Moisture Absorption in Biodiesel and its Petro-Diesel Blends

Abstract

Biodiesel has the characteristic of absorbing more moisture than petroleum diesel. High moisture content in biodiesel can cause problems such as water accumulation and microbial growth in fuel handling, storage, and transportation equipment. Currently, there is a lack of information on moisture absorbance in biodiesel and biodiesel/diesel blends. Experiments were conducted to determine the water absorbance in biodiesel of different feedstocks (three vegetable oils and two primary alcohols) at three temperatures. The effects of temperature and blending levels were explored through a central composite experimental design. Dynamic moisture absorption was studied at three constant relative humidities. Petroleum diesel was used as a reference. It was found that there were no significant differences in moisture absorbence among the biodiesel samples of different origins at given temperatures. Saturation moisture in biodiesel ranged from 0.10 to 0.17%wt in the temperature range of 4C to 35C, which was 15 to 25 times higher than that of diesel. Results also showed that in biodiesel/diesel blends, both temperature and level of blending affected the moisture absorbence. Moisture content of the blends was not a simple addition of the two moisture contents of biodiesel and petro-diesel. Blending created a mixture that had a lower capacity for moisture absorption.