One of the latest initiatives when it comes to circular economy, is the recycling of used nappies. Waste processing company ARN in Weurt has developed a special reactor for it that has been tested on a small scale. From the end of this year, nappies will be recycled on a large scale.
Nappies make up some 5-8% of residual waste in the Netherlands, from households, nurseries and care homes for seniors. ARN has found a method, based on the technique of 'thermal pressure hydrolysis', to solve this problem. Together with Elsinga Beleidsplanning & Innovatie (EBI), a special processing method and reactor tailored to that method were developed. In that reactor, separately collected nappies and sludge from the Rivierenland Water Board's adjacent sewage treatment plant come together.
Sludge
"Tests have shown that this method works best when the nappies are treated mixed with sewage sludge. This may sound strange, but in fact the contents of a nappy are no different from the composition of sewage sludge. For this reason, Waterschap Rivierenland is involved in applying this technique."
Special added value of this technique is that in addition to germs, residual medicines are almost completely broken down. The construction of one 'reactor' will be started, and if it proves to work, the installation will be extended with two more reactors. A total processing capacity of 27,000 tonnes per year can thus be realised.
Biogas
In the reactor, the mixture is heated with high-pressure flow. The flow causes wet slurry to form. An agitator keeps this slurry moving. The plastic covering of nappies melts.
After some time, the pressure is removed from the boiler after which the temperature drops. This causes the plastic particles to solidify from the nappy and float on the liquid. The reactor vessel is then emptied. From the liquid, the plastic particles are sieved after which they find their way to the plastic recycling industry. There, they are made into new products. With the remainder, the poo and pee residues including the processed sewage sludge, biogas is produced in a sludge digester, which is then used as green energy.
Special about the technology is that in addition to germs, remnants of medicines are almost completely broken down. Elderly people, in particular, use a lot of medication and some of it ends up in the urine. So that also ends up in the incontinence nappies. ARN conducted its own research with five medicines that give a good picture of degradation. All five were completely degraded. This is mainly due to the thermal treatment. According to ARN, other nappy recycling techniques have not previously been shown to break down medicine residues properly.
Large reactors
So far, it has been working with a small reactor. From the end of this year, the first of three large reactors will be installed. These will have a capacity of over 9 million kilos of dirty nappies (accounting for about 8 per cent of nappies in the Netherlands). The first of the three reactors that will soon be installed in the large plant should be ready by the end of December. The investment will cost ARN around 5 million, but the company expects to make a profit of 300,000 to 400,000 euros each year.
Should the processing capacity of 27,000 tonnes of nappies a year eventually be realised, it could save care homes and nurseries tens of thousands of euros a year.
Afvalcentrale Amsterdam is also building a nappy recycling plant. To do so, it is working together with Procter & Gamble, which is testing a technique that, among other things, uses the plastic and cellulose from used nappies to make caps for detergents, for example.
By: Kelly Bakker
Source: vanluiernaargrondstof.nl
