Footwear to Energy

Kuchl, 19.01.2016

In developing countries within South East Asia, ever-depleting landfill space, fast-growing populations and an increasing need for more concrete to build, are just some of the factors that make for a compelling alternative fuel production argument. But to what extent is a lack of waste infrastructure holding such countries back? Is legislation the missing ingredient? Or do global brands need to be the ones to drive progress? A closer look at a new Solid Recovered Fuel (SRF), built by Holcim in Vietnam, provides some potential answers.

To pass comment on the waste landscape in Asia is no easy task. The sheer size of the continent means the market is very fragmented. So, just as an analysis of mindsets and progress within Europe would present quite varied results, so too does a review of waste management in the East. 

South Korea, for example, may only be in the infancy of its Waste to Energy journey, yet the nation has formed a very sophisticated and disciplined approach to its waste roadmap, relatively quickly. Legislation is in place to drive the production of <50mm SRF, and the necessary infrastructure is fast evolving to accommodate this.

Compare this to developing ASEAN countries and the picture is somewhat different. Again, it would be ignorant to generalise the approach to waste management in this part of the world. Singapore, for instance, was the first country to declare waste a national resource. Thailand has now followed suit, as a result of a pro-environment Government defining the country’s energy policy, and waste issues making the national news. Yet in developing economies such as Vietnam, there is much more work to be done.

Here there is no waste collection system, meaning a stream referred to as Municipal Solid Waste (MSW) will look very different to MSW in Europe. The waste is incredibly mixed, with organic content as high as 60%, moisture typically 70% and construction and demolition waste often present. Without any careful pre-separation of materials, producing a specification-driven fuel such as SRF is therefore no mean feat.
That’s not to say the value of alternative fuel production has not been acknowledged – whilst admittedly a recent development, the role of resource recovery is emerging. Landfill sites are near to full, so another option is needed. Many people have also realised that, with millions of tonnes of old dumped waste ripe for remediation, the country is sat on a gold mine. 

One of the current exceptions to this trend is Holcim. This global cement giant is actively pursuing a worldwide ‘green manufacturing’ strategy to reduce CO2 emissions, improve energy efficiency, reduce non-renewable fossil fuel use and lower the clinker factor in finished cement. The use of waste as an alternative fuel fulfils this brief entirely. 

A prevalent ‘waste’ material in Vietnam is that from footwear production. This is a notoriously difficult product to shred, largely due to the mixture of tough materials – rubber, textiles, plastics, metals, sponge, reinforcements, and more – that make up a typical sports shoe. So rather than rely solely on the knowledge, and limited technology, available in the immediate vicinity, Holcim began a global search for the most suitable solution for its complex vision.

This was not going to be an exercise whereby different technologies were reviewed, before shaping a brief for a less robust equivalent that could be manufactured in neighbouring China. Instead, the group sought the input of a centralized, Swiss-based team of Holcim’s co-processing technology experts. This panel has continued to harness best practice findings from its global operations, which proved critical during the marketplace audit for this project. 

A container of untreated footwear production waste was shipped to Europe for shredding trials. The specification was to produce a 95% < 80mm Solid Recovered Fuel (SRF), with consistently high (15-20GJ/t) calorific value, at an uninterrupted rate of 10 tonnes per hour. Given power supply restrictions in the new SRF facility, the shredder’s electricity consumption could also not exceed 300kW.

There was no such technology readily available, therefore UNTHA extensively configured, re-engineered and trialled the flexible XR3000C waste shredder, until it was perfectly suited to this demanding application. The cutting concept was refined and two 113kW motors installed to provide sufficient, yet energy efficient, power.

Designed to introduce maximum efficiencies, UNTHA devised a single step shredding solution which required only one machine, rather than a pre and post shredding operation. Complete with discharge conveyor, over band magnet and control room, the entire plant was fully pre-fabricated and pre-assembled in Salzburg, for acceptance testing by the client, Holcim Vietnam, and the Swiss technical support group. The 95%<80mm specification was exceeded, with 97% of materials consistently achieving the required particle size, and the continuous rotor speed proving the system’s uptime robustness.

For heightened safety, the equipment was also manufactured with an anti-explosive Atex-specification coating, and intelligent in-built fire suppression technology. Carefully positioned UV, infrared, heat and spark detectors on the inlet hopper and conveyor can sense if a fire is likely to start. In the event of a significant temperature increase, extinguishing nozzles, positioned in the same place as the sensors and thus pointing directly at the fire risk, will automatically spray water onto the targeted area. If the risk is within the shredder, the materials can be cooled and/or the fire put out before anything is discharged from the machine. If the problem is on the conveyor, the nozzles prevent hot, glowing fractions from entering the pile of output material, where a fire could otherwise break out. 

To make the 10,000km journey to Holcim’s Hon Chong plant in Vietnam’s capital Ho Chi Minh City, all equipment was carefully packed for sea freight shipping. Two 40ft containers held the shredder, conveyors, FE-separator and support frames, whilst a third 20ft container housed the control cabinet room. A carefully planned installation plan meant a team of UNTHA technicians was on site in Vietnam when the equipment arrived. The installation began the next day, the commissioning phase was underway only four days later, and 11 days thereafter, the final acceptance test took place. 

Whilst simple to operate, by design, the XR was installed with full operator and maintenance training. Should Holcim’s fuel specification change, the shredder’s indexable cutters and interchangeable screens can be alternated to achieve an even more precise shred.
By striving to be ever-more environmentally smart in their own manufacturing activities and achieving exemplary Thermal Substitution Rates, Holcim is resolving a number of societal waste issues in the process. Wouldn’t it be great to see other companies adopting pioneering strategies that make better use of the world’s resources? 

Holcim is not the only company in ASEAN capable of closing the waste gap. Other companies could, and should, demonstrate this considered foresight, even in countries where the waste roadmap is relatively embryonic, to make productive use of materials that may otherwise be dismissed, by some, simply as rubbish.


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