composition of ligno-cellulosic biomass, 2) development of modern plant genomics and genetic transformations to enable advanced studies of photosynthesis and metabolomics aimed at increasing cell conversion efficiency, 3) definition of sustainable agricultural practices with special focus on water and soil preservation, energy and feedstock requirements and logistics, 4) identification of new biochemical conversion routes, which involve enzyme structural biology and protein engineering, with special relevance to biofuels and added value biochemicals, 5) development of innovative industrial scale processes and equipment for cost-competitive biomass transformation and 6) construction of tools for assessing economic viability, ecological footprint and social impacts of these new technologies. To meet these expectations it will be necessary to orchestrate induced and exploratory research, the first being responsible for scientific discoveries which are the basis of disruptive technologies enabling large evolutionary leaps, the second promoting its consolidation through a series of incremental steps resulting from experimentation, refinement, and increasingly realistic testing.