All wood based materials like leaves, twigs, paper and card can be composted and will decompose over time spent steaming in the HOTBIN.
We know that small pieces of wood with high surface areas will decompose faster than lumps – sawdust decomposes faster than shavings which compost faster than the original wood branch. If we assume the surface area is the same and the temperature is the same, the speed at which wood products compost is directly related to the amount of lignin contained in the wood.
A hard wood decomposes slower than soft wood. It is easy to think ‘paper comes from wood, so all paper products will decompose at the same rate’- but this is not the case. Newspaper and white A4 office paper decompose at very different speeds.
To explain why, we need to look at the Kraft paper pulping process as illustrated in the table below:
| Speed (At 60°c) | Paper/card type | Notes |
| Fast (days) | White paper
(eg. office, A4 copier, coffee filters, disposable nappies) | The caustic part of the Kraft paper pulping process removes lignin to leave only cellulose fibres. Cellulose is easy for bacteria to digest when compared to lignin. Shred it rather than crunch it up. Do not pre-soak, this must be dry. Sprinkle in little and often - thick layers will quickly get wet and form an impervious mush that prevents airflow. |
| Fast (days) | Corrugated brown cardboard boxes, egg cartons | Corrugated cardboard is highly processed and only 5-10% lignin remains. Corrugated cardboard has the advantage of trapped air/air channels. Shred or tear up - large sheets will block airflow - please do not pre-soak, this must be added dry. |
| Medium (weeks) | Newsprint / Papers, sheets of card
(eg cereal packets) | This is low cost paper – the expensive lignin removal stage is not undertaken. The paper is made from small wood fibres not cellulose fibres per office paper and corrugated card. These are best recycled in your paper collection waste. If you do use, ensure sheets are torn or scrunched up. It will compost far more slowly than food, grass and most other wastes, so do expect it to be present in final compost – normally as blobs of very compressed paper. |
| Medium (weeks) | Gloss printed, waxy papers | Wax coatings are slower to decay. Higher temperature allows addition in HOTBIN, but again add sparingly. Better collected and recycled. |
| Medium (weeks) | Autumn leaves | The stems of leaves are woody. For fast results, ensure leaves are shredded. Mix large amounts (>10 litres) into easy to compost food waste to avoid them forming a matted thick layer which will prevent airflow. Large volumes will also need extra nitrogen - so have chicken poo or blood bone meal on hand. |
| Slow | Woody twigs | All wood (lignin) is harder and slower to compost. When trying to compost wood - shred and chop as small as possible - surface area will determine the speed of decomposition. Sawdust composts faster than shavings (but can block aeration if too much is added), which are easier than wood chips which compost faster than a whole branch. The speed really depends on particle size - 1-3 months (fine particles like sawdust, to 9-12 for hardwood twigs of 1cm diameter) |
| Slow | Soft woods |
| Slow | Hard woods |
You can find a highly technical article that explains how lignin affects composting and the rate of decomposition at the Cornell University Composting website
