As a product category, Energy from Waste (EfW) shredders are not new. However, with the world of engineering advancing apace, the technological capabilities of such machines are continually evolving. The result is equipment that can process a greater variety of waste materials to produce fossil fuel substitutes of a quality and capacity people wouldn’t have previously thought possible. Our MD, Marcus Brew, recently looked at how ‘performance’ of modern EfW shredders is being defined in this feature for Energy Engineering – if you missed the original article, catch up here…

The world of shredding is changing. What was once a robust – but somewhat ugly – workhorse, is now becoming an increasingly sophisticated machine, particularly with regards to aesthetics. However, beneath the clean lines of many such innovations is, more importantly, greater functionality that is changing the scope of what’s possible in the Energy from Waste sector.

The catalysts for these shredder advancements are two-fold.

In many manufacturing organisations, intelligent engineers work at the heart of the business, constantly researching, developing and trialling new shredder configurations that widen the scope of the materials that can be processed to produce different fuel specifications.

But the industry is also driving progress. Operators are constantly demanding more from their investments – and rightly so.

They’re looking for an asset that will last long into the future – one that will generate a return from either the onward sale of the energy source that they manufacture, or the savings they reap from using the fossil fuel substitute to power their own site. They’re demanding higher capacities, simpler maintenance regimes and process flexibility, to name just a few criteria.

So how is EfW shredding technology evolving as a result?

Output specifications

Of course, the EfW shredder has to be fit for purpose – it must be capable of processing input waste materials, to a defined output specification.

In the cement industry, for example, a high calorific, homogenous <30mm fraction is usually required for a main burner, whereas an 80mm particle would suffice for a calciner. Typically, the more refined the particle size, the greater the energy consistency that the fuel can produce.
This sounds a fundamental design requirement and indeed it is, but quality issues with some EfW shredders can jeopardise the resulting fraction. The machine therefore needs to demonstrate an effective single-step process with in-built foreign object protection, to uphold the end specification requirements.

Capacity expectations

Capacity can of course be evaluated in terms of throughputs, but it is important to note that speed does not necessarily equal a greater tonnage of output product. Excessive rotor speeds can place increased pressures on an EfW shredder, which inevitably leads to heightened wear and maintenance issues, not to mention the creation of dust – an inherent fire hazard. The target speed for a wood shredder, for example, should be no higher than 60 rpm.
But balance a slower rotor speed with high torque, and shredding technology can maintain throughputs of up to 40 tonnes per hour, wear is significantly lessened, power consumption is often reduced and dust generation is minimised.

This dust alleviation doesn’t only help to avert the danger of fire – it also minimises the airborne pollution that employees and the nearby community are exposed to. From a commercial perspective, steps to moderate dust can result in a better fuel quality too.

Furthermore, low-speed technology can create up to 80% less fines. Because fines are non-specification particles that cannot be mixed with the output fuel, they are usually simply screened off and sent to landfill. But in high capacity plants this can result in disposal costs over £1m, not to mention an adverse environmental impact of a process that is supposed to support the world’s renewable energy strategy. Avoid the production of these fines in the first place, however, and disposal cost savings of £800,000 will soon accelerate the return on investment from the shredder and the break-even point of the wider plant.

Input materials

If the EfW shredder is flexible and able to handle different input materials to satisfy varied end-product requirements, the plant has greater operational versatility.

Commercial and industrial waste has long been the common ‘feedstock’ for SRF (Solid Recovered Fuel) production, for instance, but with supply and demand in different parts of the world being inconsistent, shredders have had to adapt.

That’s why cutting systems have been engineered to handle Municipal Solid Waste (MSW), production waste, carpets and even fabric rolls, so that they can also be processed for fuel when other ‘rubbish’ is in limited supply. Input material exploration is evolving further still, which provides flexibility and thus much-needed commercial protection during periods of market volatility. Few organisations stand still now in terms of the wastes they produce, which means alternative fuel producers – and their shredding partners – need to adapt too.

Safety considerations

Any ethical operator – and the shredder manufacturer they choose to partner with – will also prioritise safety when considering the ‘performance’ of their equipment.

The noise debate is getting louder, for example. This has been on the radar of many fuel producers for some time, given increasingly stringent legislation and the potentially debilitating impact of excessive noise exposure on employee wellbeing.

The more diligent shredder manufacturers have therefore designed shredding technology that runs below the first action point – 80dB(A). Not only is this ethically the right thing to do, but heightened wellbeing strategies also typically boost productivity too, as noisy distractions and the constant drone of equipment is lessened.

Addressing noise pollution in this manner will also help to placate neighbouring communities, which is particularly important if fuel manufacturers are to apply for planning permission to extend their facilities or operational hours.

EfW shredders have already advanced significantly in the last ten years, changing the face of the UK’s resource agenda in the process. Does this mean that’s all to come from the sector? No – far from it…