267446 Biodiesel Production From Cynara Cardunculus Crop: Economic, Environmental and Social Assessment
The generation, transport and consumption of conventional sources of energy, particularly in the transport sector, have raised many concerns about air pollution, environmental degradation, and petroleum consumption. In this sense, the development of alternative technologies is acquiring importance, and many efforts are being done in the gradual replacement of fossil fuels. Within the renewable sources of energy, the production of liquid biofuels from organic feedstocks sources represents a feasible alternative that avoids important modifications of vehicle engines, maintaining most of the infrastructures for the supply chain and can replace partially the petroleum-based fuels.
Biofuels have many advantages over fossil fuels: as well as being more environmentally friendly and a renewable source of resources, every region in the world has a raw material that can be used, to a greater or lesser extent, to produce some sort of biofuel, thus providing work for the population and improving the economies of the countries that so far have been dependent on petroleum imports.
On the other hand, there is the ethical question of the direct competition for land that is required for producing food. Several groups (Green Peace, Intermon Oxfam, etc) claim that the growing production of biofuels is responsible for the increasing food prices, and the destruction of forests. Second-generation biofuels (those that do not threaten food supplies) were developed to overcome this obstacle.
Of particular interest are the residual parts of agricultural and forest vegetation that contain cellulose for producing bioalcohols, recycled oils, and other plants that contain oils and which do not threaten food supplies (Jatropha curcas, Cynara cardunculus, microalgae, etc).
The aim of this work is to analyse the feasibility of biodiesel production obtained by transesterification of vegetable oil extracted from Cynara Cardunculus (cardoon), a wild robust perennial plant, native from the Mediterranean basin. The performance assessment of a process with a capacity of 5000 t/year biodiesel production is carried out from the triple bottom line perspective. The characterization of the process includes its rigorous simulation in AspenHysys® from which an automated evaluation tool programmed in Matlab® retrieves the inventory of relevant energy and material inputs, as well as the environmental releases. In the evaluation tool the calculations are grouped into different modules: acquisition of the simulation data, environmental, economic and social assessment, and results analysis.
The simulation performs the alkali-catalyzed transesterification with methanol and a pre-treatment section for the free fatty acids removal by esterification. The operational conditions are based on the cardoon oil characterization and the kinetic data extracted from published experimental studies (Pasqualino, 2006). The simulated process includes the methanol recovery, the catalyst neutralization and the glycerol separation and purification as valuable by-product.
In the environmental module, the Eco-indicator 99 methodology is used for the impact assessment, achieving similar results to other vegetable sources of biodiesel. With respect to the economic criterion, a profitability analysis is performed calculating the net present value, thus considering the initial investment, manufacturing costs and products revenue. As expected, the economic metric points out the necessity of government subsidies to produce positive rates of return. From a social perspective, quantitative indicators (e. g., provision of employment) and qualitative indicators (e. g., nuisance) were selected among the social metrics available in the literature. The three indicators are then aggregated in a single metric using a normalization and weighting procedure based on the geometric mean of the metrics’ ratios for pair-wise comparison of alternative processes (Torres et al., 2011).
The performance of the plant is optimized considering the potential alternatives. With this aim, the use of two different catalysts and an additional unit for the recuperation of glycerol in the pre-treatment section are considered, allowing a higher reusing of materials and reducing the waste treatment requirements. Furthermore, a sensitivity analysis is carried out to quantify the robustness of the procedure and identify the critical variables.
Pasqualino, J.C., 2006. Cynara cardunculus as an alternative crop for biodiesel production. Ph.D. dissertation. Universitat Rovira i Vigili, Tarragona, Spain.
Torres, C.M., Gadalla, M.A., Mateo-Sanz, J., Jiménez-Esteller, L., 2011. Evaluation Tool for the Environmental Design of Chemical Processes. Ind. Eng. Chem. Res. 50 (23), 13466-13474.
Torres, C.M., Gadalla, M.A, Mateo-Sanz, J.M., Jiménez-Esteller, L., 2012. An automated environmental and economic evaluation methodology for the optimization of a sour water stripping plant. J. Clean. Prod. (in press).
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