26
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications
At present, new scrap used in the secondary production of indium is mainly sourced from spent
ITO sputtering targets. Sputtering is the process used in electronics manufacturing to apply ITO
to transparent and conductive electrodes for use in LCD or flat-panel display applications. Moss
et al. (2011) state that flat-panel displays and other ITO applications represent ~84% of total
indium demand. Due to inefficiencies in the current manufacturing process, only ~30% of the
indium is successfully deposited on the ITO thin-films when using planar sputtering targets.
More expensive rotary targets can yield higher efficiencies (Gibson and Hayes 2011). Up to70%
of remaining indium is, therefore, conceivably available for recovery and reuse.
According to the USGS, before about 1996
24
very little of the indium in ITO manufacturing
waste was recycled (Brown 1996). Since then,
ITO producers in Japan, China, and South Korea
have installed significant recycling capacities. Unfortunately, because of metallurgical
complexities, not all the indium in new scrap can be recycled and reused in the manufacturing
process as losses. Overall, recovery is high and various estimates have placed the efficiency of
the ITO recycling process at 60%–70% (Phipps et al. 2007; Mikolajczak 2009). The turnaround
time for the recycling process is also an important consideration for recyclers, owing to
potentially significant inventory carrying costs and maximization of plant throughput capacity.
Market pressures and improvements in technology have enabled recyclers to decrease the recycle
claim time to about 15 days. These improvements reduce the overall demand for primary indium.
Given this level of recycling efficiency, if we assume that new scrap is sent to a recycling plant
and that the same indium continues to be used in a closed loop between the manufacturer and the
recycler, the overall effective deposition of indium in ITO applications increases from 30% (in a
single pass) to ~55%
25
(Table 9).
Of the 100 units of primary indium entering
the manufacturing process, only 30 units are
successfully deposited. With a closed-loop recycling process, manufacturers can increase the
effective indium deposition from 30 units to 55 units. Therefore, of the total 55 units of indium
used, 30 were sourced from primary supply and 25 were sourced from the new scrap. Had
recycling not taken place, the manufacturer would have had to source an additional 25 units of
primary indium, but recycling reduced the primary indium demand. For example, without
recycling, manufacturers would have required an additional 83 units
26
of primary indium to
successfully meet the demand of an additional 25 units. The introduction of a closed-loop
recycling system enabled the 25 units to be produced and reduced potential demand for primary
indium by 83 units.
24
In 1996, indium prices rose to ~$175 to ~$550/kg, indicating that at that point, indium could be recycled at a lower cost than
primary indium could be produced. Since the peaks in 1996, prices of indium dropped but did not seem to affect recycling
capacity, indicating that the recycling of indium remained profitable at prices of ~$175/kg.
25
If 100 units of indium metal enter the manufacturing process, approximately 30 units (or 30%) are deposited on thin-films in
the first round of sputtering. If the manufacturer recycles its manufacturing waste, ~65% of the 70 “wasted” units indium would
be recovered through recycling. If the process repeats itself enough times and one assumes a closed-loop manufacturing and
recycling process, the overall indium lost is ~45% while ~55% of the initial 100 units of indium is successfully deposited.
26
Calculated as: 30/100 = 25 /s. Solving for ‘s’ yields 83.333.
27
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications
Table 9. Overall Utilization of Indium in a Hypothetical ITO Sputtering Application
With Closed Loop Recycling of Manufacturing Waste
Indium Secondary Production Loop
Cycle
1
2
3
4
5
6
7
8
9
10
Total
Units available for ITO
100.0
c
45.5
20.7 9.4
4.3
2.0
0.9
0.4
0.2
0.1
183
d
Units successfully
deposited
a
30.0
c
13.7
6.2
2.8
1.3
0.6
0.3
0.1
0.1
0.0
55
e
Units available for
recycling
a
70.0
31.9
14.5 6.6
3.0
1.4
0.6
0.3
0.1
0.1
128
f
Units successfully
recycled
b
45.5
20.7
9.4
4.3
2.0
0.9
0.4
0.2
0.1
0.0
83
g
Units lost to waste
i
24.5
11.1
5.1
2.3
1.1
0.5
0.2
0.1
0.0
0.0
45
h
% of indium deposited
55%
% of indium wasted
45%
a
The deposition success rate is assumed to be 30%; therefore, 70% of indium is available for recycling. We assume that if indium
is not successfully deposited upon application of ITO, it is available for recycling. In other words, there are no “losses” at the
manufacturing stage, only at the recycling stage.
b
Indium recycling efficiency is estimated to be 65% per recycling cycle.
c
Primary indium. All other figures relate to indium that is either entering recycling or has been recycled.
d
If 100 units of primary indium are used in ITO applications with recycling, the ITO applications will appear to have consumed
100 units (primary) + 83 units (secondary) indium. The figure of 183 units of indium likely represents the figure of indium
demand reported by manufacturers.
d
Of the original 100 units of primary indium entering the manufacturing process, 55 units (55%) are effectively deposited when
factoring in that spent ITO targets and other manufacturing wastes are recycled.
f
Of every 100 units of primary indium used in ITO applications, 128 units are a quantity that might appear to be entering the
recycling plant because the same indium may enter the plant more than once per period.
g
Of every 100 units of primary indium used in ITO applications, 70 units enter the recycling plant. Because the 70 units enter
more than once, the plant appears to produce 83 units of refined indium over 10 cycles. This figure of 83 units is most likely
representative of recycling plant throughput as measured by producers.
h
Of the 100 units of primary indium entering the manufacturing process, 45 units (45%) are forever lost. This is due to a
combination of: deposition efficiency, which drives the number of times the same indium must be recycled, and recycling
efficiency.
i
Units of indium discarded in the waste stream may be recoverable at some later stage. We do not, however, have information
about the concentration of indium in the waste piles or the technical challenges of recovering this indium.
Source: Own calculations; Mikolajczak (2009)
The calculations in Table 9 also highlight the significant potential for inflated estimates of
reported supply and demand from double counting. Because manufacturers are most likely
reporting total consumption of indium in ITO applications by quoting the amount of indium
purchased, they may indicate that they used 183 units of indium over the period. However, as we
have shown, only 100 units entered the process, of which only 55 units were successfully
deposited. Similarly, new scrap recyclers may report that they produced 83 units of indium over
the period, because these would have been shipped from their facilities. Together with the 100
units reported by the primary producer, reported figures by all producers might lead one to
believe, incorrectly, that total supply over the period was 183 units. Again, total supply was only
100 units, of which 55 were deposited (30 from primary sources) and 45 were lost.