António A. Martins

Sustainability and economic evaluation of microalgae grown in brewery wastewater

This article evaluates the sustainability and economic potential of microalgae grown in brewery wastewater for biodiesel and biomass production. Three sustainability and two economic indicators were considered in the evaluation within a life cycle perspective. For the production system the most efficient process units were selected. Results show that harvesting and oil separation are the main process bottlenecks. Microalgae with higher lipid content and productivity are desirable for biodiesel production, although comparable to other biofuels feedstock concerning sustainability. However, improvements are still needed to reach the performance level of fossil diesel. Profitability reaches a limit for larger cultivation areas, being higher when extracted biomass is sold together with microalgae oil, in which case the influence of lipid content and areal productivity is smaller. The values of oil and/or biomass prices calculated to ensure that the process is economically sound are still very high compared with other fuel options, especially biodiesel.

Properties and Sustainability of Biodiesel from Animal Fats and Fish Oil

aLEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto (FEUP), R. Dr. Roberto Frias S/N, 4200-465 Porto, Portugal bDepartment of Chemical Engineering, School of Engineering (ISEP), Polytechnic Institute of Porto (IPP), R. Dr. Antonio Bernardino de Almeida S/N, 4200-072 Porto, Portugal cDepartment of Environmental Engineering, Faculty of Natural Sciences, Engineering and Technology (FCNET), Oporto Lusophone University, R. Dr. Augusto Rosa, 24, 4000-098 Porto, PortugalPortugal *tmata@fe.up.pt

Comparison of allocation approaches in soybean biodiesel life cycle assessment

This work shows the influence of using different allocation approaches when modelling the inventory analysis in a soybean biodiesel life cycle assessment (LCA). Results obtained using mass, energy and economic based allocations are compared, focusing on the following aspects: normalised potential environmental impact (PEI) categories, total PEI and relative contributions to the total PEI from each life cycle stage and environmental impact category. Similar results are obtained either using economic and energy based allocations. However, different results are obtained when mass based allocation is used when compared with the other two. This study also illustrates that using different allocation approaches in biodiesel LCA may influence the final conclusions, especially in comparative assertions, emphasising the need to perform a sensitivity analysis in the LCA interpretation step.

Sustainability Evaluation of Biodiesel Produced from Microalgae Chlamydomonas sp Grown in Brewery Wastewater

This study performs a sustainability evaluation of biodiesel from microalga Chlamydomonas sp. grown in 20 % (v/v) of brewery’s wastewater, blended with pentose sugars (xylose, arabinose or ribose resulting from the hydrolysis of brewer’s spent grains (BSG). The life cycle steps considered for the study are: microalgae cultivation, biomass processing and lipids extraction at the brewery site, and its conversion to biodiesel at a dedicated external biofuel’s plant. Three sustainability indicators (LCEE, FER and GW) were considered and calculated using experimental data. Literature data was used, whenever necessary, to complement life cycle data, thus allowing a more accurate sustainability evaluation. A comparative analysis of the biodiesel life cycle steps was also conducted, with the main goal of identifying which steps need to be improved. Results show that biomass processing, especially cell harvesting, microalgae cultivation, and lipids extraction are the main process bottlenecks. It is also analysed the influence on the microalgae biodiesel sustainability of adding each pentose sugar to the cultivation media, concluding that it strongly influences the biomass and lipid productivity. In particular, the addition of xylose is preferable in terms of lipid productivity, but from a sustainability point of view, ribose is the best, though the difference from xylose is not significant. Nevertheless, culture without pentose addition presents the best sustainability results.

Designing Eco-Efficient Biodiesel Production Processes from Waste Vegetable Oils

Abstract In this work the conventional alkali-catalyzed transesterification process for biodiesel production from waste vegetable oils is studied considering the two process alternatives normally used industrially: with and without free fatty acids (FFA) pre-treatment. Simulation models of these process alternatives are developed using the chemical process simulator ASPEN Plus® and their potential environmental impacts (PEIs) and economic potentials are determined and compared. Results show that the contribution to total PEIs of the process alternative with the FFA pre-treatment is 25% higher than the alternative without pre-treatment. Concerning the economic potential the process alternative with the FFA pre-treatment is greater showing a net present value of about 1.8 times higher than the alternative without the FFA pre-treatment. The comparison using plant data will be performed as future work.

Valorization of Waste Frying Oils and Animal Fats for Biodiesel Production

The increased demand for biodiesel and the difficulties in obtaining enough quantities of raw materials for its production are stimulating the search for alternative feedstocks. Among the various possibilities, the utilization of residual fatty materials, in particular waste frying oils and animal fat residues from the meat and fish processing industries, are increasingly seen as viable options for biodiesel production. This work reviews the state of the art regarding the utilization of waste oils and animal fats as feedstocks for biodiesel production, which are characterized by the presence of high levels of impurities such as high acidity and moisture content. The relative advantages and disadvantages of the different routes for biodiesel production are presented and discussed in this chapter, focusing on their chemical and technological aspects. Also discussed are the questions related to the viability and potential economic advantages of using this type of feedstocks in biodiesel production for road transportation.

Bio-refinery approach for spent coffee grounds valorization

Although normally seen as a problem, current policies and strategic plans concur that if adequately managed, waste can be a source of the most interesting and valuable products, among which metals, oils and fats, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, pigments, flavonoids, through recycling, compound recovery or energy valorization, following the waste hierarchy. Besides contributing to more sustainable and circular economies, those products also have high commercial value when compared to the ones obtained by currently used waste treatment methods. In this paper, it is shown how the bio-refinery framework can be used to obtain high value products from organic waste. With spent coffee grounds as a case study, a sequential process is used to obtain first the most valuable, and then other products, allowing proper valorization of residues and increased sustainability of the whole process. Challenges facing full development and implementation of waste based bio-refineries are highlighted.

Microalgae processing for biodiesel production

Abstract: Microalgae are increasingly seen as a potential alternative to traditional feedstocks for biodiesel, which are limited and may have economic, social and environmental impacts. However, processing microalgae for biofuels is remarkably different and poses significant challenges in ensuring that they are competitive when compared with the other feedstocks. This article describes and critically analyses the main aspects and methods that can be used for the downstream processing of microalgae for biodiesel production. A brief analysis is made of the current and potential biodiesel production processes from microalgae, focusing on their main advantages and problems. The biorefinery concept is also discussed, that is, how microalgae biomass can be used to produce not just biodiesel but also other biofuels and/or high value bio-products and what will enable the economic sustainability of the whole process to be increased.

Sustainability Considerations about Microalgae for Biodiesel Production

This chapter describes how to perform a sustainability evaluation of microalgae biodiesel through its supply chain. A framework for selecting sustainability indicators that take into account all three dimensions of sustainability: economic, societal and environmental, is presented. Special attention is given to a useful definition of the boundary for the system and to the identification of the relevant impacts associated with the biodiesel supply chain stages. A set of sustainability indicators is proposed for quantitative sustainability assessment, based on the impacts deemed relevant for each supply chain stage. Some qualitative arguments are also presented to support the evaluation. Although microalgae appear to be superior in some respects to other currently used feedstocks, the development of large-scale microalgae production systems still needs further research.

Life cycle assessment tool of electricity generation in Portugal

This article presents and describes the LCA4Power tool, developed in this work to assess the potential environmental impacts, as, for example, the contribution to global warming, of electricity generation in continental Portugal, not considering the Madeira and Azores archipelagos. Based on a life cycle perspective, the tool considers the life cycles of various available technologies for producing electricity, on a cradle-to-gate perspective, excluding distribution and final use. It was implemented in MS Excel™ using emission factors obtained from the literature and other sources, instead of raw life cycle inventory data. The current version of the tool includes wind and hydroelectric power as renewable energy sources, and thermal and combined heat and power generation from fossil fuels as non-renewable energy sources. The combination of the aforementioned electricity generation technologies is responsible for more than 90% of the electricity generated in continental Portugal. Results were validated comparing the tool’s predictions with data from other LCA studies of electricity production, showing a good agreement, in particular for the greenhouse gas emissions. As added value, this tool provides a user-friendly way of simulating the potential environmental impacts of different endogenous energy mixes in Portugal, thus support decision making and communication. Future developments of the tool will include other technologies for electricity generation and its application to support decision making through the analysis of future scenarios for electricity generation in Portugal.