When it comes to investing in the environment, it’s getting easier to be green.

Green Bonds have been around for a while: Washington State sold more than $3 billion worth in 2008 to combat climate change, and Massachusetts sold more than $100 million to improve energy efficiency in state buildings, river revitalization and land acquisition in June 2013.

But the space has grown since then, according to a July report by the Climate Bonds Initiative:

- The total universe of bonds linked to climate-change solutions amounts to $502.6 billion compared to $346 billion a year ago.

- $35.8 billion of that total is composed of green bonds issued by corporations and development banks.

“Investors are concerned about climate change,” Sean Kidney, chief executive officer of the Climate Bonds Initiative, wrote in the report.

“The investment opportunities we find are safe and secure investment-grade bonds. This is a Dull Green Market—just how pension funds and insurance funds like it.”

Green Bonds have underwritten projects that include transportation; clean, renewable energy (solar and wind); energy-efficient buildings and industry; agriculture and forestry; waste and pollution controls; clean water; and “brownfields” redevelopment (the development of land with environmental issues). Toyota, Nissan and Chevrolet have used them to develop electric and hybrid vehicles.

The report indicated urgency for such projects, noting the International Energy Agency has said the world has five to 10 years to avoid reaching “climate tipping points” and “trillions in additional finance will be needed.”

Bank of America Merrill Lynch started its involvement with green bonds in 2007 with the issuance of a 600 million euro Climate Awareness Bond for the European Investment Bank, said Suzanne Buchta, the bank’s managing director and global co-head of green debt capital markets. Since then, BofA Merrill Lynch has issued billions in green bonds.

Buchta said the bonds are rated anywhere between BBB and AAA and the interest rate will vary according to risk. She said she has seen bonds that will mature anywhere from between three to five years, 10 years and one that will mature in 100 years.

To the investor, she explained, green bonds are no different from any other bonds that may be in a portfolio. The credit and yield of a green bond from an issuer is the same as the credit and yield of a normal senior bond from the same issuer. But the added allure of green bonds, she said, is that some investors may want to put their money to work in helping the environment.

“What motivates me is the fact that when I was in the fifth grade, there were 4 billion people on the planet and now, during my lifetime, that number has nearly doubled,” she said, adding the increasing population has strained the world’s supply of natural resources.

Barbara VanScoy, chief impact investment officer for Community Capital Management in Weston, Fla., said “tremendous interest in green bonds started about five years ago,” when people began expressing a desire to invest with their hearts.

“A number of institutions recognized … that in a robust portfolio there was room for this type of investment,” VanScoy said. They range across the spectrum, from non-rated small issues to AAA government-guaranteed larger issues that are highly rated.

VanScoy said her entire career has been involved in community development. Her involvement in green bonds is an offshoot of that.

She added that green bonds run the gamut of risk, types of products and maturity. Investors should talk to their financial advisors, she added, because there might be something that would benefit their local communities. To some, including VanScoy, “it’s important to make things better.”

Benjamin J. Bailey, a fixed-income investment manager with Everence Financial in Goshen, Ind., an advisor to Praxis Mutual Funds, said the Praxis Intermediate Income Fund began in 1994 handling “socially responsible” investments. It excluded investments such as gambling and tobacco, and six to seven years ago got involved with “positive impact bonds,” such as a solar energy project in 2004.

As more and more money from investors who want to exercise a positive influence starts to flow into green projects, more capital will follow, he said.

“We’re excited about the growth potential,” he said. “It (the issue) is important because it gets people asking the right questions—and that will get us moving in the right direction.”