Vermicomposting vs Traditional Bin Compost
In addition to the chemical differences discussed above, the following sections discuss other differences between the two processes.
Conventional composting relies on the right ratio of carbon to nitrogen and the action of microbes to carry out the degradation process. When these conditions are right, the process produces a lot of heat, hence the term hot composting.
In vermicomposting, the process is carried out at cooler temperatures by the action of the worms and the microbes.
A hot environment releases more nitrogen into the air than a cooler process. Consequently, vermicomposting usually results in a compost with higher nitrogen levels. Since the nutrient most likely to be deficient in any soil is nitrogen, vermicomposting has an advantage.
Killing of Seed
Hot composting kills weed seed, while cold composting such as vermicomposting does not. However, in most home systems, weed seeds are not introduced as food for the worms, so this may not be a major issue. It does become a more important consideration in large scale production of vermicomposting when it uses input ingredients that contained weeds. This is more likely the case for purchased vermicomposting.
Speed of Decomposition
Conventional hot composting is a relatively fast process which is followed by a slower process in which the compost goes through a finishing step. Vermicomposting also consists of two steps, one inside the worm, followed by a slow maturation process. Compared to hot composting it is a slower process. However, it is difficult to compare the so-called finished compost from the two processes. At best, some gross level tests can be done to measure the degree of completeness, but these do not give an accurate comparison. When the two processes were compared using cattle manure the final C:N ratio was lower for vermicomposting, indicating that it was a more complete process. The other thing to keep in mind is that in the home garden, conventional composting rarely gets hot enough and therefore bin composting is a much slower process. For home gardeners it is impossible to know which process is faster – you can’t ‘see’ the completeness of the process.So-called finished compost from either source is still a long way from being completely decomposed- which is good news since it means they will feed the garden for years.
All that is nice science but which compost results in better plant growth? Some studies show one or the other as superior, but the consensus is that neither compost produces better plant growth than the other. A lot depends on the specific conditions of soil, technologies used and input ingredients. It is incorrect to say that vermicomposting produces better compost unless your soil needs more phosphorus and calcium. The high phosphorus levels actually mean that for most soils bin compost would be a better choice.
Production of Greenhouse Gases
Every composting process produces some greenhouse gases, like CO2. Because vermicomposting happens at least partially inside the worm, it is an anaerobic process which produces both nitrous oxide and methane. Both of these gases are many times more harmful to the environment, as far as global warming goes, than CO2From a global warming perspective, traditional bin composting may be a more environmentally sound process. I say ‘may be’ because such calculations are very hard to do, and I doubt anyone has done them.