Had a really fun activity this week; not exactly technology, but it was a really fun science lesson on alternative fuels.
We had just finished a unit in science on alternative energy. Being that all my students are burgeoning gear-heads, they were most interested in biodiesel. Biodiesel is a very broad term for diesel fuel that is at least partly made from natural oils such as vegetable oil. We decided that we were going to brew up a batch. Sort of.
I started by asking my students what we have a lot of in Wisconsin. Overwhelmingly the answer was dairy cows. Oil is basically a fat, and milk (especially Wisconsin milk—this is home to the happiest cows in the world) is anywhere from 3% to 5% fat. If you let that fat rise to the top, you can skim off cream, giving you cream and skimmed milk.
Now cream is about 40% fat, much better, but still a long way from being pure enough to burn. As any visitor to Colonial Williamsburg will tell you, you can then take that cream and churn it to make butter and buttermilk. The buttermilk can be used for pancakes, and the butter is now 80% fat. But it still has too much water to burn.
Here comes the fun part. You heat up the butter and allow all the water in it to boil off, paralleling the distillation process of oil refining, but in reverse. After about 30 minutes, when your room smells like butterscotch, you have pure, 100% golden butterfat, also known as clarified butter, or ghee to fans of East Indian cooking. And ghee burns….
Next year we’ll see if we can’t get some corporate sponsorship (hello, Paula Deen!) to feed a steam turbine on the stuff and charge up a go-kart battery.