Painstakingly sorted jars often end up as low-grade products
Up to a quarter of the glass sent for recycling, especially the glass sorted by households, is so dirty, pulverised, or mixed with other waste that it cannot be used for new containers. Instead, many thousands of tons of glass must be melted down into products that are much less beneficial for the environment, and used for e.g. road filling.
This is evident from the figures from the recycling company Reiling in Næstved, which annually receives 75 percent of all glass waste in Denmark, corresponding to approx. 150 000 tons.
“One of the biggest challenges we face is that when the fractions mix with each other, they contaminate each other and cause sorting losses. We can easily separate most things, but we never get it all together and it requires several sorting processes. And at some point, the profitability goes down the drain,” says Jesper Blicher-Nordkvist, Factory Manager at Reiling.
To be precise, between 20 and 25 percent of Danish glass waste is in such poor condition that it can only be used for “foam glass” used for insulation or road filling.
The glass that is collected from consumers at their doorstep is of particularly poor quality—in contrast to glass that comes directly from the industry, the deposit-refund system, or bottle banks on the street, which are all typically of excellent quality.
The problem, according to professionals, is that many consumers throw their glass out in plastic bags and into the garbage container—something that does not happen with bottle banks, where there is no room to hand it over that way.
Stig Hirsbak, External Associate Professor at Aalborg University, has worked with recycling systems since the late 1970s, when Denmark started introducing recycling.
“The bottle banks, which have proved to be an effective tool for achieving good results in recycling of glass since the 1980s, are disappearing precisely because door-to-door collection of glass has been introduced instead. One simply has to take a closer look at where things are going wrong in the chain from door-to-door collection to remelting,” says Stig Hirsbak.
Specifically, what happens is that the glass breaks a little (≈2%) every time it is moved or otherwise handled. Broken glass smaller than 4–5 mm will not be accepted by the glassworks, partly because it turns into smoke and ends up as emissions in the form of SOx, NOx, and dust. Glass becomes too shattered for circular recycling especially when it is handled together with metal that is compressed in the garbage truck.
Another common problem is that heat-resistant “glass-ceramic”, which has a significantly higher melting point than ordinary glass, is thrown out together with glass.
That is, even though citizens think they are doing a good deed by handing over their old glass-ceramic casserole dishes for recycling, they can actually be detrimental to the production of new glass containers on a par with other sources of pollution.
Door-To-Door Collection Must Be Revised
The criticism from Reiling is backed by Kenni Hansen, who is responsible for the melting process as Head of Melting Operations at Ardagh Glass Holmegaard, which supplies glass for the production of approximately two million glass products, which range from jam jars to beer bottles, every day.
“Glass has always been collected and recycled in some way. But it has been out of sight and mind of the regular user. From a political point of view, it has become easy to look at the glass and say that things are going well here. And that may well be the case—but it is not going well enough,” he says.
Kim Holmberg, CFO of Ardagh Glass Holmegaard, is horrified that more and more Danish municipalities are introducing door-to-door collection of glass because that will lead to more glass that cannot be reprocessed into new containers.
“Household waste sorting causes much more contamination of the material than other options,” Kim Holmberg says and refers to studies from Sweden, which document that door-to-door collection of glass leads to three times as much glass that is contaminated with ceramic, three times as much glass that is too pulverised to be recycled, and nine times as much glass that is otherwise too contaminated for circular recycling.
“The optimal method to recycle glass so that it can be reused for new glass are bottle banks and bring-it-yourself schemes,” says Kenni Hansen.