Un printed newpaper you can use brown kraft paper rolls it is easier and cheaper,
like

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http://www.webstaurantstore.com/suff...exTag+Campaign

Personally I use coco coir it is also cheap depending where you get it, I got a 50 kg bail from a local green house for 150$ That is 5500 L of expanded coir I used 100L every 3 months, so about 5 years worth.