Page 138 - Advances in Eco-Fuels for a Sustainable Environment

Prospective ecofuel feedstocks for sustainable production 109

4.2.5.5 Leather industry solid waste fat

In the leather industry during various processes such as prefleshing, lime fleshing,
shaving, buffing, and trimming, the waste generated forms the source of solid fat.
The water content in the fat is high and at room temperature it is solid. The water con-
tent in the fat is removed by heating to 110°C for 1h followed by filtration to remove
the insoluble material [62].

4.2.6 Algae as feedstock for ecofuels
Both macroalgae and microalgae are the best feedstocks for biodiesel production but
microalgae are easier and faster to grow and have more oil than macroalgae. Thus,
microalgae are considered the best feedstock for the production of biodiesel. The lipid
content in macroalgae is less than the lipid content in microalgae [12]. Microalgae are
photosynthetic and microscopic in nature. Macroalgae are most commonly found in
coastal areas and are commonly known as seaweed. They are classified into brown
seaweed (Phaeophyceae), green seaweed (Chlorophyceae), and red seaweed
(Rhodophyceae) based on their pigmentation. Many photosynthetic microalgae are
unicellular [73]. Microalgae contain several kinds of extractable lipids. The lipid con-
tent varies from 1% to 84% of the dry cell weight in different species of algae [74].

4.2.6.1 Microalgae as feedstock for biodiesel
Microalgae form the viable biodiesel feedstock. They can be found in soils, ice, lakes,
rivers, hot springs, and oceans, anywhere sunlight and water cooccur. They have a
simple cellular structure and are a diverse group of photosynthetic eukaryotes ranging
from unicellular to multicellular forms. The oil yield from microalgae per hectare is
more than some of the feedstocks used for the production of biodiesel. Almost
587,000L of oil per hectare can be obtained from microalgae containing 30% oil
by weight of dry biomass. In some of the microalgae species such as Botryococcus
braunii and Schizochytrium sp., the oil content can be upto 70% and by employing
these algae as feedstock, the biodiesel productivity could reach 121,104 kg/ha per
year. Microalgae can double their biomass in a day and can grow rapidly, aside from
their higher oil yields. Microalgae can also assimilate CO 2 from the atmosphere, thus
contributing to atmospheric CO 2 mitigation and high production of biomass [75].
Chen et al. [76] carried out the work of conversion of algal oil from three different
algal species and the maximum methyl ester yield of 78.3% and 56.2% from
Scenedesmus sp. cultured for seven and 14days, respectively. After degumming,
70.4% from Nannochloropsis sp. and 90.1% from Dinoflagellate were obtained
for a methanol to oil molar ratio of 12:1 at a reaction temperature of 65°C in a reaction
time of 30min using 2% KOH as catalyst. Some of the properties observed for
biodiesel produced from Scenedesmus sp., Nannochloropsis sp., and Dinoflagellate
include viscosity of 4.15, 5.76, and 3.74; an acid value of 0.52, 0.46, and
0.44mgKOH/g, and a calorific value of 39.76, 39.81, and 39.84MJ/kg for