Page 160 - Materials Chemistry, Second Edition

148 A. Singh and S. I. Olsen

found that FPPBR is the most advantageous system compared to others with lesser
limitations. Wegeberg and Felby (2010) from University of Copenhagen in a
report made for DONG Energy also stated that FPPBR is the most suitable pho-
tobioreactor for Danish conditions. The size of bioreactor considered was
2.5 9 1.5 9 0.07 m, similar to Brentner et al. (Brentner et al. (2011)), 90 %
volume of the reactor was considered as working volume, and 1.5 m distance
between one row of FPPBR and another was considered.

2.1.2 Cultivation

The seawater and CO 2 from cement industry were considered for cultivation of
algae. The transportation of seawater and CO 2 was deemed by pipelines. Nitrogen
and phosphorus were supplied by ammonium nitrate and monocalcium phosphate,
respectively. Transport of material (100 km) to the field was considered by 40 t
truck, and electricity was supplied from the grid. The productivity of Nanno-
chloropsis sp. was reported in the range of 0.24–1.7 g/l/d (Jorquera et al. 2010;
Chiu et al. 2009; Richmond and Cheng-Wu 2001; Zou and Richmond 1990;
Zittelli et al. 1999). Biomass productivity in this study was considered as 0.73 g/l/
d, lower than the average of the range of biomass productivity (0.97 g/l/d) and
similar to outdoor productivity (0.73 g/l/d) reported by Zittelli et al. (1999).

2.1.3 Harvesting

Harvesting of algal biomass was considered by three different techniques, i.e.,
centrifugation, flocculation with lime, and flocculation with aluminum, in different
scenarios. The efficiency of all techniques was assumed to be 95 %, similar to
Brentner et al. (2011). Grid electricity was taken for electricity supply.

2.1.4 Oil Extraction and Trans-esterification

Oil extraction from algal biomass is the least developed area in the algal biodiesel
production technology. In the present study, the biodiesel conversion from the
biomass was considered by two different techniques. One was pressing followed
by solvent extraction (using recovered and recycled hexane), followed by trans-
esterification. Another technique was supercritical CO 2 (sCO 2 ) extraction, which
avoids the use of organic solvents, followed by trans-esterification. Danish average
grid electricity and district heat were used to supply electricity and heat. Oil
content of Nannochloropsis sp. was reported in the range of 20–60 % dry mass
basis (Sierra et al. 2008; Rodolfi et al. 2009; Chiu et al. 2009; Jorquera et al.,
2010). 29.6 % oil content was considered in this study because most of the
researcher reported the same (Jorquera et al. 2010; Chiu et al. 2009; Sierra et al.
2008).