Bioethanol Plant Research Articles

Yeast selection for fuel ethanol production in Brazil

Brazil is one of the largest ethanol biofuel producers and exporters in the world and its production has increased steadily during the last three decades. The increasing efficiency of Brazilian ethanol plants has been evident due to the many technological contributions. As far as yeast is concerned, few publications are available regarding the industrial fermentation processes in Brazil. The present paper reports on a yeast selection program performed during the last 12 years aimed at selecting Saccharomyces cerevisiae strains suitable for fermentation of sugar cane substrates (cane juice and molasses) with cell recycle, as it is conducted in Brazilian bioethanol plants. As a result, some evidence is presented showing the positive impact of selected yeast strains in increasing ethanol yield and reducing production costs, due to their higher fermentation performance (high ethanol yield, reduced glycerol and foam formation, maintenance of high viability during recycling and very high implantation capability into industrial fermenters). Results also suggest that the great yeast biodiversity found in distillery environments could be an important source of strains. This is because during yeast cell recycling, selective pressure (an adaptive evolution) is imposed on cells, leading to strains with higher tolerance to the stressful conditions of the industrial fermentation.

Energy optimization for the design of corn‐based ethanol plants

AbstractIn this work, we address the problem of optimizing corn‐based bioethanol plants through the use of heat integration and mathematical programming techniques. The goal is to reduce the operating costs of the plant. Capital cost, energy usage, and yields—all contribute to production cost. Yield and energy usage also influence the viability of corn‐based ethanol as a sustainable fuel. We first propose a limited superstructure of alternative designs including the various process units and utility streams involved in ethanol production. Our objective is to determine the connections in the network and the flow in each stream in the network such that we minimize the energy requirement of the overall plant. This is accomplished through the formulation of a mixed‐integer nonlinear programming problem involving short‐cut models for mass and energy balances for all the units in the system, where the model is solved through two nonlinear programming subproblems. We then perform a heat integration study on the resulting flowsheet; the modified flowsheet includes multieffect distillation columns that further reduces energy consumption. The results indicate that it is possible to reduce the current steam consumption required in the transformation of corn into fuel grade ethanol by more than 40% compared to initial basic design. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Analysis and decrease of the energy demand of bioethanol-production by process integration

Process simulation was used to decrease the external heat demand during the production of bioethanol by integration in a network of facilities for heat and power generation. Models for bioethanol fermentation and purification process, the production of DDGS as well as production and utilization of biogas were developed to calculate the heat demand of bioethanol-production and the amount of heat and power generated from residues of the bioethanol process. Depending on the form of biogas utilization (CHP-plant, biogas fired boiler) and the capacity of the bioethanol plant, the conversion of stillage from the bioethanol process to biogas covers a considerable amount of the heat demand necessary for bioethanol-production and purification.

Availability of Crop Residues as Sustainable Feedstock for Bioethanol Production in North Carolina

The amount of corn stover and wheat straw that can be sustainably collected in North Carolina was estimated to be 0.64 and 0.16 million dry t/yr, respectively. More than 80% of these crop residues are located in the coastal area. The bioethanol potential from corn stover and wheat straw was estimated to be about 238 million L (63 million gal/yr) in North Carolina. The future location of ethanol plant in North Carolina was estimated based on feedstock demand and collection radius. It is possible to have four ethanol plants with feedstock demand of 400, 450, 500, and 640 dry t/d. The collection radii for these four ethanol plants are 46, 60, 42, and 67 km (28, 37, 26, and 42 miles), respectively. The best location for a bioethanol plant includes four counties (Beaufort, Hyde, Tyrrell, and Washington) with feedstock demand of 500 t/d and collection radius about 26 mile.

A simple rule for bioenergy conversion plant size optimisation: Bioethanol from sugar cane and sweet sorghum

Fuel ethanol from agricultural crops, “bioethanol”, is more expensive than petrol. Here we consider ways to reduce ethanol costs, by using mixed crops to extend the processing season and by optimising plant capacity. We derive a simple model of general applicability by balancing crop transport costs (which increase with plant size) against the (decreasing) production costs. We show that at the optimum, the cost of transporting crop, per unit quantity of alcohol, must be a predictable proportion of the unit cost of production, generally in the range 0.4–0.6. Under current Australian conditions, cane sugar and cane plus sweet sorghum bioethanol plants have optimum capacities around 245,000 and 175,000 kl/year, respectively. the model is equally applicable to any other bioenergy conversion plant which requires biomass to be transported from surrounding areas. The model also shows quantitatively how more efficient transport allows larger scale production, while lower production costs make smaller plants more economic.

Tratamiento de vinaza empleando electrodisolución y floculación química

La vinaza es el residuo más importante de las plantas de bioetanol debido a su alto potencial contaminante, por estoha recibido gran atención debido al interés de desarrollar nuevas alternativas de tratamiento. Se evaluó la capacidadde reducción del contenido de sólidos y otros parámetros de la vinaza empleando electrodisolución de hierro yfloculación química a través de etapas separadas. Las condiciones de operación adecuadas para llevar a cabo laelectrodisolución de hierro se establecieron a través de barridos de polarización lineal y análisis de espectroscopiade impedancia electroquímica. Durante la floculación se llevaron a cabo pruebas de jarras empleando Ca(OH)2como modificador de pH y como agente coadyuvante. De esta manera fue posible disminuir 84% los sólidos totales,54% la demanda química de oxígeno, 88% el carbono orgánico disuelto, y 76% el color. El consumo eléctricodurante la electrodisolución fue 0.25 kWh/m3.