NEW YORK -- The increased focus on a company's carbon footprint is creating a business opportunity for those that account for and manage emissions.

The market is nascent but growing -- it is expected to expand to $3.5 billion by 2010 from $250 million last year, according to one market participant. Fueling the growth are widely expected limits on greenhouse-gas emissions, with the U.S. Senate considering sweeping climate-change legislation and the U.S. Environmental Protection Agency having proposed an economy-wide system for reporting carbon dioxide output. And a lack of generally accepted accounting rules increases the need for professional help.

"Climate change now is a very serious business issue, and it posts financial risks, but also opportunities with future regulation," said David Rich, an associate in the Climate and Energy Program at the World Resource Institute, an environmental think tank.

Dipping into the new green accounting business are big companies like Johnson Controls Inc. (JCI) and SAP AG (SAP), and small start-ups and consultancies such as Groom Energy Solutions and Hara Software.

"This is a new process," said Jon Guerster, CEO of Groom Energy. "You have to start from scratch." Groom Energy provided the $3.5 billion estimate for the size of the market in 2010.

Based on a recent survey by business analyst AMR Research, nine out of every 10 companies believe reducing carbon emissions can ultimately save them money, and Wyeth (WYE) is an example of that. Since 1997, the company has spent $58.7 million on its energy-savings and greenhouse-gas-reducing projects, and it has saved $123.8 million as a result. The company also has cut carbon emissions relative to revenue by 40% since 2000.

Not all companies, though, have reported such dramatic change. Millipore Corp. (MIL), a life sciences company, has spent about $1 million on energy-savings projects over the past three years, and has registered $470,000 in savings.

The average payback period of new emission management is about two years, experts say.

"The savings are important to companies," said Michael Harris, vice president at Johnson Controls, one of the carbon-accounting software providers, adding that there are other benefits, such as using the carbon-footprint database as a management tool. "When you are tracking, you can see how your business is performing."

As new business opportunities are created, competition in emission management is expected to become fierce. Currently, about 50 companies are competing with each other, Groom Energy estimates, with only four or five likely to become market leaders in 2010.

SAP expects to be one of the survivors. "If you take a look at the history of the industry, there is apparent advantage of having scale," said Scott Bolick, vice president of SAP sustainability, a division of the software giant.

SAP began to provide carbon-footprint tracking and energy-efficiency business solutions to clients from the late 1990s, helping to embed environmentally friendly innovations into clients' daily businesses. And in May, the company acquired Clear Standards, a start-up making carbon-footprint accounting software.

Stephen Stokes, vice president of AMR Research, said that aside from carbon emission accounting software, consulting in how to manage a carbon footprint and improve energy efficiency also is a sizable market, attracting consulting service providers such as McKinney & Co.