Council for Sustainability and Eco Practices at SCAD

Biodiesel is often touted as a green alternative to gasoline. I was curious how green it really is, so I did a little investigating. This article from the Union of Concerned Scientists (a pro-green site) provided some helpful information. At the most fundamental level, there is this:

According to a model developed by the Argonne National Laboratory (ANL), neat (100%) biodiesel from soybeans can cut global warming pollution by more than half relative to conventional petroleum based diesel. The emissions benefits are higher for canola oil.

Sounds like we are off a good start. There are a couple things to keep in mind as we proceed, though. Biodiesel produces greenhouse gases. If you convert to biodiesel and increase the amount you drive, thinking “it’s all good’” you have made an error in judgment. Also, and we’ll get back to this in a moment, these comparisons are being made to petroleum diesel, not conventional gasoline engines.

Much of the world’s biodiesel is being produced from food crops, which involves either using existing crop land for fuel production or clearing of forests for planting. If forests are cleared for planting, we lose the carbon sequestration those trees would have provided. It is possible that the entire life cycle of carbon emissions created by producing biodiesel in this way is greater than that for petroleum. Now, the good news: “When biodiesel is made from recycled food oil or other waste products these land use considerations do not apply.” The problem is that while you might think that using waste would be the obvious way to go, there are still a number of issues with using it on a large scale. In the mean time, the soybean biodiesel industry is growing.

So, if you are running your car off of waste oil you collect from restaurants, you are indeed cutting greenhouse gases. Same if you are converting waste oil to biodiesel in your backyard. But as we press forward in our search for alternative fuels, we need to keep in mind that most people will be using commercial fuels produced from food crops, which to reiterate, may give no lifecycle benefit at all. However, there are couple of future technologies that could change the equation dramatically. One is “biomass gasification [which] may allow the use of other waste streams to be converted to synthetic diesel fuels, expanding the pool of potentially low carbon diesel.” Another is “non-conventional sources like algae [which] may have the potential to provide dramatic (90%) reductions in global warming pollution.” But those are not going to be happening any time soon.

There is one more issue, and it’s one that often seems to get little airtime these days. Remember when environmentalism was mainly about pollution—clean air, clean water, and all that. Well, when comparing biodiesel to petroleum diesel, the effects on pollution are mixed:

biodiesel can offer distinct environmental advantages over petroleum diesel fuel. … the use of biodiesel blends in an existing diesel vehicle can reduce the emissions of the tailpipe pollutants associated with conventional diesel including particulate matter (PM or soot) and hydrocarbons (HC). However, using biodiesel may result in greater emissions of smog-forming nitrogen oxides than using conventional diesel.

So, some good and some bad news there. But here’s the thing though, all diesels (bio and petrol) are bad for the environment in terms of emissions other than greenhouse gases relative to gasoline-powered vehicles:

Gasoline-powered models are better than traditional diesel and biodiesel vehicles on toxic soot and smog-forming emissions. Diesels can produce as much as 10 to 20 times more toxic particulates than their gasoline counterparts, more than can be made up for with the use of biodiesel. Diesels fair even worse when it comes to smog-forming nitrogen oxide emissions, with greater than 20 times the emissions of a comparable gasoline vehicle.

So, while biodiesel is better than petrol diesel in some ways and worse in others, both are far worse than gasoline in this regard. In the rush to slow global warming, we can’t forget about the devastating effects of other emissions on the environment. And while global warming is a long term threat to our planet, these other emissions can cause very serious short term harm (as well as long term harm). You are thus doing a better thing for the planet if you buy a gasoline car that’s gets 40 mpg than you are if you convert an older diesel that gets 20 mpg to run on 100% biodiesel. (Oh yeah, did I forget to mention that. The best cases scenarios for biodiesel assume you are using 100% of the fuel to run your vehicle. However, petrol diesels need to be converted to do this. That’ll cost you about $2,000. One more thing: I just noticed that sites that are touting biodiesel and selling related products have a decidedly different analysis of the carbon emissions related to biodiesel—in fact, calling it carbon neutral.) For now, I am going to trust a non-profit group of scientists who are concerned with the overall issues over companies trying to make a buck.

This entry was posted on Monday, July 28th, 2008 at 8:51 am and is filed under The Green Scene. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.