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More compost from underground worm hotel by shredder students

Compost yield would be of great benefit to Amsterdam soil

23 May 2017 13:59 | Communication

Four AUAS students have designed a shredder with which vegetables, fruit and garden waste (known in Dutch as GFT) can be shredded and fed to worms. This would mean that GFT waste from local residents in Amsterdam can be turned into compost quicker and more effectively. The shredder is to be placed in the first underground worm container in the Netherlands. This is in Amsterdam-Oost and is an initiative by Stichting Buurtcompost [The Neighbourhood Compost Foundation] and Amsterdam City Council.

In Amsterdam, GFT waste is not separated from household waste. And this while the soil in Amsterdam contains insufficient nutrients, and really needs good compost. For a few years now, there have therefore been (above-ground) worm hotels in a number of Amsterdam neighbourhoods, where local residents can take GFT waste. The worms then eat the peels, teabags, coffee grounds and other organic waste, creating valuable compost by wriggling through and digesting this matter.

Fatal temperatures

Peter Jan Brouwer from Buurtcompost has been working on worm hotels for some time, and noticed that winter temperatures can be fatal to the worms. Worms are extremely sensitive to temperature fluctuations. Also, the composting process pretty much comes to a standstill when it’s cold (just like in a fridge). The solution came to Brouwer in a flash: the worm hotels have to be underground – where worms naturally live.

This idea has now been implemented in cooperation with Amsterdam City Council. Since last summer, the Van der Meylaan in Amsterdam East has had the first underground worm container in the Netherlands. In terms of its looks, the compost container isn’t much different from the ‘normal’ waste containers on the streets; the locals won’t see the worms; they do their work several metres down in the ground, unseen below a partition.

Shredder

At present, some 200 households can use the underground worm containers to get rid of their GFT waste. This number can increase if the turnaround time can be accelerated (from GFT waste to compost). Brouwer approached the AUAS Innovation Lab with the question of whether they could come up with something to achieve this. Four technology students from the Engineering, Design & Innovation (ED&I) programme have spent the past few months developing a shredder to be placed in the container. Because if the feed is dosed and shredded before entering the worm hotel, the worms can feed, digest and move better. And this accelerates the composting process.

Crushing avocado seeds

The shredder developed by the students was finished last week. The prototype has sturdy steel blades that mesh together, so even hard parts like the seeds from avocados can be ground up, along with cardboard egg boxes and sawdust. Of course, the worms need the right mix of GFT, including flower stems and salad (green fed), as well as sturdy, dry material such as cardboard (brown feed) which is digested slowly and ensures good aeration of the compost.

The students will be testing the shredder for the client next week. If it works satisfactorily, Brouwer will go ahead and also install the device in other worm hotels in the future.

More students and researchers recruted

Several students and researchers at the University of Applied Sciences are working on this Buurtcompost project. Applied Psychology students, for example, are carrying out research into social cohesion in Amsterdam neighbourhoods where residents compost together using a worm hotel.

Researcher Kasper Lange has developed a measuring tool for this project with which people without laboratory experience can simply measure the quality of the compost and the GFT waste.

Lange is a researcher with the research project ‘RE-ORGANISE’, led by AUAS. He is ascertaining how economic, social and ecological value can be created for two urban farming projects by forming recycling circles. Worm composters are seen as a promising solution.

Biology student Andres Vreeken from the University of Amsterdam is also closely involved with the underground worm container. For his dissertation, he is investigating which feeds are and are not good for the worm population.

Claire shows wurms in palm of her hand

Foto: Claire Hornn