Biomedical Engineering Reference
In-Depth Information
HDPE consisted of a wide spectrum of hydrocarbons, including saturated and unsat-
urated aliphatic hydrocarbons. The bio-oil component obtained from the mixture of
Spirulina and HDPE possessed more hydrocarbons and less oxygen-containing com-
pounds. Hence, the product of the co-liquefaction of Spirulina and HDPE was similar
in nature to that of pure HDPE liquefaction with a lower reaction temperature needed
for thermal degradation of the feedstock. Hu et  al. (2012) utilized the microwave-
assisted pyrolysis of Chlorella vulgaris for the production of bio-oil with a yield of
35.83 and 74.93 wt% using microwave powers of 1,500 and 2,250 W, respectively.
It was found that using activated carbon as a catalyst could enhance the bio-fuel
yield to 87.47%. The calorific value of the microalgae was determined to be low
(21.88 MJ kg −1 ).
Tabernero et  al. (2012) evaluated the industrial potential for production of bio-
diesel from Chlorella protothecoides . It has been estimated that supercritical fluid
extraction (supercritical CO 2 ) for biomass covering a surface area of 7,500 m 2
could generate 10,000 tonnes biodiesel per year in a 150-m 3 bioreactor. Lohrey and
Kochergin (2012), in an attempt to minimize the energy consumption of algal bio-
fuels, suggested locating a biodiesel plant close to a sugar mill plant to complement
one another. It has been estimated that a cane sugar mill that discards 15% excess
bagasse of 10,000 tonnes-per-day capacity can support a 530-ha algae farm to pro-
duce 5.8 million L biodiesel per year and will also reduce CO 2 emissions from the
mills by 15%. The input in parameters of CO 2 , energy, and water are estimated at 2.5
kg kg −1 , 3.4 kW-h kg −1 , and 1.9 L kg −1 , respectively, of algae dry weight.
The fatty acid composition of feedstock plays a significant role in the quality
of the biodiesel produced. The European Standard (EN 14214) has limited the
linolenic acid (C18:3) content, to not more than 12%. Wu et  al. (2012) studied
Chlamydomonas   sp. as a  potential feedstock for the synthesis of biodiesel. It was
found that Chlamydomonas   sp. possessed linolenic acid less than 12% and an
oleic acid (a  monounsaturated fatty acid) constituent of 31.6%. The almost equal
compositions of saturated and unsaturated fatty acids in Chlamydomonas sp. are
desirable for a trade-off between the oxidation stability and low-temperature prop-
erty of the biodiesel. The FAME (fatty acid methyl ester) content in biodiesel was
found to be 25% of total volatile suspended solids from microalgae cultivated using
municipal wastewater (Li et  al., 2011). Although the ester content in the biodiesel
was low, the utilization of microalgae for the production of lipids coupled with
wastewater treatment has environmental and economic significance. Upon increas-
ing the ester content in the biodiesel by improving the technology, the process will
become far more attractive. Lam and Lee (2012) are of the opinion that biodiesel
production will be the ideal product with microalgae as feedstock. To ensure cost
effectiveness, the residual biomass after lipid extraction can contain high concentra-
tions of carbohydrates, which should be further utilized for bio-oil and bio-ethanol
production. Table  8.1 depicts the  ester content and calorific value of the biofuels
(biodiesel and bio-oil).
A unique method of thermal analysis to differentiate the oleaginous and non-
oleaginous microorganisms (fungi, algae, and yeasts) was developed by Kang et al.
(2011). Along with the synthesis of biodiesel, algal biomass residue can be used for
other purposes. A linear relationship was observed between exothermic heat and
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