Saving the Earth is hard work, especially if you're trying to convince companies to be more eco-friendly. But what if you could help a local business go green by doing nothing more than shopping there?

That's the idea behind Carrotmob, an enviro-minded consumer activism event that took place in San Francisco last weekend. The idea: Carrotmob organizes a staged buying spree at a particular business. In return, that business puts a percentage of the revenue toward energy-saving business renovations. The business wins through a boom in sales, a green reputation and lowered energy costs, while the consumers also benefit, by putting an ecological bang behind their bucks for stuff they need to buy anyway.

"People have been doing mobs for no reason, so it's nice to be in one with a cause," said Adi Cohen, who spent about an hour of his Saturday afternoon in a very nonmobbish – but long – line at the K&D Market, an unremarkable, everyday kind of bodega on 16th St. in San Francisco's Mission district.

Carrotmob is the brainchild of Brent Schulkin, a San Franciscan whose day job is conducting team-building games for corporations. He generated considerable buzz over the event, campaigning on Facebook and MySpace, via e-mail and through a Carrotmob video channel. All that online organizing paid off: Several hundred shoppers, many of them pals with the affable Schulkin, showed up on a Saturday afternoon and ponied up for way more wine, cookies, 40-ounce beer, toilet paper and chips than they'd normally buy at a convenience store.

Schulkin had asked more than 20 convenience stores in the Mission to make bids on what percentage of sales generated during a set time they'd be willing to put toward green renovations to their stores. K&D bid the highest amount – 22 percent – and got to play host. Store manager David Lee said he plans to change out the store's light bulbs and make the wall-to-wall beer and milk fridges more efficient.

The shoppers were palpably stoked by the notion that their dollars would have a positive and immediate impact on the store. And they weren't stingy with their purchases: The store's notoriously surly clerk rang up a whopping $9,400 during the four-hour spending spree. Lee said an estimated 11 percent of that sum will go to cover tax and CRV (California Refund Value), and then 22 percent of what's left, or about $1,840, will go toward renovations.

Schulkin hopes he can parlay Carrotmob into a thriving nonprofit, staging more events like last weekend's. But will the Carrotmob premise catch on – and more importantly, can it raise enough money to make a difference? Lee said a full fridge makeover is going to cost well over what the Carrotmob-generated sales percentage will cover, so the store will start with changing out the light bulbs, then try to figure out how to address the 23-year-old, energy-sucking fridges without springing for a complete replacement. It's not exactly saving the Earth, but it's a start.