Análisis bioeconómico de la valorización de subproductos de la industria cervecera en dietas funcionales para una acuicultura sostenible

Resum

The present doctoral thesis is focused on providing new solutions in the field of aquaculture nutrition, without neglecting the importance of carrying it out from an economic perspective regarding its efficiency and viability. This research has been carried out in a multidisciplinary way between economics and biology. Along with biological research, a necessary revision of the concept of sustainability applied to the production of feed for aquaculture has been faced. In addition, several economic aspects of aquaculture production have been addressed without pretending to be an exhaustive review of the sector; emphasis has been placed on those aspects that are considered as bottlenecks for its future development. On the one hand, aquaculture, like all livestock productions, is an intensive activity with regards to the consumption of natural and energy resources. Although within all the types of livestock that we carry out, aquaculture is perhaps considered the most efficient. However, the 50% of all production costs correspond to the while another 20% correspond to the purchase or production of the fry necessary for fish-fattening. On the other hand, beer production is a global economic activity with an increasing volume of production worldwide, which has a facet hidden by the enormous amount of waste (yeasts, bagasse, or wastewater, etc.) that is produced during the process of its manufacture. In Europe alone, they are estimated to represent between eight and nine million tons per year, which entails a high cost of management, disposal and treatment for the industry, as well as being a huge waste. Only in Europe, the production is estimated to represent between eight and nine million tons per year with the corresponding waste. Beer production waste is known for its high degree of humidity (around 80 – 85%) of its weight, which is a limitation to its use as raw material and to date it has not been possible to include it in significant quantities in feed, nor with promising results. Nevertheless, these by-products mainly bagasse, and waste yeasts are produced by the industry in sufficient quantities for their use in aquaculture to be viable. In the present thesis, the validation of diets made with up to 89% by-products from the canning sector and waste yeasts from the brewing industry have been validated for thicklip grey mullet (Chelon labrosus) and gilthead sea bream (Sparus aurata) in which the growth and state of the immune system of animals has been studied. The results obtained from biological experiments and economic analyses confirm that waste yeasts from the brewing industry are an excellent raw that can be used in inclusions of up to 62,5 % of the wet weight for gilthead sea bream or thicklip grey mullet. Moreover, they are an economically viable option and environmentally more sustainable than the use of other alternative raw materials.