MID MIX technique

MID MIX has the designation ‘best available technology’. With fully developed techniques and the addition of quicklime to sludge waste, the result is a reusable raw material. As from mid-2018, MID MIX will be used in the Netherlands for the processing of sludge and other waste flows.

Sustainable solution

VSGM wants to contribute to a circular, environmentally friendly society. Due to natural chemical reactions in the processing unit, MID MIX is a low energy consuming system. It has a very low CO2 footprint and emits no NOx. The end product, Neutral, can be safely reused in the manufacture of building products and in the construction of roads. The end product, Neutral, can be reused in a wide range of applications in the construction industry and in infrastructural construction.


The MID MIX technology was conceived almost 10 years ago in Croatia. Since then, Astra Engineering has continued to develop the technology. During this period, more than 130 types of material (sludge and waste) have been successfully processed with the MID MIX technology.

The MID MIX technology is patented worldwide. In large parts of Europe, the MID MIX is now marketed by VSGM.

Application and capacity

The basic MID MIX installation processes between 3 and 6 tons of sludge per hour. They can be placed at locations where sludge is collected. There are also semi-transportable installations that can be deployed flexibly at locations where sludge is produced. In principle, two operators are required to operate the production line. The system is controllable to a specific required output.

For larger volumes, bespoke installations are designed. Depending on demand, a number of installations can be deployed in parallel.

Different configurations, scalable to very large volumes, can be set up according to the needs of the customer or because of the emergence of a new demand.

The basic process

The sludge to be processed is converted into the Neutral product in a reactor by adding CaO.

The installation consists of a number of components. Dewatered sludge is taken from the feed buffer and pre-treated after which it is processed in two reactors. Here CaO is added. Moisture is extracted by exothermic reaction and various chemical and physical processes take place. The core processes that take place in the installation are solidification and molecular encapsulation of heavy metals.

The end product, Neutral, is then cooled. The ventilation air of the process is treated in a baghouse and a scrubber. Approximately 60% of the total input mass is converted into the end product, Neutral. During the process, no residual product remains that needs to be disposed of as waste.

End product Neutral

After processing sludge in the MID MIX, the circular building material Neutral is created. This consists mainly of Calcium Carbonate (CaCO3) and Calcium Hydroxide (Ca(OH)2).

Neutral can be used as an aggregate in construction, as a soil improver and as a replacement for primary building materials.