Plastic waste from the ore used to fill water bodies has entered the water bodies, because the conductors and switch parts of the impulse ignition systems commonly used in mining float in the water. Nowadays, it is written in several environmental permits that clean ore must be used in sea fills or that there must not be conductors among the ore, but the latter is not possible to implement with any method.
In the report "Plastic waste from mining ignition systems" carried out by Ramboll on behalf of the City of Helsinki in 2018, ways to collect plastic waste from the quarry have been reviewed. It was stated in the report that the collection of plastic generated from mining and mixed with the quarry is challenging and no method has been found that is clearly superior to other methods.
Among the methods of collecting plastic, the most suitable is to fill the quarry containing plastic inside a clean embankment. The use of electronic ignition systems has been found to have positive effects, e.g. to the efficiency of production, and because their plastic parts do not float, plastic cannot spread from the quarry fillings into waterways. Increasing the use of electronic ignition systems requires a requirement for the use of the method in tenders.
Watch the recording of the webinar
In September 2022, RT organized a webinar related to marine plastic waste and excavation work. The webinar was hosted by Juha Laurila, director of economic policy at RT, and a greeting from WWF Finland was also heard in the webinar. In the customer's speech, we discussed in particular what can be done about the charge wires that get into waterways with the ore.
Use of electronic ignition systems
+- Electronic ignition systems do not reduce the total amount of plastic waste generated, but since their parts do not float in water, it is less likely that plastic waste will spread in waterways.
- The operating cost of electronic ignition systems has been found to be higher than using an impulse ignition system, but their use enables more efficient and controlled production.
- The costs caused by the collection of plastic are at least equal to the additional cost caused by the use of electronic teddy bears.
- The use of magnetic separation is neither a functional nor a technically sound solution for collecting plastic.
- Implementation requires a regulation on the use of electronic teddies for tenders.
- It has been found that there are enough capable actors in the field.
- There is more user experience in Norway
Filling the inside of the embankment
+As far as possible, sea fills can be planned and implemented in such a way that a uniform edge embankment of waste-free ore is formed at the outer edge of the fill area. On the inside of the embankment, gravel containing plastic waste can be used, from which the plastic cannot enter the waterway through the edge embankment.
- The method limits both plastic conductors and microplastic to remain inside the filled quarry
- It is not possible to use the method. In this case, the aim is to plan the fills so that the sea fills built at the beginning of the fill form a protection for the area to be filled later. When filling the protected area, a protective curtain may be useful.
- Before the construction of fill embankments, the seabed must generally be dredged so that the embankment's stability is sufficient.
- The slurry can also be diverted to a temporary pool, where the floating plastic waste can be collected.
The use of a protective curtain in sea fills
+A protective curtain, boom or silt curtain that prevents the spread of waste can be used in sea fills (darkening curtain).
- The use of a protective curtain is a well-known and proven method, but it is not suitable for all locations due to e.g. wind and sea traffic.
- It is easy to collect plastic waste accumulated in the protective curtain from the surface of the water
- The spread of microplastic depends on the material of the protective curtain
- When using protective curtains, you have to invest in planning. Clear criteria are needed for durability and functionality in terms of currents, waves and wind.
Sorting storage and pretreatment of lye
+The idea is to separate tunnel excavations and opencast rock into separate dumping piles, because tunnel excavation has been found to contain more plastic waste
- The waste can be separated according to different fractions in order to enhance the beneficial use, in which case part of the plastic waste can be separated.
- It is not cost-effective and there is no evidence of separation of plastic waste.
- Grit separation is often not suitable for construction sites in urban areas.
- Cleaner open pit rock is less often used for sea fills