Making Biodiesel from Everyday Cooking Products

The combustion of petroleum accounts for almost half of the CO2 emissions in the U.S. Many alternative energy sources can help reduce CO2 and other greenhouse gas emissions such as solar energy, wind energy, wave, energy, nuclear energy, but these energy sources aren’t very compatible with a major user of fossil fuels, combustions engines. These engines are used every day in agriculture, air travel, sea travel, and for the transportation of people and resources. The most accessible, implementable, and practical replacement for petroleum is biodiesel or biofuel. In our Environmental Chemistry lab, we were able to produce a batch of biodiesel using waste oil from La Paloma cafe on campus and tested toxicity to radish seeds, fatty acid/methyl ester content, and heats of combustion. Other students were using various other oils such as soybean oil, vegetable oil, and olive oil to make biodiesel and test its properties. In this lab we found that olive oil released the most heat upon combustion and soybean oil was found to have the highest fatty acid content. Overall heat of combustion, fatty acid content, and germination success in radishes were greater with the biofuels than with fuels like USD diesel, ethanol, and methanol.

The schematic below summarizes the process we used to make the biofuel. Oils, animal and plant, are composed of three long strips of fatty acids attached to a glycerol molecule. The fatty acids vary in length and the way they are put together. Through a series of chemical reactions, these chains can be separated and what you are left with is biodiesel and glycerol, the latter which you can burn or use to make soap. It is difficult to make good biodiesel from the edible oils we used in class because there may be impurities that can affect the quality of the biodiesel as a combustible fuel. Essentially the idea is to harness the carbon-carbon bonds stored as these fats because when you burn them, energy is released.

Fossil fuels are made up of different forms of carbon but they are not able to be reproduced in a short amount of time, which is one reason why biofuels are of interest to a society that is heavily dependant on the energy stored in these carbon-carbon bonds. Along with being non-renewable, biofuels are also thought to have a much lower net production of CO2 into the atmosphere which is a large player in climate change. Since biofuels would mainly come from plants, CO2 would actually be removed from the air by the plants being grown for biofuels. Although CO2 is released when biofuels are burned, the CO2 being taken in by the biofuel crops offsets the CO2 released when burned. Other important aspects of biofuels that are essential to focus on is the amount of energy released and toxicity of the fuel. Since petroleum based diesel is energy dense and efficient it is important to choose a source of biodiesel that can compare with these competitive factors. Just as we did in this lab, many tests need to be done in order to choose the best biofuel feedstock that could replace diesel in the future.

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