• Energy Research

Combustion of fossil fuels in the transport sector represents the second largest source of greenhouse gas emissions. For this reason, governments are fostering diversification of energy sources by creating a set of governmental environmental policies and initiatives. In this context, biofuels are expected to represent a substantial part of source diversification, but it is necessary to assess the sustainability of their market to explore its effect on economical, technological, social, political and environmental dimensions. This research presents a dynamic simulation modelling of the Colombian biodiesel market and analyzes the policy support instruments for creating and managing it. A system dynamics based model is proposed to enable decision-makers to understand the influences between the different variables that describe the system and the impact of the biodiesel government policy in Colombia. The primary focus of this paper is to establish the characteristics of each sustainability dimension for the case of study and apply the system dynamics methodology with different types of validation. Finally, the Colombian market status and a sensitivity analysis are developed. The results show that in order to support the development of this sector, it is necessary to diversify the raw materials for the production of biodiesel in the medium term, which means raw materials without competence for the primary rainforest or competition with food productive lands.

Abstract Reactive extraction is a potential alternative for biodiesel production, in which reaction and glycerol separation are simultaneous, increasing conversion, yield and process productivity. This paper presents a stepwise reaction–separation model for a counter-current reactive extraction column, used in homogeneous-base-catalyzed palm oil methanolysis, and the models’ parameters are identified from the results of a set of experimental tests. In addition, multi-criteria optimisation of the process conditions was performed using an evolutionary algorithm. The optimum conditions provide for palm oil conversion of 97.7%, a yield to FAME of 99.5% and a process productivity of 1.4 m 3 FAME h −1 m −3 in a single reaction step. Finally, a comparison of the process productivity with co-current and batch processes was made. As the counter-current reactive extraction process does not require the intermediate separation stages required in co-current and batch processes, its productivity is 1.5 and 6.9 times higher than those processes, respectively.

Abstract After alkali-catalyzed transesterification reaction for biodiesel production, the glycerol-rich phases have to be separated. These phases are traditionally separated by settling, requiring long residence time, especially when soaps and gels are formed. In this work, biodiesel, and glycerol rich phases separation was experimentally assessed using poly(ether sulfone) hollow fiber membranes (PES-HFM). Experimental data were obtained in a continuous bench scale system. The effect of pressure difference through the membrane (0–0.6 bar), feed composition and biodiesel-rich phase mass fraction (0–0.8) on permeability and permeate composition were studied. In addition, a mathematical model adopting the Hagen–Poiseuille transport equation for membrane ultrafiltration, where permeate fluxes and compositions depend on the Liquid–Liquid Equilibrium (LLE), was proposed, correlated and experimentally validated. Experimental results demonstrated only glycerol-rich phase permeated through the membrane following the LLE. Glycerol-rich phase flux increased when pressure difference through the membrane augmented, and decreased when permeate viscosity increased. The highest experimental permeability (33.2 kg bar−1h−1m−2) was obtained at the highest methanol content in the feed stream, 66%wt., equivalent to a molar ratio methanol to oil 18:1 fed to the reactor. The mathematical model predicts an increase in the glycerol-rich phase flux when temperature and methanol content augment. The transport mechanism coupled to the mathematical model explained accurately the membrane role in the separation of the compounds involved in transesterification of vegetable oils, as well as the membrane selectivity.

The growing global population and its effects on world food security, as well as the urgency for climate change mitigation, are issues that foster technological, social, and political innovations to increase the efficiency of use of natural resources, such as biomass among others. While significant research efforts have been devoted to biomass conversion processes, their associated supply chains and their implication for complete process efficiency have only been studied more recently. However, most of the recent investigations into the design and optimization of biomass supply chains have focused on an economic point of view, sidelining other dimensions of sustainability, which represents a serious drawback for this kind of work. This article surveys the recent research on design and management optimization of biorefinery supply chains from a sustainability perspective. 72 published research articles from 2006 to 2015 have been analyzed to highlight the sustainability dimensions considered, as well as the inclusion of uncertainties. A typology of decision-making at three levels of analysis (strategic, tactical and operational), and the specific set of tools used to model and optimize the biorefinery supply chain have also been studied. The conclusion underlines the contributions and shortcomings of current research and suggests possible future directions.

Abstract Biodiesel is an important renewable fuel industrially produced by transesterification of fats and oils. Conventional process productivity is limited by high residence time in the reaction and separation stages. Liquid-Liquid Film Reactor (LLFR) is a new technology able to overcome this limitation. This work presents the scale-up, cost analysis and process feasibility for the LLFR. The study was made using a complete mathematical model which includes fluid dynamics, kinetics, mass transfer resistance, liquid-liquid equilibria, and cost evaluation. This study recommended the construction of plants with capacities over 5 t/h (about 40,000 t/year) in order to avoid over costs in the process and also recommended the employ of multiple reaction stages to reduce until 32% the global methanol consumption. Results also shows that to get a profit in this biodiesel production, the vegetable oil price must be less than 830 US$/t. Finally, it was found that the use of LLFR technology permit a reduction up to 60% in the required volume when two LLFR stages are employed in comparison to the traditional use of continuous stirred tank reactors (CSTR), this reduction promotes a final cost reduction up to 0.6% per kg of biodiesel.

This study evaluated the kinetic modeling of arabinoxylan (AX) extraction from Brewers’ spent grain (BSG) by alkaline pretreatment at atmospheric pressure, considering severe (low concentration of NaOH and high temperature) and moderate (high concentration of NaOH and low temperatures) process conditions. The effects of NaOH concentration and temperature on yield extraction were studied over time, as well as the concentration of weak acids and phenolic compounds at the end of the pre-treatment. The AX yield extraction varied from 41.2 % (1 M, 90 °C) to 64.8 % (4 M, 40 °C) after 1 h and 16 h, respectively. Acetic acid ranging from 420 ppm to 1020 ppm was released, while ferulic acid was the phenolic compound produced at the highest concentration ranging from 78.3 ppm to 224.1 ppm. In addition, rates of chemical reactions were correlated mathematically from the experimental data with a good fit, and a sensitivity analysis was performed to understand the kinetic behavior. The first-order kinetic model demonstrates that increasing AX extraction requires both low temperatures (between 30 and 40 °C) and low NaOH concentration, but at the same time, this effect increases the time required (16 h) to obtain the maximum AX yield (64.8 %).

AbstractIndustrial biodiesel production from crude palm oil (CPO) by homogeneous transesterification requires some conditioning stages. One is deodorization, where free fatty acids (FFA) are stripped out from the CPO. The FFA from the deodorizer is esterified using a homogeneous acid catalyst to produce more biodiesel and improve process profitability. This work studied the sulfuric acid‐catalyzed esterification of FFA with methanol. The factors evaluated were temperature (between 40 and 60°C) and catalyst concentration (between 0.15 and 1.5 wt% based on the mixture). The parameters of a reversible second‐order kinetic model were adjusted from experimental data using a genetic algorithm. The kinetic model, which adequately represents the esterification reaction, according to the Fisher–Snedecor test, was used to perform a sensitivity analysis in isothermal, adiabatic, and non‐isolated continuous tubular esterification reactors using ASPEN HYSYS V10. The results showed that the highest conversion (~96%) was predicted using an isothermal reactor. However, its installation and operational costs could also be the highest. An adiabatic reactor was preferred, which optimal conversion of 94.5% was predicted at temperature, catalyst concentration, residence time, and methanol‐to‐FFA molar ratio of 140°C, 0.3 wt%, 47 min, and 6.7, respectively, its predicted operational cost was 0.63 dollars per biodiesel kilogram. Therefore, the adjusted and validated model has a relevant importance in the biofuel sector, not only in Colombia, but also worldwide.

The effect of temperature and catalyst concentration on palm oil ethanolysis using 0.2 to 1 wt% NaOH based on the mass of palm oil was studied at temperatures ranging from 60 to 80 °C, keeping constant the ethanol to oil molar ratio (6:1). A 100% conversion of palm oil and a 96% yield of FAEE (fatty acid ethyl ester) were obtained after 60 min of reaction with 1 wt% NaOH at 70 °C. The increase of temperature between 60 °C and 70 °C on palm oil ethanolysis enhanced the reaction rate, but increase it from 70 °C to 80 °C had the contrary effect. The effect of temperature was higher during the first ten minutes of reaction. Increase of catalyst concentration between 0.2 wt% and 0.5 wt% strongly promoted the yield to FAEE, although this effect was not observed with further increments in the catalyst concentration. A second order kinetic model that predicts the behavior of the intermediate products and the effect of temperature and catalyst concentration was proposed and validated by the Fisher–Snedecor test of unbiased variances. Kinetic model parameters of palm oil ethanolysis and methanolysis were compared and demonstrated similar behavior and orders of magnitude.