Héctor Campbell

Lipase Production Through Solid-State Fermentation using Agro-Industrial Residues as Substrates and Newly Isolated Fungal Strains

ABSTRACT Extracellular lipase production by Penicillium chrysogenum, Trichoderma harzianum and Aspergillus flavus was carried out through solid state fermentation using agro-industrial residues as substrates. For all three strains, the growth temperature was 29±1 °C, and 65% w (g/gds) moisture content. The effect of three factors on lipase production rate was investigated: initial pH (6.0 and 7.0), time of fermentation (72 h, 96 h and 120 h), and type of mixed substrate (wheat bran-olive oil, and wheat bran-castor oil cake). The process was optimized applying a mixed level factorial design. Fermentation time and pH were found to have positive effects on lipase production and secretion rates. However, the time effect was larger than initial pH. Type of substrate demonstrated minor effective importance than the other two factors, and Aspergillus flavus showed the larger lipase production among the three strains. Results indicated that the three fungal strains were able to grow and produce lipase in both culture mediums. The maximum lipase activity achieved was 121.35 U/gds by Aspergillus flavus, which was five and nine times the lipase produced by Trichoderma harzianum and P. chrysogenum respectively, at the same conditions. An initial neutral pH and 96 h of fermentation time were the optimum conditions for lipase production by Aspergillus flavus.

Feasibility Analysis for a Tidal Energy Pilot Site in the Gulf of California

Baja California is located in the northwestern region of Mexico and is a peninsula that borders the west by the Pacific coast and on the east by the Gulf of California, with 1,280 km of coastal area of which 560 km belong to the Gulf California and the rest to the Pacific Ocean. It is privileged with renewable energy resources and already has 720 MW of geothermal, 10 MW of Wind and 5 MW of Solar that presently are under construction. With the growing demand for electricity especially in the summer period, the use of tidal power is an opportunity to use a resource of this type in the coastal towns.This paper presents an analysis which assesses the bays of Santa Maria, San Luis Gonzaga, Los Angeles, El Pescador, El Soldado, Las Animas and San Rafael, as sites with ideal features for the implementation of tidal power generation technology. The analysis, weighed the constructive feasibility, site bathymetry, environmental impact to the area, roads, generation capacity and population of nearby sites. The Port of San Felipe with a population of 16,945 inhabitants, is located in the Gulf of California, having a population growth rate of 2.3 % year, and has 4,579 users in the residential sector who demand 27,483 MWh annually, being the months of July to August when they consume 60% of the year’s energy.It was calculated that the maximum estimated power potential was in the Bay of San Rafael with 14 MW, and the minimum power value was obtained for Bay of Soldado with 1.3 MW. However the Bay of Santa Maria with a maximum power of 2.5 MW is considered the most viable site for the development of a tidal project according to the weighing used primarily, due to its proximity to the Port of San Felipe.One of the main restrictions for the development of tidal energy on these sites is the high environmental impact that could occur in these areas. Due to the that as biophysical characteristics and coastal geomorphology of these bays, these sites are very fragile in terms of negative impacts that could be generated by changes in ocean currents due to the construction of infrastructure for tidal generation.Copyright

Renewable Energy Integration: Economic Assessment of Solar Energy to Produce Biodiesel at Supercritical Conditions

In recent years, research on noncatalytic methods for biodiesel production has increased, mainly processes under supercritical conditions that allow the processing of waste vegetable oils (WVO) without the need to use catalysts, where the absence of catalyst simplifies the processes of purification of biodiesel. The high consumption of alcohol and energy to maintain the appropriate conditions of pressure and temperature of the reaction has turned the processes of supercritical conditions into an unfeasible method. However, the stages of biodiesel purification and methanol recovery are more straightforward, allowing the reduction of the total energy consumption by 25% compared to alkaline methods. Therefore, the present work describes a study through Aspen Plus® of the production of biodiesel by a process in supercritical conditions with WVO as raw material. Also, a solar collector arrangement was structured using the TRNSYS® simulator to supply energy to the process. To evaluate the economic feasibility of the proposed process, the installation of a pilot plant in Mexicali, Baja California, was considered. The internal rate of return (IRR) and the net present value (NPV) were determined for ten-year period. The planned system allows supplying solar energy, 69.5% of the energy required by the process, thus reducing the burning of fossil fuels and the operation cost. Despite the additional investment cost, for the solar collectors, the process manages to maintain a competitive production cost of USD 0.778/l of biodiesel. With an IRR of 31.7%, the investment is recovered before the fifth year of operation. The integration and implementation of clean technologies are vital in the development of the biofuels.

Solar Water Heater Design for Houses in Arid Zones

This paper shows the simulation and design of a flat plate solar collector system, used to feed hot water to a typical home located in the city of Mexicali, Baja California, Mexico. The system consists of a solar collector, a storage tank, a water pump and accessories and special tools that allow its proper operation. Analyzing the consumption and end use of water in a typical House, a demand profile is established, which combined with the weather information of the region, constitutes the input parameters required for the simulation of the system, which is performed with the software package TRNSYS. Mexicali, due to its location (latitude 32 °, longitude 114 °) and semi-desert condition presents high temperatures in the summer and low in winter, so the design and operation of such systems require special features, not always considered in the conventional ratings. This paper presents methods for simulation and design oriented to optimize the dimensioning and operation of this type of solar heaters in regions with extreme temperature conditions.Copyright