Ethanol can be produced from crude oil by hydrating ethene, which is derived from the cracking of crude oil. The hydration of ethene requires steam at 300°C, a pressure of 60 atm, and a phosphoric(V) acid catalyst.

Glucose undergoes fermentation by yeast to produce ethanol and carbon dioxide. The ethanol is then separated and purified using fractional distillation.

1. Addition of yeast because it produces an enzyme needed to break down glucose.
2. Temperature of 30-40°C to optimise enzyme activity i.e. rate of reaction.
3. Anaerobic conditions (absence of oxygen) to prevent oxidation of ethanol to ethanoic acid.

C₆H₁₂O_6(aq) ➔ 2C₂H₅OH_(aq) + 2CO_2(g)

A biofuel is a renewable fuel derived or produced from biological sources, such as plants, algae, or organic waste materials.

Ethanol made in this way is called bioethanol.

6H₂O + 6CO₂ ➔ C₆H₁₂O₆ + 6O₂

Bioethanol is not completely carbon-neutral because there are other carbon costs associated with its production, such as the energy used in transportation, processing and crop cultivation.

C₂H_4(g) + H₂O_(g) ➔ C₂H₅OH_(l)

C₂H₅OH + 3O₂ ➔ 2CO₂ + 3H₂O

Bioethanol is considered carbon-neutral because the CO₂ released during the fermentation of glucose and the combustion of bioethanol is balanced by the CO₂ absorbed by the plant during photosynthesis.

1. Vehicle compatibility - Vehicles may need modifications to their engines to run efficiently on fuels with higher ethanol content.
2. Land use competition - Dedicating agricultural land to grow crops for bioethanol production can lead to reduced land availability for food production.

1. Sustainability - Bioethanol is derived from renewable resources, such as crops that can be continuously grown and harvested.
2. Reduced carbon footprint - The CO₂ absorbed by the crops during growth can partially offset the emissions released when bioethanol is used as a fuel.