Sustainability in Metalcasting: The Green Foundry Project
AFS Environmental Health & Safety Division
Click here to see this story as it appears in the December 2017 issue of Modern Casting
Many foundries recognize that being environmentally responsible and improving the bottom line aren’t mutually exclusive goals. A strong sense of environmental responsibility can achieve better growth and cost savings, improve brand recognition, strengthen stakeholder relations, and boost their profitability by making changes to be more environmentally responsible, which leads to improved efficiency at the same time. From implementing management systems and metrics to waste management and beneficial reuse, metalcasters can play a key role in the sustainability of natural resources.
In 2010, the American Foundry Society (AFS) formed a technical subcommittee to explore what it means to be a “green” foundry. The subcommittee was tasked with compiling a list of best management practices metalcasting facilities could implement to promote environmental responsibility and sustainability. The results of this effort formed the roots of what has since been termed the Green Foundry Project. The Green Foundry Project, now available on the AFS website (www.afsinc.org/sustainability), is comprised of a searchable database of practices along with a select number of full page case studies.
These Green Foundry practices are categorized into the following five areas:
- Management systems and metrics.
- Air emissions.
- Water use and discharge.
- Materials and resource conservation.
- Waste management and beneficial reuse.
Here are examples from each category.
Management Systems and Metrics
Environmental management systems and metrics are developed to define a set of processes and practices that enable foundries to reduce environmental impacts and increase operating efficiency.
Metrics should be designed to be measurable in the form of project target completion dates, standardized units of measure and with established initial baselines to measure improvements against. Such metrics have the advantage over qualitative metrics (e.g. yes/no, green/red, or ahead of schedule/behind schedule) in that they allow for the tracking of improvements and viewing of trends.
Metrics should be easy to understand and apply, repeatable and collected in a consistent way.
At one metalcasting facility, refractory was stored in multiple locations throughout the plant and managed by three different departments that made their own purchases. Many times, refractory would be delivered to multiple locations without tracking between departments. Consequently, one department would order duplicate material because they didn’t have it in their customary storage location, when it may have been located elsewhere. This often resulted in inventory error, inconsistent stock and shelf life issues.
In 2016, the facility centralized the inventory of refractory. An abandoned building was repurposed to house refractory that must be kept in climate controlled conditions. Building holes were sealed, new windows were installed and a layer of insulating plastic was applied to the windows. A heater was installed to maintain temperatures above freezing during winter.
Now, refractory inventory is set at a certain level, and material is not reordered until needed. In addition to implementing a secure centralized inventory, the foundry restricted access to the storage area to purchasing personnel. End users must submit an issue ticket and an email when material is needed. Purchasing then releases inventory, and it is delivered to the desired location.
Since this program began, refractory has not been discarded as waste. This project eliminated approximately 46,000 lbs. per year of waste refractory resulting from unnecessary over-stocking and/or improper storage or expiration of product. Natural gas usage has been reduced due to heating a single, smaller storage building in the winter rather than multiple larger storage buildings.This project resulted in estimated savings of $116,000 per year in raw material purchasing costs and an estimated savings of $3,000 per year in disposal costs. The company also reduced refractory costs from $5.67/ton to $4.03/ton of iron produced. Production personnel do not have to worry about inventory levels. They get what they need when they need it. Fresh refractory is much easier to install, and they have less inventory to store and handle.
Any processes which utilize combustion, industrial chemicals (substances that undergo chemical reactions and may release vapor/fumes/gases in the process) or produce large amounts of dust have the potential to generate air emissions. Potential air pollutants may include carbon monoxide, lead, carbon dioxide, nitrogen oxides, VOCs (volatile organic compounds), PM (particulate matter) and sulfur dioxide.
VOC Reduction With Switch to Water-Based Paint
In one case study, a facility switched from a high VOC solvent-based asphalt paint to a lower VOC water-based asphalt emulsion paint. The outdoor underground paint storage tank was replaced with an aboveground bulk storage tank located indoors.
VOCs were reduced by approximately 58%, including using 1,200 gallons less thinner and 2,500 gallons less solvent-based asphalt paint. The switch led to a reduction in reportable spill risk by moving the entire process indoors, and it also eliminated the risk of an undetected leak occurring from the old outdoor underground paint storage tank.
The total cost for the indoor dip tank was $41,000. This included the tank, built-in secondary containment, crane, cover and hoist system. There was an additional $10,000 fee to have the outdoor tank removed.
There was a calculated savings of over $25,000 per year due to reduced solvent and paint usage.
Unlike the solvent-based paint, the new asphalt emulsion paint is non-flammable. The change reduced the hazard of team members slipping or falling on ice and snow because the task is no longer performed outdoors.
Team members were previously required to scrape the dried asphalt off the dipped part transport trays, which was very labor intensive. The old outdoor dip tank was flush with the ground and even though safety rails were installed, there was a slight possibility for someone to accidentally fall into the tank. The new tank sits at ground level and the sides are about 5 feet high, thus decreasing the likelihood of falling in.
This process is now performed in the same work area in a continuous sequence without the need to transport machined parts by forklift to and from the outdoor dip tank (500 ft. away), thus improving process efficiency.
This dipping process now can be performed year-round and is no longer weather or temperature dependent. In the past, team members could not dip parts when the temperature was below 14F (-10C) or during stormy weather.
Team members appreciate being able to work indoors rather than outdoors in cold temperatures.
Several team members were involved with this project from beginning to end, and they appreciated the opportunity to offer their opinions to improve the process. Team members who were not directly involved with the change were kept informed of the upgrades through tool talks and electronic communication boards.
Water Use and Discharge
Water can be consumed in metalcasting operations in several ways, including contaminated process water requiring treatment as a result of air pollution control activities, or non-contact cooling water used to cool running machinery. A reduction in the use of water for these purposes may represent a tremendous improvement opportunity for a facility. Water may be discharged via various drainage systems such as sanitary sewers or dedicated permitted outfalls. Stormwater exposed to metalcasting processes also may drain to storm drain systems from streets, parking lots, loading docks, roofs and other surfaces that receive rain water.
Water use may be avoided, reduced or reused within the industrial process via example technologies such as air cooled heat exchange and closed loop systems. Additionally, recycled water can satisfy other facility water demands once adequately treated or recovered to ensure water quality appropriate for the use.
Eliminating the Generation and Discharge of Non-Contact Cooling Water
In this example, a metalcaster installed closed-loop cooling water equipment to reduce, or in some cases eliminate, the need to discharge cooling water. Previously, water for machine cooling was used once and then discharged. Now, it is processed through a series of pump skids and cooling towers to reduce the temperature and recirculate the water so that it can be reused over and over for non-contact cooling purposes.
The facility’s historical average water usage of 0.75 millions of gallons per day is now recovered and recirculated to plant equipment. The project resulted in a 30–95% reduction in cooling water use dependent upon seasonal cooling demands, and even an elimination of discharges in some cases.
The plant also saw a reduction of water usage, and strengthened business continuity and simplified regulatory permitting due to reduced water dependence.
Materials and Resource Conservation
Resource conservation management is a coordinated effort to manage the resources used and waste generated to reduce operating costs, increase efficiency, and promote environmentally conscious operations. This involves tracking resources and improving operational efficiency while enhancing overall cost-effectiveness.
Sometimes conservation is used synonymously with “protection.” However, it also refers to the protection of sustainable uses of resources. Renewable resources such as steel, iron, and even energy may be reused in foundries, reducing the amount of the resource that must be newly acquired to maintain the future of the organization.
Cupola Waste Heat Recovery for Facility Heating
Historically, one metalcaster discharged waste heat via a heat transfer system from the cupola iron melting process to the atmosphere. A heat recovery loop was added to provide heat to the building during the colder months. The closed-loop system was designed to transfer heat via a propylene glycol solution circulating through heat transfer coils. The heating coils pre-heat the ambient air prior to intake by the space heating units in various zones throughout the facility.
The completed heat recovery system provides 70% of the plant’s heating requirements for a typical winter, resulting in significant energy conservation. As an added benefit, the system provides hot water to the facility throughout the year. Heating costs have been reduced and carbon dioxide emissions have been cut by 4,600 metric tons of carbon dioxide per year. The initial cost of equipment was paid for within two years by savings on heating costs.
The switch strengthened business continuity due to reduced energy dependence. The project earned the 2009 State Governor’s Award for Excellence in Environmental Performance.
Waste Management and Beneficial Reuse
Many foundries already are involved in waste management and beneficial reuse programs in their respective states. These programs promote the reuse of foundry by-products in lieu of landfill disposal. Beneficial reuse of materials such as foundry sands and slags preserves landfill space, conserves natural resources, reduces carbon dioxide emissions, strengthens local economies and saves money. Substantial savings may be derived from converting a hazardous waste stream into either a non-hazardous waste or a beneficial reuse material with a slight change to the process or raw materials used in the process.
A beneficial use program identifies appropriate alternative uses for foundry byproducts to replace or supplement a raw material or competing product (like roadway construction material, cover, mulch mixture, etc.).
Foundry Byproduct Beneficial Reuse
In 2014, approximately 16,800 tons of non-hazardous industrial process wastes were generated by a ductile iron foundry and moved to its onsite state permitted industrial landfill. Of these waste by-products, approximately 40% (6,782 tons) consisted of dry sand/cement, while another 30% (5,061 tons) consisted of cupola iron slag. In the absence of state guidance for beneficial reuse of industrial by-products, the facility developed its own plan in conjunction with the regional regulator. Under the approval and authorization of the regional regulator, the facility implemented an initial 10-year written agreement with a partnering construction company to beneficially reuse the cupola iron slag and dry sand/cement waste by-product as engineered fill in local construction projects.
In the second half of 2015, the facility sent approximately 2,590 tons, or 2,750 cubic yards of cupola iron slag and dry sand/cement for beneficial reuse as engineered fill. This equates to a 14% reduction in the total amount of waste diverted from the facility’s landfill in 2015.
It is estimated that this single diversion event extended the life of the onsite landfill by approximately one month. The beneficial reuse of foundry materials is expected to continue over the remaining years per the written agreement and will continue to divert otherwise unusable material from the landfill. In addition, the close proximity of the metalcasting facility to the construction company’s operations has reduced the total round trip mileage required by the construction company to transport its engineered fill to construction sites.
Landfill occupancy conserved from implementation of the beneficial reuse plan was approximately 2,592 tons (2,750 cubic yards) in 2015. This extended landfill availability is valued at approximately $250,000, assuming the onsite permitted landfill was not available, and the by-product had to be shipped offsite to a permitted facility.
Fuel consumption was reduced due to shorter transport distances between the metalcasting facility and the construction site.
The project cost was zero dollars to implement. The construction company used its own crushing and blending equipment to develop the engineered fill onsite prior to transport to the construction site.
Assuming the construction company continues to take all the material produced, the diversion of foundry by-products from the onsite landfill is anticipated to extend the life of the onsite landfill by approximately 10 years.
Promoting sustainability within the foundry industry not only saves natural resources for future generations, it also improves the bottom line. Visit the AFS website (www.afsinc.org/sustainability) for ideas to improve the sustainability of your foundry. You can also share your sustainability efforts by submitting a request through the website to be included in the Green Foundry database.
The Green Foundry Project is updated periodically as more best management practices are submitted.