Combating Climate Change

truck Used oil from kitchens can help protect the climate through biofuel programs like SFGreasecycle. Every gallon of waste vegetable oil “greasecycled” into biodiesel displaces a gallon of petroleum diesel, which equals to 17.3 lbs net reduction of carbon emissions.

Every gallon of burned diesel fuel emits 22.2 lbs of carbon dioxide.

When diesel, which contains carbon, is ignited in the presence of oxygen—which is what happens when we drive a diesel vehicle—the carbon atoms bond with two oxygen atoms to form CO₂. The additional oxygen atoms add the additional weight.

The density of diesel is approx. ~7.1 lb/gal and is nearly all carbon. By adding two heavy oxygen atoms to form CO₂, the weight is nearly tripled. Therefore, five gallons of burned diesel fuel emit 111 lbs of CO₂ (22.2 lbs x 5 gallons).

This is also true for biodiesel, except that the vegetable crops used to produce this oil absorb CO₂ out of the atmosphere, offsetting 78% of the carbon emissions. That’s net CO₂ reduction. Meaning, biodiesel still produces CO₂ at the tailpipe. But in the “life cycle” of the fuel, the crops grown to produce the fuel will consume 78% of the CO₂.

As a result, 78% of 111 is 86.6 lbs of CO₂ not invading the atmosphere.

Apart from this fairly simple calculation, biodiesel displaces imported petroleum, as a renewable alternative fuel. Biodiesel itself is non-toxic, non-flammable and non-volatile, making it safer to handle & store. It contains little sulfur that causes acid rain and adds desertification and no aromatics that mutate cells and cause cancer (except maybe the smell of French fries!).

From what was once a great liability as “pollutant of concern,” FOG (fats, oil and grease) is now evolving into an asset: a renewable energy source, supplying alternative, clean-burning fuels, helping combat climate change.

“Biodiesel provides a life cycle emissions reduction of 78% compared to petro-diesel. When carbon (with Molecular weight of 12) and hydrogen based fuel is burned (whether that is in an engine or otherwise) it combines with oxygen (molecular weight of 16) to make CO₂ and water (H₂O). So, CO₂ (weight 44) is more than 3 times the weight of carbon (12).

“However, that is only part of the explanation. Most people don’t realize that almost all the material given off by any vehicle is CO₂ and water—the regulated emissions are only a very small fraction of the gases coming out the back of a tailpipe. For example, if the particulates coming out of the back of an engines measure 0.1 grams, the CO₂ would measure around 650 grams. So when you combine these factors—and the fact that biodiesel takes up CO₂ when it is produced and provides a 78% life cycle reduction in CO₂—that is why the CO₂ reductions for biodiesel are so large.”

- From the National Biodiesel Board