Evaluation of Different Operational Strategies for Biodiesel Production by Direct Transesterification of Microalgal Biomass

Abstract

In this study, different operational strategies for biodiesel production by direct transesterification of microalgal biomass (Botryococcus braunii) were evaluated. These operational strategies include the use of different acyl acceptors and the application of different catalysts and solvent mixtures. All these strategies were performed in two reaction systems: a conventional batch reactor (CBR) and a reflux extraction reactor (RER). The highest biodiesel production yields (80.6 wt %) were obtained in the RER using methanol as acyl acceptor and H 2 SO 4 as catalyst. On the opposite, the lowest biodiesel production yield (64.5 wt %) was observed in the CBR system. Moreover, when a low proportion of cosolvent (i.e 3:1 v/v solvent/cosolvent) was incorporated in the reaction, an increase in biodiesel production yields was observed. A higher cosolvent content in the reaction mixture provoked however a diminishment in FAAE (fatty acid alkyl esters) yield in both systems, due to a drastically reduction of alcohol−lipids molar ratio.

Botryococcus braunii for biodiesel production

“…The optimal reaction time to achieve a high lipid conversion depends on the operating conditions and the catalyst type and varies from one minute [99] to two days [100]. Due to the incomplete lipid extraction from the B. braunii biomass (high contents of residual biomass rich in lipids), improvements to existing methods are directed towards the integrated concept of simultaneous extraction and trans/esterification, also known as direct trans/esterification or in-situ trans/esterification (ISTE) [89,101]. ISTE in batch and reflux extraction reactors in semi-continuous laboratory scales are performed under solvent/cosolvent/catalyst [89,101] conditions.…”

“…Due to the incomplete lipid extraction from the B. braunii biomass (high contents of residual biomass rich in lipids), improvements to existing methods are directed towards the integrated concept of simultaneous extraction and trans/esterification, also known as direct trans/esterification or in-situ trans/esterification (ISTE) [89,101]. ISTE in batch and reflux extraction reactors in semi-continuous laboratory scales are performed under solvent/cosolvent/catalyst [89,101] conditions. The highest FAME yield of 480% is obtained in a reflux extraction reactor using the homogenous H 2 SO 4 catalyst and a low solvent/cosolvent ratio (3:1 methanol/chloroform).…”

Direct biodiesel production from wet spent coffee grounds

“…21,28,29 Several studies have shown that simultaneous extraction and transesterication in different chambers in one system could produce biodiesel directly from biomass with a high yield. [30][31][32] Continuous contact of fresh solvent with biomass facilitates the lipid transfer which is further converted to biodiesel with a catalyst. In addition, Liu et al 25 successfully impregnated the dry SCG biomass with H 2 SO 4 and the simultaneous extraction-transesterication reaction was processed in the extraction chamber with methanol.…”

Recent Trends in Biodiesel and Biogas Production

“…The complexity of lipids extraction from algae is the limiting step of this process. Therefore, innovative methods are developed such are pressurized fluid extraction method (100) or in-situ transesterification of biomass into biodiesel (101,102). The pressurized fluid extraction method was successfully used for polyunsaturated fatty acids (PUFAs) extraction from Nannochloropsis oculata where the maximum fatty acid yield of 16.7…”

“…Furthermore, addition of co-solvent also causes the increase of saturated and monounsaturated methyl esters content and improves its stability (101,102).…”