Biofuels

What are biofuels?

Biofuels are fuels made from biomass. 

Examples: Bioethanol, Biodiesel, D-Limonene

How are some biofuels derived from biomass?
Below demonstrates how biodiesel and D-Limonene can be derived from biomass.
1. Biodiesel can be derived from vegetable oil. Biodiesel will first undergo hydrolysis to form 3 fatty acids and glycerol - a necessary step because vegetable oil molecules are 3 times as large as biodiesel molecules. Thereafter, transesterification occurs where the ester transforms into another and biodiesel is thus formed. 

Vegetable oil placed in beaker and onto hot plate for heating. Ethanol / KOH mixture was added to the beaker as it heated, at regular intervals of 5 minutes.

After 8 additions of the mixture, the resulting mixture was of the above shown colour. 

2. D-Limonene can be extracted from fruit peel through steam distillation. Since fruit peels are often discarded after consumption of the fruit, these fruit peels can be reused here instead.

Coloured parts of the orange peel were cut out and blended prior to steam distillation to prepare orange rind.

Orange rind then transferred to round-bottom flask at left of set up. A hot plate was initially used but changed to a bunsen burner, as shown above, which heated up the orange rind quicker. As the orange peel puree began to boil, liquid was collected in the conical flask at right of set up. 

Acetic acid was added to the liquid collected to increase separation of 2 layers. Contents of flask were then poured into a separating funnel, the funnel was inverted 5 times and the liquid was left to settle, as shown above. The orange oil rose to the top of the mixture while the water, which formed the bottom layer, was drained out.

The orange oil was collected into test tubes, placed in water baths, and removed of last remaining strains of water which sank to the bottom of the test tube, resulting in the figure as shown above.

All biodiesel was eventually collected in this conical flask.

What are the uses of biofuels?
1. Bioethanol can be used to power car engines.
2.  D-Limonene as an essential oil has many benefits e.g. anti-carcinogenic properties.

Why are biofuels considered to be a sustainable source of energy while fossil fuels are not?

In terms of the 12 principles of Green Chemistry,

	Biofuels	Fossil Fuels
1.	Biofuels prevent waste, which is better than to treat or clean up waste after it is formed. Biofuels are carbon neutral - though they give out carbon dioxide during combustion, carbon dioxide had also been taken in during photosynthesis by the plant of which the biofuel was derived from, achieving net zero carbon emissions.	On the other hand, fossil fuels do not prevent waste. When fossil fuels are burnt, the sulphur which it contains is converted to and released as sulphur dioxide gas. Sulphur dioxide is an acidic air pollutant that dissolves in rainwater to form sulphurous acid, contributing to acid rain.
2.	Biofuels makes use of a raw material which is renewable rather than a depleting one. Biofuels are made of living organisms, usually plants which can be grown e.g. D-Limonene can be extracted from orange fruit peel.	On the other hand, fossil fuels do not make use of a renewable raw material. Fossil fuels e.g. coal and oil are in fact depleting quickly today.