• Energy Research
• PT close

Abstract Crambe abyssinica is a non-edible crop able to adapt to adverse climatic conditions, arising as an alternative feedstock for biodiesel production. With this objective, an eco-friendly route for biodiesel production from crambe oil by enzymatic transesterification was evaluated in order to maximize fatty acid methyl esters content. Response Surface Methodology and central composite design (two factors, three levels, one central point, two replicas) was used to obtain predictive models considering catalyst concentration and methanol:oil molar ratio as independent variables. Since the reaction was monitored overtime, a predictive model considering three independent variables (three factors, three levels) was also obtained. Enzymatic transesterification is a good alternative process to obtain high FAME yield, with 84 ± 5 wt % being obtained after 2 h using a methanol:oil molar ratio 6:1 and 8 wt% of enzyme, a value which predictably can increase to almost 99 wt% after 24 h. The results showed that the methanol:oil molar ratio and the enzyme’s concentration considerably influence the FAME content during enzymatic catalyzed reaction. The polynomial regression models obtained can help to balance the concentration of enzyme and alcohol to improve FAME production and to predict the resulting yield.

Abstract No studies are reported on ethylic biodiesel integrated processes, considering raw materials, reaction optimization and product purification. The present study aims to: i) select key variables for experimental optimization of ethanolysis using a virgin vegetable oil; ii) perform an optimization study using a waste oil; and iii) evaluate the effectiveness of water free purification methods. Sunflower oil ethanolysis was conducted at different temperatures (30 – 80 °C), catalyst concentrations (0.3 – 2 wt.%), reaction times (0.5 – 4 h) and ethanol: oil molar ratios (2:1 – 12:1). Optimization experiments on waste oil ethanolysis were performed at different temperatures (30 – 50 °C) and ethanol: oil molar ratios (6:1 – 12:1), during 1 h and using 1 wt.% catalyst. Quality parameters were measured according to EN 14214. A cation-exchange resin and a ceramic membrane were evaluated for water-free purification. Regarding sunflower oil ethanolysis, when successful, conversion ranged from 75.2 to 97.7 wt.%. Using both oils under optimized conditions (45 °C, 6:1 ethanol:oil molar ratio), a product with a very high purity (> 98.0 wt.%) was obtained after water washing purification. The 0.1 μm ceramic membrane was more effective than the cation-exchange resin, but it was not possible to obtain a good quality product using both methods.

Biodiesel is an alternative fuel to fossil diesel whose major disadvantage is the dubious economical viability of the production process, due to the high raw material costs. In the work here reported, biodiesel was produced from poultry fat, a potentially good alternative raw material due to its low price and availability. The specific objectives of the work were (i) to study biodiesel production from poultry fat by homogeneous alkaline transesterification; (ii) to evaluate and improve the parameters affecting the reaction, namely, temperature, time, methanol to fat molar ratio, and concentration of the catalyst; and (iii) to evaluate the quality of the obtained biodiesel, according to the European biodiesel quality standard EN 14214. The product yield varied from 73 to 86 wt %. Regarding the product quality, independently of the reaction conditions used, density, acid value, flash point, copper corrosion, linolenic methyl ester content, and iodine number fulfilled EN 14214; however, viscosity and purity ...

Abstract In order to contribute for a more sustainable biodiesel production, its synthesis from animal fat through heterogeneous catalysis was studied, by focusing on: (i) selecting a heterogeneous catalyst for pork lard transesterification; (ii) studying the influence of the reaction conditions on biodiesel purity, namely by using response surface methodology (RSM); and, (iii) evaluating the re-use of the catalyst. Calcium manganese oxide was the selected heterogeneous catalyst for the transesterification of lard obtained from a meat processing industry. RSM studies allowed the development of a second-order model representing the influence of the reaction conditions on biodiesel purity; the temperature and the combined effect of the temperature and catalyst concentration were the conditions which mostly influenced product purity. Catalyst was reused without significant loss of activity indicating that catalytic behaviour was heterogeneous.

Many European countries are developing the use of pellets or wood briquettes for the supplying of local energy. Many industries are being forced to replace fossil fuels with biomass because of its neutrality in relation to CO2 emissions, thus creating an interesting market for pellets. In Portugal, the most common undergrowth includes: esteva (Cistus ladanifer), tojo (Ulex europaeus), giesta (Sarothamus scoparius), feto (Pteridium aquilium) and silva (Rubus ulmifolius). These undergrowth specimen are attractive due to the large volume available, but are not usually used for making pellets. It is possible to prevent large fires cleaning the forests, but this is an expensive task that could be compensated if the undergrowth can have some commercial value. The use of the common undergrowth for the manufacture of pellets and briquettes will allow the undergrowth to be considered not as a problem to be removed from the forest but an opportunity as renewable energy. The aim of this work is to obtain pellets with standard properties and evaluate the parameters that can qualify the performance of these pellets: moisture content, particle size distribution, high heating value, height of flame and burning time, pressure and temperature of the pelletizing process and mechanical durability. The pelletizing process was first simulated on laboratorial scale using small amounts of each vegetal specimen which was pressed in a heated mould. Some samples were submitted to a torrefaction treatment. After the laboratorial screening, the selected material was processed using a pellet mill to prepare pellets with 6 mm of diameter. The durability test was performed using a tumbling device following the ASAE S 269.4 standard. Burning tests of pellets with the same weight were performed and video images analysed, where height of flame and ignition time were measured. It was found that undergrowth pellets had good power of agglomeration and allow an easy ignition. The apparent density varies around 1,260 kg/m3. The moisture content of different pellet varied between 2.79 and 7.46 %, ash content was less than 3 %, the calorific value is between 16 and 18 kJ/kg, the durability results respect the values recommended by standards. After ignition the flame increases to an average height of 25 mm. The total burning time was in all cases dominated by the cinder combustion without visible flame and the total complete burning time varied between 400 and 600 s. The results showed that it is possible to produce pellets of undergrowth with physical and thermochemical characteristics similar to the existing in the market at the present time.

Abstract In the present work, biodiesel production using a glycerol enriched heterogeneous catalyst was studied. For that purpose, the catalyst performance at different glycerol concentrations and reaction conditions (under ambient atmosphere) was evaluated and two triglyceride sources were used. The most active catalyst was produced using CaO, glycerol and methanol at a mass ratio of 1:1.6:13.4, respectively. By performing the transesterification reaction under ambient atmosphere during 2 h at 333 K, using 0.4 wt.% of catalyst and 7:1 methanol to oil molar ratio, a good quality product was obtained (EN 14214) using both soybean oil and waste frying oil. The catalyst could be re-used during four cycles and could also be prepared by using ethanol instead of methanol (with differences

Abstract Portugal’s performance concerning the Refuse Derived Fuel (RDF) strategy, with particular focus on perspectives for the Northern Region based on the current status of integrated municipal waste management systems in that region, was evaluated. Legal documents, official reports and the market were analyzed. The 2015 national installed capacity of waste treatment technologies, from which the high calorific value fraction (HCVF) for RDF production is obtained, is not far from what was predicted for 2013. However, only around 11% of the HCVF had such destiny and the amount of effectively produced RDF was only 30% of the material sent to RDF production (around 30 kt). In Northern Portugal, no RDF production plant was in operation in 2015; the amount of HCVF was estimated to range from 105 to 204 kt for 2015 and around 2.4 times more is expected in 2020. The strategy laydown for RDF failed so far, and thus, low diversion of waste from landfills is observed, mostly due to low landfill taxes and low HCVF quality, resulting in RDF being non-competitive with the imported higher quality product from countries with very high landfilling fees. Moreover, co-incineration and dedicated recovery solutions are scarce. In the Northern region, the HCVF may be treated in the existing municipal waste incinerator or the RDF might be recovered in new dedicated plants, receiving also non-hazardous waste fractions from other origin. Overall, to ensure a sustainable municipal waste management, the intensification of the reuse, preparation for reuse and recycling of waste components from source segregated collection must be significantly promoted.

The objective of the present work was: (i) to enable biodiesel production from acid waste lard; (ii) to study the esterification reaction as possible pre-treatment at different temperatures, catalyst amount and reaction times; (iii) to evaluate biodiesel quality according to EN 14214 after basic transesterification of the pre-treated fat; and (iv) to predict the impact of using such waste as raw material in mixture with soybean oil. Temperature and catalyst amount were the most important reaction conditions which mostly affected biodiesel quality, namely viscosity and purity. The selected pre-treatment conditions were 65 degrees C, 2.0 wt% H(2)SO(4) and 5 h, which allowed obtaining a product with a viscosity of 4.81 mm(2) s(-1) and a purity of 99.6 wt%. The proposed pre-treatment was effective to enable acid wastes as single raw materials for biodiesel production with acceptable quality; however, low yields were obtained (65 wt%). Alkali transesterification of a mixture of waste lard and soybean oil resulted in a product with a purity of 99.8 wt% and a yield of 77.8 wt%, showing that blending might be an interesting alternative to recycle such wastes. Also, because in addition to using conventional and relatively economical processes, some biodiesel properties depending on the raw material composition (such as the iodine value) might even be improved.

Rice is one of the most consumed cereals in the world. From rice processing, rice bran is obtained, and only a part of this by-product is effectively used. Rice bran oil can be obtained and used as an alternative feedstock for biodiesel production, although few studies exist to support its exploitation. In addition, pretreatment is required to reduce its acidity and allow for its integration in the conventional industrial process. This work evaluated two pretreatment processes aiming to reduce the free fatty acids (FFAs) content of rice bran oil by employing an acid-catalyzed process and a biocatalyzed process. The results allowed us to assess the efficiency and effectiveness of both pretreatments. For that purpose, acid (45, 55 and 65 °C, using H2SO4 concentrations of 2 wt.% or 4 wt.% and a methanol:oil molar ratio of 9:1) and enzymatic FFAs conversion (35 °C using a 6:1 methanol:oil molar ratio and 5 wt.% of Thermomyces lanuginosus) were evaluated using rice bran oil with an acid value around 47 mg KOH.g−1, and the reaction kinetics were assessed. Acid esterification enabled a 92% acidity reduction (65 °C, 4 wt.% of catalyst) after 8 h, with the final product presenting an acid value of 3.7 mg KOH.g−1 and a biodiesel purity of 42 wt.%. The enzymatic process allowed an acidity reduction of 82%, resulting in a product with an acid value of 7.0 mg KOH.g−1; however, after 24 h, the biodiesel purity was 87 wt.% (almost a two-fold increase compared to that obtained in the homogeneous process), revealing the conversion of both free fatty acids and glycerides. The study of the reaction kinetics of the homogeneous (acid) esterification showed that, for temperatures > 45 °C, the constant rate increased with temperature. A higher constant rate was obtained for the temperature of 55 °C using 4 wt.% of catalyst (k′ = 0.13 min−1). For the heterogeneous (enzymatic) esterification, the constant rate obtained was lower (k′ = 0.028 min−1), as expected. The study revealed the technical viability of the esterification pretreatment of rice bran oil and the important parameters concerning the performance of the pretreatment solutions. Finally, the enzymatic process should be further explored, aiming to develop more ecofriendly processes (water and energy savings) to produce biodiesel from oils with a high acidity (low-cost raw materials).