Does Sawdust Do the Same Job as Bulking Agent?
Tuesday, 4 April 2017 | HOTBIN Composting
Does Sawdust do the Same Job as Bulking Agent?
No, unfortunately not. Sawdust is too fine and wood shavings are not thick enough to be a substitute for bulking agent.
Bulking agent is simply wood chippings; in our case we provide partially composted wood chippings which will break down faster than those that aren’t partially composted.
The job of bulking agent is to create air pockets in amongst the waste as it is added to the HOTBIN. These pockets allow air to circulate through the HOTBIN feeding bacteria with oxygen and keeping them composting aerobically. Without these air voids and access to oxygen, bacteria will start composting anaerobically which means a colder bin and often bad odours.
Adding bulking agent is the trade-off for not having to turn and tumble a compost heap.
One of the most common causes for a HOTBIN not getting up to temperature is a lack of bulking agent (air voids) and/or shredded paper. Insufficient bulking agent prevents the contents from being sufficiently aerated whilst a lack of shredded paper can result in the contents becoming overly wet.
If you do not add bulking agent or a suitable alternative the HOTBIN is unlikely to operate as a hot composter. It is important for a bulking agent to have a certain particle size; sawdust for example is so fine it will just simply fill those voids blocking aeration.
Although sawdust does have some water retention properties, unfortunately they are not sufficient to control the moisture levels in the HOTBIN which is why we recommend shredded paper. The fine nature of sawdust also means that when it becomes wet it has the ability to clump together forming a damp impermeable mass in the HOTBIN.
Struggling to locate enough shredded office paper, here are a couple of alternatives.
Pet bedding (wood shavings and sawdust) can be added into the HOTBIN but only when it’s hot (40-60°c) and in small quantities mixed with other waste. The key here is to remember not to restrict airflow so don't forget to mix in paper and bulking agent too.