Vermikomposztálás, mint a szennyvíziszap-komposztálás alternatív megoldása ─ Szemle ─ = Vermicomposting as an alternative way of composting sewage sludge

Draskovits, Eszter and Németh-Borsányi, Barbara and Rivier, Pierre-Adrien and Szabó, Anita (2017) Vermikomposztálás, mint a szennyvíziszap-komposztálás alternatív megoldása ─ Szemle ─ = Vermicomposting as an alternative way of composting sewage sludge. Agrokémia és Talajtan, 66 (2). pp. 397-418. ISSN 0002-1873

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Abstract

Agricultural utilisation is one of the most promising uses of sewage sludge in Hungary. Sewage sludge can be applied to agricultural fields in two ways: the injection of dewatered sewage sludge and the application of sewage sludge after composting. Vermicomposting is a special type of composting, where the organic residues are broken down by earthworms. The worms facilitate the decomposition process both by mixing the sludge and by physically degrading it. Earthworm species have various morphotypes requiring different habitats. Compost worms have great adaptability to extreme conditions and are capable of exploiting organic matter in a state of decomposition. Eisenia sp., Eudrilus eugeniae and Perionyx excavatus are important species for vermicomposting. When examining the role and possibilities of vermicomposting, it is important to compare it with traditional composting methods. The most important aspect of producing vermicompost is to ensure optimum environmental conditions for the earthworms, especially in terms of temperature, humidity and aeration, which requires constant attention. An important feature of traditional composting is the thermophilic phase, during which the pathogenic organisms in sewage sludge are destroyed. The thermophilic phase is omitted during vermicomposting due to the thermal sensitivity of the earthworms, but the presence and activity of the earthworms results in similar sterility. Regarding its nutrient content, vermicompost contains larger quantities of total and plant-available macroelements than conventional composts. A further advantage is the presence of the plant hormone agents excreted by earthworms. From the environmental point of view, the ability of earthworms to accumulate heavy metals and the role of their special gut flora in the decomposition of organic pollutants could contribute to the wider use of vermicomposting to dispose of sewage sludge. While vermicompost has many advantages, a number of obstacles need to be overcome before it can be routinely used in Hungary. Many landowners regard sewage sludge compost as hazardous waste that could contaminate their soil and crops rather than as a nutrient and soil amendment. Although numerous studies have been published on sewage sludge, the assessment of long-term effects, including the issues currently of most concern in Hungary, is still lacking. Vermicomposting is therefore a promising, innovative technology for sewage sludge recycling. Sewage sludge and sewage sludge composts with pollutant contents greater than the limits laid down in Government Regulation 50/2001. (IV.3.) can be made suitable for agricultural use by vermicomposting.

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