The idea of whether to use cardboard as an ingredient for making compost has been very confused over the years ? There are people who advocate using cardboard as a part of compost, while others totally stay away from it and claim that there is no point of using cardboard, that it does not add anything to the compost. Well, should you ? Difficult question. I would like to say ‘it depends’, but most probably would find a book flying towards my head. So, let me just write my experiences about compost from the perspective of cardboard.
Before starting, some description of cardboard. Cardboard is used to refer to many different kind of material, and you would have experience of many of them. Three of these are:
1. Corrugated cardboard (can see images of this here at Google Image Search (click here))
2. Waxed cardboard containers. These are containers similar to the corrugated ones, but with a difference. Here the cardboard can be a bit less thick than the corrugated one, and in most cases, one of the sides of the cardboard container have a shiny / waxy finish on top. The finish is smooth, and much different from the corrugated cardboard.
3. The even thinner ones. These don’t even feel like cardboard, more like thicker paper. Used for smaller items, such as these cake packing (link here)
There can be more varieties, but these are enough for the discussion. So what do you do about using them in compost ? Well, for starters, the corrugated ones, as described in point 1 above, is ideal for the purpose of composting. You need to shred it in small pieces (I normally leave it in sizes that are not more than the length of a finger) and I have found that within a month of the composting process, these pieces mostly vanish. On the other hand, there are people who keep them in water for upto a day, or use a shredder to cut them into much smaller pieces to add to the compost. All these steps to make the pieces of cardboard smaller before adding to the compost pile help, but even just shredding them into smaller pieces will work (as long as your compost pile is working fine).
For the other varieties, I have also put them into composting in the past, and have had varying experiences with some of them. For the ones described in #3 above, in many cases, they have a thin plastic sheet that forms part of their structure. Once you think you are done with the composting and it is prepared, I have found that there will be bits of plastic in the compost (along with small bits of cardboard attached to them). It is effort to remove these bits of plastic (I know that plastic in the compost will not really cause significant harm but I like to ensure that I can remove whatever contaminants as possible) from the finished compost, and depending on your ability to spend this effort, it may not be worth it to use this kind of cardboard.
For the cardboard described in #2, there is a worry about the type of waxy coating, as well as the type of coloring used. I am apprehensive about having these in the compost, and hence, if the packing is thick, I try to strip the inner part of the packing which is similar to corrugated cardboard, while the coating side is sent off for regular recycling.
Why to use cardboard ?
– The compost pile requires a steady supply of brown material apart from the green part which is contributed by kitchen and garden waste. If there is enough quantity of dry leaves available, then that is ideal; but a lot of people do not have excess to material such as dry leaves or other organic dry stuff. In which case, can easily use cardboard for the same, shredding it into small pieces. Cardboard adds much needed carbon content to the compost.
– Cardboard has another advantage. If there is too much water in the pile, if it is more moist than you would like, adding cardboard to the pile ensures that this water gets absorbed; so within a range, one can use it for controlling the water content of the pile.
– When this shredded cardboard is mixed with the kitchen waste, the decomposing cardboard helps to ensure that there is aeration inside the pile (the microbes within the compost are getting air). If you use only kitchen or garden waste, then as it decomposes, it starts clumping together and reduces the availability of air). With cardboard in between, there is enough space to ensure that there is air for the process to remain aerobic.