9 de fev de 2014

BIOREFINERIES: DEVELOPMENT STAGE AND PERSPECTIVES


The development of alternatives to fossil resources is a global priority. However, the development of sustainable processes for large scale biomass production and conversion into energy vectors is an open challenge requiring multidisciplinary research approaches ranging from plant breeding, crop production, harvesting, and industrial processing, to economic and environmental sciences. From the point of view of the process, this problem can be structured into three interdependent instances or compartments: 1) agricultural production, 2) feedstock logistics and 3) industrial conversion. A sine qua non condition to the optimization of such three-compartment problem is that all processes must be concerted altogether, possibly to the detriment of sub-instances of the overall process. For example, once sugarcane is cut, photosynthesis stops and its sucrose content decreases until it is processed at the industrial site. Thus, it may be better to use faster trucks in crop transportation, even at the cost of increased fuel consumption per transported ton.
In general, the industrial production and conversion of biomass is viable within a specific range of production/processing scales, which can be characterized by the plantation area. Lower limits are generally determined by initial and fixed costs (equipment, staff, rent, land and buildings, taxes, etc.), while upper limits are determined by agricultural and logistics costs. Higher added value bio-products, such as tannin obtained from acacia bark or essential oils, justify the exploitation of larger areas around the industrial site. Biofuels and electricity are actually low added value products and, consequently, economicity is achieved through intensive use of land (minimum crop rotation and increased use of fertilizers) and high use of capital to improve economies of scale. Many large scale agro-industrial enterprises fit into this model, such as sugarbeet, maize, wheat and sugarcane processing industries.
Biomass has become an important alternative feedstock for energy production and carbon based chemicals. Recent reports reveal that global biomass technical potentials could supply as much as four times the current global needs. Although the assumptions behind these calculations lead to overestimated numbers, because they ignore all competing land uses and socioeconomic constraints, these results give a real perspective of the important role that biomass can play is displacing fossil resources. The biorefinery concept emerged as new agro-industrial paradigm in which biomass is carefully deconstructed to produce low-value/large-volume liquid transportation fuel such as biodiesel or bioethanol and, additionally, to produce low-volume/high-value products such as pharmaceuticals and nutritional compounds. It is just realistic to suppose that many of these new biorefineries will evolve from the existing biomass processing industries. This actually constitutes the central objective of this work: to investigate and quantify the impact of integrating new biomass deconstruction technologies into an existing agro-industrial production model in terms of its new multi-objective optimal operating conditions. Although we will base our work on the Brazilian sugarcane sector, the same approach is applicable to other agricultural crops.

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