In an apparent effort to go greener, a German city has banned coffee pods — such as those sold by Nespresso and Keurig — from all government-run buildings.

The city government of Hamburg released a 150-page Guide to Sustainable Procurement in January, which included a provision banning the use of tax dollars to buy products that don't adhere to the city's high sustainability requirement. K-Cups and similar brands just aren't up to that standard.

"These portion packs cause unnecessary resource consumption and waste generation, and often contain toxic aluminum," the city's government concluded in the guide.

The use of single-serving coffee makers has been on the rise in Western Europe, where pod machine sales outpaced drip coffee makers for the first time in 2013, according to Quartz. The same study also showed that about a quarter of U.S. households own a pod machine, with that number expected to grow as drip machine sales remain stagnant. This is troubling to many environmentalists and even the inventor of the modern pods, John Sylvan, who sold his invention to Keurig in 1997.

“No matter what they say about recycling, those things will never be recyclable,” Sylvan told the Atlantic. "I feel bad sometimes that I ever did it.”

In 2015, NPR reported that more than 60 billion K-cups have made their way into landfills, largely due to the non-recyclable plastic and aluminum used to make them. According to Keurig, finding alternate materials for pod production has proved difficult.

"It's a very complex challenge ... the pods must keep coffee fresh before brewing, withstand the heat and pressure during brewing, and be easily punctured with a needle as part of the brewing process," according to Keurig's website.

The company has been looking for ways to increase the sustainability of its products and in 2015 it released a partly-recyclable version of the cup. That pod, called the K-Mug, is made with polypropylene plastic that can be separated from the lid and filter for recycling.

Keurig — which earned more than 4.6 billion in revenue in 2014 — has also pledged to make "100% of its products recyclable by the year 2020." That change will be incremental, according to a news release.

For the city of Hamburg, however, it appears that pledge is too little, too late.