The world is facing growing concerns about greenhouse gas emissions and environmental sustainability. A recent study reveals that 62% of the world's emissions global markets come from the extraction of materials, their processing and manufacture of goods, while the construction and maintenance of urban structures is responsible for almost half of the world's material use and approximately 20% of greenhouse gas emissions. This situation raises a serious question about how to address the impact on the environment.
Municipal solid waste (MSW) is the waste generated in urban and suburban areas as a result of people's daily activities and business operations. According to data from the Spanish Ministry for Ecological Transition and the Demographic Challenge, around 22.7 million tonnes of this waste was generated in 2019, which is equivalent to approximately 481 kilograms of MSW per person per year. Globally, according to estimates by the UN Waste Knowledge Platform, approximately 2.01 billion tonnes of MSW were generated in 2020, equivalent to about 259 kilograms of MSW per person annually.
MSW incineration is a process by which solid waste is burned at high temperatures in special facilities known as waste incineration plants or incinerators. The main objective of this practice is to reduce the volume of waste, minimise its environmental impact and generate energy. However, this process produces ashes (bottom ash or slag and fly ash) which represent between 10-30% of the original weight of the incinerated waste, so that for each tonne of MSW incinerated, between 100 and 300 kilograms of ash are generated. Bottom ash is the main waste generated in the incineration process. This material is porous, greyish, coarse material containing mainly glass, ceramics, minerals, ferrous and non-ferrous materials, together with small amounts of unburned materials and organic carbon. Fly ash is the minority by-product and is in the form of fine, dark grey powdery particles.
The options for these wastes are the landfill disposal or recyclingbut the leaching of pollutants such as heavy metals, chlorides, sulphates and organic matter toxic which can be carcinogenic, mutagenic and genotoxicposes a risk to the environment. The use of these ashes as a secondary building material can generate various problems such as the leaching of pollutants mentioned above and/or the weakening and low durability of cementitious materials due to expansion problems.
It is therefore clear that there is a need to pre-treatment of ashes before use as secondary construction material and even before landfilling at the end of its useful life.
The leaching tests have become an essential component in studying the various solutions. These tests assess the mobility and release of material components solids when they come into contact with liquids. The results of these tests are essential to determine whether recycled materials are safe and viable for use in construction.
In this context, Royal Decree 646/2020 of 7 July 2020 establishes a legal and technical framework for the disposal of waste by landfilling with the aim of the objective of ensuring waste reduction and establishing measures and procedures to reduce and prevent negative effects on the environment related. It defines limit values for waste according to its landfill fate and requires compliance with specific criteria related to leaching and other soluble organic substances such as TOC (total organic carbon), DOC (dissolved organic carbon), TDS (total dissolved solids), among others.
In summary, recycling and reuse of highly available waste, such as MSW, is essential to reduce the consumption of natural raw materials and CO2 emissions. However, it is crucial to addressing the associated environmental challenges and ensuring their environmental viability. Pre-treatment and appropriate regulation can pave the way for a more sustainable future in construction and waste management.
The project TECNOCIRwhich is currently being implemented, aims to to study pre-treatments applied to different wastes, including MSW ashesin order to improve their properties and reduce the harmful elements present in them. for subsequent use in the manufacture of building materials. The implementation of this project is being carried out in collaboration with a consortium of companies characterised by a multidisciplinary approach and interregional scope. The 8 companies and 9 technology centres and research institutes involved represent a wide variety of sectors of high relevance in the construction industry. The total budget of the project is 5.087.870 €..
CTCON will contribute to the project by working in partnership with the companies VALORIZA ENVIRONMENTAL SERVICES and URDECON using highly available waste to develop new technological, circular and sustainable solutions applicable in the construction sector, enabling the development of products such as cements, geopolymers, concretes and bituminous mixes.
