Podcast: Decarbonizing the manufacturing supply chain—A look at metal production
Key takeaways
- Carbon neutrality goals for 2035 and 2050 will reshape metal supply chains and impact sourcing strategies across manufacturing.
- Mazda’s use of biomass in cupola furnaces shows a viable path to decarbonizing iron casting processes in automotive manufacturing.
- Manufacturers must assess and reduce carbon liability at every production stage to align with future regulations and investor standards.
- Solar-powered electric arc furnace steelmaking, like Pacific Steel’s project, points to scalable, low-carbon alternatives for rebar production.
In this episode of Great Question: A Manufacturing Podcast, Robert Brooks, editor in chief of Foundry Management & Technology and American Machinist, explores the evolving pressures on the manufacturing supply chain as carbon neutrality and net-zero emissions targets accelerate industry-wide. With a focus on the metal casting and machining sectors, he highlights the emerging concept of carbon liability and its implications for manufacturers. A notable case study features Mazda’s development of carbon-neutral cupola melting using biomass fuels, underscoring how environmental goals are reshaping production strategies. As regulations tighten and global timelines approach, the conversation emphasizes the cascading effects these changes will have across all levels of manufacturing.
Below is an edited excerpt from the podcast:
Today, I want to fill you in on some developments at the far end of the manufacturing supply chain, where metal is made and component parts are produced. Like all manufacturers, there's a lot of frustration and concern among these businesses about stability and predictability—and about the scope of tariffs and the availability of products and materials. But there may be a wider problem developing.
Today we're in the fifth month of 2025, and the issue of carbon neutrality—and beyond that, of net-zero carbon emissions—is advancing fast on all manufacturing industries. The particular focus of my work is on the metal casting industry, which produces metal parts, and on the machining and manufacturing technology sector, which produces engineered components.
In the strict accounting of what I'm referring to as carbon liability, metal components are responsible for a lot of carbon emissions. And neutralizing those emissions is going to affect a lot of downstream manufacturing.
Let me take a moment to define carbon liability, a phrase I'm using in connection with the concept of carbon neutral and net-zero emissions.
In 2015, most of the world's nations entered into what is called the Paris Agreement, an international treaty that aims to reduce carbon emissions in order to limit global warming to less than two degrees Celsius above pre-industrial levels. The treaty sets 2035 as the date for the signatory nations to achieve carbon neutrality—nine years and seven months from now. And it sets 2050 as the date for achieving net-zero carbon emissions.
These time frames are essentially arbitrary. They are adopted by businesses in order to match the targets set by the Paris Agreement, to conform to their national and regional regulations, and also to meet credit rating standards adopted by major investors and lenders.
So if you're a manufacturing business that sources metal or metal components, you should expect some changes in the supply chain.
In April, in Foundry Management & Technology and on foundrymag.com, we reported on a development at a ferrous foundry in Hiroshima, Japan, where Mazda Motor Corp. casts engine blocks and transmission cases from iron produced in cupola furnaces. I commend to your attention that article, which is titled “A Nutty Plan for Carbon Neutral Cupola Melting.”
https://www.foundrymag.com/melt-pour/article/55276608/a-nutty-plan-for-carbon-neutral-cupola-melting-technical-development-april-2025
The importance of this development is that Mazda reports it has achieved carbon neutrality there. For those uninitiated, cupola furnaces are used by iron foundries all over the world. And although they differ in scale, they function on a similar principle as blast furnaces used to produce iron for steelmaking. Blast furnaces are larger and produce much greater volumes of molten iron. But like cupolas, they are shaft furnaces with a tall stack at the top of the vessel, through which a solid charge of ore is fed. The charge moves downward by gravity, and as it is heated, the metallic ore reacts with hot gases flowing upwards through the vessel. The ore is refined and becomes molten iron. And the gases become emissions—most notably, carbon emissions.
The iron is valuable, and the carbon is the problem.
At foundries, the cupola iron will be treated and cast into molds or ingots. A steelmaking operation will require more refining of the iron and further alloying to achieve a final quality—which I mention to emphasize that converting ore to metal is not a one-step process anywhere. There are many different routes and stages from start to finish, and every step of production has some potential for carbon liability.
So whether it's a cupola furnace or a blast furnace, the gases emitted by the process include carbon emissions, particularly from the fuel used to initiate the thermal transformation of ore into metal.
Instead of coal, the Mazda foundry developed biomass fuel briquettes derived from coconut shells. There are other sources of biomass in development too.
Like most large manufacturers, Mazda aims to achieve carbon neutrality—meaning that it balances the amount of carbon dioxide it releases into the atmosphere with an equivalent amount of carbon removed from the atmosphere, so that it can demonstrate no overall increase in carbon emissions.
It is confident about its progress in this instance, which may give some direction to other cupola furnace operators around the world. But this also spotlights how the objective to reach carbon neutrality is going to require foundries, steelmakers, and all manufacturers to isolate every production sequence and neutralize the carbon liability there.
There will be consequences all through the supply chain.
Mazda has three strategies to achieve carbon neutrality for its global operations by 2035. First is energy conservation. Second is shifting to renewable energies where possible. And third is introducing carbon neutral fuels—which is the example we’ve reported on.
Looking beyond 2035, the automaker is aiming for net-zero carbon emissions throughout its supply chain by 2050. So one can imagine how extensive that effort is going to be.