E-waste and end-of-life vehicles (ELVs) are fast-growing waste streams in the EU and beyond that require specific collection and treatment activities to avoid environmental pollution and resource depletion fed by the linear economy model. This paper aims to investigate the links between e-waste and ELVs streams and the circular economy approach of the EU. Romania is examined as a relevant case study for the central and eastern European Region regarding: (i) the current e-waste and ELVs management deficiencies and challenges in line with circular economy principles promoted by EU; (ii) analysis of E-waste and ELVs flows data; and (iii) best circular economy initiatives related to e-waste and ELVs in Romania, including the opportunity to create new jobs in treatment activities that the simple operations from the first stages of e-waste recycling can produce locally and regionally in Romania. This work points out the current knowledge gaps and future research directions for these special waste streams in Romania and beyond.

Organic waste has the potential to produce methane gas as a substitute for petrol-based fuels, while reducing landfilling and possible environmental pollution. Generally, anaerobic digestion (AD) is used only in wastewater treatment plants as a tertiary stage of sewage sludge treatment, generating a fraction of the energy that such process plants require. In this study, four different wastes—food waste (FW), dairy industry waste (DIW), brewery waste (BW), and cardboard waste (CBW)—were tested for biogas production. The biochemical methane potential (BMP) of each sample was evaluated using an automatic methane potential system (AMPTS). Operating parameters such as pH, temperature, total solids, and volatile solids were measured. Experiments on the anaerobic digestion of the samples were monitored under mesophilic conditions (temperature 37 °C, retention time 30 days). Specific methane yields (SMYs), as well as the theoretical methane potential (BMPth), were used to calculate the biodegradability of the substrates, obtaining the highest biodegradability for BW at 95.1% and producing 462.3 ± 1.25 NmL CH₄/g volatile solids (VS), followed by FW at an inoculum-to-substrate ratio (ISR) of 2 at 84% generating 391.3 NmLCH₄/g VS. The BMP test of the dairy industry waste at an inoculum-to-substrate ratio of 1 was heavily inhibited by bacteria overloading of the easily degradable organic matter, obtaining a total methane production of 106.3 NmL CH₄/g VS and a biodegradability index of 24.8%. The kinetic modeling study demonstrated that the best-fitting model was the modified Gompertz model, presenting the highest coefficient of determination (R²) values, the lowest root means square error (RMSE) values for five of the substrates, and the best specific biogas yield estimation with a percentage difference ranging from 0.3 to 3.6%.