Gestión rentable y sostenible de los residuos agrícolas generados en la agricultura intensiva de Almería en el marco de la economía circular

Abstract

In recent decades, ecosystems have suffered various environmental im-pacts due to anthropogenic activities, food production being one of them. Some of the most important environmental impacts are caused by excessive application of agrochemicals and poor or non-existent management of waste from primary production. For this reason, the European Union has developed an environmen-tal policy in accordance with the situation. The aim is to achieve a sustainable economic model. The new update of this policy is the Green Deal. The aim is to achieve a stable economic model that is decoupled from the consumption of nat-ural resources and greenhouse gas emissions and is based on the circular econ-omy. Ambitious targets have been set for agriculture, including a 50% reduction in the use and risk of phytosanitary products and a 20% reduction in the use of fertilizers through the Farm to Fork strategy. In addition, all by-products ob-tained from production processes should be used or appropriate recycling treat-ment should be applied in cases where they cannot be reused to minimize their environmental impact. In agriculture under shelter, biomass and agricultural plastics are highlighted as the most important residues. Therefore, greenhouse agriculture in the province of Almeria has a major challenge ahead, even more so when the poor management of agricultural waste is an endemic problem that has been dragging along since its inception. The ob-jective of this Doctoral Thesis was to analyze the current state of the opportunities available to the different agents involved in the management of plastic waste generated in the Almeria Model within the framework of the circular economy and to evaluate the suitability of different organic amendments (i.e., plant debris from the previous season and Brassica carinata pellets) to act as the sole source of nutrition for a circular tomato crop model. This Doctoral Thesis is structured in three chapters. The first chapter iden-tifies the state of the art of agricultural plastics in greenhouse agriculture in Al-meria. Thus, there is an increase in the production of plastic waste and by-prod-ucts due to the increase in the physical area of greenhouses that has been regis-tered in recent years. The current management model is not adapted to the needs of the sector, as plastic waste is still being dumped in natural areas. However, different opportunities for improvement are identified within the framework of the circular economy. In addition, a relationship is established between the price of a barrel of oil and the proportion of recycled plastics. Therefore, the interest of establishing some kind of bonus to encourage the use of by-products and recy-cling of plastics is suggested. The second and third chapters analyze the feasibility of substituting inor-ganic synthetic fertilizers with a circular production model fertilized only with tomato plant debris combined or not with Brassica carinata pellets, applying biosolarization in long tomato cycles. A field trial carried out during three con-secutive years. The circular production model, based on the reuse of tomato plant debris, obtained a similar productive and economic yield to conventional cultivation with inorganic fertilization during the tomato production cycles, while the addi-tion of Brassica carinata pellets significantly reduced the economic benefit of the crop as a result of increased production costs. Biosolarization temporarily reduced the ex situ culturable soil microbiota, but this was replenished at the end of the production cycle to a level similar to that identified before the biodisinfection treatment was applied. On the other hand, an improvement in soil fertility was observed, which resulted in a signifi-cant decrease in the water endowment of the circular production model com-pared to conventional cultivation. The results suggest that using a circular production model taking ad-vantage of agricultural biomass represents an opportunity of interest to help in-crease the sustainability of the Almeria Model and help producers mitigate the stability of agricultural prices due to the decrease in production costs caused by the reuse of the vegetable by-product.