Continuous vs Batch Composting
An e-mail question from one of my readers yesterday reminded me that it might not be a bad idea to write a quick post about the difference between ‘batch’ and ‘continuous’ composting.
A continuous composting system is one that receives waste materials on an ongoing basis – but not necessarily according to a specific schedule. This is typically the most common and easiest form of composting for the average home owner. You simply start up a compost heap or bin and add your waste materials to it as they become available.
Apart from ‘average joe’ backyard composting, another prime example of this approach is vermicomposting. Technically, you could create a batch vermicomposting system, but if you add too much waste at once there is a good chance the materials will generate too much heat for the worms, among other potential hazards.
One of the major advantages of continuous composting, particularly in the case of vermicomposting, is that you are not limited by scale – your system can be as small or large as you want it to be. As such, you can more easily compost indoors, and utilize waste materials right away, rather than stockpiling them until you have enough for batch composting.
The downside however is that you are essentially mixing fresh materials with those that have already been composted – so it can be more of a chore to separate out the ‘good stuff’. If you are composting with worms, this can be accomplished quite easily by using some sort of ‘continuous flow’ system. Such a system relies on the fact that composting worms will generally move away from their own wastes (worm castings) in the direction of the most recently added waste materials. In stackable bins like the “Worm Chalet” for example, the movement is upwards, whereas in a ‘wedge system’ (moving windrow) movement occurs laterally.
Batch composting simply involves mixing ALL your materials together at once then letting everything sit without adding more materials (aside from water), until it becomes compost. This approach is most applicable on a larger scale, and almost always will involve some variation of ‘hot composting’.
One of the main advantages of this approach is that all materials in the system will finish composting around the same time and there will be no contamination from newer materials. This approach is also very handy when you need to deal with large quantities of waste (whether at one particular time or on an ongoing basis). In comparison to vermicomposting systems, using a batch approach saves a lot of space as well (since materials can simply be mounded upwards) – thus more waste can be composted per given unit of area.
One disadvantage of this approach is the fact that you need to stockpile waste materials until you have enough for the next batch – obviously not a big deal if you do have a sizable waste stream at your disposal, but a little more inconvenient if it takes you awhile to obtain enough for a decent sized compost heap. You also generally need to pay more attention to the C:N ratio and overall properties of the materials in your mixture, proportioning them more carefully so as to obtain the results you desire.
So which one of these approaches is better?
It totally depends on what you are trying to accomplish and how much waste material you can get a hold of. I like continuous composting because it is so easily adapted to different situations, and because I don’t have a massive amount of waste to deal with (and even if I did, I’d likely just set up more worm composting systems).
By the way, there is no reason you can’t combine the two approaches. ‘Pre-composting’ large quantities of material before adding them to a vermicomposting system is actually a great way to speed up the composting process, while also getting rid of weed seeds (and possibly pathogens) – so it’s a ‘win win’ situation!
[tags]composting, compost, vermicomposting, worm composting, vermicompost, worm castings, continuous flow, compost bin, compost heap, compost pile, worm bin[/tags]