LIFE CYCLE ASSESSMENT (LCA) OF A BIO-FUEL CELL FED WITH WASTE BIOMASS: POTENTIAL FOR SCALE-UP AND PROCESS OPTIMIZATION

Nowadays dealing with waste as efficiently as possible is a very important and widely studied topic1. Indeed, in this way it is possible to turn a waste into a valuable resource. For this reason, a team from the University of Bologna has developed a biofuel cell as a treatment process for waste biomasses, especially from agricultural origin. This cell aims to valorize biomass by producing electricity and soil conditioner. This study is focused on to investigate the efficiency and environmental sustainability of this fuel cell through the Life Cycle Impact Assessment (LCA) methodology. This instrument is a great help for conscious choices toward sustainability because it considers the potential impacts associated with the entire life of the system studied2. After building an inventory, working in collaboration with the development team, it was possible to run the LCA analysis. This made it possible to understand which parts of the process are the most impactful to the environment and to design alternatives that aim to optimize the use of the biofuel cell. It was realized that the impacts related to the production of the cell (infrastructure) can be negligible if it is used for at least about 400 times. It was also observed that the greatest impact comes from energy consumption and the usage of phosphoric acid. The negative impact, due to avoided products, is mainly due to the recovery of phosphorus present in H3PO4. In addition, potential benefits are related to the energy and soil conditioner recovery. Alternative scenarios were created to test different combination of acids and bases. Nitric acid and potassium hydroxide were used instead of phosphoric acid and sodium hydroxide. The use of KOH seems promising because it adds potassium to the nutrient output, increasing the whole efficiency. Because of the large portion of impacts due to energy consumption, scenarios based on renewable mixes have been studied. In particular, the use of solar energy. A further model was also assessed to verify the benefits from the heat recovery during the hydrolysis reaction. Finally, all these scenarios were compared with traditional treatments for biomass waste, such as composting and anaerobic digestion. Average distances were assumed to reach such plants. From the results of this study, it can be said that this technology is promising and can be competitive as long as energy consumption is minimized, and nutrients used among the reagents are recovered.