Pyrolysis is a promising way to reuse of waste tires. However, the carbon black generated in the process is often contaminated with various pyrolysis products. This study aims to recycle low-quality recycled carbon black (rCB) from waste tire pyrolysis, addressing the challenges posed by organic residues (up to 5 wt% bituminous substances, 112.2 mg/kg PAH). This causes the agglomeration of particles and decreases the active specific surface area. Cavitational vortex milling (both wet and dry) emerges as a promising method to valorize contaminated rCB, allowing for a significant reduction in the concentration of contaminants. This novel method allows for the generation of hydrophilic and hydrophobic black pigments. In parallel experiments, low-quality rCB is incorporated into solid biofuel to enhance its calorific value. The addition of 10 wt% rCB) to peat residues significantly elevates the calorific value from 14.5 MJ/kg to 21.0 MJ/kg. However, this improvement is accompanied by notable increases in CO₂ and SO₂ emissions. This dual effect underscores the necessity of considering environmental consequences when utilizing recycled carbon black as a supplement to solid biofuels. The findings provide valuable insights into the potential of cavitational vortex milling for carbon black valorization and highlight the trade-offs associated with enhancing biofuel properties through the addition of rCB.

Using kukersite oil shale ash for the stabilization of organic-rich soils has been extensively studied but without much success. The main reason for this is the retarding effect of humic acids present in organic-rich soils on the formation of the C–S–H (calcium–silicate–hydrate) phase, which effectively prevents the solidification of cementitious materials in peat soils. Based on the studies performed at the University of Tartu, we have developed a novel method for the in situ mass stabilization of peat soils using waste materials (calcareous fly ash and silica fume). In this manner, the perfect hardening of peat–ash mixtures (to each 1 m³ of soil, 150–400 kg ash, 25–50 L pozzolanic additives, and 2.5–5 kaNaOH were added) can be achieved. A test road embankment was constructed under extremely hard conditions in a peat quarry that is currently in use.

HydroThermal Liquefaction (HTL) is a process that involves the reaction of polymer compounds such as cellulose, lignin, synthetic plastics, etc. with near-critical or supercritical water to form low molecular weight liquid compounds, similar to natural oil which is believed to have formed over millions of years. Compared to other biomass recovery methods such as pyrolysis or anaerobic digestion, HTL is highly efficient with an energy efficiency of up to 90%, while the others have an efficiency of only around 30%. However, traditional HTL requires extremely high temperatures (250–450 °C) and pressures (100–350 bar), which are challenging to achieve using large-scale industrial equipment. This study proposes the use of ultrasonic cavitation to induce a supercritical state in water locally, rather than throughout the entire reactor, making it possible to perform HTL reactions using inexpensive and simple devices. The study demonstrates the successful conversion of pure cellulose to low molecular weight liquid compounds using potassium hydroxide as a catalyst.

Polyvinylidene fluoride particles and film were chemically modified by grafting with polystyrene without a preliminary treatment of the fluoropolymer surface. The modification was performed using surface-initiated atom transfer radical polymerization with Cu⁺–Tris (2-aminoethyl)amine as the catalytic system in a styrene/acetonitrile mixture. A small amount of Cu(II)Cl₂ was added to control the polymerization process. The amount of covalently bound polystyrene was quantified using Fourier transform infrared spectroscopy, and the extent of grafting was found to be a time-dependent process at 60 °C. The formation of polystyrene brushes, which may form a uniform polystyrene layer over the surface of fluoropolymer particles, was observed via scanning electron microscopy.

North Africa, including the Sahara Desert, was historically forested, but over the past 10,000 years, the region has undergone significant desertification due to climate change and human activity. The use of wood for heating and grazing destroyed grass cover, which was replaced by shrubby vegetation. The slow-growing nature of the forest flora, often taking thousands of years to mature, has hindered natural regeneration, accelerating desert expansion. Today, desert encroachment is a critical issue, exacerbated by intensive farming and deforestation, which have caused severe soil erosion and the loss of the humus layer, diminishing the soil’s ability to retain water and nutrients. A project led by the Estonian University of Life Sciences and Ecole Nationale Supérieure Agronomique (Algiers) under the EU Climate Action program aims to develop effective methods for reforesting arid areas and restoring the soil’s humus layer. This approach is also suitable for establishing urban greenery in arid and semi-arid climates. The method involves planting tree seedlings equipped with individual water reservoirs in holes lined with water-impermeable biodegradable pipes. These holes are filled with a hardening composite that stores water, sustaining the plants until their roots reach deeper water sources. The composite is primarily made from locally sourced organic waste and ashes. The Djelfa region in central Algeria has been selected as the test site for this method, following comprehensive studies of the area’s soil, climate, and ecosystems. Due to COVID-19 pandemic, the work was transferred to Kenyatta University in Kenya where the preliminary tests show excellent results. The conditions in Nairobi during the dry season are comparable to Djelfa area. The results reveal a significant increase in plant biomass without watering during a dry period. This is extremely important for a desert region where watering is not feasible.