Mueller Embraces Sustainable Path Forward With Silicon-Based Brass




Guidance in terms of minimum requirements and lead-free options for valves and fittings are provided by the AWWA C800 Underground Service Line Valves and Fittings standard. The standard historically was built around the use of one leaded red brass alloy. Over the last two decades, as the water industry transitioned to lead-free alloys for surfaces that contact potable water, many options became available for most waterworks products. However, only three lead-free brass options were introduced for C800 products, all of which are alloys that contain bismuth — a material that presents concerns.  

In 2018, the U.S. Department of the Interior identified bismuth as one of 35 “critical” minerals. By earning this designation, bismuth is characterized as a non-fuel mineral essential to the economic and national security of the U.S., with a supply chain that is vulnerable to disruption, and that serves an essential function in manufacturing that would otherwise have significant consequences if absent. Moreover, according to the Mineral Commodity Summaries 2023 report from the U.S. Geological Survey, the U.S. is highly reliant on imports of bismuth, with China controlling 80% of total global production. These concerns and the availability of other proven lead-free alloys led to a revision of the AWWA C800 standard to include three silicon-based brass options.

Life Cycle Assessment Confirms New Path Forward

The changes to the AWWA C800 standard, coupled with the risks of bismuth, prompted Mueller Co. LLC to pursue its own course of action. This took the form of a life cycle assessment (LCA) covering the range of available bismuth- and silicon-based brass alloy options. The LCA methodology was selected to systematically analyze and compare the environmental impacts of the different alloys across all life stages. Most importantly, as a decision-making tool, the LCA uncovered key insights into the processes and operations of each option — providing Mueller with a more comprehensive understanding of how these considerations might affect customers, employees, and the company from different perspectives.  

Mueller’s evaluation considered technical performance, environmental impacts, and human health impacts across five life stages spanning beginning-of-life, alloy manufacturing, component manufacturing, use, and end-of-life. The major findings revealed the benefits and competitive advantages of silicon-based brass C87850 as opposed to bismuth-based alloys, including:   

  • The scarcity of bismuth creates significant negative environmental and human health impacts during sourcing.
  • The lower melting temperature, density, and melt loss of the silicon-based brass alloys provide substantial and compounding advantages during the melting cycles of alloy and component manufacturing — reducing energy consumption, carbon dioxide creation, fume emissions, silica and flue dust generation, and the foundry sand waste stream.
  • The superior mechanical strength of silicon-based brass C87850 in relation to previously recognized AWWA C800 listed alloys provides robust structural integrity to a degree that has never previously been available for service brass products.
  • Silicon is easily separated from copper through standard smelting processes. In contrast, bismuth is not easily removed from copper in post-consumer recycling streams, potentially limiting recycling options and value.
  • The extra processing required for bismuth-based brass alloys during post-consumer recycling negatively impacts energy consumption, carbon dioxide generation, and metal recovery.

It’s important to note that Mueller’s concern with regard to the risks of bismuth do not solely pertain to its designation as “critical.” For example, silicon-based brass C87850 has a nominal zinc content of 20%, and in the Mineral Commodity Summaries 2023 report, zinc was added to the U.S. critical minerals list. The inclusion of a mineral on the critical list, and the extent to which it impacts sourcing, should be considered in the context of a larger evaluation strategy.

Mueller Builds New Brass Foundry

The LCA provided Mueller with both the evidence and rationale to construct a 125,000-square-foot state-of-the-art brass foundry in Decatur, IL, that is dedicated to manufacturing waterworks products made exclusively from silicon-based brass C87850. Opened in February of this year, the new foundry includes the latest in manufacturing equipment and is anticipated to significantly increase the availability of C87850 brass alloy finished products, helping to meet the imminent and expected demand for lead-free service brass.  

In the months to come, Mueller will continue to ramp up production of waterworks products using silicon-based alloy C87850 — mitigating risks associated with those elements, and particularly, the risk of potential lead exposure for employees.

The new foundry is integral to Mueller’s focus on contributing to a sustainable future with its finished goods that will give water utilities options that not only comply with the U.S. Environmental Protection Agency’s new Lead and Copper Rule Revisions but also allow them the opportunity to specify products that potentially align with broader sustainability goals.

Click here to read the article in Water Online