“Green” has gotten so big, it even has its own college major.

While the idea of environmental sustainability might come across as amorphous or even downright vague, it’s certainly a growing industry. In the renewable energy industry, $71 billion has been spent on energy last year, which helped employ 2.4 million people around the world, according the Renewable Energy Network.

For instance, General Electric (GE) plans to spend $1.5 billion this year as part of its “ecoimagination” campaign. The company also expects to bring in $14.5 billion in revenue from its environmentally-friendly products.

To capture this growing trend, a number of universities have created majors or graduate programs that focus on teaching students how to merge “greenness” or “sustainability” with the often not-so environmentally friendly business world.

These programs have churned out students who are being scooped up by large corporations including Wal-Mart (WMT), GE and other Fortune 500 members eager to make a dollar and help the environment at the same time.

One of them is University of Michigan student Jeff LeBrun, who spent his summer working for mining giant BHP Billiton (BHP) in the poor African country of Mozambique.

A former environmental scientist, LeBrun said he decided to get his Master’s in Business Administration to focus on how to bring change through business instead of an environmental organization or government agency.

Working for BHP Billiton, a strip-mining company commonly named as one of world’s largest polluters, might come across as contradictory. However, LeBrun said he enjoys working with a company like BHP because it makes the work even more challenging and fun.

“I wanted to be proactive for the environment,” LeBrun said. “And I thought that doing work inside a business would be a better way of producing change.”

The University of Michigan’s master program in sustainability is just one of many programs out there.

Arizona State University in Tempe founded a School of Sustainability in 2007 in order to train students for green industry-related careers, while Yale created a dual-degree program that combines its School of Forestry and Environmental Studies with the Yale School of Architecture train architects to create environmentally-friendly skyscrapers and homes.

“As individual buildings continue to use more and more energy, every architectural firm is clamoring for candidates with sustainability-related specialties,” said Michelle Addington, a professor of architectural at Yale who’s directing the program.

The vast majority of the programs that focus on green issues were created in the past 10 years or so. One example is Michigan-based liberal arts school Aquinas College, which created an undergraduate major in sustainable business in 2005.

Deborah Steketee, executive director of the Aquinas’s Center for Sustainability, oversees the students in the major.

“When we started our program, I could not tell our students that when they started they would have a job,” Steketee said. “Now we’re placing our students with some of the largest companies in the region."

Tom Lyon, director of the masters program at the University of Michigan -- which has been around for fifteen years -- had a similar story.

“Even five years ago, my students were doing self-directed career searches where they would make their own jobs,” he said. “Now big companies are coming to Michigan looking for candidates to fill sustainability analysts or sustainability managers.”

GE spokeswoman Lisa Lanspery said the company-wide EcoImagination campaign is an essential part of the company, and GE looks for people who can work on that effort.

“We are attracting students who want to work for a company that is helping to solve grand challenges for the environment,” she said.

University of Michigan student Devon Douglas worked as a summer intern in Wal-Mart's sustainability marketing division.

“There’s a large educator role that comes with someone who specializes in sustainability,” she said, referring to working with the tens of thousands of diverse employees on the retailer's payrolls. “Even if someone cannot tell about the science of climate change, every associate has it on their radar. They are very proud of Wal-Mart is doing in the area of sustainability.”