Nickel Recycling
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Nickel in Waste Streams
There are two waste streams. Waste generated during the production of materials and products (see below) and
waste generated at the end of life of materials and products, sometimes also called post-consumer waste.
Note: The word "waste" and phrase "waste stream" are used because they are commonly used in society. It is
unhelpful to apply the pejorative word "waste" to material that has a positive value and which is traded
around the world. "Scrap" is better although again it carries a negative connotation. Phrases such as
"secondary material" or "discard material" are more accurate and more neutral in meaning but are not widely
used. True "waste" will go to landfill sites.
The Value of Nickel
Nickel prices are the highest of the common non-ferrous metals. It follows that the commercial motivation for using it effectively in the first place is very strong: to waste nickel is to waste money. Similarly, the incentives for recovering and recycling nickel effectively at all stages of the fabrication and use cycle, are also very strong.
Most applications of nickel are based upon the nickel-containing product having resistance to corrosion. The high initial cost of using nickel is justified by the long expected service life and the resultant low lifetime costs.
This basic resistance to general corrosion in use means that, at end-of-life, most nickel-containing articles are still intact and easily identifiable (e.g., a kitchen sink made of stainless steel). This greatly facilitates the initial collection and sorting of nickel-containing end-of-life products.
Alloys
Unlike other non-ferrous metals, nickel is rarely used by itself but is commonly mixed with other metals to produce alloys. There are thousands of different alloys containing nickel - each developed to offer a particular combination of technical properties (corrosion resistance, mechanical properties and service life) relevant to particular conditions of use.
The nickel content of these alloys varies widely from, as examples, 1-3% for special engineering steels, 8-14% for stainless steels, 15-40% for special engineering alloys, 40-90% nickel for special alloys for the aerospace and electronic industries.
It is usual practice for special alloys to be recycled as the same special alloy wherever possible: they will have their own closed loops. The motivation is commercial - maintaining the identity of the alloy during fabrication, use and recycling allows the alloy producer to use (and value) all the alloy components in the recycled alloy, not just the nickel. It also allows the producer to achieve high quality product specifications without incurring extra refining or qualification costs. It follows that the environmental impacts are also minimized as a result.
In practice, both in fabrication and in use, it is not always possible to maintain and segregate products and scrap into specific alloys. Alloys and products get mixed. The nickel recycling industry has various ways of handling mixed nickel-containing scraps in order to optimize the retained value of the scrap. One common technique is to melt the mixture in order to produce "remelt" ingot of a known composition for subsequent resale.
A variant of this is to adjust the composition of the remelted scrap by adding controlled amounts of primary metals in order to produce ingot to a required specification for resale. A further technique is to "blend" recycle material from different sources to produce a mixture which, when subsequently melted by the purchaser, will produce a melt with a specified composition. This blending process is of increasing importance in stainless steel.
"Scrap" in this paper refers to material that has been used and is available for recovery. A common synonym also used is "secondary" material. This is in contrast to "primary" or "virgin" material that comes from mine production.
It can be seen that the nickel recycling "loop" is not a single loop but many, many separate alloy loops. In any methodology to quantify nickel recycling (indices, recycling rates, etc.), it is important that the nickel cycle be defined broadly enough to embrace all these "alloy loops". If all these loops are included, then the demonstrable recycling rate for nickel will be high. If all these alloy loops are not included then the apparent recycling rate for nickel will appear to be anomalously low because very little nickel is recycled as nickel.
Stainless steel
The main first-use industry for nickel is stainless steel.
Nickel-containing stainless steels (there are other kinds) commonly contain between 8 and 14% nickel, and account for approximately 60 percent of primary nickel use. For more on stainless steel, see "Recycling by First-Use Industry"
The modern refining processes used to produce stainless steel allow a wide range of raw materials to be used economically, of which scrap from stainless steel products is only one.
Sophisticated "blending" processes are used by specialist suppliers in order to provide quality-assured feed to stainless steel mills. These blending processes can utilise nickel-containing products from a very wide range of fabricating or end-of-life sources - including low-nickel steels; high nickel alloys; mixed turnings; end-of-life engineering assemblies; reject products from primary nickel producers; and re-melted ingot from processing nickel-containing slags, dusts, batteries, and spent plating fluids.
This "omnivorous" character of the stainless steel industry means the stainless steel industry puts a higher value on many of these products than does the industry which originally generates the products. Hence, many products become feed for the "stainless steel loop" rather than feed for the industry sector that originally produced the products.
Any attempt to model the recycling of nickel has to include all aspects of the stainless steel loop.
The high price of nickel also encourages commercial users to use nickel very efficiently in the first use. This can result in the nickel content of a fabricated product being too small at end-of-life to commercially motivate the collection and sorting of the product primarily for its nickel content.
Examples of this can be engineering steels containing as little as 0.5% nickel, and steel or brass products which are plated with very thin nickel, or chromium-nickel, layers to protect the "substrate" product from corrosion. These products are occasionally identified, collected and sorted for the combination of the value of the substrate material (usually steel or brass) and their nickel content; they can then find their way into a special blended feed for producing a nickel-containing alloy - e.g., stainless steel, cupro-nickel.
More often though, the products are collected and sorted according to their substrate alloy. In this case, the nickel is "diluted" and as it goes into the general steel or brass pools; the nickel can therefore be considered to be "lost" to the specific nickel and nickel alloy pools. It is important to note that the "loss" is from the nickel pool to the steel or brass pools; it is not "lost" into the environment, e.g., as landfill.
Nickel is considered metallurgically to be a "benign" element - that is, it alloys with most other common metals to produce beneficial, not negative, metallurgical effects. The very small increase of the nickel content of general steels and brasses does not generally cause commercial or technical problems to those industries.
Inevitably though, some nickel-containing products do end up in land-fill. This may be because the products are too small or too well concealed (e.g., plated screws, stainless steel spoons, nickel alloys in small electronic products), because the consumer is not able and/or willing to make the effort to segregate metal from non-metal on disposal, or because the municipal waste handling and processing facility is unable or unwilling to segregate metal from non-metal.
If such segregation can be achieved, it is generally within the existing capability of the metals recycling industry to sort and segregate the metals fraction to optimise economic reuse.
Nickel in landfill is a "loss to the environment": another form of emission. But the very forms in which such nickel goes into landfill (e.g., stainless steel, chromium-nickel plating, ferro-nickel alloy) means that these products will be stable in landfill environments. They do not constitute a risk to the environment. (The special case of nickel cadmium batteries is discussed below.)
Trade
Nickel is traded globally and so are most products which are fabricated from nickel. There are few significant tariff barriers distorting free trade in nickel, and barriers to the trade of semi-finished and finished goods containing nickel have been steadily reduced. The price of nickel and nickel-containing products is generally high compared to the costs of shipping regionally and internationally.
This explains the very strong growth in world trade of nickel and nickel products at each stage of the nickel loop - primary nickel, semi-finished product, finished goods and product available for recycling from each stage of the chain.
For example: primary nickel from Australia can be shipped to Korea to be melted - together with other nickel from Russia and stainless steel scrap from Korea, China and the USA - to produce stainless steel for export to China where it is fabricated into kitchenware for export to Europe.
Supplies of nickel-containing material for recycling will be found in those areas of high fabrication activity (as manufacturer's offcuts or rejects) and in those areas of high use (as end-of-life products). These areas are not necessarily matched with areas where the nickel is in high demand, that is, where stainless steel is made.
This suggests that we should expect to see different "steady state" rates of utilization of nickel-bearing scrap in stainless steel manufacture in different parts of the world. How much scrap is used will depend on whether the manufacturers are operating in areas that are plentifully supplied with scrap (e.g., parts of the USA) or that are remote from major flows of scrap (e.g., South Africa, Finland).
In any methodology to quantify nickel recycling, it is important to consider this global nature of the distribution of material available for recycling. It is also important to consider the effects of any local or regional regulations that have the effect of restricting the free import or export of nickel-containing scrap.
The only indices or ratios which will be meaningful are global. If local or regional indicators of nickel
recycling are required, then it is important that these reflect local inflows and outflows within a global
market and a global mass balance.
Next: Production Scrap
