Biofuel is a renewable clean burning ethanol or methanol fuel made from grain or wood byproducts.

Can you explain how this works?

Only part of the reason petroleum products are an issue is because they are nonrenewable. The primary complaint is that their combustion produces CO~2~ (and other greenhouse gases like NOx).

Ethanol, methanol, and any other hydrocarbon that undergoes combustion produces CO~2~ (and other gases). That's how combustion works. For example, the combustion equation for methanol is: 2CH~3~OH + 3O~2~→2CO~2~ + 4H~2~O.

The only way around this while still performing combustion is by combusting hydrogen, where the combustion equation is simply: 2H~2~ + O~2~→2H~2~O.

Biofuel combustion still produce CO~2~, and I don't believe at a significantly different rate than petroleum combustion, even if it does have the added benefit of being renewable.[^1]

[^1]: Yes, this view is missing a few variables. For one, biofuel production itself can be less carbon-intensive than oil drilling and processing processes. Biofuels can also be used to "recycle" other carbon-containing (waste) material. That being said, combustion is still the largest problematic factor at play here.