Abstract
The dry washing method is an alternative to replace water washing, thereby reducing the negative impacts of contamination. However, commercial adsorbents come from industrial processes that, due to their composition, may not be such a sustainable resource in the global biodiesel production process. In this study, the use of organic residues, such as sawdust, coconut fiber, nutshell, rice husk, and water hyacinth fiber, were proposed as bioadsorbents for the purification of biodiesel from waste cooking oil. Quality parameters such as the acid number, water content, and free and total glycerin content were evaluated and compared with those after purification with commercial adsorbents (Magnesol and Amberlite BD10DRY). Promising results were obtained using sawdust in the purification process, achieving a reduction in the acid number value of 31.3% respect to the unpurified biodiesel. Indeed, the reduction with sawdust was more efficient than with Amberlite BD10DRY (that increased the acid number). In addition, sawdust reduced free glycerin by 54.8%, again more efficient than Amberlite BD10DRY. The total glycerin values were similar between commercial adsorbents and sawdust. Water content after purification with sawdust was similar to the obtained with Amberlite BD10DRY and better than with Magnesol (399, 417, and 663 mg/kg respectively). These results show that sawdust can be used as an alternative bioadsorbent in a dry purification method for biodiesel, generating less environmental impact.
Highlights
This article aims to (a) evaluate the efficiency of sawdust, coconut coir, nutshell, rice husk, and water hyacinth fiber in the removal of free and total glycerin, water, and acid number from biodiesel derived from waste cooking oil (WCO), and (b) to compare them with conventional purification methods, such as using Magnesol, Amberlite BD10DRY, and water washing
Among the bioadsorbents that reduced the acid number to levels below those established in the ASTM standard are water hyacinth fiber, rice husk, sawdust, and coconut coir
The use of some of the bioadsorbents even proved to be more efficient than conventional methods, demonstrating their ability to remove free fatty acids associated with a high acid number
Summary
The high dependence on fossil fuels for industrial, transportation and domestic purposes has led to research on alternative energy sources [3]. Biodiesel is an alternative to petrodiesel with the aim to mitigate the problem of fossil fuel depletion and environmental impact [4]. The main raw materials are vegetable oils or animal fats, which are transformed into fatty acid methyl ester (FAME) through the transesterification process [3,4]. This method involves the conversion of triacylglycerides into methyl esters (methanol) or ethyl esters (ethanol) in the presence of a catalyst [4,5]. The biodegradability, low cost, and high availability of biodiesel if it is produced from waste cooking oil (WCO) are additional benefits [4,6]
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