Sustainable Development Goals

▶ Addresses a wide range of timely environment, economic and energy topics ▶ A forum to review, analyze and stimulate the development, testing and implementation of mitigation and adaptation strategies at regional, national and global scales ▶ Contributes to real-time policy analysis and development as national and international policies and agreements are discussed and promulgated ▶ 94% of authors who answered a survey reported that they would definitely publish or probably publish in the journal again

Mitigation and Adaptation Strategies for Global Change

Production of liquid biofuels from renewable resources

Cultivation, photobioreactor design and harvesting of microalgae for biodiesel production: A critical review

Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. In this review, the fatty acid (FA) profiles of 12 common biodiesel feedstocks were summarized. Considerable compositional variability exists across the range of feedstocks. For example, coconut, palm and tallow contain high amounts of saturated FA; while corn, rapeseed, safflower, soy, and sunflower are dominated by unsaturated FA. Much less information is available regarding the FA profiles of algal lipids that could serve as biodiesel feedstocks. However, some algal species contain considerably higher levels of poly-unsaturated FA than is typically found in vegetable oils. Differences in chemical and physical properties among biodiesel fuels can be explained largely by the fuels’ FA profiles. Two features that are especially influential are the size distribution and the degree of unsaturation within the FA structures. For the 12 biodiesel types reviewed here, it was shown that several fuel properties – including viscosity, specific gravity, cetane number, iodine value, and low temperature performance metrics – are highly correlated with the average unsaturation of the FAME profiles. Due to opposing effects of certain FAME structural features, it is not possible to define a single composition that is optimum with respect to all important fuel properties. However, to ensure satisfactory in-use performance with respect to low temperature operability and oxidative stability, biodiesel should contain relatively low concentrations of both long-chain saturated FAME and poly-unsaturated FAME.

Review of biodiesel composition, properties, and specifications

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO 2 , wastewater treatment, in human health, as food additive, and for aquaculture.

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Microalgae for biodiesel production and other applications: A review

The use of fossil fuels as the main source of energy for most countries has caused several negative environmental impacts, such as global warming and air pollution. Air pollution causes many health problems, causing social and economic negative effects. Worldwide efforts are being made to avoid global warming consequences through the establishment of international agreements that then lead to local policies adapted to the development of each signing nation. In addition, there is a depletion of nonrenewable resources which may be scarce or nonexistent in future generations. The preservation of resources, which is a common goal of the Circular Economy strategy and of sustainable development, is not being accomplished nowadays. In this work, the calculation of indicators and mathematical and statistical analysis were applied to clarify and evidence the trends, provide information for the decision-making process, and increase public awareness. The fact that European countries do not possess abundant reserves of fossil fuels will not change, but the results of this analysis can evolve in the future. In this work, fossil fuel energy consumption, fossil fuel depletion, and their relationship with other variables, such as energy dependence and share of renewable energy in gross final energy consumption, were analyzed for 29 European countries. Furthermore, it was possible to conclude that many European countries still depend heavily on fossil fuels. Significant differences were not found in what concerns gross inland consumption per capita when the Kruskal–Wallis test was applied. It was possible to estimate that by 2050 (considering Jazz scenario) it will only remain approximately 14% of oil proven reserves, 72% of coal proven reserves and 18% of gas proven reserves. Given the small reserves of European countries on fossil fuels, if they need to use them, they will fast disappear.

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Analysis of fossil fuel energy consumption and environmental impacts in european countries

Parametric study of a brewery effluent treatment by microalgae Scenedesmus obliquus.

Bio-refinery approach for spent coffee grounds valorization.

This work evaluates the use of spent coffee grounds (SCG) for biodiesel production. The SCG were characterized for their moisture content (12.1 wt%), total carbon (TC) and total nitrogen (TN) (52.2 and 2.1 wt% respectively), cellulose and total lignin contents (33.6 wt% and 13.8 wt% respectively), carbon/nitrogen mass ratio (C/N = 24.8) and higher heating value (HHV, of 19.3 MJ/kg). For extracting the oil from the SCG, several solvents were tested at different contact times: hexane, ethanol, isopropanol, heptane and a mixture of hexane/isopropanol in the proportions of 50:50; 60:40; 70:30 and 80:20 (vol/vol). Results revealed an oil content ranging from 6.3 to 28.3 wt%, depending on the extraction conditions. For example, using hexane/isopropanol (50:50, vol/vol) a 21.5 wt% of oil recovery was obtained after 3 h of contact time, while using isopropanol a 21.0 wt% of oil recovery was obtained in 6.8 h, but at higher operating cost, considering the energy and solvent consumption. Regarding the oil characterization the following parameters can be highlighted: HHV of 36.4 MJ/kg, iodine value of 54.4 (g I2)/(100 g oil), water content of 2004 ppm and acid value of 118.4 (mg KOH)/(g oil). Finally, the possibility of using the recovered coffee oil for biodiesel production was evaluated. In this regard it was performed the oil esterification in three consecutive steps (using 1% of H2SO4 and 40 % of methanol for 2 h of reaction time at 60 oC and 500 rpm) followed by one transesterification step (1 % of NaOH and 40 % of methanol during a 2 h reaction time at 60 oC and 500 rpm). The resulting biodiesel was characterized for its acid value, density, viscosity at 40 oC, iodine value and esters content (65.7 to 72.9 %), of which only the iodine value of 26 and 58.4 (g I2)/(100 g biodiesel) was within the NP EN14214:2009 standard limits. The reaction yield varied between 58.8 and 62.2 wt%. Results suggest the need for a further process optimization in order to obtain a biodiesel complying with this standard quality requirements.

Nídia S. Caetano

Papers

Microalgae for biodiesel production and other applications: A review

Analysis of fossil fuel energy consumption and environmental impacts in european countries

Parametric study of a brewery effluent treatment by microalgae Scenedesmus obliquus.

Bio-refinery approach for spent coffee grounds valorization.

Valorization of Coffee Grounds for Biodiesel Production