Composting cardboard and paper

Cardboard and paper  provide a readily available  source of carbon  in most home composting systems  but often  the volume of waste paper produced by a household is such that it cannot all be composted using a single bin. It is also the case that where paper material is recyclable it is a likely to be a better  environmental option to recycle most of it  while retaining just sufficient to maintain the appropriate Green/Brown ratio for home composting.  However, before deciding to send all the excess cardboard and paper for recycling the use of additional composting techniques should be considered where there is enough space.

Other possible methods that could be adopted are trench, sheet and Lasagne composting the latter providing a cheap means of filling a raised bed.

In deciding on whether to compost or recycle paper and cardboard waste the are occasions when  home composting is the route of choice. One such case is  where cardboard has been  contaminated with food materials which would contaminate the recyclable waste stream if put into the kerbside collection system operated by councils e.g. greasy pizza boxes. Home composting is much better than the alternative of sending it to landfill.

Home composting can also deal with some types of paper, such as tissues and shredded paper, which in many areas cannot be recycled or composted via the council kerbside collection and would have to be fed into the council landfill system. While shredding and composting confidential paperwork containing financial and personal information provides security this should not be the primary reason for composting shredded paper. Shredded paper is an excellent source of carbon (cellulose) and a means of absorbing moisture from kitchen and catering waste.  When composting shredded paper, it should  be  mixed and aerated in the bin so that it does not form a wet mat restricting airflow with the risk of creating  localised anaerobic conditions.

Concern is often expressed in some forums that printing inks are toxic and therefore printed paper should not be composted, this may well have been the case in the past, but these inks are now banned, and modern vegetable inks are safe to compost.




Hot Composting Paper & Cardboard

Paper can be produced by one of two techniques and these  effect the time taken to compost the paper.  The chemical process used when producing office and computer paper removes most of the lignin, leaving only about 5% in paper and 10% in corrugated cardboard compared with 30% in newspaper which is produced using mechanical means. As mentioned, this is relevant to composters as lignin is slow to compost while the cellulose, left after treatment, breaks down quite quickly. In cold composting the actual time taken for the paper to decompose is relatively unimportant as the normal processing period is much longer and it does not matter if some recognizable paper is present in the final compost as it can easily be put back into the bin. However, if a hot composting batch system is being used so as  to produce compost quickly, the lower the lignin content of the paper the better as the woody lignin is slow to breakdown  .

 Hotbin reports that office paper and corrugated cardboard will break down in days or weeks when hot composted in one of their bins compared with months in the case of newsprint. This is why I tend to recycle my newspapers while shredding and composting my “office” paper.


Faster  to decompose

The papers with the highest cellulose and lowest lignin content are computer paper, envelopes (in the case of window envelopes it may be necessary to remove the windows [see below] corrugated cardboard, writing and drawing paper, pages torn from telephone directories (some still exist) and instruction leaflets/ sheets.


Slower to decompose

The slower decomposing, higher lignin group includes  cereal packets, printed cards (avoid glitter – see Christmas        ), newspapers and cardboard egg cartons (good for trapping air in the bin).

Glossy leaflets and magazines are best recycled.

Wrapping paper should be subjected to the scrunch test before deciding whether to compost or recycle

Windows Envelopes. Some of the windows are made from industrial compostable PLA while others are made  from glassine (a recyclable paper product), but many are polystyrene, polypropylene, polyester, acetate or plastic. Unfortunately, the householder  cannot always tell the difference as not all envelopes are printed with content information so it is best to assume that the window will not decompose when composted. But it is not important  the window can be removed before the envelope is put in the bin  or it can be picked out at the end of the composting process if it has not decomposed. After all most composters will be used to removing the remains of parcel tape that has somehow managed to get into the bin or wormery unseen on corrugated cardboard.


Envelopes : The EMA Guide to Envelopes & Mailings [PDF] 



07.06.2022 21:48

Anna B

Hello I am a high school student designing a product around composting. It is in the context that you have a home compost caddy.