Types of waste: what you should know

Transforming waste into resources

Waste classification is essential to minimize the environmental impact and maximize recycling. Here we tell you what you need to know.

Technological advances and greater concern for the environment have brought a new production model to the table: the circular economy, which, as opposed to the traditional approach that discarded what was considered waste, uses these resources to optimize their life and convert them into new products or raw materials, just as nature does.

In Spain, approximately 138 million tonnes of waste was generated in 2021, according to the latest data from the Spanish National Statistics Institute (INE). A good part of it was recycled, but the percentage of reuse varies greatly depending on the types of waste: while 80% of paper and cardboard was recycled that same year, and more than 70% of glass, only between 20 and 25% of organic waste found a new life.

In order to advance in their treatment, it is important to know the types that exist and how waste classification is carried out, so that we can extend the useful life of these resources.

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Types of waste

There are several criteria for classifying waste depending on its origin, its capacity to decompose naturally in the environment (biodegradability), its composition (the material it is made of), its hazardousness, or its physical state (solid, liquid, or gaseous).

Each type of waste will determine the most appropriate management for each one: the forms of collection, the possibility of reuse or recycling, and the type of treatment that can be given to these resources. This differentiation is key to complying with environmental regulations and reducing the carbon footprint produced by human activity.

Why classify waste?

Waste classification, and doing it correctly, is very important for several reasons. Firstly, it reduces the amount of waste sent to landfills, which, in addition to reducing the carbon footprint, helps to conserve natural resources. In addition, separating materials that can be reused (such as organic matter, paper, glass, or plastic) facilitates the recycling process.

This separation by types of waste also makes it possible to identify and properly manage hazardous waste, which minimizes risks to human health and the environment.

The most effective waste classification, towards which circular economy models point, is the separation of waste at source: separating it before disposal according to its characteristics, thus ensuring its arrival at the plants where it will be recycled, while promoting a more responsible management mentality for natural resources.

Type of waste according to its biodegradability

A criteria for the distinction of types of waste is to classify it according to its biodegradability, a fundamental aspect to understand its environmental impact. According to this classification, waste can be biodegradable or non-biodegradable. The former is waste that can decompose naturally by the action of microorganisms such as bacteria and fungi; the latter, that which does not decompose naturally or does so at an extremely slow rate.

Examples of biodegradable waste is food waste, paper, cardboard, wood, garden waste, and agricultural waste. Non-biodegradable waste is, for example, plastics, metals, glass, or batteries.

When decomposed, biodegradable waste can be transformed into compost, which serves as organic fertilizer, or into renewable fuels, such as those produced by Repsol from organic waste, such as used vegetable oils, biomass, and waste from the agri-food industry.

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Type of waste according to its origin

For its part, the type of waste according to its origin is fundamental for the proper management and treatment of these resources. According to this classification, waste can be:

Domestic waste. That generated in homes as a result of daily activities: food waste, packaging, paper, cardboard, plastics, or organic waste, such as used cooking oil. The latter can be recycled and converted into renewable fuels if it is transferred to any collection point. If you live in the Community of Madrid, Repsol has put its network of service stations at the disposal of users who wish to dispose of their used oil. Moreover, in Galicia, the cooperative Mulleres Colleteiras, collaborating with Repsol, will contribute to the collection and treatment of oil to produce renewable fuels.
Commercial waste. That coming from commercial activities, from offices and services: paper, cardboard, packaging, food waste, cleaning waste...
Industrial waste. Produced as a result of industrial processes, such as production waste, chemical waste, metals, plastics, and industrial subproducts.
Health waste. That generated in hospitals, clinics, and health centers: disposable medical materials, biological waste, expired drugs, infectious waste, etc.
Mining waste. Derivatives from mineral extraction and processing activities, such as rocks, soils, sludges, and mineral processing waste.
Agricultural and livestock waste coming from these activities: crop residues, manure, animal feed waste, or agricultural plastics, among others.
Construction and demolition waste such as rubble, wood, metals, bricks, and concrete.

Waste according to its composition

Another way to classify waste is to do it according to its composition. This classification of waste results in the following types of waste:

Paper and cardboard. They represent a significant part of the waste we generate and are easily recyclable.
Glass. It is also highly recyclable. Moreover, recycled glass can be used to manufacture a wide range of products, from packaging to construction materials.
Plastics. They represent another important part of the waste we generate. They are further subdivided into different types according to their chemical composition. While some plastics are recyclable, others are more difficult to process and may require specialized technologies for efficient recycling.
Organic waste. Easily recyclable if it is separated correctly at source.
Hazardous waste. It requires a special treatment to minimize its impact on the environment.
Electronic waste. Like the former, it needs a proper treatment to ensure reuse and recycling of its components.

Waste management at Repsol

At Repsol, we adopt the circular economy in all countries and businesses in which we operate: from the production of energy and raw materials to ecodesign in the marketing of our products. In this way, we optimize resources, reduce consumption of raw materials, and reduce the carbon footprint.

An example of this waste management based on the circular economy is the start-up in Cartagena of the first plant on the Iberian Peninsula dedicated exclusively to the production of 100% renewable fuels from waste, which will prevent the emission of 900,000 annual tonnes of CO₂, by representing a reduction of 90% of net CO₂ emissions compared to the fuel of mineral origin it replaces, because of the lower carbon intensity of the renewable fuel.

At Repsol, we have also launched in Puertollano our RECPUR plant, where up to two thousand tonnes of polyurethane foam from old mattresses will be recycled each year. This is the first plant in Spain for the chemical recycling of polyurethane foam, which has already contributed to the recycling of approximately 50 tonnes of mattresses.

In the new plant, 300,000 tonnes of organic waste will be processed per year, such as used cooking oil, prioritizing national and European origin. At Repsol, we have launched at our Puertollano Industrial Complex, our RECPUR plant, where up to two thousand tonnes of polyurethane foam from old mattresses will be recycled each year, which has already contributed to the recycling of approximately 50 tonnes of mattresses.