Biodiesel

October 4, 2007 in biodiesel, chemistry, environment, green chemistry, science, science and society, sustainability
Tags: biodiesel, biofuels, energy vs. food, ethanol, fishing industry, food, Jane Goodall, olive oil, peanut oil, rain forest, straight vegetable oil, SVO

There are good and bad sides to biofuels, as Jane Goodall points out. I will explore this in detail in a series of articles that express my opinion and cite scientific reports or discussions. First, a bullet-point summary of key points is given below.

Much of the good/bad duality of biofuels has to do with the following questions:

• where do the biofuels come from?
• what are we destroying in order to generate biofuels?
• what are we consuming in order to generate biofuels?
• what are we failing to produce in order to generate biofuels?
  • maybe we are destroying or giving up nothing
  • maybe we are neglecting food production
  • maybe we are neglecting crop rotation
  • maybe we are destroying the rain forest
  • maybe we are consuming large amounts of fertilizer and/or pesticides

• Many (most) of the crops being planted for biofuels are destined to generate biodiesel, not bioethanol.
• Some plants grown for fuel are intended to produce a type of diesel called straight vegetable oil (SVO).
  • SVOs contain a number of impurities, at least as far as fuel oil is concerned. Even water is an impurity here.
  • Just as an example, you only have to press the oil out of the olives to remove it.
  • Peanut oil and practical coconut oil can be also be collected mechanically, like pressing olives.

• SVO can be used in a compatible diesel engine.
• The properties of SVO, such as the high viscosity of soybean oil, or the impurities in SVO, may cause problems.
  • There is dispute about the effects of SVO on engine wear and the relative value of SVO and biodiesel.
• Waste vegetable oil (WVO), typically used cooking oil, is another impure oil that can be used as liquid fuel.

• Biodiesel is more pure than SVO or WVO (if made properly). It is made by chemically splitting animal fat or vegetable oil into two parts, followed by purification.
• The standard chemical reaction to make biodiesel uses alcohol (methanol or ethanol) and a catalyst.
• This reaction, called transesterification, generates fatty acid esters and the byproduct known as glycerol.
• One example that seems to me to have little or no downside is the generation of biodiesel from fish oil:
  • Fish oil is already generated by the fishing industry.
  • Fish oil is potential waste that already exists and may not be used as efficiently as possible.
  • Fish oil conversion to biodiesel still needs to be pushed forward by invention and commercial development.
• Another example of a method that exhibits great potential is the conversion of all of a plant’s dried matter (known as biomass) into biodiesel:
  • Plant oils are only about 10% of total plant biomass in most cases
  • Using all the biomass to generate biodiesel captures much more of the value of a plant, and the energy that went into growing it, than using only plant oil does
  • Cellulose and lignins are components of typical biomass and are hard to convert into liquid fuel, compared to oils

© James K. Bashkin, 2007

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