Our planet is drowning in plastic pollution. As of 2015, approximately 6300 metric tons (Mt) of plastic waste had ever been produced in the world, of which about 9% had been recycled, 12% was incinerated, and 79% was either
landfilled or discharged to the natural environment (Geyer et al. 2017). In 2010 alone, more than 270 Mt of plastic waste was generated in 192 coastal countries, with approximately 5 to 13 Mt of it leaking into the ocean (Jambeck et al. 2015).
Moreover, a minimum of more than 5 trillion plastic particles weighing over 260,000 tons afloat at sea was estimated in 2014 (Eriksen et al. 2014).
Now, plastic pollution is a globally recognized and non-negligible problem as it has been recognized as a “serious issue of global concern” by The United Nations Environment Assembly (UNEA 2016). However, it must be noted that Asian countries, especially East Asia & Pacific (EAP) region contributes to it
Figure 1. 1 Global map with each country shaded according to the estimated mass of mismanaged plastic waste in 2010 (Source: Jambeck et al. 2015)
most. As shown in Figure 1.1, the countries generated mismanaged plastic waste in 2010 are heavily biased toward EAP region. Table 1.1 shows that 13 of the top 20 countries which generated mismanaged plastic waste in 2010 were Asian countries (Jambeck et al. 2015). Moreover, it can be seen from the table that the top five polluters had caused more than half of global marine plastic pollution:
China, Indonesia, Philippines, Vietnam, and Sri Lanka, and all of them are Asian countries. By doing a simple calculation, more than 2.5 trillion plastic particles weighing over 130,000 tons can potentially afloat at Asian seas.
Plastic waste entering the oceans adversely affect marine life and indirectly threaten human life. Although the research on health hazard caused by the marine plastic pollution is still underdeveloped (Law and Thompson 2014), it has been evidenced that plastic waste and micro-plastic ingested by marine life can enter the human food chain; thus human health could be threatened (Gallo et al. 2018). Therefore, massive removal of plastic waste that can leak into the sea must be dealt with immediately.
Table 1. 1 Waste estimates for 2010 for the top 20 countries ranked by mass of mismanaged plastic waste (Source: Jambeck et al. 2015)
The reduction of plastic waste can be classified into four ways: landfilling, incineration, recycling, and reusing (Hidayat et al. 2019). The effective
treatment method has been discussed for decades, and the pros and cons of each method have ever been reported from various aspects such as energy, cost, or pollution by each process (Bernado et al. 2016). Although the superiority of landfilling and incineration for specific products such as newspaper has been reported (Finnveden et al. 2000), many researchers still support recycling
(Denison 1996, Eriksson et al. 2005). Therefore, continuous recycling promotion in various industries is essential.
The construction industry is known as the second-largest consumer of plastic (Figure 1.2), but it is also one of the significant seven sectors contributing to plastic waste generation (Figure 1.3). However, the use of plastic waste in the construction industry has recently started to get attention. Although there are
Figure 1. 2 Estimated consumption of plastic by end-used sector (Source: Geyer et al, 2017)
various applications of plastic waste utilization in the construction industry, they are not originally designed for intending the “massive recycling” of plastic waste.
As shown in Figure 1.4, the applications can mainly be classified into six. The first application might appear as a replacement of aggregates used for creating concrete or bitumen. Grounded plastic waste can be added to them at a certain percentage before they are formed. Apart from such auxiliary use, plastic waste can also be a major building material. The first attempt of plastic bottles house in Africa was in the village of Yelwa in Nigeria. Plastic bottles have been used instead of bricks, bounding the bottles together with string, and at the end applied the plaster. The application as bottle-shaped hollow material can also be seen in Asia, as represented by EcoARK in Taipei, Taiwan (Figure 1.5).
Figure 1. 3 Annual primary plastic waste generation by sector (Source: Vezér and Morrow 2018)
Figure 1. 4 Classification of the utilization of plastic waste in the construction industry
However, massive consumption of plastic waste by these applications could hardly be realized. Brick-shaped solid materials have been developed mainly in South Africa against the backdrop of low-income housings. Since it can use 100% of discarded plastic waste (plastic bags, milk bottles, etc.) as a raw
material, it is regarded as a “green” material. Similarly, bricks impregnated with plastic waste has recently been developed and researched, but only a few studies could be found. The last application, wood-plastic composite (WPC), can also use recycled plastic as a raw material. WPC, especially those containing
recycled materials, are called as wood-plastic recycles composite (WPRC). For its creation, generally particles made of plastic waste and wood waste (sawdust, planer shavings, chips, etc.) are mixed and melted together, then molded and injected in any shapes.
For the massive recycling of plastic waste, the application as replacement of aggregates can first be excluded from the options because the used amount of plastic waste seems relatively small. The replacement is generally up to around
Figure 1. 5 EcoARK in Taipei as an example of building made from plastic bottles (Source: Inhabitat®)
25% (Khajuria and Sharma 2019), and it has also been reported that the material strength decreases in proportion to the volume ratio of plastic content (Siddique 2008). The bottle-shaped hollow material should also be excluded because of the same reason, due to its hollow shape. On the contrary, brick-shaped solid
materials (Figure 1.6) seems promising, but the material has just recently been introduced in South America, so it does not seem applicable in EAP region. On the other hand, WPC can be mixed up to around 60% of plastic waste, and is widely manufactured and distributed in the region. However, there are no studies that have evaluated WPC’s potential from the perspective of the massive
recycling of plastic waste, although the material seems to have high potential.
As a new destination for large amounts of abandoned plastic waste, seeking WPC’s potential is crucial now.
Figure 1. 6 BRICKARP in Colombia as an example of building made from plastic bricks (Source: TRT World)