Avoiding excess fertilizer, improving the health of agricultural soils and their capacity to sequester carbon, while promoting the circular economy of waste management, are some of the objectives of a new project to be carried out by the Applied Research Group in Agrochemistry and Environment (GIAAMA) of the Miguel Hernández University (UMH, in Elche, Spain). The OPTIFANGS project, funded by the Valencian Agency for Innovation, will serve to improve the management of sludge produced by sewage treatment plants for agricultural application through cutting-edge digital techniques that include Artificial Intelligence and the development of an electronic nose. In addition to the researchers of the Center for Agri-food and Agri-environmental Research and Innovation of UMH, the company Agricultores de la Vega de Valencia and the company Telenatura S.L. will also participate.
According to the professor of Soil Science at the UMH and leader of the study, Raúl Moral, the European Union is currently facing a major problem: soil contamination and the risk of desertification in many areas. Spain is severely affected by this phenomenon: 40% of the soils have been declared in a severe state and another 40% with moderate erosion. One of the areas where soil destruction is progressing the most is the Mediterranean area. The main causes are the accumulation of heavy metals, nitrate contamination and the salinity and toxicity of certain ions.
In view of this problem, the reuse of nutrients from waste is proposed as an effective solution and, at the same time, more consistent with sustainable practices. In addition, nutrient mining from waste has been boosted in recent years due to the rising price of fertilizers.
Two chemical elements naturally present in healthy soil are key to agricultural fertilization: nitrogen and phosphorus. These elements are also found in sewage sludge. Sludge consists of a mixture of water and solids separated from wastewater as a result of natural or artificial processes. According to data from the National Sludge Register, around 1,200,000 tons of dry matter are produced annually in Spain from sewage sludge. Therefore, the application of this sludge in the field involves a double use: on the one hand, the waste is managed, instead of being discarded as waste, and on the other hand, the nutrients available in it are valorised.
Professor Moral explains that organic matter is the major component in WWTP sludge, and is key for agricultural uses. However, its study is complex. In the framework of the OPTIFANGS project, researchers will use advanced instrumental techniques such as Near Infrared Reflectance Spectroscopy (NIRS), Fourier Transform Infrared Spectroscopy (FT-IR) and thermal analysis. The use of these techniques makes it possible to obtain a “fingerprint” of the analysed material with which to extract a sufficiently precise estimate of the agronomic and environmental composition of the particular material.
Subsequently, modelling of the analysed sludge will be performed under different conditions, which will facilitate real-time handling and dosing decisions and significantly improve process optimization. For this analysis, chemometrics will be used, which is an artificial intelligence (AI) discipline that merges the value of “chemical” and “analytical” intelligences and enables feature extraction such as data-driven preprocessing in model optimisation.
In addition, the project will develop an electronic nose, a device to identify and measure volatile organic compounds and gases produced by the agricultural application of sewage sludge.
The development of these tools will allow for decentralised sludge management that will have a lower environmental impact. Likewise, the expected results point to a 25% reduction of the excess of nutrients that are not absorbed by the crops linked to the WWTP sludge, a 12% increase of the carbon sequestered in the amended soils, the mitigation of emissions and odours at low cost; as well as the possibility of implementing the OPTIFANGS system in neighbouring countries.
The OPTIFANGS project has an initial investment of 503,496.12 euros, funded by the Valencian Innovation Agency (AVI) and the European Union under the European Regional Development Fund Program (ERDF) Comunitat Valenciana 2021-2027.