Food processors are looking to substitute paper for plastic in packaging but are finding it’s not so easy.

An increasing number of food companies are interested in reducing their overall use of plastic, for environmental reasons. This is especially prevalent among companies that do a lot of business in Europe, wher environmental regulations are stringent, the Wall Street Journal reports. According to one estimate, paper will take an 11% market share away from plastic packaging in Europe by 2031.

Nestlé and Unilever are among those trying to use paper for flexible packaging. But this has been done to date only for a few lines and in a few countries. The problem is that paper doesn’t have the barrier properties and other desirable aspects of plastic.

Attempts to improve barrier properties with coatings have led to problems with recyclability. Possible long-term fixes include a liner that melts in the recycling process, now being used by Nestlé for Yes! snack bars and Nesquik cocoa powder, and a detachable lining for bag-in-box packaging.