Martin Tobias at Deep Green Crystals points to a post on the Google blog about Google’s use of biodiesel in its Bay Area shuttle bus.

Here’s some of the Google math:

It does cost more than regular diesel, but consider this: The Google shuttle carries an average of 155 employees a day. Each run totals about 75 miles - that’s 11,625 miles a day we’re not driving. If the average car gets 25 mpg, then we’re saving some 465 gallons of gas a day, or 2,325 gallons a week—weekly savings of $4,998.75 (figuring $2.15/gallon).

Let’s look at those numbers another way. Earlier in November, the IRS bumped up the 2005 standard mileage rate for computing the deductible costs of operating an automobile for business by three cents from this year’s rate—the largest single-year jump ever. The primary reasons: higher fuel and vehicle prices.

Some businesses use that IRS figure in reimbursing employees for business travel. Using that rate, and assuming a company with comparable usage figures as Google (and a company that would allow employees to expense those trips), that works out to a potential daily savings of $4,708.13. Yes, some people would probably drive together,  but the point is that shuttles can work from a cost point of view—and more than offset the short-term cost delta between biofuels, alternative fuels and petroleum fuels. Good for the bottom line, good for the environment.