Ethanol environmental effects can be summarized as follows:

• Pure ethanol is nontoxic and biodegradable.
• When ethanol degrades it breaks down into harmless substances.
• When used as a fuel or fuel additive, ethanol burns more cleanly than pure gasoline.
• Ethanol emits CO2 when burned, but it is a considered carbon-neutral burning, because the plants used in generating ethanol absorb an equivalent amount of CO2 in the course of photosynthesis.
• Raising crops like corn to generate ethanol for fuels decreases the land available for growing food. This diminishes food crops and puts pressure on the poor, who must pay more for the crops that are grown for food.

The environmental effects of biodiesel can be summarized as follows:

• Biodiesel is nontoxic and biodegradable.
• Biodiesel contains fewer contaminants than does petroleum diesel, so when it burns it does not emit as many pollutants.
• Biodiesel is carbon-neutral when burned, since the plants from which it was produced used CO2 in about the same quantity as that released in the burning of biodiesel.
• Biodiesel is sometimes produced from crops grown on land cleared and burned for the purpose of growing biodiesel-producing crops. This can have a significantly negative effect on the people and ecosystems in that area.

The environmental impact of using biomass is mixed in its good and bad effects. Burning crops such as wood or switch grass is simply a recycling of CO2. It has a net zero effect on the presence of most greenhouse gases. On the other hand, burning such products can produce smoke with pollutants that can cause harm. Also, if the growth of vegetation, such as wood, cannot keep pace with the use of it as a fuel, then depletion of the vegetation (e.g. deforestation) can produce considerably negative impacts on the local population.

Burning animal or human waste in disposal plants can result in the release of chemicals hazardous to both local people and the environment in general. These types of problems can be solved, but only by installing and maintaining expensive removal processes for the hazardous compounds emitted in the smoke from the burning or the ash remains of the combustion process.