Valorización de subproductos agroindustriales mediante la aplicación de tecnología de membrana / valorization of agroindustrial by-products through the application of membrane technology

Laburpena

Waste does not exist in nature: the waste of some life forms is the raw material of others. Working in waste management makes it possible to see the great potential contained within residues that still can be extracted. In this line, this thesis is part of a new approach to explore innovative strategies and technologies that allow impacts produced by waste to be minimized, while at the same time recovering its remaining value. This thesis is focused on organic waste from the agro-industrial industry, such as manure and food residues. These wastes have been traditionally managed by using them as organic fertilizers, but it has been stated that this practice can be ineffective, due to nutrient imbalance in the soil and also to potential polluting emissions to the atmosphere, water and soil as result of nutrient losses. Among these emissions, NH3 emissions stand out. These emissions are very harmful to the health of people and animals and to ecosystems. Fortunately, there are some technologies, such as the gas-permeable membrane technology, that are capable of converting these NH3 emissions into a valuable nitrogen based fertilizer that can be used directly on crops. The objective of this thesis is to study different applications of these gas-permeable membranes, and answer the questions that arise in their potential applications. The gas-permeable membrane (GPM) technology has the potential to be applied on different wastewaters to recover nitrogen as a nutrient. This work studies whether the GPM technology can also be applied in existing waste treatment processes, such as biogas plants, where they can not only improve the amount of biogas produced, but also its quality. In addition, it is possible to apply them in the digestate produced by biogas plants, and to obtain high percentages of nitrogen recovery. We have also tested its capability to be combined with other existing techniques for the recovery of other nutrients, such as phosphorus, which is another essential nutrient for plants. The results obtained have shown the great potential of these membranes and the importance of the application of novel nutrient recovery technologies. It is time to apply the best known technologies for waste valorization, changing the waste management approach and to start considering wastes as resources.