Written by: Julio Casal Ramos
Generally speaking, there are many definitions of ‘waste’ but its most intuitive description is ‘any substance or object generated by a productive activity or after usage and is no longer useful for its generator or owner, who seeks to get rid of it by obligation and/wish’.
For instance, on 30th May 2018, the European Parliament and the Council of the European Union established the Directive (EU) 2018/851 , which updated/replaced the original 2008/98/CE about waste. In this document, the definition of waste goes as follows: ‘any substance or object whose owner gets rids of, must, or plans to’.
Undoubtedly, it is evident that today waste is an environmental, social and health problem. Waste can be classified according to multiple criteria, depending on their aggregate state (solid, liquid, gas), its origin (industrial, municipal, rural or urban, among others), its chemical composition (organic and inorganic), or even classifications with mixed criteria and more specific (plastic waste, food waste, etc.)
Waste management plays a fundamental role, especially in develop and developing countries due to a scale problem. The more people/industries, the greater the amount of waste due to the traditional linear economic model. Waste management deals with the reduction of the negative effects of waste. It also tries to make some profit out of it as a way to complement the originally available resources.
Depending on the bibliography, different descriptions of what the foundation for waste management would be can be found. For instance, Xavier Elías  points out that it can be summarized in three big principles: minimization, valorization, and treatment. Within the valorization concept, the three ‘R’ can be found: recuperation, recycling and reuse.
Furthermore, the Directive (UE) 2018/851 of the European Parliament and the Council of the European Union establish a priority order in the legislation and policies around waste management and prevention through the following waste hierarchy:
- Preparation for reuse.
- Other types of valorization.
Firstly, there are differences between the previously-mentioned points of view but, with some analysis, they present more similarities. The first approach for a correct waste management must focus on reduction, a preventive approach that encompasses both the producer’s (generating efficient products from their conception to their production) and the consumer’s (who must use the products in the best way possible, making the most of them during their useful life before disposing them) point of view.
Secondly, a proper waste management must focus on a wide and incredibly important concept: valorization. A product may generate value or be useful as long as one of these conditions is fullfilled:
- The product is used again for the function it was designed, either immediately or after being fixed (reuse).
- The product is transformed, through a series of physicochemical processes, into a raw material to be used in the recollection of the original product or an alternative product (recycling).
- The product, through a series of physicochemical processes, acquires a function that implies the total or partial replacement of other materials or substances that would have been used to perform a particular function (other kinds of valorization). As an example, it is worth highlighting the valorization of energy.
Finally, the last operation for a proper waste management program is the final waste disposal. In this sense, it is recommended that waste is always disposed of after being correctly treated to reduce its environmental and health impact. There are many possibilities for disposal, depending on the type of waste. Its selection is generally based on the physicochemical characteristics of the waste and on environmental, logistic and economic parameters. Some possible ways to manage waste are remediation, incineration, pyrolysis, among other processes.
After this basic definition of concepts related to waste management, the wide spectrum of valorization must be talked about. Valorization is, without a doubt, the fundamental base of circular economy since it is the main responsible for its cyclical nature. Both reduction/prevention and disposal/treatment do not take the waste back to the classic cyclical scheme of circular economy, they are alternatives to fight the negative consequences of waste.
As previously mentioned, waste valorization includes the implementation of physicochemical processes to transform the product or substance in something else with value. As a result, professionals directly involved in waste valorization are familiar with processing areas such as Chemical Engineering, Materials Engineering, Industrial Engineering or Metallurgical Engineering, among others, since these professionals are prepared to understand the base materials’ physicochemical characteristics and the application of specific processes that lead to the raw materials’ transformation into materials or substances with a certain use.
Because of the wide range of waste and processing ways, there are countless examples of valorization success-cases. Putting them all in one classification is a complex task, which is why some examples can be mentioned at industrial and research level:
R. Sani and A. Nzihou  obtained ceramic materials from agricultural waste. Delvasto, Orta, and Blanco  came up with a method to obtain composites from rare soils and a nickel-cobalt alloy through Ni-MH. Díaz-López and collaborators  were able to synthesize a nickel-cobalt coating through electrochemical techniques from the processing of Ni-Mh batteries, generating an approximation to what would become the inclusion of this waste in electro-disposal processes. Casal-Ramos and collaborators  synthesized organic salts from solid waste from the gal electroplating industry through hot water immersion. This waste has the potential to be used as a raw material in alternative industries like cosmetics and drug industry.
Besides, from an industrial point of view, the most striking example of waste valorization focuses on energy valorization. In this case, waste is used considering its calorific value so that, when subject to controlled combustion processes, emit enough energy to be used and later transformed into electric energy. Currently, there are plants like AEB in Amsterdam, Netherlands, and over 30 plants located in different cities in Sweden. There are also the 2 world biggest Waste-to-Energy (W2E) plants under construction, one in Shenzhen, China, and the other in Dubai, United Arab States. Each of them will process over 5,000 metric tons of non-recyclable waste, generating enough electricity to power 120,000 homes each.
Waste valorization can be seen as a lifestyle philosophy that encompasses multiple ranges and can be applied both at home, at the smallest scale, and at an industrial level as energy valorization. The range of applications for waste valorization is very wide but it has only point in common: the search of sustainable development through optimal use of the available resources for the generation of goods and services for humankind.
 Noticias Jurídicas (10 de abril de 2019). Recuperado de http://noticias.juridicas.com/base_datos/Admin/dir2008-98-ce.html#c1.
 Xavier Elias. (2012). Reciclaje de Residuos Industriales: Residuos sólidos urbanos y fangos de depuradora.
Madrid: Díaz de Santos.
 Sani, R., & Nzihou, A. (2017, septiembre 15). Production of clay ceramics using agricultural wastes: Study
of properties, energy savings and environmental indicators. Applied Clay Science, 146, 106-114. 2019, abril
10, De Sciendirect Base de datos.
 Delvasto, P., Orta, R., & Blanco, S. (2016, febrero 12). Processing of spent Ni-MH batteries for the recovery
of cobalt, nickel and rare earth elements bearing materials by means of a chemical and electrochemical
sequential process. Journal of Physics Conference Series, 687 (1), S.P. 2019, abril 10, De IOP Science Base de
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