Domestic organic waste treatment through vermitechnology

Vermitechnology has become a popular method for the safe and cost-effective treatment of domestic and agricultural solid wastes. Since 2010, a remarkable number of excellent papers have been published in Waste Management & Research on this environmentally friendly transformation of energy-rich organic matter into humus-like product. Among these, the work of Rajpal et al. (2010), is of special interest, as the indigenous earthworm species Perionyx sansibaricus and Perionyx excavates are successfully used in India instead of exotic species for vermicomposting. These authors claim that the vermicomposting process is limited, because the users have to purchase non-native earthworm species (usually Eisenia fetida) and if they are lost for some reason, they have to be purchased again. In this study it was shown that the performance of indigenous species was comparable with that of the exotic species, although the exotic species degraded the organic matter faster. However, after continuous application of vermicompost produced by Eisenia fetida, the local earthworm species vanished from that area. Kurian and Velmourougane (2010) have shown in India, that both exotic (Eudrilus eugeniae) and native earthworm (Perionyx ceylanesis) species can be used in vermicomposting, and that the efficiency of composting with indigenous species was found to be higher in their study. In Estonia, Eisenia fetida is one of the native earthworm species inhabiting manure and compost piles. Vermicomposting has not found wide usage in Nordic countries, due to insufficient efficiency at low and moderate temperatures. However, on-site small-scale vermicomposting of kitchen waste could be a reasonable way of obtaining valuable fertilizer for the gardens and small fields of private households. We conducted a comparable on-site vermicomposting experiment in the range of temperatures from 16 to 31 °C, using kitchen waste that consisted of fresh and boiled fruits, vegetables and plants, coffee grounds and teabags, eggshells, kitchen paper, milk and meat, etc. As a result of this study, it may be concluded that on-site vermicomposting using Eisenia fetida is a beneficial way of treating kitchen waste in Estonia. The biomass of the earthworms doubled during 120 days, the pH increased from 5.4 to 8.3, the change in the content of total phosphorous increased from 0.3 to 0.7%, and a two-fold reduction of organic carbon was observed. These results are in good agreement with the results obtained by Rajpal et al. and they clearly show that there is no need to adapt non-native earthworm species for vermicomposting in Estonia. Moreover, the legislation of Estonia determines that the release of non-native species into the wild should be fully excluded. Vermicomposting is an efficient way of reusing organic waste materials and indigenous earthworm species should be preferably used for this purpose. Most of the relevant studies have been carried out in countries with a warm climate. Novel intelligent protocols should be developed, so that this attractive approach could also be widely applied in regions with a moderate climate. We propose that the editors encourage the scientists dealing with vermicomposting to publish the results of their studies in Waste Management & Research more actively.