“Corporates in the U.S. have been AWOL,” says Sean Kidney, chief executive of the nonprofit Climate Bonds Initiative in London.

That's left a gaping hole for investors looking to build out a diverse portfolio of sustainable investments. APG Groep NV, the Dutch pension manager that oversees about $540 billion in assets, issued a public appeal last month for U.S. corporations to issue more green debt.

“Investor demand for corporate green bonds continues to be high, but the U.S. market remains constrained by limited supply,” the firm lamented.

While U.S. financial services firms, utilities, and energy companies have joined their worldwide rivals in becoming regular issuers of green bonds, corporate stalwarts have largely sat out. Of the $592 billion of green bonds ever issued to finance sustainability projects, less than $7 billion has come from U.S. companies outside the financial services, utilities, and energy sectors, according to Bloomberg NEF.

That compares with roughly $16 billion in Europe, where industrial players are more apt to tap the market. Apple Inc. has been the biggest non-financial U.S. issuer of green bonds, raising $2.5 billion in two deals since 2016.

Verizon plans to use the money raised from the green bond to support investments in renewable energy and energy efficiency projects, such as its plan to source half of its annual electricity usage from renewables by 2025. The company's campus in New Jersey already gets between 30 percent and 60 percent of its energy from renewable investments, depending on the season, Gowen says. It could also use the funding for developing its new 5G network in a climate-sensitive way, he says.