Page 78 - Materials Chemistry, Second Edition

Life Cycle Assessment of Beneficial Reuse of Waste Streams 59

process includes heat for keeping the reaction at 60°C for 30 min, power for
mixing, and power for the rotary evaporator to remove methanol.
5. Glycerol wash: Extra glycerol was added to the mixture oil to separate
FAME from glycerol, catalysts, and impurities. Based on the experiment
conducted, the best conditions are an added glycerol-to-oil mixture ratio of
1:2 by weight, mixed at 60°C for 15 min. Then, the upper layer is collected
for further upgrading. The collected FAME is 92.6 wt.% of the total oil
input of the process. The lower layer is sent to the glycerol recycling pro-
cess. The energy use for this process is heat for evaporating methanol and
power for mixing.
6. Distillation: The FAME mixture from the glycerol wash is introduced into
a customized vacuum rectification column system, and finally, biodiesel is
obtained. The biodiesel yield in this process is 88.2 wt.% of FAME input.
−1
The heat used in distillation is 2.51 MJ kg biodiesel, and the power used
−1
for the vacuum is 0.045 kWh kg biodiesel, which is based on industrial
data.
7. Methanol and glycerol recycling: Two additional processes are added to
recycle extra methanol and glycerol. Extra methanol applied in acid esterifi-
cation and base transesterification can be recycled for use in the next batch.
A rotary evaporator is used after acid and base esterification to separate
excess methanol out. The energy use in the rotary evaporator is 1.1 MJ
kg methanol, which is based on theoretical heat for methanol evaporation.
−1
A distillation process will be used to recover the glycerol to a technical
grade. Energy use will be electricity and heat for distilling glycerol (10%
of oil weight). The extra glycerol produced in the process will be used as
carbon resources for algae production if mounted in the plant.
The LCA and technical economic analysis (TEA) tools were used to
evaluate the Scum-to-Biodiesel technology and compare it with incinera-
tion and anaerobic digestion (Mu et al., 2016). The energy conversion effi-
ciency of the Scum-to-Biodiesel technology was found to be 60%, which is
much higher than for conventional methods of scum treatment (digestion
5% and combustion 33%). The LCA concluded that the Scum-to-Biodiesel
technology has lower fossil fuel depletion, GHG emissions, and eutrophica-
tion potential compared with combustion and digestion. The TEA showed
that the Scum-to-Biodiesel process has the greatest financial potential,
while the incineration of scum yielded the largest potential of reclaimed
energy. Altogether, the Scum-to-Biodiesel technology can achieve higher
revenue and significant environmental benefits when compared with scum
digestion and combustion processes (Mu et al., 2016).

4.3.4 algae culTivaTion anD algal biofuel
proDucTion froM liQuiD WasTe sTreaMs
Recently, algal biofuels have gained popularity among the scientific community,
showing promise as a sustainable energy alternative (Menetrez, 2012). Microalgae
have been proposed as a biomass feedstock for producing transportation fuels due