Green Economy biofuel

domingo, 4 de maio de 2014

Optimal engineered algae composition for the

integrated simultaneous production of bioethanol

and biodiesel

Mariano Martína, 1, Ignacio E. Grossmannb

aDepartamento de Ingeniería Química. Universidad de Salamanca. Plz. Caidos 1-5 37008 Salamanca (Spain)

bDepartment of Chemical Engineering Carnegie Mellon University. Pittsburgh, PA 15213

Abstract.

In this paper we present the optimization of the composition of the algae for the simultaneous production of bioethanol and biodiesel. We consider two alternative technologies for the biodiesel synthesis from algae oil, enzymatic or homogeneous alkali catalyzed, the most promising based on previous work, and we coupled biodiesel production from oil with bioethanol production from algae starch. In order to determine the optimal operating conditions we not only couple the technologies, but simultaneously optimize the production of both biofuels and heat integrate them. Multieffect distillation column for the beer column is included in the flowsheet to mitigate the energy and cooling water consumption derived from the ethanol dehydration. In both cases the optimal algae composition results in 60% oil, 30% starch and 10% Protein. The cheaper alternative for the production of biofuels corresponds to a production price of 0.35 $/gal, using the enzymatic catalyzed path with promising energy and water consumption

values (4.20 MJ/gal & 0.61 gal/gal).

Keywords: Energy; Biofuels; Bioethanol; Biodiesel, Process integration

Química Nova - Chemistry and sustainability: new frontiers in biofuels geracao tecnologicas

http://www.scielo.br/scielo.php?pid=S0100-40422013001000002&script=sci_arttext

ABSTRACT

This contribution discusses the state of the art and the challenges in producing biofuels, as well as the need to develop chemical conversion processes of CO₂ in Brazil. Biofuels are sustainable alternatives to fossil fuels for providing energy, whilst minimizing the effects of CO₂ emissions into the atmosphere. Ethanol from fermentation of simple sugars and biodiesel produced from oils and fats are the first-generation of biofuels available in the country. However, they are preferentially produced from edible feedstocks (sugar cane and vegetable oils), which limits the expansion of national production. In addition, environmental issues, as well as political and societal pressures, have promoted the development of 2^nd and 3^rd generation biofuels. These biofuels are based on lignocellulosic biomass from agricultural waste and wood processing, and on algae, respectively. Cellulosic ethanol, from fermentation of cellulose-derived sugars, and hydrocarbons in the range of liquid fuels (gasoline, jet, and diesel fuels) produced through thermochemical conversion processes are considered biofuels of the new generation. Nevertheless, the available 2^nd and 3^rd generation biofuels, and those under development, have to be subsidized for inclusion in the consumer market. Therefore, one of the greatest challenges in the biofuels area is their competitive large-scale production in relation to fossil fuels. Owing to this, fossil fuels, based on petroleum, coal and natural gas, will be around for many years to come. Thus, it is necessary to utilize the inevitable CO₂ released by the combustion processes in a rational and economical way. Chemical transformation processes of CO₂ into methanol, hydrocarbons and organic carbonates are attractive and relatively easy to implement in the short-to-medium terms. However, the low reactivity of CO₂ and the thermodynamic limitations in terms of conversion and yield of products remain challenges to be overcome in the development of sustainable CO₂conversion processes.