What about fry grease for biodiesel? [Alan]

According to a study conducted in Thailand (where else??) comparing conventional biodiesel with re-purposed waste cooking conventional biodiesel results in 32.57 KG of CO2e per 100 km driven whereas the cooking oil produced 2.35 Kg of CO2e  a surprising 93% saving for the cooking . http://www.sciencedirect.com/science/article/pii/S0959652609000201.  Another analysis (in Asutralia) placed the same comparison at an 87% savings: https://www.sciencedaily.com/releases/2007/11/071127101930.htm

Apparently, biodiesel is 74% more efficient in terms of GHG emissions than petroleum diesel – because of engine efficiency

Here’s another assessment: https://www.consumerreports.org/cro/2012/05/diesel-vs-biodiesel-vs-vegetable-oil/index.htm

Comparing emissions

Our testing showed that emissions from the biofuels were the same or better than from regular diesel by most measures. None of the four fuels generated significant amounts of carbon monoxide. Cooking oil produced less smog-causing NOx than regular diesel, while our B100 produced a little more.

Hydrocarbons are related to smog formation. Cooking oil and B100 turned out to produce slightly more hydrocarbons than either regular diesel or B5. HC emissions reflecting unburned fuel and cooking oil racked up 14 parts per million and B100 put out nine ppm. B5 and regular diesel produced only 3 ppm each. Since the Connecticut limit on HC is 150 ppm, all far exceeded the requirements.

Particulates. Particulates are a concern with diesel engines. In Connecticut and some other states, particulate content (aka soot) is measured by the opacity (cloudiness) of the exhaust smoke. It’s expressed as a percentage, and the Connecticut state limit is 20 percent. All four fuels had a much lower percentage, though B100 and cooking oil produced less than the B5 and standard diesel.

NOx. Cooking oil had the lowest oxides of nitrogen emissions, while B100 had the highest.

CO2. Carbon dioxide is considered a major contributor to global warming, and CO2 emissions are the same no matter what liquid fuel an engine burns: about 19 pounds of CO2 for every gallon of fuel. But advocates claim that the CO2 from burning biofuels is offset by the plants absorbing carbon as they grow. Critics dispute that claim.

  Diesel Cooking oil B100 B5
Unburned hydrocarbons, ppm 3 14 9 3
Carbon monoxide, % 0 0.01 0 0
NOx, ppm 237 214 248 240
Particulates (opacity %) 2.9 1.6 1.1 2.4
City, mpg 20.1 20.8 22.3 22.6
Highway, mpg 44.9 42.1 44.2 48.5
0-30 mph, sec. 4.5 4.5 4.5 4.5
0-60 mph, sec. 15 14.9 14.5 14.2
1/4-mile, mph 69.9 70.3 71.3 72.2