The environmental group Sustainable Pittsburgh is hosting a “Green Workplace Challenge” competition for the city’s businesses.

Sustainable Pittsburgh Program Manager Matt Mehalik said the friendly competition will rank businesses in the Pittsburgh area, based on how many green design features they can implement and how much energy and water they can save over the next year.

Any “green” work done in the past year will be credited to the company retroactively, said Mehalik. He said Sustainable Pittsburgh requires last year’s utility bills as a baseline for comparison. Mehalik said the attention to detail sets this competition apart from similar ones in other cities.

“It’s not entirely clear how they awarded the points to companies, and a lot of times it wasn’t for actions that clearly demonstrated a measurable difference, so we’ve built this competition to ensure that the rewards are directly tied to their energy-efficiency and resource-efficiency achievements,” said Mehalik.

Mehalik said there will be different categories in the competition to group the businesses by size and type. Winners will be recognized at the end of the year-long challenge.

The competition begins this September 14, and ends on October 31, 2012. About 30 businesses have signed up so far, and Mehalik said he expects about 40 altogether. The registration deadline is September 30.