Optimization of microalgae systems for CO2 mitigation and biodiesel production

Author(s)

Lucy Mara Cacia Ferreira Lacerda

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2013-10-07

Examining board members

Telma Teixeira Franco; Ana Teresa Lombardi; Francisco Maugeri Filho; Leonardo Brantes Bacellar Mendes; Ranulfo Monte Alegre

• Advisor: Telma Teixeira Franco

Abstract

The use of microalgae in environmental carbon dioxide mitigation processes and renewable energy production are gaining attention, but the optimization of "upstream" and "downstream" process is essential to promote technical and economic feasibility and make with the industrial scale became true. The conditions that maximize biomass growth, carbon dioxide mitigation, lipid content, and produce a fatty acid profile suitable for a high quality biodiesel was evaluated as function of different temperatures (18-42 ºC), carbon availability as CO2 (air-40%), light intensity (4-192 ?mol.m-2.s-1), and nitrogen availability as NaNO3 (0.25-1.00 g.L-1). Biomass harvesting using flocculation process was evaluated as function of flocculant type (organic and inorganic), flocculant dosage (0.005-0.3 g.L-1), pH (4-11), and biomass concentration (0.1-1.0 g.L-1). The selected conditions were: 108 ?mol.m-2.s-1, 26.5 ºC and 8.05% de CO2, with the following results: Xmax/X0=14.78 (maximum and initial cell concentration ratio); ?max=1.02 d-1 (maximum specific growth rate), ?=0.50 d (lag phase duration); Pmax=0.58 g.L-1.d-1 (maximum productivity); Pmean=0.31 g.L-1.d-1 (mean productivity); CBmax=1.06 g.L-1.d-1 (maximum carbon incorporation rate); CBmean=0.55 g.L-1.d-1 (mean carbon incorporation rate); 50% of lipid content, and 90% of samples FAMES (fatty acid methyl ester) corresponding to the mainly biodiesel FAMES (C16:0, C18:0, C18:1, C18:2 e C18:3). Biodiesel quality prediction using samples of microalgae oil show the following results: CN=56 (cetane number), CFPP = 0.8 °C (could filter plugging point), ? = 863 kg/m³ (density), II = 97 gI2/100g (iodine index), ?HC = 39.2 kJ/g (heat of combustion), OSI = 13.8 h (oil stability index), and ? = 3.93 mm².s (viscosity), and the values were compatible with different quality standards ASTM-D6751, EN14214/14213, and ANP 255/2003. Recovery efficiency (RE) of 95% or more can be obtained with pH 4,0 to 11,0 (organic flocculant); 5,0 to 7,0 (FeCl3), and 7,0 to 8,0 (Al2(SO4)3; gflocculant/gbiomass of: 0,08gorganic/gbiomass, 0,40gAl2(SO4)3/gbiomass). The impact of light availability in the center of photobioreactor was predicted as function of cell concentration, pigments concentration and photobioreactor design, being observed approximately 85% of loss in the incident light availability in cultures is less than 2 g.L-1. Biomass production process and biofuels production process were simulated using a commercial software SuperPro Designer v8.5 followed by economic analysis (AU)

• FAPESP's process: 09/07919-4 - Development of a system for production in large scale of cyanobacteria biomass.
• Grantee: Lucy Mara Cacia Ferreira Lacerda e Silva
• Support Opportunities: Scholarships in Brazil - Doctorate