(Reuters) - Washington Governor Jay Inslee on Tuesday signed a bill that paves the way for the state to create what is believed to be the first system in the United States to certify marijuana as organic.

Socks with marijuana leaves are pictured at Cannabis City during the first day of legal retail marijuana sales in Seattle, Washington July 8, 2014. REUTERS/Jason Redmond

The sponsor of the bill, Republican Senator Ann Rivers, said marijuana certified as organically grown is likely to be on sale in Washington in about a year and a half.

Washington is among a handful of U.S. states where voters approved the sale of recreational marijuana. Washington was the second state to begin legal recreational pot sales, in mid-2014, after its voters in 2012 approved it.

“This is consumer-driven,” Rivers told Reuters by phone on Tuesday night. “As we have moved forward in the legal marijuana market, we’re hearing people say, ‘We don’t want any pesticides, fungicides, none of that stuff in our weed.’”

The new law “creates a voluntary program for the certification and regulation of organic marijuana products,” to be administered by the Washington agriculture department, according to a state analysis of the new law.

Rivers said the “heavy lifting” in certifying marijuana has been done by the system of doing the same for a multitude of food products on supermarkets shelves across America. That process just needs to be adapted for pot, she said.

Rivers said that legal recreational marijuana is “the gift that keeps on giving....this year, we’ll make $768 million” in revenue for the state of Washington. This pays for drug education and drug addiction treatment as well as public education, she said.

Organic pot was just one of a myriad of marijuana-related measures in the bill.

Many state legislators wanted to vote for only one marijuana-related bill rather than have to go on the record favoring marijuana several times, Rivers said. The November 2012 measure to allow recreational marijuana in Washington passed 56 percent to 44 percent.

While it is legal for adults to smoke marijuana in Washington, it is not legal to grow industrial hemp. The new law allows for the study of a method to allow hemp to be grown and used for industrial purposes.

Last week, Vermont’s legislature approved a bill to legalize recreational use of marijuana. Unless the measure is vetoed, Vermont would be the first state to legalize pot without a public vote.

Voters have approved legal recreational marijuana use in Colorado, Washington, Alaska, Oregon, California, Nevada, Maine, Massachusetts and the District of Columbia.