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Behandlingsteknologier for batterier - Fase 1

Summary and conclusions

The purpose of phase 1 in this description - especially focusing on alkaline manganese batteries and zinc-carbon batteries - has been to describe the existing treatment methods for spent batteries. In phase 2 we have carried out a practical test for pre-treatment of alkaline manganese batteries and zinc-carbon batteries in a pilot plant.

Batteries can be divided into primary batteries that can only be discharged and secondary batteries that can also be recharged. Primary batteries include the well-known alkaline manganese batteries and zinc-carbon batteries, and they comprise the majority of the batteries used in Denmark. These are increasingly being used in households.

The consumption of primary batteries in Denmark has been estimated at app. 2,500 tonnes annually, and app. 2,400 tonnes of these are alkaline manganese batteries and zinc-carbon batteries/1/. To this must be added the consumption of secondary batteries, but there is no overall statement of this consumption. For closed NiCd batteries consumption has been estimated at 218-328 tonnes in 1997 /20/. The consumption of lead accumulators, primarily used in cars, is 15-16,000 tonnes annually /21/,

In Denmark there is no organized collection scheme for all types of batteries. However, a special scheme has been established for lead accumulators and NiCd batteries. The collection rate for lead accumulators is today close to 100% /21/, while it has been estimated at app. 50% for NiCd batteries/37/.

Excluding the big secondary batteries, the collection potential for primary as well as secondary small batteries is estimated at 2,500-3,000 tonnes annually, also taking into account the “hoarding effect” and the “pipeline effect”. Estimating a collection rate of 75%, the collected quantity will be 1,900-2,300 tonnes annually.

Concerning the further treatment of the collected batteries, it is necessary to separate the batteries into different types. Systems for automatic separation have been developed, and it is estimated that today's technology is so advanced that an automatic separation plant can compete with manual separation as regards costs and quality. Automatic separation is expected to be easier in the future as an increasing number of the mercury-free alkaline manganese batteries being collected have been marked with a UV marker, which can easily be detected.

Any future battery collection scheme in Denmark should include a central, automatic separation plant.

The collected quantities for lithium, NiCd and NiMH batteries as well as button cells will be so small, that it will not be economical to establish a treatment plant for Danish batteries alone. For NiCd and NiMH batteries and mercury containing button cells, treatment capacity today exists in Europe, whereas for lithium batteries European treatment possibilities are being established.

Alkaline manganese batteries and zinc-carbon batteries form by far the greatest fraction (80-90%), and therefore it may be relevant to establish some kind of treatment in Denmark. The most essential substances in alkaline manganese batteries and zinc-carbon batteries are: zinc (20-25%), iron (15-20%) and manganese (20-25%). Alkaline manganese batteries of more recent date and produced in Europe do not contain mercury, and it is illegal to import mercury-containing batteries into EU. Like zinc-carbon batteries, mercury-free alkaline manganese batteries are not considered as hazardous waste, but can in principle be incinerated in household incineration plants or be deposited at ordinary refuse dumps. However, it is probable that old batteries, containing up to 1% mercury, will be collected for some time yet.

By incineration in ordinary incineration plants or by depositing at refuse dumps, the resources in the batteries are lost. This loss is annually app. 500 tonnes of zinc, 400 tonnes of iron and 500 tonnes of manganese.

In principle, two different processing methods for recovery of these resources exist, i.e.:

1. Processing within the metal industries (steelworks, zinc works etc.)
2. Processing in plants, primarily designed for batteries

From an economic perspective, processing within the metal industries is most attractive. The price level is often under DKK 2,000 per tonne, if the batteries are added as a substream to the raw material. The problems of this method are, however, that the plants in general are not able to handle mercury and too much organic material (plastic etc.). In treatment processes of batteries this might result in emission problems. They are therefore added as a substream (typically of 5%), and by doing this, the emissions might be diluted.

Processing in steelworks might also result in technical problems, as copper from the batteries can accumulate in the steel and thus destroy the characteristics of the steel. There is some disagreement whether this is a problem, and it depends to a high extent of the steel quality being manufactured. Finally the degree of recycling is relatively low (20-40%).

There are no steelworks in Denmark able to treat batteries, so with this solution it would be necessary to transport the batteries for treatment abroad. At 1,000-2,000 kilometres of transport, the transport costs would be app. DKK 500-1,000 per tonne.

Processing in special plants is typically more expensive because the plants are considerably smaller compared to the metal works. The price level is typically between DKK 5,000 and 10,000 per tonne. At one of the special plants the price is more than DKK 10,000 per tonne.

On the other hand, several of these plants are adapted to treating batteries containing mercury. The organic content of the batteries can be treated and finally the recycling rate is high (50-70%). Apparently there is a connection between price level and quality, meaning that the most expensive companies in general have the highest environmental standard and degree of recycling.

In table 1, a simple comparison of advantages and disadvantages of processing alkaline manganese batteries and zinc-carbon batteries in metal industries and special plants is shown respectively.

Tabel 1.: Processing of alkaline manganese batteries and zinc-carbon batteries. A simple comparison of advantages (+) and disadvantages (-) in metal industries and special plants is shown respectively.

Because of the comparatively small quantity of alkaline manganese batteries and zinc-carbon batteries to collect in Denmark, the best solution for these batteries is:

• Pre-treatment/detoxication of the batteries in Danish plants
• Final processing abroad

Pre-treatment of alkaline manganese batteries and zinc-carbon batteries can be a pyrolysis or incineration of the batteries in a separate process, during which plastic, possible mercury, cadmium and lead are removed from the batteries. Then the batteries are “detoxicated” and can be used anywhere in the metal industries without environmental problems. The problem with this method is, however, the low degree of recycling at 20-40%. If a higher degree of recycling is requested, it is necessary to subdivide the batteries after detoxication, separate the material in fractions and send these to specialized processing companies. In this way a rate of recycling of up to 70% can be obtained.

In phase 2 in this project, the possibilities of pre-treating alkaline manganese batteries and zinc-carbon batteries are further examined by making practical tests with pyrolysis at a pilot plant at Kommunekemi.

Overall, a Danish treatment model might look as follows:

1. Collection of all batteries
2. Separation into types at a centrally located separation plant
3. NiCd, NiMH and lithium batteries and button cells etc. are sent for processing abroad due to the small quantity
4. Alkaline manganese batteries and zinc-carbon batteries are pretreated/”detoxicated” at a plant in Denmark, after which final processing will take place at plants abroad.

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