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Mechanical Biological Treatment (MBT) & Zero Waste

Mechanical biological treatment (MBT) and zero waste

Many cities have established mechanical biological treatment facilities (MBT) in the past decade to reduce waste that is eventually dumped or burned. The result depends on each situation, but it is clear that MBT alone is not the solution. However, it can play a role in transition strategies to reduce residual waste without having to rely on more expensive bad options, such as incineration. A well-designed ideal zero waste strategy should not require MBT.

What is MBT?

MBT covers a wide range of activities and technologies to treat residual waste-that is, waste that has not been sorted for recycling or composting. As the name suggests, it consists of a mechanical part (where waste is mechanically separated to recover recyclables) and a biological part (used for composting or digesting the organic part).

The three main outputs of the MBT factory are: recyclables—such as PET plastic that can be sent for recycling—low-quality soil—the bio-stable part is used for land reclamation, and is almost never used for agriculture—and RDF, Refuse-derived fuel, which is the value of a mixture of homogeneous heat-generating materials burned in incinerators or certain cement kilns.

With the entry into force of the Landfill Directive, MBT has become popular, which requires member states to reduce the amount of biodegradable waste entering landfills. MBT has the ability to reduce waste volume and methane emissions, and because it is modular, it has a certain degree of flexibility and is cheaper and faster to build than any other large-scale centralized option.

The disadvantage of MBT is that the compost they produce is of poor quality; almost always the pollution is too serious to be used as a soil amendment. Therefore, some authorities see MBT as a way to meet the recovery rate without actually recycling and producing RDF that is intended to be burned in incinerators and cement kilns.

MBT in Europe

The use of MBT in Europe has achieved varying success. For example, in Germany, they have been used for more than 10 years. Although some good results have been achieved, the larger the plant, the more foul smells and bacteria nearby. Experience has proven that when biological waste collection works well and high-quality separate collection of other waste streams is combined with good product policies that promote chlorine/PVC, heavy metals and flame retardant prevention, MBT is unnecessary.

In Barcelona, ​​Spain, the MBT facility is called an ecological park and has been in operation for 10 years. Although they have managed to greatly reduce the amount of waste sent to landfills and are recovering materials for recycling, the truth is that these facilities are not producing good compost while their RDF production has increased. In fact, after all the expensive investments in MBT, the City of Barcelona realized that the only way to obtain high-quality compost was to use inputs from the separation of biological waste sources, and finally implemented separate collection of organic matter (2010).

MBT and zero waste

The zero-waste strategy means preventing waste and maximizing source separation. If all the products on the market can be recycled and properly separated and collected, there will be no waste, so MBT is not needed. If MBT has a place in the zero waste strategy, it is only when dealing with 20-30% of current municipal solid waste that cannot be separated and collected at source. In these cases, MBT can be a temporary solution, but always keep in mind the goal of continuing to minimize residual waste.

In fact, the real name of MBT in the Zero Waste Strategy is the combination of the Material Recycling Center and the Zero Waste Research Center. In these facilities, recyclable materials are recycled, and the remaining small amount of residues are stabilized so that they can be safely landfilled after they are analyzed by the Zero Waste Research Center for design defects, so that they can work upstream to make them recyclable in the future .

One of the pillars of zero waste is the source separation of organic matter—the only way to obtain clean, high-quality compost—experience has proven that this is irreplaceable by MBT.

Unfortunately, there is no European legislation requiring separate collection of organic matter, so European waste policies still lack the drivers that might make MBT unnecessary. However, more and more zero-waste cities are collecting biological waste and other waste parts separately, and have achieved high recycling rates and job creation.

The more separation at the source, the less separation (MBT) required in the end and the fewer disposal facilities (landfills and incinerators) needed!

One of the pillars of zero waste is the source separation of organic matter—the only way to obtain clean, high-quality compost—experience has proven that this is irreplaceable by MBT.

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