As for the sustainability factors concerning PlanetCare filters, let us first check the composition of the filter. It consists of three main parts :
- the filter housing with inlet and outlet openings,
- the filter cartridge body with a 50 micrometre mesh integrated in the cartridge wall,
- the internal filter composed of a tubular filter holder and the tailored filtering medium.
For the prototypes currently used the filter housing (a) and the tubular filter holder (part of c) are manufactured by means of 3D printing from polyamide 6, which is a thermoplastic fully recyclable material. In full production these parts will be manufactured by means of injection moulding using polypropylene (PP). PP is an easily recyclable thermoplastic material selected due to a good compromise of properties and price. PP is fully and easily recyclable and has sufficient chemical and physical resistance to withstand expected conditions even under repeated use. PP also does not degrade easily and does not release chemicals. If incinerated it is an acceptable fuel since it is a pure hydrocarbon (no sulphur, nitrogen or halogens). The filter housing will be used for longer periods and should not result in large quantities of waste. If broken it can be returned to PC or discarded with other plastic items.
There are no limits on using recycled PP in the manufacturing of these parts.
The cartridge body and integrated mesh (b) are composed of polyethylene which is a widely recycled thermoplastic material. At the moment this part is purchased from third parties and (will) not (be) manufactured by PC.
The tailored filtering medium is the part of the filter that will get replaced regularly and will produce significant amounts of waste. The filling is composed of a syntered polypropylene non-wowen mesh that is produced in large quantities from virgin PP by a producer other than PC. The mesh is tailored and formed by PC to produce cartridges. Such meshes are used in food treatment technology so they have food contact approval. In addition we are using a mesh with a bonded external surface that ensures that fibers from the mesh are not released out of the mesh.
End of life aspects
For the overall acceptability and sustainability of the PlanetCare business concept it is very important what we will do with used cartridges (incorporating collected fibres) after use. The goal is to manage all the waste in line with two principles:
- fibres and plastics never have the chance to be released into the environment and
- waste is properly disposed and preferably reused or recycled so that finally no waste occurs.
The first principle will be ensured rigorously since any deviation would defeat the main mission and efforts of PlanetCare.
The second principle however will be followed in accordance to feasibility. Key factors will be volume and geographic spread of use which will define the quantity of waste and its distribution.
The ideal cycle is to establish a collection of spent cartridges, removal of used filter fillings and replacement with new fillings. The renewed cartridges are then sent to the consumer again. This is a logistic undertaking that requires technical solutions and the participation of users. The benefit is a reuse of cartridge housings (or recycling in case of damage) and making sure that filter fillings are disposed, incinerated or recycled. The choice between these end-of-life options will be based on the quality (dirt!) and quantity of collected materials. A simpler approach is to allow users to replace the filter filling and instruct them to dispose of the waste in their local solid waste management system according to existing rules. Here again the least desired option is disposal in mixed solid waste and probably the optimal to dispose with packaging or plastics so that the waste is used in preparation of refuse derived fuel and is then incinerated. Recycling under delocalized conditions is unlikely since quantities will not be sufficient.
PlanetCare filters are designed to reduce environmental pollution by microplastic fibres which represent an estimated 35% of all microplastic pollution (Boucher et al., 2017). For the first year of PC filter marketing we estimate a market penetration of 0,0134 % of EU households (29.976 customers) and 0,05 % of new washing machines sold (9.418 customers) the combined number of households using PC filters is therefore 39.394 (PC Business plan may 2018). Further we estimate 2 washing cycles per week/household (a conservative value) and each household (conservative compared to 55 washing cycles of 4 kg per year/capita by Pakula and Stamminger (2010)). Based on this one can calculate the mass of clothes that will be washed by PC filters:
39.394 households x 55 washings/household year x 4 kg clothes/washing = 8.667 tonnes/year
One can follow the data that synthetic fibres represent 60 % of global fibre production and assume the same ratio in textiles and clothes being washed:
Quantity of synthetics washed = 8.667 tonnes/year x 0,6 = 5,200 tonnes (of washed synthetics per year)
One can assume the fibre release data 900 mg/kg synthetic per wash (Lassen et al, 2015) and a 80 % reduction of emissions due to the use of the PC filter. Thus we can estimate the cumulative amount of fibres that will be prevented from polluting our environment in one year:
5.200.000 kg x 0,9 g/kg x 0.8 = 3.744 kg
This is a conservative figure for the impact for the first year of PC filter sales. With following years the number of sold filters will grow and accumulate (following a 1,3,6,10,15... fold growth pattern by years) thus increasing the effect. For example, not counting sales growth this translates to a reduction of fibre emissions by 56,2 tonnes in year 5 of PC filter sales. The cumulative emissions reduction over this five year period in excess of 131 tonnes.
The overall sustainability of the filter and the entire product cycle could be best assessed through a full LCA. At this stage we are to early in the product and process development and do not have the resources to initiate such an analysis. We are attempting to control the impacts through considerations presented above. A more in-depth analysis will be possible after our process cycle will be established and tested with representative customer groups.
Microplastic pollution affects sea life in numerous ways. It destroys ecosystems, changes the behaviour of species in the sea by affecting their brain an increases mortality rates of the species. Since we consume seafood and sea salt it also affects humans. We know that microplastic particles are entering our bodies and also that the particles transport molecules that are harmful to humans at certain concentrations. Effectively removing microfibers released during the washing and drying therefore also links environmental impact to social impact by promoting wellbeing of people.