Coal Share Reduction Options for Power Generation during the Energy Transition: A Bulgarian Perspective

The sustainable energy transition to a low-carbon and climate-neutral economy by 2050 requires a consistent increase in the share of renewable energy sources (RESs) at the expense of the share of fossil fuels. The coal power plants in the Republic of Bulgaria have provided about one third of the annually produced electric power for decades, utilizing mainly locally available sources of lignite. The present work aimed to review the progress of the energy transition, its rejection and acceptance at the national and international scene alongside the available research for cleaner coal combustion in Bulgaria, as well as discuss a Bulgarian perspective for coal share reduction options for power generation during the energy transition. A comprehensive review was carried out, based on freely accessible data such as research and open media articles, officially published field reports, legislative and strategic acts as well as validated statistical data. Three groups of critical gaps (socioeconomic, sociotechnical and cultural and political) were indicated, claimed to be capable of guiding the just transition. Key factors influencing the process dynamics were identified and categorized in the context of the critical gaps. The peculiar policy criteria for the carbon-intensive regions are as follows: the dominant energy carriers, existing infrastructure, involved actors and choice of strategy. The observations allowed us to conclude that in addition to the efforts achieved and ambitious political will, the identification of reliable technological and socioeconomic measures is needed more than ever (accompanied by interdisciplinary research involving the technical, social and environmental and policy factors), while renewables still have long way to go towards complete substitution of the fossil fuels for power generation, transport, and manufacturing. Limited literature was found for reducing the share of coal from currently operating Bulgarian coal-fired power plants (CFPPs). Herein, short- and/or medium-term measures for carbon emission reduction were discussed, capable of promoting the limited operation of existing CFPPs, thus paving the road towards a sustainable, long-term transition. These measures concerned the typically used power units in the largest CFPPs located at the Maritsa Iztok Mining Complex (MIMC). Analyses of the biomass production, supply and cost for the same type of power units were proposed, considering the use of 100% biomass. Estimated costs, unit efficiencies and power generation were discussed along with the evaluations about the land use, ensuring a given annual productivity of wood chips from fast growing plants, e.g., Paulownia.