Optimization and Production of Biodiesel from Spent Coffee Ground Oil Using Acid -Base Catalyzed Method
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Date
2019-06
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Abstract
In Ethiopia large amount of spent coffee ground are generated from various coffee houses,
restaurants and households a result of the high consumption of coffee. Until now, there are no
current profitable uses, and their adequate disposal constitutes a major environmental problem.
The aim of this study was optimization of reaction variables and production of biodiesel from
spent coffee ground oil using acid base catalyzed method. For this study, spent coffee grounds
were collected from different coffee houses, Addis Ababa. The collected spent coffee grounds
were dried in an oven at 105° C for 8 hours. The oil was extracted by applying a soxhlet
extraction using n-hexane and then extracted oil was converted to biodiesel using acid catalyzed
esterification followed by alkali-catalyzed transesterification. The physicochemical properties of
the extracted spent coffee ground oil were found to be oil yield (13.09%), density (898kg/m
),
kinematic viscosity at 40℃ (45.91 mm
3
/s), saponification value (192.5mgKOH/g oil), acid value
(12.2mg KOH/g),free fatty acid (FFA) (6.1%) ,iodine value (81.9 g I2/100g) and calorific
value(37.74MJ/kg). The FFA in the spent coffee ground oil was reduced from 6.1 to 0.69% with
6:1 molar ratio of methanol to oil in the presence of 3.5wt% sulfuric acid at 90min. For the
second step, an optimum biodiesel yield of 91.5% was obtained with 9:1 methanol to oil molar
ratio, 1.5% KOH catalyst and 90 min reaction time. The fatty acid methyl ester composition of
the biodiesel produced from SCG oil was done with using GC-MS and 17.65% of saturated and
82.5% unsaturated fatty acid methyl esters were identified. The physicochemical properties the
produced biodiesel were found to be density (870.3kg/m
2
), kinematic viscosity at 40℃ (4.13
mm
3
2
/s), flash point (162℃) ,calorific value(40.39KJ/kg), cetane number(57.4), acid value (0.65
mg KOH/g and iodine value (178.5 g iodine/g). The results indicated that the properties of
biodiesel produced agree with the limit ASTM D6751and EN 14214 standard. Therefore, the
studied physicochemical properties of the waste coffee biodiesel suggest that this fuel can be
used as a fuel in diesel engines.
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Keywords
Spent coffee ground, Biodiesel, Optimization, Esterification, Transesterification