Earthworms – A Boon to Mankind

Lakshmi Priya Thyagarajan^a, T.Meenambal^b

a Department of Biotechnology, Government College of Technology, Coimbatore-641013.

b Department of Civil Engineering, Government College of Technology, Coimbatore-641013.

Industrialisation, urbanisation and overpopulation are the main reasons of increase in solid waste. The disposal of wastes now-a-days has become a prime concern. According to an estimate that India produces about 3000 million tones of wastes annually and more than 60% are of decomposable. With the progressive increase in the size of the world population resulted large volumes of organic wastes produced all over the world. The disposal of bio-degradable solid wastes from domestic agriculture and industrial sources has caused increasing environmental and economic problems, especially in developing countries has alarmed authorities on waste disposal issues. Therefore, various alternatives have been looked into to reduce waste disposal strategies like landfills, incineration and bioremediation. The bioremediation allows the conversion of putrescible wastes into value added products such as vermicompost and optimising this sludge waste to becoming an organic fertiliser.

Earthworms play an important role in soil as ‘environmental managers’. The Greek Philosopher, Aristotle, named them the ‘Intestine of Earth’. In India, so far, 509 species referable to 67 genera and 10 families have been reported (Kale, 1991). Earthworms promises to provide cheaper solutions to several social, economic and environmental problems of human society. They are both ‘protective’ and ‘productive’ for environment and society. They protect the environment (by remedifying contaminated soil, degrading the solid wastes and purifying wastewater) and also produce nutritive ‘protein rich feed materials’ for cattle and ‘organic fertilizers’ for the farmers to grow safe and chemical-free organic foods for society (Lee, 2003).

Earthworms occur in diverse habitats specially those which are dark and moist. They can tolerate a temperature range between 5℃ to 29℃. A temperature of 20℃ to 25℃ and moisture of 60-75% is optimum for good worm function. Earthworms multiply very rapidly. Studies indicate that they double their number at least every 60-70 days. Given the optimal conditions of moisture, temperature and feeding materials earthworms can multiply by 28 i.e. 256 worms every 6 months from a single individual. Each of the 256 worms multiplies in the same proportion to produce a huge biomass of worms in a short time. The total life-cycle of the worms is about 220 days. They produce 300-400 young ones within this life period (Hand, 1988). Earthworms continue to grow throughout their life.

Some of the virtues of earthworms:

a)      Disinfects the waste

Earthworms routinely devour on the protozoa, bacteria and fungus as food in any waste materials or soil where they inhabit. They seem to realize instinctively those anaerobic bacteria and fungi are undesirable and so feed upon them preferentially, thus arresting their proliferation. More recently, Dr. Elaine Ingham has found in her research that worms living in pathogen-rich materials (e.g. sewage and sludge), when dissected, show no evidence of pathogens beyond 5 mm of their gut. This confirms that something inside the worms destroys the pathogens, and excreta (vermicast) becomes pathogen-free (Satchell, 1983; Hand, 1988). In the intestine of earthworms some bacteria and fungus (Pencillium and Aspergillus) have also been found (Singleton et al., 2003). The earthworms also release coelomic fluids that have anti-bacterial properties and destroy all pathogens in the waste biomass (Pierre, 1982).They produce ‘antibiotics’ and kills the pathogenic organisms in the waste and soil where they inhabit and render it virtually sterile. It was reported that the removal of pathogens, faecal coliforms (E. coli), Salmonella spp., enteric viruses and helminth ova from sewage and sludge appear to be much more rapid when they are processed by E. fetida. Of all E. coli and Salmonella are greatly reduced (Bajsa, 2003).

b)      Lowers Green House Gases emissions

Studies have established that vermicomposting of wastes by earthworms significantly reduce the total emissions of greenhouse gases in terms of CO₂ equivalent, especially the highly powerful GHG nitrous oxide (N₂O). Worms significantly increase the proportion of ‘aerobic to anaerobic decomposition’ in the compost pile by burrowing and aerating actions leaving very few anaerobic areas in the pile, and thus resulting in a significant decrease in methane (CH₄), nitrous oxide (N₂O) and also volatile sulfur compounds which are readily emitted from the conventional (microbial) composting process (Mitchell, 1980). Analysis of vermicompost samples has shown generally higher levels of available nitrogen (N) as compared to the conventional compost samples made from similar feed-stock. This implies that the vermicomposting process by worms is more efficient at retaining nitrogen (N) rather than releasing it as N₂O. 

c)      Reducing the loads on landfills

Millions of tons of municipal solid waste generated from the modern society are ending up in the landfills every day, creating extraordinary economic and environmental problems for the local government to manage and monitor them for environmental safety (emission of greenhouse and toxic gases and leachate discharge threatening ground water contamination). Earthworms have real potential to both increase the rate of aerobic decomposition and composting of organic matter, and also to stabilize the organic residues in them earthworm participation enhances natural biodegradation and decomposition of organic waste from 60 to 80% over the conventional composting. Given the optimum conditions of temperature (20-30℃) and moisture (60-70%) about 5 kg of worms (numbering approx.10,000) can vermiprocess 1 ton of waste into vermicompost in just 30 days (Visvanathan, 2005).

d)      Bioremediation of contaminated sites

Polyaromatic Hydrocarbons (PAHs) are priority pollutants and cause great concern with respect to human health and environment. They are inherently ‘recalcitrant hydrocarbons’, and the higher molecular weight PAHs are very difficult to remediate. Earthworm species  L. rubellus degraded spiked PAHs phananthrene & fluoranthene (100 μg/kg of soil). Losses of both PAHs occurred at a faster rate in soils with earthworms, than the soil without worms. After 56 days 86% of the phenanthrene was removed.  E. fetida was also found to degrade the  PAHs. The concentration of anthracene decreased by 2-fold after addition of earthworms, benzo(a)pyrene decreased by 1.4-fold and phenanthrene was completely removed (100%) by earthworms (Contreras-Ramos et al., 2006).

Studies with earthworm species Eisenia fetida on oil contaminated soil revealed that worms significantly decreased oil contents in comparison to the control. It also successfully treated high molecular weight hydrocarbons ‘asphaltens’ from the Prestige Oil Spill. Earthworms mineralized the asphaltens thus eliminating it from the system. It also decontaminated complex hydrocarbons polluted soil (Tomoko, et al., 2005).

Polychlorinated Biphenyls (PCBs) are a group of oily, colorless, organic fluids belonging to the same chemical family as the pesticide DDT. They constitute a family of chemicals with over 200 types, and are used in transformers and power capacitors, electrical insulators, as hydraulic fluids and diffusion pump oil, in heat transfer applications, as plasticizers for many products. PCBs are categorized as ‘unusually toxic’ and ‘persistent organic pollutant’ (POPs). They have serious adverse effects on the human health and the environment. PCB contaminated soil treated with earthworms resulted in significantly greater PCB losses (average 52%) when compared to the soil without earthworm (Singer, 2001).

e)      Recycling of industrial waste

Recycling of guar gum waste done using vermicomposting technology for a period of 150 days by the earthworm Perionyx excavates, the author reported that the treatment with 60:20:20 ratio of guar gum industrial waste: cow dung: saw dust were ideal for the growth, reproduction and zero mortality of earthworms producing nutrient rich vermicompost (Surendra Suthar,2006).

Surender Suthar and Sushma Singh (2008) investigated the use of distillery sludge with cow dung in different proportions viz. 20%, 40%, 60% and 80% using earthworm species Perionyx excavates for 90 days. They concluded that the treatment with 40% of cowdung was ideal for the vermicomposting of distillery sludge. They reported resulting vermicompost showed reduction in the concentration of metals like Zinc, Iron, Manganese and Copper when compared to the raw sludge, thus reducing metal toxicity and increasing nutrient profile in the sludge. The biological sludges from the municipal sewage plants were stabilized by vermicomposting with Eisenia foetida variety earthworm, thereby reducing the toxicity of direct application of these wastes (Masciandro et al 2000).

f)       Medicinal Value

Traditional medicinemen in China and Philippines used earthworms in forkloric healings of many sickness such as to cure fever, inflammation of different parts of the body, stomach-aches and toothaches, rheumatism and arthritis, to cure mumps and measles and even to make child delivery easier by faster contraction of the uterus and reducing labour pains. China has been using earthworms in traditional healing for 2,300 years (Wengling, 2000).

Lumbrokinase (LK) is a group of 6 ‘proteolytic enzymes’ and recent researches suggest  that it may be effective in  treatment and prevention of ‘ischemic heart disease’ as  well as ‘myocardial infarction’, ‘thrombosis’ of central vein of retina, ‘embolism’ of peripheral veins, and ‘pulmonary embolism’. It is now being used in the treatment of ‘cerebral infarction’. Japanese scientists also confirmed the curative effects of ‘lumbrokinase’ experimentally in the 1980s (Qingsui, 2003).

Scientists in the University of Colorado, U.S. believe that researches into earthworms may provide an insight into increasing the longevity of humans up to around 120 years. By exposing the earthworms to stress they identified the genes (biomarker of ageing) which may allow modifying humans ‘stress response system’ in order to extend their life.

g)      Wonder Probiotics

Worms are rich in Vitamins A and B. There is 0.25 mg of Vitamin B1 and 2.3 mg of Vitamin B2 in each 100 gm of earthworms. Vitamin D accounts for 0.04-0.073% of earthworms’ wet weight. Thus worms are wonderful probiotic feed for fish, cattle and poultry industry.

Hence earthworms no doubt justifying the beliefs of Dr. Anatoly Igonin one of the great contemporary vermiculture scientist from Russia who said ‘Earthworms create soil and improve soil’s fertility and provides critical biosphere’s functions: disinfecting, neutralizing, protective and productive’. It’s true to conclude that earthworms are ‘Boon to Mankind’.

                References

1.       Bajsa, O, J. Nair, K. Mathew and G. E. Ho “Vermiculture as a Tool for Domestic Wastewater Management,” Water Science and Technology, IWA Publishing, Vol. 48, No. 11-12, 2003, pp. 125-132. 

2.       Contreras-Ramos S. M., S. Alvarez-Bernal and L. Den-dooven, “Eisenia fetida Increased Removal of Polycyclic Aromatic Hydrocarbons (PAHs) from Soil,” Environmental Pollution, Vol. 141, No. 3, 2006, pp. 396-401.

3.       Hand.P, “Earthworm Biotechnology,” In: R. Greenshields, Ed., Resources and Application of Biotechnology: The New Wave, Macmillan Press Ltd., US, 1988.

4.       Kale, R.D. 1991. Vermiculture : Scope for new bio-technology. Ed. Director, Zoologica Survey of India, Calcutta. PP 101-103.

5.       Lee.C, “Environment Protection, Biotechnology and Earthworms Used to Enrich Farmers for Organic Farming,” Taihai Publishers, Beijing, 2003.

6.       Masciandaro. G, Ceccanti. B,Garcia.C, 2000. “In situ” vermincomposting of biological sludges

and impacts on soil quality ,Soil Biology & Biochemistry, 32, 1015-1024.

7.       Mitchell.M.J, S. G. Horner and B. L. Abrams, “Decomposition of Sewerage Sludge in Drying Beds and the Potential Role of the Earthworm Eisenia fetida,” Journal of Environmental Quality, Vol. 9, No. 3, 1980, pp. 373-378.

8.       Pierre,V., R. Phillip, L. Margnerite and C. Pierrette, “Anti-bacterial Activity of the Haemolytic System from the Earthworms  Eisinia foetida Andrei,”  Invertebrate Pathology, Vol. 40, No. 1, 1982, pp. 21-27.

9.       Qingsui, C, “A New Medicine for Heart Diseases Containing Enzyme Activator Extracted from Earthworms,” In: Lopez & Alis,  The Utilization of Earthworms for Health Remedies, 2003.

10.   Satchell,, J. E.  “Earthworm Ecology—From Darwin to Vermiculture,” Chapman and Hall Ltd., London, 1983, pp. 1-5.

11.   Singer.A.C, W. Jury, E. Leupromchai, C.-S. Yahng and D. E. Crowley, “Contribution of Earthworms to PCB Bioremediation,” Journal of Soil Biology & Biochemistry, Vol. 33, No. 6, 2001, pp. 765-775.

12.   Singleton, B. F D. R.. Hendrix, D. C. Coleman and W. B. Whitemann, “Identification of Uncultured Bacteria Tightly Associated with the Intestine of the Earthworms Lumbricus rubellus,” Soil Biology and Biochemistry, Vol. 35, 2003, pp. 1547-1555.

13.   Surender Suthar and Sushma Singh  2008, Feasibility of vermicomposting in bio-stabilization of sludge from distillery industry, Sci Total Environ, doi:10.1016/j Scitotenv.2008.02.005.

14.   Surendra Suthar, 2006.  Potential utilization of guar gum industrial waste in vermicompost production, Bioresource Technology.97, 2474-2477.

15.   Tomoko, Y, K. Toyota and S. Hiroaki, “Enhanced Bioremediation of Oil-Contaminated Soil by a Combination of the Earthworm (Eisenia fetida) and Tea Extraction Residue,” Edaphologia, Vol. 77, 2005, pp. 1-9.

16.   Visvanathan.C, J. Trankler, K. Jospeh and R. Nagendran, (Eds.) “Vermicomposting as an Eco-tool in Sustainable Solid Waste Management,” Asian Institute of Technology, Anna University, India, 2005.

17.   Wengling,C and S. Jhenjun, “Pharmaceutical Value and  Uses of Earthworms: Vermillenium Abstracts,” Flower field Enterprizes, Kalamazoo, 2000.