About the Author
Professor Mark Jolly is Head of the Sustainable Manufacturing Systems Centre, at Cranfield University
In an energy-intensive sector like manufacturing – making up one third of all energy consumption in the UK – foundries are a hotspot, using casting processes that typically demand 75 GJ per tonne. In the UK there are more than 450 of them, reportedly about 26,000 in China, more than 2,000 in the USA and around 600 in Germany – large numbers of mature, small and medium-sized operations that tend to lack the ability and motivation to become more energy efficient.
More than 100 million tonnes of metal were cast in foundries globally in 2016, producing 400 million tonnes of CO2 – 1.5% of global CO2 emissions. A particular issue is the shift to more manufacturing using lightweight materials, in this case the dramatic increase in demand for aluminum. Lightweighting is only increasing the scale of CO2 emissions. In 1997, aluminum emissions were 41 million tonnes (17% of the global total from foundries); this has now become 123 million tonnes (31% of the total).
In our conversations with 100 foundries and industry experts, it became obvious that energy efficiency and emissions weren’t a key decision-making factor and there was no detailed monitoring or analysis of energy use, the focus was solely on energy bills in themselves.
Foundries are an eye-catching example, but clearly aren’t the only manufacturers that have just come to accept extravagance, living with high levels of energy use and waste of resources as a norm.
“Small is Beautiful” is a new philosophy for the sector that aims to ensure that resource efficiency (both in material and energy terms) is included in every aspect of planning and management, from the design stage onwards. Crucially, at the heart of this way of thinking is the need for measurement: “If you can’t measure it, you can’t manage it”. And any monitoring of environmental impact has to consider all the stages of the materials. That means not only the energy consumed directly through the manufacturing process, but also what’s involved in extracting, preparing, recycling and disposing of the materials used in processes.
Looking at foundries in particular, there are some straightforward wins when the whole cycle resource costs are taken into account. Using a software tool to visualize energy and material flows, it’s been possible to create a detailed analysis of the entire production chain from charge to waste, and benchmark against other foundries internationally. This has highlighted opportunities for more efficient processes and new metrics as a basis for auditing.
Take aluminum melting – an energy-intensive process using crucible furnaces and natural gas consuming more than 60% of the total process energy. Using the Constrained Rapid Induction Melting Single Shot Up-Casting (CRIMSON) process was shown to reduce overall environmental impact by 57%, in terms of reduced waste of materials and use of energy. CRIMSON uses an induction furnace for melting the metal in a closed crucible, meaning only the quantity of metal required to fill a single mold is molten, rather than large batches that use unnecessary energy and increase the number of rejects. Due to the rapid melting, transfer and filling, the holding time of molten metal is minimized and there’s a huge energy saving.
The lesson for the manufacturing sector from Small is Beautiful is around being clear-sighted – breaking from assumptions and traditions and looking againProfessor Mark Jolly
We’ve also compared a number of the processes used for casting modern small aluminum alloy cylinder blocks – High Pressure Die Casting, Gravity Die Casting and Low Pressure Sand Casting – a full analysis of all the materials life cycles, including raw materials production, recycling loops of alloys, mould materials, heat treatment, machining. The results show a variation in energy needed from 98 GJ/tonne to over 180 GJ/tonne (2.5 – 4.6 MJ/block) compared with Cast Iron which only uses 32 GJ/tonne (1.2 MJ/block) – demonstrating the importance of taking into account the costs of the manufacturing process when materials are substituted.
The lesson for the manufacturing sector from Small is Beautiful is around being clear-sighted – breaking from assumptions and traditions and looking again. Only by understanding the full and detailed costs of processes is there a basis for cost-savings and long-term sustainability.