A Pedal-powered Cable Shredder

Burning plasticThe problem

The way in which e-waste components are dismantled is usually what generates the hazard, rather than the components themselves. Cables, for instance, are burnt to recover copper, producing toxins and liberating brominated flame retardants. Hazardous e-waste processing methods are damaging Agbogbloshie. Open burning of cables is also a big hazard in other African countries.

The idea

We study how a pedal-powered cable shredder can reduce this hazard. It consists on a shredder attached to a modified bike. It reduces cables to tiny bits, separating plastic by flotation. The machine is called “E-source”, as an antagony to the term “E-Waste”. It’s a 15156969710_biciCablesdesign by Hal Watts, built by himself and Matt Batchelor at the Makerversity in London. It’s an open source machine, designed to be replicated locally and whose materials cost less than 125€.

An operator pedals, and the chains activate 3 components: a shredder, a water pump for the separator, and the vibration of a separation bed. The result is that cables are reduced to pieces, and the combination of flotation and vibration make plastic slip forward and copper jump backwards.

The trip

In June 2014 we took E-source to Accra to find out under which conditions it would work. We interviewed cable burners finding out more about their lives and work. We partnered with the Agbogbloshie Makerspace Platform (AMP) who shared their network and knowledge with us, and who are now in possession of the cable shredder. We received a great help from engineering students from the Creativity Group at KNUST University.

Together we fixed a broken holder, found a workshop to drill a shaft to improve the machine’s transmission, bought different kinds of cables in Agbogbloshie to test the machine, modified the feeder for a better shredding, and improved the separator. However, we did not have time to fix the chain that kept coming off when pedalling at high speed.

15157880148_GrupoTrabajoThe positive results

The innovative potential of E-source is high. Shredding is considered as a “best applicable technique” and a “suitable engineering design”, being potentially key for the improvement of informal techniques. It has low net costs, low capital costs, low use of electricity, low use of freshwater, and a low health and safety impact.

There is enough local capacity to build and repair E-source. There are workshops in the area that can repair, and even have expertise building other machines with pieces similar to those used in the shredder. A Makerspace, like the one AMP is building in Agbogbloshie, is an ideal place to continue this experiment. The help of the Creativity Gorup is key to finding new solutions. Not only the technology seems appropriate, but the environment around it too.

15344429145_biciCables2Where more work needs to be done

There are still problems to work out. In its current design there is a maximum size of cable that can be processed. Those thick, or those coming taped together (as it’s usually the case with car cables) would still need to be burnt. Speed of processing is a second problem. Fire is fast: a full pushcart of cables can be processed in 10 minutes. Cable shredding requires removing impurities like harder plastic bits.

Shredding can be slower but still competitive if it offered a higher income at the end. For instance, fresh copper (not burnt) is 0,8 – 1 GH¢ (0,20 – 0,25€ as of June 2014) more expensive per kilo than burnt copper. Adding value to the plastics removed can also be decisive. Liquid Crystal Polimer Molex connectors could potentially be reused, and PVC insulation could be pelletised and resold. We need to research this further.

Cable burners are vulnerable to be cut off from their supply source if scrap dealers find a way to do the processing themselves. This needs to be taken into account when implementing E-source, making the device first available to the cable burners.

Conclusions

We have found several positive aspects in which we can base our future work. We believe the environment of a Makerspace community is the right one for this kind of device, and we have seen that there are local workshops able to carry out repairs and even machine making. We have identified some problems ahead, whose solution is crucial.  We look forward to resuming E-source testing.

Detailed information can be found on the article submitted to the E-waste Academy: Pedal-powered cable shredding: an alternative to cable burning.