Assessing Waste Cooking Oils for the Production of Quality Biodiesel Using an Electronic Nose and a Stochastic Model

Abstract

Around 1% of waste cooking oil (WCO) is currently recycled to make biodiesel in Brazil, mainly because used oils can acquire physicochemical characteristics that render them unsuitable as raw materials. To make biofuel production from waste oils and fats more efficient and economically feasible, it is important to develop simple, rapid, and low-cost methods for testing the quality of WCOs. With the objective of establishing the applicability of stochastic modeling of e-nose profiles in assessing the suitability of WCO for biodiesel production, the synthesized biodiesel samples from 36 pre-used frying oils, obtained from domestic and commercial premises, were analyzed regarding ester content, acidity index, density, viscosity, and iodine index. Olfactory profiles of the WCO sources were obtained using a Cyranose chemical vapor-sensing instrument and interpreted by application of stochastic modeling and quadratic discriminant analysis. The predictive model obtained by stochastic analysis exclusively from the olfactory profiles of the samples of WCO allowed the latter to be classified according to their ability to generate biodiesel that would be compliant with standard specifications and with an overall accuracy greater than 80%. Our results demonstrated that stochastic modeling is a promising tool for predicting the quality of biodiesel based only on the WCO olfactory profiles and its origin, since it allows qualitative assessments of the principal biodiesel properties and eliminates the need for complex and time-consuming laboratory tests.

Applications of an electronic nose in the prediction of oxidative stability of stored biodiesel derived from soybean and waste cooking oil

“…The pH of the residual water from each of the biodiesel washings was monitored in order to determine the stage at which all remaining catalyst had been removed. The biodiesel was submitted to rotary evaporation at 80 °C for 40 min and dried over anhydrous sodium sulfate [19] .…”

“…This instrument comprises an array of 32 thin-film nanocomposite sensors (NoseChip® array) and employs algorithms to detect VOCs based on variations in electrical resistance of the sensors. Prior to analysis, the samples of biodiesel were stabilized at 23 °C and ten replicates of each sample were analyzed [19] under the following conditions: baseline readings 10 s, sample readings 20 s and purge and sensor update 35 s.…”

“…An alternative approach involved the use of a stochastic model based on the average behavior and variability of the e-nose signal during sorption and desorption of biodiesel as represented by the parameters a , b , c , k and p described previously by Siqueira et al [19] , [32] . According to this model, the maximum signal value can be estimated from the value of b while the function m (defined as a + bk ) is proportional to the concentration of VOCs present in the sensor region.…”

Design and development of a low-cost reactor for biodiesel production from waste cooking oil (WCO)

“…Besides, fossil fuels are a limited resource and their value depends on various geopolitical and economic issues. This scenario presents problems to the increasing world energy needs as well as risks of catastrophic and irreversible consequences to the environment, which have led scientists to propose intensive actions to prevent them [1][2][3][4]. A transition of energy sources beyond fossil fuels has become one of the greatest challenges of the twenty-first century and innovation in this sector depends on studies of alternative fuel sources for overcoming the economic and environmental impacts of fossil fuels consumption around the world.…”

“…Biofuels synthesized from biomass, especially biodiesel, offer a promising alternative substitute for petroleum-based fuels. Biodiesel has been considered as a potential fuel to reduce the green house effects, since it is environmentally friendly due to characteristic such as being biodegradable, non-toxic, renewable and for emitting less CO2, CO and sulfur [1,2,5]. Despite all these advantages, biodiesel does not compete economically with diesel derived from fossil fuels due to its high production cost [4].…”