The experiment was launched in April 2026. Under a cooperation agreement signed between the two organizations, specialists from PKS-Vodokanal prepared a planting substrate based on products from their wastewater treatment facilities – sewage sludge mixed with sawmill waste and composted over a long period of time.
– To obtain the soil substrate, the sludge is mixed with tree bark and sawdust. The mix is then shaped into special heaps, where the compost ripens. The mass must be turned every three days to aerate it. After three weeks, the resulting soil substrate is transported to a warehouse for curing. To accelerate composting, a turner is used, – explained Vitaly Ostapchuk, Technical Director of PKS-Vodokanal.
Scientists planted five groups of a model plant – Dubok var. lettuce: four groups in the provided substrate at different concentrations, and a fifth group in a different soil (control). All plants were maintained under identical conditions in the Laboratory of Plant Biotechnology in the Vilga building. After some time, the scientists assessed the plants' morphometric parameters:
– Preliminarily, we can assess the result as positive: the sludge-based soil substrate has performed well as a plant growth stimulant. The lettuce grown on the test substrate exhibited accelerated growth and increased biomass, which is important for producers. At this point, before the results of chemical analyses are available, we cannot yet speak of the possibility of using these soil substrates for growing agricultural crops. However, we can already state that this is a good alternative soil for ornamental plants, – noted Maria Yurkevich, Head of the Laboratory of Plant Biotechnology at DMR KarRC RAS.
Maria Yurkevich, Head for Plant Biotechnology Laboratory, DMR KarRC RAS
Now that the crop has been harvested, the experiment has entered its final stage – assessing the chemical components of the lettuce. Scientists will evaluate whether the plants accumulate heavy metals and other macro and micronutrients that are undesirable for consumers. Based on the findings, an expert judgment will be issued on the applicability of these soil substrates in agriculture and other sectors.
Specialists from PKS-Vodokanal believe the results can help find optimal ways to market the soil substrates so that excess sludge is not accumulated at the facility and the composting system can operate steadily in the long term. Collaboration with the scientific community is a new step in the development of the circular economy. Its goal is to put all the generated soil substrate into economic circulation, closing the loop.
The experiment carried out in cooperation with PKS-Vodokanal is part of a broader research theme on the agricultural use of various industrial wastes implemented at DMR KarRC RAS. Previously, researchers from the Laboratory of Plant Biotechnology analyzed the effects of fertilizing soil with a range of pulp-and-paper mill wastes. Staff of the Vilga Laboratory of Agrotechnology are investigating the efficiency and safety of using bottom sediments from fish farms as fertilizers.