Two large hills at ecomaine’s ash landfill appear to be made of colored gravel. Closer inspection shows that it’s finely ground glass, 1,429 tons worth last year of assorted food containers that residents recycle, perhaps with an expectation that the glass will be sold and turned back into pickle and jam jars.

Glass is very cheap to make, and used glass has never been worth much. But with the declining prices now paid in commodity markets, the cost of trucking the material out of state to melt it down in a furnace to make new containers is more than ecomaine is paid for it. So glass is being crushed and stockpiled, waiting to be used as aggregate to replace sand and gravel for drainage and road projects at the landfill where ash from ecomaine’s trash-to-energy plant is buried.

In fact, some of the gravel roads that wind through the 240-acre landfill complex, which straddles Westbrook, Scarborough and South Portland, are built upon ground glass.

And there are other uses. In Falmouth, the local rod and gun club used 182 tons of it last year to underlay a 600-foot pathway to make the facility wheelchair-accessible.

For ecomaine, it still makes sense to get glass out of the waste stream to save disposal costs, even if the material has no economic value by itself.

But that’s not true everywhere. In Savannah, Georgia, city officials were surprised last month when they learned that the private company that handles recycling had landfilled 1.1 million pounds of glass since August. The company said it continues to seek markets, but that it’s cheaper now to landfill glass, according to news reports.

Glass recycling does have one bright spot in places with returnable container laws, such as Maine.

Maine’s bottle bill directs beverage containers to redemption centers, where they are sorted by color. Because the glass is generally free from metal or other contaminants, it has a higher value for manufacturers.

TOMRA of North America crushes up to 15,000 tons a year of beverage bottles from redemption centers and takes them to a major recycling processor in Massachusetts. Clear glass – the most valuable grade – now is worth $30 a ton, according to Beth Milligan, the general manager at TOMRA’s facility in Portland.

But it costs $15 a ton to truck the clear glass. And the income has to help cover the cost of green glass, used mostly by Canadian beer brewers. Green glass, Milligan said, is worth only $10 a ton.