Biodiesel is an alternative fuel made from renewable sources. Compared to petroleum, it burns cleanly and can be burned by itself or combined with diesel to make a biodiesel/petroleum blend. It is derived from feedstocks such as soybeans, corn and sugarcane.
There are several means of producing biodiesel, the batch model being most common. Supercritical processes, ultrasonic processes and even microwaves are used.
It is made from a process called transesterification, whereby glycerins are separated from vegetable oil, leaving two byproducts, methyl esters (biodiesel) and glycerin, which can be turned around and made into soap, if you’re crafty.
Biodiesel production uses alcohols to transesterify the oil. Common alcohols used in the process are methanol which makes methyl esters and ethanol, which produces ethyl esters. Isoproponol and butanol are sometimes used in the process. A process call lipid transesterification is then undergone, removing any lipids, or free fatty acids. This is where glycerin is removed. The free fatty acids can also be esterified further with acid, yielding more biodiesel. The finished product has a combustion rate similar to conventional diesel.
Rapeseed oil is sometimes used in the process, although virgin soybean oil accounts for the vast majority of biodiesel production in the United States. It is also possible to use fats such as tallow (animal fats, such as lard or chicken fat), or by-products of fish oil production. There are plans in the works to build a chicken-fat rendering biodiesel plant in southeastern Missouri, to collect the waste fat from a nearby Tyson chicken plant. Algae can be used, using sewage to grow it. Halophytes, plants that grow in barrier areas with high salinity can be used as well.
Currently, feedstocks comprising of plant matter and animal fats could not produce enough fuel to meet global demand. The caveat should be that any level of contribution that biofuels could make towards lessening fossil fuels’ immense impact on global climate change would be helpful, to say the least. And perhaps, through some level of conservation, people could use less fuels in the first place.
Biodiesel at face value has the ability to reduce greenhouse gas emissions and pollution. Where it becomes contentious is when the economics of using edible feedstocks to produce fuel are put up against the specter of global food insecurity. Demand for biodiesel was a major contributor to the global food crisis of 2008, which sparked riots all over the world. Second-generation biofuels, which use inedible feedstocks that are produced sustainably will help the green viability of biofuels and biodiesel.