Cast Iron, though one of the oldest engineering materials in the world is popular in the casting industry for its sustainability and environmental impact. Here are a few points on the sustainability of cast iron:

1. Cast Iron does not rust; it simply oxidises, and that too, very slowly. This is why it is good for the environment as the carbon-based iron ashes are easy to manage in comparison to PVC. The carbon gasses that are emitted help in the growth of plants and enhance planktonic life in oceans, and thus check global warming.
2. Cast Iron is completely recyclable, and not downcycled, in the case of which the material may lose out on some of its key properties.
3. The basic raw material is pig iron. It can be manufactured from a mix of steel from construction and automotive industry and foundry scrap also. The scrap is subjected to melting to obtain new iron. Thus, waste is turned into wealth.
4. Cast iron products, when properly maintained, will last the lifespan of the building, although the capital cost may be on the higher side. Even when the building is pulled down after its full life, cast iron can be recycled and used in several different applications.
5. Cast iron is the most popular material in the area of construction such as soil drainage, windows, structural support, etc.  
6. Because it is long lasting, cooking in cast iron utensils is highly sustainable.
7. Many prefer cast iron utensils to Teflon coated ones, which are quite hazardous. This is because they have natural non-stick properties, and its skillets need to be oil-coated to give it a non-sticky nature.
8. You need to wash the dishes only using hot water and a stiff brush; therefore, the use of soaps can be prevented as they are known to possess high chemical content. Heat distribution is uniform and it makes cleaning lot easier.
9. Other properties of cast iron include wear resistance, castability, greater fluidity and comparatively lower melting point. This makes it suitable for making pipes in the area of construction engineering and for making gearbox cases and cylinder heads in the automotive industry. Cast iron is resistant to weakening and destruction by oxidation and therefore goes into the making of cooking utensils.
10. In conclusion, Iron is the fourth commonly found element in the world that can be readily recycled every time without losing any of its natural properties, and thus sustainable.