PROVIDENCE, R.I. (AP) — Less than half of Rhode Island’s cities and towns are complying with a state law that they recycle 35 percent of their solid waste.

Lawmakers voted in 2008 to require cities and towns sending trash to the state’s main landfill to meet the 35 percent goal by July 1 of this year. The intention was to encourage the reuse of valuable recyclables while saving space at the landfill in Johnston.

So far, only 15 of the state’s 39 municipalities have met the requirement, even when composted yard waste and scrap metal is included in the definition of recyclables. Statewide, the average is 32.8 percent, according to the most recent statistics. Recycling rates are lowest in Johnston, at 18 percent.

The rates are even worse when a simpler measure is used — how much residents place in recycling bins compared to garbage cans. By that measure, only South Kingstown and Middletown boast recycling rates of more than 35 percent.

The slower-than-expected progress shows how hard it can be for municipalities — and consumers — to adjust their habits. While there are no penalties for cities and towns that fail to meet the mandate, municipalities face added fees if they send too much trash to the landfill.

‘‘There are a lot of things we can do that we should be doing and that we can increase,’’ said Sarah Kite, director of Recycling Services at the state’s Resource Recovery Corp., which operates the landfill and the state’s recycling programs. ‘‘We really want to change how people look at waste.’’

Despite the lack of compliance, local officials say they are making progress in encouraging residents to recycle more.

Providence’s household recycling rate was 14.6 percent before the city rolled out new recycling bins this year and began accepting unsorted recyclables. The rate now is higher than 20 percent. Sheila Dormody, the city’s director of sustainability, said the city expects to continue those gains.

‘‘We know there are a lot of things going in the trash that could be recycled,’’ she said.

The increased recycling rate comes after the state’s recycling program opened a new $17 million facility that better separates recyclables, allowing consumers to recycle more materials without sorting first.

Barrington has banned plastic shopping bags effective Jan. 1 in an effort to reduce the use of plastic and save landfill space.

Middletown has enjoyed one of the state’s highest recycling rates since it started a pay-as-you-throw policy, which charges residents based on the amount of trash they produce.

Officials in Narragansett recently adopted a new recycling policy that, as of Jan. 1, will require residents to separate recyclables from trash and compel waste haulers to provide recycling services.

‘‘There are great efforts going on, and we need to keep pushing,’’ said state Sen. Susan Sosnowski, D-South Kingstown and one of the lawmakers who pushed for the recycling mandate in 2008.

The state law also required cities and towns to reduce the percentage of their overall waste sent to the landfill to 50 percent or less. So far, Tiverton, Middletown and South Kingstown are the only communities to hit this goal, and nearly 70 percent of the state’s municipal waste overall still ends up at the landfill.

Environmental advocates said additional actions such as higher fees at the landfill may be needed to encourage more recycling and composting. Jamie Rhodes, director of Rhode Island Clean Water Action, said that unless the state improves its rates, it may have no choice but to build an additional landfill in the future.