The 10 Best Compost Tumblers

Regardless of the composting method, there is an exacting science to composting that will need to be understood. In a composting tumbler, this is especially true, as the limited amount of space equates to less room for error. The first thing to understand is what is known as the carbon/nitrogen ratio, which is a very important factor in composting. If the compost mix is too low in nitrogen, it will not heat up. If the mix is too low in carbon and too high in nitrogen, it may heat up too much, killing off the beneficial composting microbes.

The best way to avoid these scenarios is to keep the carbon to nitrogen ratio at 30:1 when starting out. Then, as the carbon gets converted into carbon dioxide through the composting process, the ratio will naturally level off to around 10:1. This is the ratio that should be used for the rest of the process.

It is also important to understand particle size and composting speed. As a rule of thumb, smaller particles will break down much faster than larger ones. This is because the microorganisms eating at the pile can only get to the outside surface of the compost. The more surface area they can reach, the quicker the process of composting becomes. The importance lies in the ratio of surface area to volume. Typically, particles with more surface area for their volume are desirable, as they speed up the process of composting, and result in a more even product.

Because composting happens through the action of aerobic bacteria, the importance of oxygen flow within a composting method cannot be overlooked. In compost tumblers, this usually comes in the form of various small vent holes and through the action of turning the compost barrel. This also keeps the temperature within the desired range; quickly preparing the compost for its journey to the garden.

A good pile of compost, and therefore a good compost tumbler, is full of bacteria. They are what is at the heart of every compost pile, and without these bacteria; the soil would be arid and lifeless. Understanding the bacteria in a compost tumbler helps to create a better understanding of composting and the bacteria themselves.

In the first few days of the composting process, the tumbler is overrun with bacteria known as mesophiles, which help to break down the soluble, easily degradable nutrients within the tumbler. Some examples of mesophilic bacteria include Staphylococcus aureus, Salmonella, and Listeria monocytogenes. This is also the reason it is important to avoid foods such as meats, bones, and high-protein foods in compost tumblers; unfavorable mesophilic bacteria reproduce quite quickly on high-protein foods.

Mesophilic bacteria act to raise the temperature of the compost and set the stage for the thermophilic bacteria. These bacteria cause temperatures in the tumbler to rise even further; and many human or animal pathogens are destroyed in the process. These bacteria can take the heat in a compost tumbler too high, however. Temperatures of 65 degrees Celsius and above will kill many forms of microbes which are responsible for decomposition. This is why it is so important to watch the temperature of the compost tumbler closely.

After the bulk of their energy sources are spent, thermophilic bacteria begin to be replaced by beneficial mesophilic bacteria once again in a process known as curing. In a tumbler, this means leaving the vents open and leaving the tumbler alone; allowing the pile to mature itself and cool down its internal temperature.