Science & Technology in Action

3rd Edition

Biofuels — Alternative Energy


A blend of bio-esters and diesel fuel is known as bio-diesel and at 5% concentration it can be used in conventional diesel engines without modification.

Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

With increasing pressure being placed on our non-renewablesources of energy, focus has been placed on developing alternative renewable sources of energy. Biofuel is any fuel produced from renewable biological sources such as food crops or biological wastes. The term is generally applied to fuel that is used to power motor vehicles.
Biofuels are not new. When Rudolf Diesel introduced his new engine at the World’s Fair in 1900 he made a point of running it on peanut oil, but that was superseded by the cheaper petroleum-based product. When Henry Ford introduced his Model T in 1908 it could run on either petrol or alcohol. It was in fact designed to run on alcohol but once again cost became the deciding factor and has remained so until recently.

Types of biofuels
Biofuels are generally classified as either first or second generation.

First Generation biofuels are those that are made from food crops. The most significant of these are ethanol and bio-diesel.

  1. Ethanol is produced by fermentation of wheat, sugar beet, sugar cane etc.
  2. Bio-diesel contains bio-esters which are produced from rape-seed oil, recovered vegetable oil (e.g. used oil from deep-fat fryers) and tallow (animal fat)

Second Generation biofuels are made from biomass residuessuch as woodchips and straw (agricultural and forestry waste). These fuels will not be available in commercial quantities for some years.  Other second generation biofuels are:

  1. Methane
  2. Methanol
  3. Dimethyl ether
  4. Hydrogen

In Ireland and in Europe generally, work on alternative fuels has mainly focused on biofuels that can be blended in low concentration (5% – 10%) with existing fuels and which require no vehicle modifications. Vehicle modifications are generally necessary if higher biofuel blends are used.

Quiz questions

  1. Biofuels have been in use for a hundred years or more true
  2. First generation biofuels are made from food crops. true
  3. Biofuels are non-renewable false
  4. Biofuels contain relatively high levels of sulphur. false
  5. Biofuels are less expensive than petrochemical fuels. false
  6. Biofuels may lead to a reduction in biodiversity. true
  7. Biodiesel is a blend of bio-esters and diesel oil. true
  8. Biodiesel reduces CO2 emissions. true
  9. Methane is a second generation biofuel. true
  10. Biofuels will totally replace petrochemical fuels within the next decade. false