Eudrilus eugeniae and Vermicomposting
by Jessie Ross
BIOL/WATER 361, Fall 2012
The world seems to be tending towards more economically and more environmentally friendly ideas. Individuals are buying more efficient cars and household appliances. More ideas continue to be implemented to better our future. It used to be that these ideas were supported by much smaller groups, but it seems to have taken a greater hold and spread through the world. With more populations being informed by these ideas, and larger companies and businesses investing in the movement, more economical ideas will continue to rise. Many researchers and scientists have focused their environmental efforts in helping eliminate current and future problems of growing waste products. Specifically this paper will discuss how a species in the class Clitellata, is helping do its part in managing waste products. Eudrilus eugeniae, the African Night Crawler, has become of interest for its high efficiency in decomposition of organics. This essay describes what a worm does in the vermicomposting process, various benefits of implementing E. eugeniae as a sustainable technique, three main factors that influence levels of production and waste decomposition of E. eugeniae, and the end result.
Worms are a great candidate for helping with the decomposition of waste products. Many times an organization has a flow of waste products that needs to be eliminated, but not all of their solutions are feasible or environmentally-friendly. Decomposition of certain waste products can take a very long time on their own, and worms have been found to speed up decomposition. The special term used to describe the organic matter that the worms produce is called vermicompost. Vermicomposting is not a one man battle though. Worms work together with certain species of microbes. When worms “eat” their way through the substrate they create castings. These castings are what the microbes decompose, providing a greater surface area than the original substrate. When surface area is increased the microbes are able to work faster and more efficiently on the packaged waste and break down the compounds further (Deka et al., 2011; Aira et al., 2005). Through decomposition the worms turn waste into minor and major nutrients in the form of enzymes, vitamins, and or plant growth hormones that are especially beneficial to plants (Yih et al., 2010). The worms are also able to package otherwise harmful heavy metals into safe utilizable sources for plants (Coulibaly et al, 2010). Not all species of worms are good candidates for vermicomposting, but they can be found to be very helpful in eliminating various forms of waste products.
Eudrilus eugeniae has been found to be one of the best candidates for vermicomposting as a sustainable technique. Waste products are everywhere. Most developed nations already have some form of waste control, but not so much in some undeveloped nations (Coulibaly et al., 2010 and Yih et al., 2010). A lot of research being done on vermicomposting tends to be focused on animal and plant waste materials. These products would be the most likely candidates for these under-developed nations where there may be little to no formal Municipal Solid Waste (MSW) removal system. When this occurs, many individuals resort to removing their wastes illegally by dumping them in open spaces, bodies of water, drainage systems, or on the side of the road (Yih et al., 2010). These wastes are not just banana peels or apple cores; they are animal wastes, plant wastes, and human fecal wastes. Under-developed nations are not the only ones that can benefit from vermicomposting. Any location, from industrial to domestic to agricultural, can utilize the sustainable techniques from vermicomposting (Dominguez et al., 2011). In locations with large landfills, vermicomposting can eliminate the need to have waste continually build up and possibly let toxins leech into the water systems. Species E. eugeniae has already been used to help with, city, household, vegetable, paper, animal, and human wastes, which can be large components of landfills (Dominguez et al., 2011 and Yih et al., 2010). Not only can this species compost a variety of different substrates, but it needs hardly any maintenance. Most forms of composting need to be rotated frequently to aerate the soil for even decomposition, where vermicomposting does not. E. eugeniae is able to churn their own soil by the way they move through it and create their castings (Yih et al., 2010). With new ideas come concerns. Is vermicomposting a safe practice? This is one of the main questions that are being asked. With any new idea research needs to be done, and with any sort of business idea a HAACP (Hazard Analysis and Critical Control Points) plan needs to be practiced. As long as the correct measures of containment and bio-security are in place, the system is simple and quite safe to run (Yih et al., 2010). Utilizing E. eugeniae in a beneficial way, like this, should show to be an environmentally friendly way to help with the growing world population and waste that it produces.
Just like anything else, worms are not perfect, and have factors that affect their production. Eudrilus eugeniae has been the most effective worm for vermicomposting due to its high productivity and ability to compost a variety of different substrates. First, temperature for this species has a large impact on production. When temperatures are higher, around 25°C, E. eugeniae has the best productivity (Deka et al., 2011). The temperature preference, for this species, is substantially higher than most other Clitellata species. This allows E. eugeniae to work best in the summer and in more tropical regions (Deka et al., 2011 and Dominguez et al., 2011). Although E. eugeniae works best at 25°C, their temperature tolerances, for good productivity, range from 15°C- 30°C (Dominguez et al., 2011). When the temperature is at the more optimal range for this species, growth rate increases, fecundity increases, and speed of hatching and maturation increases. At 25°C hatching takes twelve days, maturation takes thirty-five days and the worms grow 280mg per week (Dominguez et al., 2011). This is a much faster life cycle and growth rate than comparable species that take anywhere from twelve weeks to forty-two weeks to grow and reproduce (Dominguez et al., 2011). Even though there are species that have broader ranges in temperature for successful life cycles and production, none are as productive as E. eugeniae is (Yih et al., 2010).
Second, growth of Eudrilus eugeniae is impacted by number of individuals in a population. The more individuals in a population the lower the growth rate (Dominguez et al., 2011). This is primarily due to higher competition for food. Biomass also has a direct relationship to population density. The greatest biomass results in the highest population density (Dominguez et al., 2011). This basically means that E. eugeniae does not have a very strong negative impact when it comes to population density; they will still grow and reproduce, just not as rapidly when population densities are higher.
Third, different substrates can change the productivity and outcome of the soil. In one study, with various forms of animal wastes, scientists found that the worms had the highest growth rate and cocoon production in chicken feces, and the lowest was found in pig feces, with sheep and cow consecutively in the middle of the range (Coulibaly et al., 2010). Many other studies have been done in other papers that make a comparison on the productivity of E. eugeniae on various forms of substrates. In a different study done on water hyacinth, E. eugeniae was able to work on larger pieces of substrate but favored those that were pre-composted, spent, in smaller pieces, and or had cow manure added (Gajalakshmi et al., 2002). Waste in these forms shortens composting time simply because some of the work has already been done, and they are able to manage the waste better. Pre-composting is a large contributing factor on its own. E. eugeniae can be sensitive to the pH of the substrate, and by pre-composting this allows the soil to stabilize in pH and for populations of micro-organisms to grow. E. eugeniae not only needs micro-organisms to help with the composting process through their castings, but they also eat various species of micro-organisms (Aira et al., 2005; Yih et al., 2010). E. eugeniae is selective on what species of micro-organisms it eats, eating mostly different types of fungi and protozoa (Yih et al., 2010). With its selective feeding, studies usually showed a decrease in microbial biomass, but an increase in micro-organism diversity (Aira et al., 2005). Even though E. eugeniae eats many micro-organisms as part of its diet, its castings provide a better more nutritionally rich environment for new micro-organisms to exist on. Another way to benefit the soil can be through the addition of cow manure. Adding cow manure initiates decomposition by the microbes and also starts mineralization which is important to releasing the elements from the waste product increasing the nutritional levels (Deka et al., 2011 and Yih et al., 2010). The addition of manure also increases the overall biomass of the worms which in turn speeds up maturation and eventually productivity (Deka et al., 2011; Yih et al., 2010). As seen above, these three factors play the biggest role in the productivity of E. eugeniae.
The end result is rich in nutrients and creates better soil for future plant growth. Through vermicomposting pH levels tend to decrease (which is more optimal for plants), nitrogen levels increase, phosphorous levels increase, and potassium levels increase (Deka et al., 2011; Yih et al., 2010). All of the previous elements are very beneficial and necessary for plant growth. The only levels that seem to decrease in vermicomposting are the levels of carbon. This is due to the fact that Eudrilus eugeniae utilizes the carbon as its main energy source (Deka et al., 2011; Aira et al., 2005). This is not necessarily bad, as long as nitrogen is added when the carbon-to-nitrogen levels drop below the desired range (Yih et al., 2010). The variety of nutrients produced from vermicomposting is one of the key things that make vermicomposting a sustainable practice.
Eudrilus eugeniae is a great species for vermicomposting based upon how it manipulates the soil, the variety of ways it can be implemented as a sustainable technique, the three main factors that influence its productivity, and the final result. Employing worms to help manage large landfills or in developing nations is a great way to eliminate waste products while also creating fertilizers for crops. Maybe the worms will find other uses other than for composting. Maybe scientists will find a way to use them as a protein source. It is interesting to see how one species of worm can have so much potential. With small steps like these, new ideas will continue grow as the world grows. Maybe someday neighbors will be vermicomposting in their back yards.
- Aira, M., F. Monroy, and J. Domínguez. 2005. Changes in microbial biomass and microbial activity of pig slurry after the transit through the gut of the earthworm Eudrilus eugeniae (Kinberg, 1897). Biology and Fertility of Soils 42: 371-376.
- Coulibaly, S. S. and I. A. Zoro Bi. 2010. Influence of animal wastes on growth and reproduction of the African earthworm species Eudrilus eugeniae (Oligochaeta). European Journal of Soil Biology 46: 255-229.
- Deka, H., S. Deka, C. K. Baruah, J. Das, S. Hoque, and N. S. Sarma. 2011. Vermicomposting of distillation waste of citronella plant (Cymbopogon winterianus Jowitt.) employing Eudrilus eugeniae. Bioresource Technology 102: 6944-6950.
- Dominguez, J., C. A. Edwards, and J. Ashby. 2001. The biology and population dynamics of Eudrilus eugeniae (Kinberg) (Oliogochaeta) in cattle waste solids. Pedobiologia 45: 341-353.
- Gajalakshmi, S., E. V. Ramasamy, and S. A. Abbasi. 2002. Vermicomposting of different froms of water hyacinth by the earthworm Eudrilus eugeniae, Kinberg. Bioresource Technology 82: 165-169.
- Yih S. S., Edwin and T. Yeong Wu. 2010. The potential reuse of biodegradable municipal solid wastes (MSW) as feedstocks in vermicomposting. Journal of the Science of Food and Agriculture 90: 2153-2162.