Nowadays, one of the biggest challenges faced by EU countries is the pursuit of zero-emission economies. Certainly, it is crucial to determine the role of fossil fuels in the energy transformation. In light of the European Green Deal, EU countries should cease the consumption of hydrocarbons, i.e. coal, crude oil and natural gas, by 2050. Nevertheless, there are significant differences regarding the possibility of decarbonizing the energy sectors of the different EU Member States. For many years, Romania has been successively implementing an energy transformation, the main goal of which is the significant reduction of fossil fuels in the energy mix. Just a few years ago, one of the most important energy resources was coal, which is to be eliminated within the next decade. However, a much greater challenge is the reduction and subsequent abandonment of natural gas and crude oil. The key task facing Romania is to ensure energy security, which is why decarbonization will be strongly coupled with the country’s economic and political capabilities. The exclusion of fossil fuels in power engineering means that there is a need to develop alternative generation capacities, in particular in nuclear, wind and solar energy. This article presents the current condition of the energy sector in Romania, with a particular emphasis on the role of fossil fuels in its transformation. An analysis of documents and field research shows that there will be a dynamic decarbonization in the coming years, which will result in a significant reduction in the consumption of fossil fuels. The priority of Romania’s energy policy is to achieve a zero-emission economy, but ensuring stability and security in the energy sector will be of key importance in this process.

Two types of submerged membrane bioreactors (MBR): hollow fiber (HF) and hollow sheet (HS), have been studied and compared in terms of energy consumption and average shear stress over the membrane wall. The analysis of energy consumption was made using the correlation to determine the blower power and the blower power demand per unit of permeate volume. Results showed that for the system geometries considered, in terms the of the blower power, the HF MBR requires less power compared to HS MBR. However, in terms of blower power per unit of permeate volume, the HS MBR requires less energy. The analysis of shear stress over the membrane surface was made using computational fluid dynamics (CFD) modelling. Experimental measurements for the HF MBR were compared with the CFD model and an error less that 8% was obtained. For the HS MBR, experimental measurements of velocity profiles were made and an error of 11% was found. This work uses an empirical relationship to determine the shear stress based on the ratio of aeration blower power to tank volume. This relationship is used in bubble column reactors and it is extrapolate to determine shear stress on MBR systems. This relationship proved to be overestimated by 28% compared to experimental measurements and CFD results. Therefore, a corrective factor is included in the relationship in order to account for the membrane placed inside the bioreactor.