BIOFUELS

What are Biofuels?

fuel sourced from organic matter

What happens to glucose made in photosynthesis?

- Converted into cellulose and starch
- Helps forms plant biomass

Why are biofuels considered potentially carbon neutral?

- Plants absorb CO2 during growth which roughly equals the released CO2 when burnt

What is Biogas

- gaseous fuel produced by the anaerobic breakdown of organic matter
- mostly used for electricity generation

What is Bioethanol?

fuel produced by the fermentation of glucose in organic matter by the microorganism yeast

What is Biodiesel?

fuel produced by the transesterification of triglycerides with an alcohol, forming biodiesel and glycerol

How is biodiesel formed

transesterification that takes triglycerides and an alcohol, turning them into fatty acid esters and glycerol

What is a Triglyceride

fat or oil composed of three fatty acid tails and a glycerol backbone

What are the three main bioethanol feedstocks in Australia?

- sugar cane (high in sucrose)
- wheat (high in starch)
- forest waste (high in cellulose)

Difference between sucrose, starch & cellulose in bioethanol production

- Sucrose: already fermentable, direct fermentation by yeast, fastest and simplest processing
- Starch: polysaccharide of glucose that must be enzymatically hydrolysed into glucose before fermentation
- Cellulose: structural polysaccharide, requires pre-treatment + hydrolysis to release glucose. Slowest + most energy intensive processing

Why is distillation needed for bioethanol?

- Fermentation produces around 10% v/v ethanol
- Ethanol must be separated from water

How does distillation separate ethanol and water?

- Solution is heated so liquids vaporise
- Ethanol vaporises first while water remains in lower column
- Ethanol vapour collected + condensed into liquid ethanol

Equation for Photosynthesis

6CO2 (g) + 6H2O (l) → 6O2(g) + C6H12O6 (aq)

Equation for fermentation of glucose (35°C) (production of bioethanol)

C6H12O6(aq) → 2CH3CH2OH (aq) + 2CO2 (g)

What is Biogas made up of?

mostly methane, some carbon dioxide and a mix of other gases

Production of Bioethanol

C6H12O6 → 2CH3CH2OH (ethanol) + 2CO2(g)

Define sustainable

meeting the needs of the present without compromising the ability of future generations to meet their own needs

biogas vs natural gas

- The energy released per gram of biogas is less than that of natural gas because the methane content in biogas is significantly lower