The answer depends on your setup. The most important thing to remember is that as soon as you begin sorting your household waste properly — including plastic, paper and cardboard, glass, metal and compost — the amount of trash you’re left with drops drastically. Also remember that mindful buying habits that emphasize reduced consumption will naturally generate less waste.
Here are a few solutions:
Use other bags you already have around the house, like the plastic packaging around toilet paper.
Line the bottom of your trash can with newspaper and empty your can directly into the bin. The city of Reykjavík has issued a statement that residents need not package their garbage in bags before placing it in the collection bins (although residents are responsible for keeping their bins reasonably clean). You can also use biodegradable bags (like cornstarch bags or sugarcane bags) instead of plastic liners, although in that case you’re still replacing one disposable material for another.