FFWT MENDELU scientists have found a use for sewage sludge, an unavoidable by-product of the wastewater treatment process. By mixing stabilized sludge with other waste materials, glauconite and biochar, they obtained a substrate usable in forestry and arboriculture. This innovation also has an environmental impact. The product is made from local raw materials and can at least partially replace the use of peat, imported from the Baltic countries, in the aforementioned fields. The prototypes have already been verified in the form of utility models (a form of patent protection) and a certified methodology that summarizes the process the sewage sludge must go through before being mixed into the substrate.
In forestry, the substrate is used on cultivating beds in forest nurseries and in forest stands that are no more than ten years old in the form of point revitalization, when the substrate is laid on the soil surface around the tree trunk. Above all, it can be used in areas where trees have difficult living conditions, mainly due to human activity. “It can be various areas of re-cultivation, for example quarries, or places where the trees have a destroyed layer of humus for some reason. By supplying organo-mineral matter, we will improve their vitality and prosperity in locations with extreme soil and climatic conditions,” said Aleš Kučera from the Department of Geology and Soil Science, describing the use of the substrate in forestry.
In arboriculture, it is expected that the substrate will be used in the preparation of rooting space for standing trees and also in the planting of new trees. “Trees in the city are exposed to extreme levels of chemicals, the soil is often compacted and, alkaline, or the root system of the trees is shallow. In these cases, arborists use techniques in which the soil is partially replaced, for example by exposing a certain zone of the root system by means of a “pneumatic spade”. In this way, the soil can be loosened and the addition of new substrate stimulates deeper rooting,” explains Valerie Vranová from the Department of Geology and Soil Science.
In terms of planting new trees, the team focused on substrates containing a large amount of stones, so-called structural substrates. “These substrates play an irreplaceable role in urban development. By making the substrate very stony, we make it resistant to compaction. The filling between the stones should be a nutrient medium, in our case a sludge-based substrate,” adds Vranová.
The granulated substrate consists of three primary waste components: stabilized and composted sludge, biochar – charred organic matter that remains unchanged in the soil for hundreds of years, and glauconite – a clay mineral that is naturally present in glauconitic sandstone and which is extracted by washing out. The substrate is supplemented with crushed bark, wood fibre and other additives which also contain other substrates.
An important stage in the substrate production process is ensuring it is not harmful. Before application, the substrate undergoes a series of analyses that check its chemical integrity and the content of plant-accessible nutrients. “After verifying risk-free status, we applied the substrate in several ratio variants to the experimental arboriculturally area, which we prepared for this purpose in cooperation with the arboricultural company CVVMZI s.r.o.(Ltd). It is the first, and so far the only, experimental arboricultural area in the Czech Republic. In the case of forestry, the research is taking place in the forest nurseries of the Forest Training Enterprise at Křtiny and several other nursery trial areas. It is already evident that the trees are thriving after application of the substrate enriched with waste components. We will further study the long-term effects, for example how the roots develop in the substrate, any recognisable increase in thickness or height of the trees and other parameters,” Kučera concludes.
Contact for further information: Ing. Aleš Kučera Ph.D., Department of Geology and Soil Science FFWT MENDELU, +420 737 471 471, ales.kucera@mendelu.cz
Doc. Ing. Valerie Vranová, Ph.D., Department of Geology and Soil Science FFWT MENDELU, valerie.vranova@mendelu.cz
The project is financially supported by EU structural funds within the Operational Program for Entrepreneurship and Innovation for Competitiveness (Application support program, Call VIII)
Project name and grant title: Optimization of treatment and processing of sludge from wastewater treatment plants in the production of cultivation substrates and their safe use, project registration number CZ.01.1.02/0.0/0.0/20_321/0024778
Principal implementor of the project: Rašelina a.s. (plc) Na Pískách 488, Soběslav II