Beyond the Basics: Key Factors That Maximize Biodiesel Yield
Table of Contents
Introduction
Creating high-quality biodiesel isn’t as simple as just mixing oil and alcohol. It’s a precise chemical balancing act where every variable matters. Achieving a high yield efficiently and cost-effectively requires a deep understanding of the core factors that drive the transesterification reaction forward. This scientific excerpt from Dr. Abdul Haq’s research illuminates the critical parameters that every biofuel engineer must master.
From the exact ratio of alcohol to oil, to the precise reaction time and temperature, this detailed analysis reveals how controlling these variables is the key to unlocking the full potential of feedstocks like Jatropha curcas and making biodiesel a truly competitive green fuel.
Excerpt
“The efficiency of biodiesel process depends upon certain variables such as molar ratio of alcohol to oil, reaction time, catalyst concentration and agitation.
Alcohol to triglycerides molar ratio play an important role in biodiesel production. The stoichiometric ratio of alcohol to triglycerides is 3:1 for biodiesel production, but practically an excess of alcohol is needed to carry out the reaction in forward direction and reduce the chances of evaporation of alcohols.
In most of the previous reports, a molar ratio of alcohol to oil (6:1) has been determined to be the optimum ratio for biodiesel production. If the molar ratio alcohol to oil is increased than the optimum ratio (6:1), it does not increase the yield, rather cost of the process is increased. However, higher molar ratios of alcohol to oil up to 15:1 are required for the feedstocks having higher concentration of free fatty acids, especially in case of acid catalysts (Yaakob et al., 2013).
The conversion of triglycerides into esters also depends upon the reaction time. Initially, the reaction proceeds slowly due to the mixing and dispersion of alcohols in fats/oils. Later on, the reaction rate is increased reaching maximum at optimum reaction time.
It has been reported that the biodiesel yield reaches maximum at reaction time ≤ 90 min and increasing time beyond this limit did not improve the esters yield (Alamu et al., 2007).
Moreover, the increase in reaction time beyond the optimum range reduce the product yield, ultimately leading to esters loss and formation of FFA to form more soap (Yaakob et al., 2013, Eevera et al., 2009).
The transesterification reaction temperature also influence the biodiesel yield. The increase in temperature reduces the viscosity of oil and also the reaction time.
However, if the reaction temperature is increased beyond the optimum range, it will lead to the formation of soap. The temperature must not be increased than the boiling point of alcohol because it will lead to rapid alcohol evaporation.
Normally, the optimum temperature for biodiesel production ranges from 50 to 60 °C depending upon the type of oil (Leung and Guo, 2006, Ma and Hanna, 1999).
The catalyst concentration plays an important role in increasing the esters yield. An increased amount of catalyst is required for an efficient biodiesel production process.
However, if the catalyst is increased beyond its optimum limit, further addition will lead to the formation of soap resulting in esters loss and higher cost of the process.
A number of studies had reported 1.5% as an optimum catalyst concentration for an increased biodiesel yield (Eevera et al., 2009, Leung and Guo, 2006).
As the J. curcas seed oil has higher potential for biodiesel production that has been discussed earlier. The J. curcas seed also has higher potential for biogas production which is discussed below.
Biogas is a mixture of different gases produced by anaerobic and facultative anaerobic bacteria in the absence of oxygen. Crude biogas is composed of different gases such as CH₄ (40-75%), CO₂ (15-60%), H₂S (0.005-2%) and other trace gases including N₂ (0-2%), water vapors (5-10%), CO (< 0.6%), etc. (Ryckebosch et al., 2011).
J. curcas seed cake has been used in a number of studies for biogas production. Jatropha seed were reported to yield about 60% more biogas than cow dung.
The previous literature showed that J. curcas produced 355 L biogas per kg of seed cake with a 70% methane content (Raheman and Mondal, 2012). Similarly, the biogas produced by J. curcas seed cake codigested with paddy straw corresponding to C/N ratio (27:1) was 10.5% higher than monodigestion of seed cake (Raheman and Mondal, 2012).
In another study, it was reported that the biogas yield of J. curcas seed cake was 30.7% higher at 10% TS than 15% TS (Singh et al., 2008). A number of technologies are used for biogas production from agricultural residues and waste materials. However, anaerobic digestion is one of the most commonly used process for biogas production.”
Source Citation
Researcher’s full name: Abdul Haq
Guide(s): Dr. Malik Badshah
University: Quaid-i-Azam University, Islamabad
Completed Date: 2020
Excerpt Page Numbers: 47, 48
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