The safe management of waste from biomass combustion is a global problem, as the use of biomass for energy purposes is increasing around the world. Many rapidly developing countries in Asia, Africa, and South America have weak legal regulations regarding the composition of biomass combustion waste, such as ashes. As a result of the improper management of ashes, some of the pollutants may enter agricultural soils and pose a long-term risk to human health through the accumulation of harmful compounds in food. For this reason, research was carried out on the possibility of reducing harmful contaminants contained in ash in the composting process. The work presents the results of the content of 16 polycyclic aromatic hydrocarbons (PAHs) in the created composts, followed by an analysis of the toxicity, mutagenicity, and carcinogenicity of the created fertilisers. Based on the results obtained, a positive impact of the composting process on the reduction in PAHs contained in ash was found. Composting the mixture at 20 °C resulted in a slight decrease in the ΣPAH₁₆ content from 2185.46 µg∙kg⁻¹ to 2063.48 µg∙kg⁻¹. A greater reduction in ΣPAH₁₆ was obtained in the mixture incubated at 40 °C, where an overall decrease in the ΣPAH₁₆ content was recorded from 2185.46 µg∙kg⁻¹ to 1372.38 µg∙kg⁻¹. The composting process also had a positive impact on the TEQ = CEQ, MEQ, and TCDD-TEQ coefficients, causing their decrease.

This study aimed to investigate the physicochemical properties of fertiliser granules and compare their fertiliser value. The study used analytical methods, including potentiometric pH determination, the Kjeldahl method for nitrogen determination, spectrophotometry for phosphorus determination, and flame photometry for potassium and sodium determination. The content of heavy metals (Cr, Ni, As, Cd, Pb) was determined by inductively coupled plasma mass spectrometry (ICP-MS). The test material consisted of pellets made from compost (consisting of green waste: grass cuttings, leaves, and pruned branches) and slurry made from dried nettle. The results showed that the granules had pH values ranging from 7.44 to 8.20. The nitrogen content ranged from 1.77 to 2.18%, phosphorus from 0.17 to 0.38%, potassium from 0.77 to 0.90%, and sodium from 0.02 to 0.05%. In addition, the concentrations of heavy metals (Cr, Ni, As, Cd, Pb) were within acceptable limits for organic fertilisers. Studies have shown that granules made from compost and nettle slurry have favourable physicochemical properties that allow their use as a supplement to mineral fertilisation. They are characterised by an optimal pH value and a balanced content of key nutrients such as nitrogen, phosphorus, potassium, and sodium while maintaining acceptable concentrations of heavy metals. The results confirm that the tested materials meet standards for nitrogen, phosphorus, potassium, and heavy metals, confirming their suitability as safe and effective organic fertilisers. Their use can contribute not only to improving soil quality and increasing crop yields but also support sustainable development goals and fit into the concept of a circular economy.

Plant-derived residues may provide locally available components for mushroom cultivation substrates, but their variable composition requires preliminary physicochemical characterization. The aim of this study was to evaluate the physicochemical parameters of selected plant-derived residues in terms of their suitability as substrate components for the cultivation of Pleurotus ostreatus. The primary raw materials used were: oak sawdust, birch sawdust, wheat straw, triticale straw, rapeseed straw, and hemp shives. In addition, spent coffee grounds and apple pomace were applied as supplements enriching the substrate. The tested materials were subjected to physicochemical analyses including the determination of pH value, nitrogen, phosphorus, potassium, magnesium, calcium, sodium, organic carbon, and heavy metal content. The lignocellulosic materials showed high C:N ratios (80–257), indicating the potential need for nitrogen supplementation. Spent coffee grounds had the highest nitrogen content (21.61 g·kg⁻¹ DM) and the lowest C:N ratio (25.96), while apple pomace showed the lowest pH (3.85). Wheat and triticale straw supplemented with spent coffee grounds were identified as promising candidates for further cultivation trials, supporting the valorization of plant-derived residues in line with circular economy principles. As the study was limited to preliminary physicochemical screening, lignocellulosic-fraction analysis, physical characterization, and cultivation trials are required before the technological suitability of the proposed mixtures can be confirmed.

This paper defines the concept of organic and conventional agriculture and presents the differences in the quality of produced food resulting from the farming system. The test materials were the same groups of food products from certified organic and conventional production. As a result, the dry matter content, water activity and the content of potassium, iron, copper, manganese and lead were compared. The obtained results showed that food from organic farming is characterized by higher dry matter content and lower water activity. Conventional products are characterized by higher content of the examined elements, which is due to, among others, geochemical background, the use of mineral fertilizers, and the development of industry and transport. Ecological management influences the increase in the quality of consumed food by limiting the migration of nutrients and other pollutants to the environment.