Journal of Fundamentals of Renewable Energy and Applications
Open Access

Direct supercritical transesterification of wet unwashed pastes from green microalgae (Nannochloropsis gaditana, Chlorella sp. and Nannochloris sp.) for biodiesel production

International Congress and Expo on Biofuels & Bioenergy

August 25- 27, 2015 Valencia, Spain

Souhir Jazzar1, Joaqu�­n Quesada-Medina2, Pilar Olivares-Carrillo2, Mohamed N�©jib Marzouki1, Francisco Gabriel Aci�©n-Fern�¡ndez3, Jos�© Mar�­a Fern�¡ndez-Sevilla3, Emilio Molina-Grima3 and Issam Smaali1

Posters-Accepted Abstracts: J Fundam Renewable Energy Appl

Abstract :

With the over-consumption of fossil fuel reserves and their impact on climate changes, the search for renewable and clean
biofuels is becoming necessary. Biodiesel is considered nowadays as one of the most promising alternative for replacing
petroleum diesel. For biodiesel production, microalgae have received a particular attention due to their photosynthetic
efficiency, high cellular lipid content, CO2 fixation and growth on non-arable lands unsuitable for food crops. However, the
main drawbacks of microalgae-based biodiesel process are the biomass drying step responsible of high energy consumption
and the difficult lipid recovery from the thick algal cell walls. In this work, biodiesel was produced by a single-step catalyst-free
process using direct or in situ supercritical methanol transesterification from wet unwashed green microlgae (Nannochloropsis
gaditana, Chlorella sp. and Nannochloris sp.). The main process parameters were first optimized for Nannochloropsis gaditana
(Lubián CCMP 527) by studying the effect of methanol to microalgae ratio (6:1-12:1 vol./wt.), reaction time (10-50 min) and
temperature (245-290°C). A maximum biodiesel yield of ~46 wt% was reached for a methanol to microalgae ratio of 10:1
(vol./wt), reaction time of 50 min and temperature of 265°C. These optimized parameters were then applied for newly isolated
species of Chlorella sp. and Nannochloris sp., issued from the south-western Mediterranean Sea, and maximum biodiesel yields
of 45.62% and 21.79% were achieved, respectively. Additionally, the effect of the supercritical process on the algal cell wall
structure was investigated by scanning electron microscopy observations.