Electrochemical sensors based on sewage sludge-derived biochar for the analysis of anthocyanins in berry fruits

The reutilization of waste and the reduction of the general environmental impact of every production are fundamental goals that must be achieved in the framework of a circular economy. Recycled carbon-rich materials may represent a promising alternative to other less-sustainable carbonaceous materials used in the production of electrochemical sensing platforms. Herein, we propose an innovative carbon paste electrode (CPE) composed of biochar derived from biological sludge obtained from municipal and industrial wastewater treatment plants. The physicochemical properties of the biochar after a chemical treatment with an acidic solution obtained from industrial by-products were investigated. The electrode surface characterization was carried out by analyzing common redox probes and multiple phenols bearing varying numbers of –OH and –OCH(3) groups in their structure. Furthermore, the CPE was also tested on the evaluation of the phenolic fingerprints of Vaccinium myrtillus, Vaccinium uliginosum subsp. gaultherioides, and Fragaria × ananassa. Standard anthocyanin mixtures and extracts of the aforementioned fruits were analyzed to provide a phenolic characterization of real samples. The obtained results show that the sewage sludge–derived biochar can be a promising material for the development of electroanalytical sensors. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00216-022-04062-y

Assessing the Impact of Sustainable Biochar-Enriched Substrates on Safety and Quality of Tomato (Solanum lycopersicum L.) as Relevant Model Crop

Forestry-waste biochar was tested as a commercial substrate (peat:lapillus 1:1 v/v) amendment in growing tomatoes (Solanum lycopersicum L.). Substrates were 0% (control), 5%, 10%, 20%, and 40% (% v/v) biochar-enriched and were characterized for their textural and physicochemical properties. After harvesting, tomato production (i.e., plant and fruits), quality (e.g., nutrition and nutraceutics), and safety (i.e., biochar-related pollutants) were assessed according to the different growing media. 10-to-40% biochar-enriched substrates only exceeded the pH threshold set by L.D. 75/2010. Ni and Mn exhibited a similar trend between substrates and fruits, while Cr, Pb, and Cd were absent. Plant biomass increased (up to 11–29%) according to biochar content, which conversely diminished fruit production (∼25–60% reduction). Only acenaphthene exhibited an increasing profile (11–12 μg kg–1) according to the treatments, nevertheless complying with the European regulations. PLS-DA confirmed practice suitability by substrate–crop correlation, providing prediction models for quality and safety assessment