Microalgae as a renewable fuel source: Fast pyrolysis of Botryococcus braunii

ROXANA PILONI; INES DAGA; CARLOS URCELAY; ELIZABETH L. MOYANO

Rio de Janeiro

Simposio; International Symposium on Advancing the Chemical Sciences (ISACS); 2015

Royal Society of Chemistry

The high consumption of fossil fuels, along with the decline in the number of exploited oil fields and an excessiveincrease in CO2 emissions and other pollutants, have created the need for researching new sources of fuels,which have the property of being renewable and environmentally friendly, and develop new methods for theirpreparation. In this context, algae emerge as a new source of renewable fuels or bio-fuels, due to numerousadvantages offered in relation to the higher vascular plants implemented nowadays, and because algae currentlyproliferate massively due to the pollution of watercourses.For obtaining biofuel from algal material the fast pyrolysis technique was used, which consisted of thermaldegradation of organic matter in the absence of oxygen under vacuum conditions. Botryococcus braunii alga wasused as starting material because it contains a high percentage of lipids, which ensures a good production andquality of bio-oils1. Previous characterization of the alga was carried out by elemental and proximate analysistechniques.Fast pyrolysis experiments were conducted in a fixed bed reactor on a laboratory scale. Temperature scanbetween 300 and 600 °C was performed in order to find the best conditions for mayor bio-oil recovery. For eachreaction the amounts of liquid an solid were determined by direct weight, and the gas fraction was calculated bydifference of the first two.It was observed that the alga contains over 50% w/w lipids in its composition, which is very beneficial if the goalis to get long-chain hydrocarbons and fatty acids. Also, the protein content is low, and therefore the content ofnitrogenated compounds is also low. This is also beneficial because nitrogen compounds are unwanted for a fuel,since the energy efficiency is reduced and in the combustion process generates nitrogen oxides as environmentalcontaminants. In the elemental analysis study it was observed that B. braunii alga has a high carbon content,which correlates with the high lipid content, and a low percentage of nitrogen which correlated with the lowamount of protein. The results of the fast pyrolysis experiments are shown in the next table:We found that the highest bio-liquid recovered was obtained at 500°C (60% yield). Bio-oil composition wasanalyzed using the GC-MS technique and there is no great difference between the samples with the change oftemperature. The chromatograms showed a high concentration of mono-insaturated long-chain hydrocarbonswith traces of oxygenated compounds such as phenol and long chain derivatives (alcohols and carboxylic acids).Thus, the resulting bio-oils, with a simple upgrading can be an interesting alternative as new biofuels.Reference1. Y. Ghasemi, Rasoul-Amini, S., Naseri, A. T., Montazeri-Najafabady, N., Mobasher, M. A., Dabbagh, F., Appl. Biochem.Microbiol. 2012, 48, 126