“Green manufacturing” is often popularly understood as the production of environmentally-friendly products, like solar panels, organic cotton of bamboo garments or additive-free packaged foods. These are important, but far greater environmental and economic impacts can be achieved by “greening” the industrial processes that deliver the materials, components and products that our mass, global markets demand; thereby potentially reducing the environmental footprint of everything around us. This can be achieved by rethinking the energy, raw materials, resources and inputs we use in manufacturing. What if we could derive many of the same resources from waste? Instead of viewing waste as a growing global burden, we could consider the significant financial and environmental savings to be had by ‘mining’ the world’s landfills.

Using waste as an industrial input is not the same as laboriously sorting through the world’s rubbish to extract single streams of the same materials, then reprocessing them back into the same form, like recycling glass back into more glass. Our waste streams are increasingly complex - mixed plastics, e-waste and auto waste, for example – and, as such, much waste simply cannot be recycled using conventional approaches. This means more and more waste is now destined for landfills. However, we can overcome these technical and cost barriers by looking at waste at its elemental level. The world’s waste mountains are packed with useful elements like carbon, hydrogen, silica, titania and metals that we would otherwise source from virgin raw materials. By redirecting waste, as a valuable resource, back into our industrial processes we can transform it in the production of previously unimaginable value-added materials and products, simultaneously delivering both new economic value and environmental benefits.

This article focuses on such transformations of ‘waste’ into value-added materials and the associated development of green manufacturing. The examples selected demonstrate how innovative scientific research and development is delivering economically viable, real-world solutions for industry by reimagining waste as a resource for the future.

The future of green materials and green manufacturing

The impetus for researchers to innovate to help solve the global waste challenge has never been greater. Worldwide, the cost of raw materials continues to rise, while on the sales side pressures for industries to deliver competitively priced products are only intensifying. Conversely, waste stockpiles are accumulating at a rapidly increasing rate, reflecting the pace of economic activity, shorter replacement cycles and the increasing intensity of global trade and transportation. Rapid industrialisation across Asia and other developing nations from the 1960s, the dramatic fall in the prices of consumer goods and the accompanying rise of consumer cultures has driven an eightfold increase in materials consumed over the last century. Rising incomes across many developing nations are coinciding with sharp increases in the volumes of waste generated and increasingly complex waste streams, such as e-waste and industrial waste. The World Bank recently reported that the world’s three billion urban dwellers generate an average of 1.2 kg of solid waste per person per day, double that of a decade ago. Without innovation, World’s landfill sites will become increasingly clogged, exacerbating the loss of potentially valuable secondary resources and risking environmental contamination.

We are committed to pursuing a wide range of novel and innovation means of transforming waste into valuable materials for reuse. We believe that the current environmental mantra of ‘Reduce, Reuse, Recycle’ needs an additional ‘fourth R’. That is; ‘Reform’.

We are also working with another problematic, but potentially valuable waste stream, automotive shredder residue (ASR). Every year, tens of millions of the 1.4 billion cars on the world’s roads are decommissioned, as are millions of commercial vehicles. While the ferrous and other metals that make up about 75% of a vehicle by weight can be readily, and profitably, recovered and recycled, the remaining plastics, glass, composites, complex materials and contaminants are mainly destined for landfill as ASR. For every car, some 100 – 200 kg of complex and potentially toxic waste ends up in landfill, posing a growing technical and environmental challenge worldwide, and representing a significant waste of finite resources. We are investigating a range of transformations using ASR, including new pathways for creating alternative resources /inputs for the production metal alloys such as ferrosilicon alloy, or ceramic materials like SiC and TiN composites. Instead of using conventional raw materials, including silica from quartz and carbon bearing resources such as coke, waste automotive glass and plastic can be used. The plastics within ASR are also proving useful.

Likewise, significant opportunities lie in the development of lighter bricks by mixing clay with various waste streams. Clay bricks are conventionally fired at 1100-1200 °C in a rotary kiln – requiring significant energy. However, by using a mix of clay and waste, the conversion of the waste to gases aids rapid heating, so reduces the energy needed for the kiln, while at the same times expanding the clay through the formation of tiny gas bubbles. As the bricks then cool and the clay solidifies, the gases are trapped to create a lightweight, durable product.

We believe that for everything we are currently putting into landfill we can ask the question; could we be reforming this waste? We already understand that the sun can give us green energy. We need to similarly recognise that waste can give us green materials and processes. But, when we ask this question we also need to ask important real world questions about costs and incentives to do so. To drive the uptake of green manufacturing solutions we need to partner with industries and businesses who understand the benefits of substituting expensive raw materials for resources derived from waste. Thinking ahead, I believe that waste as a resource – that is available locally to virtually every community – may prove a positive disrupting force. We are currently working on reforming a range of different waste plastics. Imagine combining the ability to reform plastics with other new developments like 3D printers. In future we may use waste as an input that will enable us to locally print off something new; closing the materials loop.

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