Sunday, September 23, 2007

Inital Thoughts on the Carbon Balance of SVO

The phrase "emissions reductions" seems to be wholly misconstrued by a disturbingly large portion of biofuel advocates, critics, and average folks with limited information on the issue. Last month, during a forum on plant-based fuels at Burning Man, a representative from one unnamed biodiesel manufacturer stated plainly that "biodiesel is emissions free". When pressed, the speaker admitted uncertainty about the definition of "emissions free", and whether or not biodiesel fits that bill.

I can clear that up right now: anything the burns produces emissions. What the spokesperson was trying to say is that biodiesel may offer emissions reductions over regular diesel fuel. And this is true: biodiesel reduces the emissions of most pollutants by about 50% (see my biodiesel mythbuster for more detail).

That being said, it's always important to qualify statements about emissions reductions with the source of the fuel under discussion. Why? Because NET emissions are different for all of them. Just last Friday, researchers released a new study showing that ethanol made from most feedstocks, and biodiesel made from rapeseed (canola), actually increase net greenhouse gas emissions (via increases in Nitrous oxide - N2O).

That's quite a buildup to the purpose of my post: How does Straight-Vegetable-Oil fare in the battle to obtain the most significant GHG emissions reductions (I'll deal with other pollutants later)? Here are some initial thoughts on the issue.

SVO reduces net greenhouse gas (GHG) emissions (when compared to biodiesel) for the following reasons:

  • SVO is typically a recycled waste product collected from restaurant fryers. GHGs produced in cultivating, harvesting, and processing the feedstock shouldn't be counted since they would occur anyway.
  • SVO requires almost no processing or transport when compared to biodiesel. Oil, even used vegetable oil, must be transported to a biodiesel manufacturing facility, processed, shipped to a distributor, and then shipped to local retailers.
  • Here's an interesting tidbit that warrants further research: According to the Greasecar exhibit at this year's Burning Man, waste oil is typically picked up by chemical companies that ship it to China for processing. There, it's turned into pet food or cosmetic bases and shipped back to the United States. If this is true, using SVO domestically actually circumvents significant CO2 emissions and therefore is carbon negative. You could even call it a carbon sink.

While I can't substantiate this yet, I also don't have any reason to believe it's not true.

The moral of the story is this: any discussion about biodiesel/SVO pros and cons must take into account the specific oil source. The best answer is almost always 'it depends..."