REMEX Processing

Sustainable mineral waste management

Developments over the past years have contributed to the significant improvements in qualities of recycled products from incinerator bottom ash processing, offering ever more possibilities for use. This process was greatly influenced by the Green Deal in the Netherlands, where the REMEX Group created a lead position with its subsidiary HEROS, resulting in benefits to all our customers – from the Waste-to-Energy industry as well as metal processing companies to the construction sector that use our aggregates.

The Dutch Green Deal

Erwin Pieters, Managing Director HEROS Sluiskil B.V.

"The Green Deal for incinerator bottom ash is unique in Europe. In the Netherlands, it has induced significant changes - all involved are
committed to sustainability."

"The Green Deal is all about sustainability, about reducing carbon-dioxide and protecting the landscape and its biodiversity. The Green Deal was signed in 2012 between representatives of the waste-to-energy industry and the government, targeting the recycling and treatment of bottom ashes.

Every year, the waste-to-energy industry in Holland produces a combined volume of 1.5 million tonnes on bottom ashes. Up until 2017 these bottom ashes were used after being stripped from their metal content in road constructions and big infrastructural works but under so-called protective circumstances and measures, actually targeting or dealing with the possible leaching or emissions out of the material.

The Green Deal imposes an additional recycling step, making sure the material meets brand new quality standards which makes it not necessary any more to have these protective measures in place. By 2017, actually this year, 50% of our output on minerals has to meet these new quality requirements, and by 2020 the target is actually 100%."

From waste to recovery

Arie de Bode, Managing Director HEROS Sluiskil B.V.

"The path from incineration to recovery – at HEROS, we are responsible for the processing of bottom ash stemming from the municipal waste of circa 6 million people."

"We are here today on the 45-hectare site of Heros Sluiskil in the Netherlands. Heros is situated on the canal from Gent to Terneuzen, which connects the major ports of Antwerp, Rotterdam, Vlissingen and Gent. The channel is particularly important for us because it is here that we receive the majority of our primary materials by ship - including approximately 650,000 tons of incinerator bottom ash every year.

Bottom ash is residue left over from the thermal treatment of municipal solid waste, also called household waste, which has been incinerated to produce energy. After this process, bottom ash remains that is further treated.

The incinerator bottom ash we process is supplied from different regions in the Netherlands and Belgium; including the cities of Rotterdam, Roosendaal, Harlingen and not least Brussels. The overall 650,000 tons of ash represent the remnants of household waste from about 6 million residents.

The ash is delivered by ship, unloaded and treated at our facilities, where the mineral recycling takes place, including the extraction of iron and recovery of non-ferrous metals such as aluminium, copper, zinc and nickel from a particle size of 1 millimetre upwards.

This way, what’s thrown away is not lost. Because Heros recycles waste using treatment techniques that ensure what is delivered is able to re-enter the market as raw material.

In the future, our mineral recycling will improve even further. Currently, the recycled ash is mainly used in road construction. In the Netherlands, however, this is set to change and new fields of application are being developed. That’s why we’ve been allocated the task under the “Green Deal” from the Dutch Environment Ministry to cleanse the ash even more thoroughly, or, in other words, to make it more sustainable.

This means that in addition to our current processing methods, we introduce new and innovative ways to clean the ash. On the one hand, in order to recycle more metals within the concept of "urban mining". And, on the other hand, to greatly enhance the quality of the resulting mineral material by means of these additional methods.

Therefore, we’re expanding our facility with newly developed technologies. This includes a hydro-mechanical treatment, in which we wash the ash in a specialized process, so that its environmental characteristics are enhanced. In a further facility, we turn the ashes into a high quality granulate.  The resulting mineral material is so good that it can be used as aggregate in concrete or asphalt."

Quality secondary aggregates from bottom ash

Dr. Ulrike Kalthof, Managing Director MAV Lünen GmbH

"MAV processes around 250,000 tonnes of incinerator bottom ash per year in its enclosed processing facility at the harbour of Lünen."

"We are standing next to the discharge area of the MAV processing site in Lünen. The processing of the bottom ash consists of several stages. In the first stage, a drum sieve separates the ash from coarse, stony components and coarse scrap metals.

The central processing takes place in a hall. Here, ferrous metals are separated from the ash using multi-stage sieving processes and magnets - while non-ferrous metals, such as aluminium, nickel, copper and lead are recovered using eddy current separators.

Additionally, we use a wind sifter to remove light residual waste particles such as paper and wood from the ash.

The finished product is transported over a conveyor belt onto a stockpile, from which we later ship the construction material.

The result you see here is a quality secondary aggregate that is manufactured in strict accordance to national and international regulations and which, over the years, we’ve successfully marketed in German earth and road works projects."

Laboratory analyses to track results

Arie de Bode, Managing Director HEROS Sluiskil B.V.

"With our various analyses, we are able to monitor that we really have achieved optimum metal recovery levels and best secondary aggregate qualities."

"What you see here is our laboratory. The activities carried out here form an important part of our company. This particular HEROS laboratory, with its function and size, has been in operation for over 10 years, and enables us to examine the ash in much greater detail.

Nowadays, we conduct analyses of municipal incinerator bottom ash in a comprehensive manner. We document the composition of the ash and identify which raw materials can be extracted and recycled.

For this, different instruments are available, including a number of breakers on a laboratory scale, which reduce the particle size, at the same time releasing the metals.

Of course, sieving processes are an integral part of the lab equipment. They are used to separate the different sized fractions, which serve as basis for an extensive ash analysis.

Following this, we remove the metals from the ash with a mobile eddy current separator, which you see here. The entire procedure is a simulation of the treatment processes carried out in our facility.

The extracted metals are separated into light and heavy fractions with the aid of a liquid. We do that with this instrument, which has been developed in collaboration with the technical university Delft.

Thus, we always know how much metal the ash contains, so that we can best manage our operational processes in order to extract even more and even finer ferrous and non-ferrous particles.

Moreover, we are improving the quality of the mineral ash in accordance with the Dutch Green Deal. We do this by identifying and examining numerous data on the mineral fraction’s chemical composition – which is also carried out in this laboratory.

To this effect we examine – among many other parameters – the heavy metal content and the chloride content in the ash. This particular facility for example tests the eluates, with which we determine the salinity of several ash samples to prove that our hydro-mechanical process delivers the required results and thus meets stated provisions."