Advertisement

Waste Disposal & Sustainable Energy

, Volume 1, Issue 4, pp 237–249 | Cite as

Recovery of plastics from dumpsites and landfills to prevent marine plastic pollution in Thailand

  • Avi Sharma
  • Vincent Aloysius
  • Chettiyappan VisvanathanEmail author
Review

Abstract

Marine plastic pollution has become a major threat to the ecosystem. The increasing production and use of plastic, combined with limitations of waste management practices, mean the leakage of plastic waste into the environment is bound to increase. This study focuses on the determination of plastic recovery potential from dumpsites and landfills in Thailand, to potentially prevent marine plastic pollution. In this study, two dumpsites were analysed wherein an average of 42% of plastic was found to be present. This value, when extrapolated for Thailand, is equivalent to 187.9 million tonnes of plastic waste in dumpsites and landfills. While there are 2380 dumpsites in the country, this study suggests that 973 of these spread over 42 provinces are located near water bodies or coastline, which should be considered as a priority. The plastic waste recovered from these dumpsites can be treated by co-fuelling in cement industries. Cement kilns can valorise plastic waste as they can reach up to 75% energy recovery from waste, which is much higher compared to traditional waste-to-energy plants. With adequate incentives and sound regulations, cement industries could help in the reduction of marine plastic pollution with controlled emissions and a very large capacity to co-fuel cement production, there is a readily available solution to manage the large volumes of solid waste generated.

Keywords

Plastic recovery potential Dumpsite waste analysis Waste-to-energy Waste-to-heat Co-fuelling Cement kiln Marine plastic pollution 

Introduction

Since its invention in 1907 by Leo Hendrik Baekeland, plastic has replaced many other forms of material and has proved its versatility. The persistent nature of plastic and ease of production has led to an increase of production, by 200 times, from 2.0 million tonnes in 1951 to 381.0 million tonnes in 2015 [1]. Because of its longevity, most of the plastic produced continues to exist for a very long time in the form of waste.

The utilisation of plastics has increased multi-fold in developing countries where economic growth and improved quality of life have increased the consumption of consumer products leading to a further increase in waste generation. The efforts on waste management in developing countries have not been able to catch up with growing amount of waste generated. Most developing countries still depend on traditional waste treatment methods, which consist of collection and disposal of waste either in dumpsites and landfills or illegal dumping.

This kind of waste collection and disposal leads to a very high possibility of leakage of waste at every stage of the process. Leakage of plastic waste into the environment is a global phenomenon and is not restricted to any particular country. Most leaked plastic waste ends up in oceans with an estimated 8 million tonnes added every year [2]. Plastic waste in the ocean is known to cause a decline in marine life around the world.

Plastic is known to photo-degrade over time into micro-plastics, which due to their smaller size can be consumed by aquatic animals and thus enter the food chain. The spread of awareness regarding micro-plastics has gained momentum recently as one of the leading global challenges due to its presence in oceans and sediments [3]. Once entering the body of an organism, micro-plastics are known to cause health ailments [4]. Apart from that, plastic is also a known source of greenhouse gas emission, as the raw material required for the production of plastic requires mineral oils and energy. Plastic waste has 590 kg carbon material per tonne, which is highest compared to other categories of waste in municipal solid waste (MSW). Plastic production, therefore, releases fresh carbon which was earlier present inside the earth. Land-based activities produce 80% of marine plastic, where dumpsites are known to add 1.1–1.3 million tonnes of marine plastic every year [5]. According to the report published by Ocean Conservancy and Mckinsey Center for Business and Environment, where the focus was kept on plastic waste entering into oceans by five countries, i.e., China, Indonesia, the Philippines, Thailand and Vietnam, 55–60% of the global plastic waste leakage is added by these five developing countries. Where it was also concluded that open dumps lying near the oceans and which are lying in the water ways are a major contributor in the plastic waste leakage and in these five countries, it adds between 1.1 million and 1.3 million metric tonnes of plastic waste per year. Hence, it is important not only to reduce the generation of plastic waste but also to reduce its accumulation in dumpsites or landfills.

Half of all marine plastic pollution is known to enter from a small geographic region involving only five countries, i.e., China, Indonesia, The Philippines, Thailand and Vietnam [5]. These countries have recently seen rapid economic growth and fast urbanisation, which has led to a drastic increase in consumer product utilisation, most of which are made of single-use plastics. Also, due to the lack of advanced waste management systems and on account of long coastlines, these countries are using oceans as a sink for their wastes.

Like the other four countries, Thailand is surrounded by ocean with the southern part of the country having a coastline of 3219 km. Meanwhile, the central part of Thailand is well connected by rivers and tributaries. It is a developing nation with rapid urbanisation and lifestyle growth, with 54.82% of citizens living in the urban area [6]. Plastic consumption habits of Thai citizens are equivalent to the use of 8 bags per day per person, which amounts to 200 billion plastic bags per year [7].

At present, 37 million people live in Thailand’s urban areas. This group produced 24.11 million tonnes of MSW in 2009 before reaching 27.82 million tonnes in 2018 [8]. Although consistent efforts are being made by the Thai government to reduce waste generation, these efforts are not enough, as only 9.58 million tonnes of waste (about one-third) was utilised in 2018. Inevitably, Thailand largely depends on dumping wastes either in landfills or dumpsites. Hence, it is important to reduce the accumulation of plastic waste in landfills and dumpsites to curb marine plastic pollution in Thailand.

Although there efforts are made in Thailand to curb the marine plastic pollution, but due to the dependence of waste management system on informal sector, the direct dumping of waste into the oceans is a common phenomenon [9]. 3% of the total plastic waste generated in Thailand, finds its way to the marine environment [10]. In 2019, the Thai government has declared to put a ban on the use of three plastic, i.e., microbeads, cap seals and oxo-degradable plastics [11]. These efforts are although a welcome step towards reducing plastic waste, are still small when compared to the problem. The recent clean-up by PCD on beaches, coral reef and mangrove forests in 24 provinces collected 33 tonnes of waste, where the major contributor was plastic bags (18.9%), plastic bottles (8.6%), thin shopping bags (8.4%), food packaging (6.1%), straw (4.6%), etc. Most of the residual waste retrieved was plastic waste in some form. The current policy changes and steps taken by Thai government will help in the reduction of plastic waste generation, however, the amount of plastic which is present in the dumpsites or landfills are still prone to leakage. As Thailand is prone to floods and heavy rainfall, the waste in dumpsites and even landfills are very much prone to leakage. This study analyses an effective method to reduce the indirect marine plastic pollution, which is coming from dumpsites and landfills.

On a broader scale, plastic can be divided into two forms: thermoplastics and thermosetting plastics. While thermoplastics can be remoulded and recycled into newer forms of material, thermosetting plastics cannot be recycled. Meanwhile, single-use plastics, due to their mixed components, are extremely difficult to recycle and repurpose. It is these plastics that will exist in its chemical structure, if not physical, for a long period. Single-use plastics are typically light in weight and difficult to valorise, which reduce their desirability among recyclers.

Plastic waste can be reduced by two methods. Segregated plastic can be taken through various steps and recycled into new products as part of a process known as Waste-to-Material (WTM). In WTM, plastic will sustain its chemical structure but only its physical outlook changes. Another method is to use plastic waste to generate energy since plastic can be used as fuel for feedstock to generate energy. This process is called waste-to-energy (WTE). Plastic waste has good calorific value, ranging between 15 and 45 GJ/tonne, according to the kind of plastic and can be used as solid-recovered fuel [12].

Plastic waste present in landfills or dumpsites is a heterogeneous mixture of different forms of plastic, which is mainly composed of single-use plastic. Single-use plastic is non-recyclable due the presence of various layers and types of plastic and non-plastic materials combined in packaging. Therefore, incineration of single-use plastic either is a possible option in the cement industry or power generation industry [13]. When plastic waste is co-fuelled in a cement kiln, it is subjected to high temperatures reaching 1400–1800 °C and long residence times, which ensures complete combustion, while the pollution control system and the kiln environment with calcium oxide rich fine powder material controls the emission of pollutants. As for heavy metals and dioxins emissions, the cement kiln process is well researched and extensive data are available from decades of waste co-fuelling proving emissions to be well below the most stringent national emission standards [14].

The objective of this study was to determine the plastic recovery potential from dumpsites and landfills in Thailand and to identify the priority provinces, which are contributing to marine plastic pollution. This study also analyses the technical and economic superiority of co-fuelling of plastic wastes in the cement industry over traditional waste-to-energy plants.

Materials and methods

Dumpsite selection

The waste analysis was carried out in two dumpsites to find out the plastic recovery potential of dumpsites and landfills in Thailand, namely Nong-Khae and Nakhon-Nayok. These dumpsites are located in Saraburi province and have been in operation to produce RDF for co-fuelling cement kilns in Siam City Cement Company. Nong-Khae dumpsite is situated 50 km from INSEE Ecocycle’s (a wholly owned subsidiary of Siam City Cement Company) waste-processing plant and has been in operation during the last 10 years. This dumpsite has a capacity of 50,000 tonnes and uses two, 80 mm trommel screens to process waste. Nakhon-Nayok, on the other hand, is situated 70 km from the INSEE Ecocycle plant and has received waste for the past 20 years. The capacity of this dumpsite is much more than Nong-Khae and stands at 0.175 million tonnes. Nong-Khae and Nakhon-Nayok dumpsites are processing 1000 tonnes and 500 tonnes of waste per month, respectively, for RDF production.

Both dumpsites have receiving waste for more than a decade, because of which the amount of organic content is reduced drastically due to microbial activities. This increases the concentration of combustible material present in the dumpsite, while the moisture content of the waste is reduced. As the concentration of organics gets reduced, the concentration of combustible material increases making the waste more attractive for RDF production. Such waste found in dumpsites like Nong-Khae and Nakhon-Nayok can be easily processed into RDF, without complex treatment methods.

The dumpsites chosen for this study are located away from urban settlements and are surrounded by paddy fields and small clusters of residential buildings. However, it is the canals situated in close proximity of these dumpsites that make them plausible culprits of marine plastic pollution. The distance between the nearest canal and Nong-Khae dumpsite is only 120 m and 1.5 km in case of Nakhon-Nayok. Having a canal in such close proximity to a dumpsite increases the probability of waste leaking into canals, especially during monsoon seasons when the water level in canals can easily rise resulting in the waste flowing from dumpsite into the canal. In Thailand, most canals are directly connected to major rivers making it easier for water to carry waste from dumpsites to canals which flow into the river and from there into the oceans. Hence, it becomes important to quickly reduce the amount of plastic waste at such dumpsites so that their impact on marine plastic pollution can be reduced.

The operational period of these dumpsites, however, is limited to 8 h/day, which is much less than the capacity of equipment installed at the dumpsites reducing the rate at which waste can be processed. Trommel screens are used to process waste at these two dumpsites, which may create noise pollution, while the excavation of waste from the dumpsite releases gases, such as methane, into the atmosphere and may create a stench in the surrounding area. Longer operating hours, considering sufficient illumination to ensure safe operating conditions will further benefit the operations with the large quantities of waste arriving at the site that also make operations more economically viable.

Sample collection

Waste from two dumpsites were analysed in compliance with the method suggested by [15] to analyse waste composition according to diminishing marginal returns, using the following formula (1):
$$\Delta N_{i} = K[({\text{CV}}_{i}^{j + 1} )^{2} - ({\text{CV}}_{i}^{j} )^{2} ],$$
(1)
where Ni = number of samples, CV = Si/Xi, Si = standard deviation, Xi = mean of sample, K = 29.88 (constant Z = 1.64 @ 90% confidence).

If value of \(\Delta N_{i}\) is less than 1, then the number of samples taken are considered as adequate.

The number of samples to be analysed for dumpsite waste in Thailand using formula [1] is five. However, ten samples were analysed in this study to offset the initial instability of the confidence level. All the samples were collected by simple random sampling procedure keeping the volume equal and not haphazard in their spatial orientation [16]. This method is used to reduce the number of samples required for dumpsite waste analysis. As noted earlier, waste from two dumpsites was analysed in this study, as both the dumpsites were using trommel screens to process waste; three different categories of waste were generated at each dumpsite, i.e., dumpsite waste, trommel processed waste and trommel rejected waste. A total of 30 samples were collected from each dumpsite, 10 each from the three categories.

Out of these three categories, trommel processed waste is taken to the INSEE Ecocycle facility for further processing into RDF. As the trommel rejected waste is left at the dumpsite, it was important to analyse the composition of such rejected waste to understand the amount of plastic waste, which is left at the dumpsite, and to find out the other forms of waste present in the rejected waste, which can be utilised or those that can be segregated as potentially harmful ones.

PCD data analysis

Data for dumpsite and landfill capacities were obtained from the Pollution Control Department (PCD), Ministry of Natural Resources and Environment, Thailand. The data are compiled in the form of a separate list for each province, which includes locations, coordinates, year of operation, area of the site and incoming waste for landfills, dumpsites and WTE plants present in Thailand. Using these data, the amount of incoming waste per day in dumpsites and landfills is multiplied by the number of years of operation to determine the amount of waste present in dumpsites and landfills.

There are 2380 dumpsites in Thailand and only data for 203 (8.53%) of the dumpsites were not available. Although the data provided had information for the majority of the provinces, only two provinces, i.e., Chiang Mai and Samut Sakhon did not have data on more than 50% of the dumpsites. Some segments of data were missing in a few other dumpsites, e.g., the amount of incoming waste or the opening year of operation. For such dumpsites with missing data, an average value of the data was taken for that province to determine the amount of waste present in the dumpsites.

The coordinates of the dumpsites obtained from PCD were used to locate the ones that could be potentially responsible for marine plastic pollution. Geographical locations of all the dumpsites were marked and those present in the provinces situated on the coastline or in the vicinity of rivers were marked as priority dumpsites using the coordinates. Although there are other dumpsites which are present near smaller water bodies, the ones which are located directly in the river shed area or on the coastline are considered as more susceptible to plastic waste leakage. Hence, waste at these dumpsites should be treated before other dumpsites to quickly reduce the growing rate of land-based marine plastic pollution.

Results and discussion

Dumpsite analysis

As mentioned in Sect. 2.1, two dumpsites were analysed during this study. The waste analysed was sorted into nine categories, as shown in Table 1, along with composition of different waste present at dumpsites.
Table 1

Dumpsite waste analysis

Dumpsite

Nong-Khae

Nakhon-Nayok

Unit

Percentage

Tonnes

Percentage

Tonnes

Waste category

Dumpsite waste

Rejected waste

Processed waste

Waste at dumpsite

Dumpsite waste

Rejected waste

Processed waste

Waste at dumpsite

Composted organic + soil

39.83

83.46

31.66

19,916.20

44.87

60.90

26.67

78,522.5

Paper

1.45

0.00

0.31

726.25

1.92

0.00

2.22

3,360

Plastic

45.25

12.22

58.84

22,625.69

39.12

26.28

60.44

68,460

Glass

1.68

3.20

1.02

837.98

1.58

3.42

0.89

2,765

Metal

2.23

0.00

0.20

1,117.31

2.71

2.56

1.33

4,742.5

Rubber

1.12

0.07

0.00

558.65

3.27

0.85

3.78

5,722.5

Textile

5.08

0.46

2.66

2,541.89

2.14

3.42

3.78

3,745

Yard

1.62

0.00

3.98

810.05

1.69

0.64

0.44

2,957.5

Ceramic

1.73

0.59

1.33

865.92

2.70

1.92

0.44

4,725

Waste present at both the dumpsites contains 45.25% and 39.12% of plastic waste, respectively, averaging 42.18%. The organic waste averages out at 42.35%, which is equal to the amount of plastic waste present at the dumpsite. Although the amount of organic waste present in raw MSW in Thailand is about 64%, its concentration decreases to 42.35% over time due to microbial degradation. As the concentration of organic waste reduces, the concentration of plastic waste increases from only 18% in raw MSW to 42.18% at dumpsites. The organic waste present at the dumpsite is largely composed of soil; therefore, it is mentioned as composted organics and soil in Table 1. While there are other forms of waste present at the dumpsites, their concentration is much smaller when compared to plastic waste or organic waste.

Except for metals, ceramics and organics, every other form of waste at the dumpsites are combustible in nature. Whereas the concentration of metals and ceramics is much less compared to organics, it is essential to reduce the amount of organic waste. The trommel screens present at dumpsites are very effective in separating the organic waste, as seen in Table 1 wherein there is a considerable reduction in the concentration of organics from dumpsite waste to trommel processed waste. This is because the major constituent of organic waste consists of composted organic fraction and inorganic soil, which has a much smaller particle size and can easily pass through the sieves of a trommel screen. There is an average increase of 17.45% in plastic composition from dumpsites waste to trommel processed waste because the plastic waste present at the dumpsites is largely composed of plastic bags, which are larger than the 80 mm sieve holes of the trommel screen. Hence trommel screens can effectively increase the concentration of plastic waste. The trommel processed waste, which is used to prepare RDF for the cement kiln, has to be further processed to remove metals and ceramics. Although smaller in concentration, they can still cause hindrance in the cement production process or reduce the quality of the final product.

The trommel rejected waste, left at the dumpsite, is mainly composed of organic wastes having an average value of 72.18%. There is still some plastic waste left forming an average of 19.25%. But most of the plastic waste left at the dumpsite is mixed with large amounts of organics and soil. Moreover, the size of plastics in rejected waste is smaller than 80 mm. Therefore, it will be held within the organic wastes and soil and hence difficult to percolate into water bodies. Rejected waste also comprises many other forms of waste, but their concentration is insubstantial to further sort and extract them as secondary raw materials.

Although the amount of composted organic waste with soil reduces to a certain extent, still it is large enough to make the trommel processed waste unsuitable for co-fuelling in the kiln. Therefore, it is important to further process this waste and remove unwanted material. There are other forms of combustible material that could be found in the dumpsites, but their quantity is miniscule compared to plastic waste, which makes plastic highly attractive to be extracted from waste. Moreover, most of the plastics present in the dumpsites are single-use plastic wastes, which are non-recyclable and can only be incinerated.

Plastic recovery potential of landfills

There are 104 landfills in Thailand of varying capacities complying with Pollution Control Department (PCD) norms. About 214.34 million tonnes of waste is present in these landfills. Extrapolation of the results obtained from the current study implies that the plastic recovery potential for landfills is about 90.42 million tonnes. As the waste stored in landfills is below the ground level, it is less vulnerable to the effects of rain or flooding and will have reduced impact on the addition of marine plastic pollution. Still, it is important to reduce the amount of plastic waste in the landfills but it can be considered less of a priority over dumpsites.

Plastic recovery potential of dumpsites

There are 2380 dumpsites spread across Thailand. Taking the average composition of waste analysis from the current study, the total capacity of dumpsites in the country is 231.08 million tonnes.

Although the number of dumpsites is much larger than landfills, their capacities are much smaller. Hence, the amount of waste present in dumpsites is comparable to that of landfills. About 97.48 million tonnes of plastics and 97.86 million tonnes of organic waste are present in the dumpsites.

The dumpsites in Thailand are divided into two categories, open dumps and controlled dumps. In both cases, the waste is open in the atmosphere and can easily trickle into water bodies during rainy season or floods. Wastes present in open dumps are much more prone to the effects of the environment because these sites lack any control structures or boundaries and are more likely to add to marine plastic pollution. The study recommends considering dumpsites, especially open dumps, as a greater threat to marine plastic pollution and should, therefore, be considered a priority to reduce their impact on marine plastic pollution.

Plastic waste recovery potential of Thailand

Based on the total potential amount of plastic waste present in landfills and dumpsites, the plastic waste recovery potential of Thailand works out to 187.9 million tonnes. As the current waste management practices work on the linear model of waste management where waste is collected and stored away from the urban environment, this waste is bound to exist in the same uncontrolled conditions and will remain open to the effects of the environment. Such a large amount of uncontrolled and unaccounted plastic waste can have a widespread effect on the surrounding areas of the dumpsites and landfills. As the practice of uncontrolled dumping continues, marine plastic waste leakage will increase from the dumpsites located in the vicinity of water bodies.

It is of utmost importance to reduce this plastic waste in dumpsites and landfills to reduce their impact on the marine environment. Co-fuelling of plastic waste in the cement industry is one of the most practical and sustainable methods available to reduce waste. Reducing plastic waste in dumpsites and landfills will not only lessen marine plastic pollution, but will also reduce their impact on the surrounding areas. Moreover, as waste is removed from the landfills and dumpsites, the available space to store waste will also increase. This subsequently increases the lifetime of waste storage facilities and reduces the obligations to create new facilities.

Plastic waste flow in Thailand

There has been steady growth in MSW generation in Thailand along with the economic and urban population growth. Being a rapidly developing country, Thailand is witnessing brisk development of urban centres and equally fast-growing consumerism. This is reflected in MSW generation being at an all-time high. But the growth of municipal solid waste management (MSWM) has not been able to catch up with the growth of MSW generation. A small fraction of the 25.24 million tonnes of waste generated in Thailand, 25% [2] or 6.31 million tonnes of waste, was managed properly in 2017. Most of the managed waste ends up in landfills and controlled dumping, which is the final stage in MSWM. Although there are five WTE plants, the amount of waste treated by these plants is limited due to the lack of high-quality, segregated waste.

As much as 75% mismanaged waste ends up either in uncontrolled open dumps or in the oceans. The amount of waste which is leaking from waste collection and disposal sites is not fully accounted and to reduce marine plastic pollution it is extremely important to increase the collection capacity of MSW. The amount of uncontrolled waste directly dumped into rivers and oceans should be reduced drastically and rapidly.

It can be seen from Fig. 1 that plastic waste comprises 18% of the raw MSW in Thailand. This is 6% higher than the world average [6]. The amount of plastic waste generated in raw MSW is more than the world average and it is bound to increase further in the dumpsites or landfills where it can reach up to 42%. Although most of the waste in Thailand is still mismanaged, the amount of plastic waste going into dumpsites and landfills is quite substantial. As the existing dumpsites and landfills are filling up rapidly the need to create new dumpsites and landfills is increasing to cope up with the growing MSW generation. Without any manageable location for storing waste, the extent of uncontrolled dumping will further increase potentially adding more marine plastic pollution. Therefore, if waste in dumpsites and landfills is reduced, more space will be freed to dispose of new waste that is generated. This way existing waste in the dumpsites and landfills, which is left intact for years, will be put to good use. Utilising waste in dumpsites and landfills for co-fuelling will reduce direct and indirect marine plastic pollution.
Fig. 1

Plastic waste flow in Thailand

Location of landfills

There are 104 landfills in Thailand containing 214.34 million tonnes of waste out of which 90.42 million tonnes is plastic waste. The locations of these landfills in Thailand can be seen in Fig. 2, along with five WTE plants. The majority of landfills in Thailand are sanitary landfills, which means the waste is stored inside the ground with leachate controlling liners and good surface drainage systems. As the waste is stored below the ground surface the available capacity of a landfill is fixed according to the given land area. The PCD regulations set the amount of incoming waste to a landfill according to the available land area, making the lifetime of a landfill approximately 20 years. If a landfill is receiving waste in excess of the suggested value by norms, its expected lifetime will decrease. Out of 104 landfills in Thailand, 22 are receiving waste above their capacities, reducing their lifetime to be less than 20 years. Once these landfills are filled, the incoming waste has to be transferred to other locations or it may result in uncontrolled dumping at existing facilities. Six of these landfills are located in provinces along the coastline of Thailand. Therefore, it is necessary to reduce the amount of waste present in these landfills, so that their capacities and lifespan can be increased reasonably.
Fig. 2

Landfills in Thailand

Location of dumpsites

As mentioned earlier, there are 2380 dumpsites in Thailand and most of them are still uncontrolled. Dumpsites are more affected by the ambient weather conditions whereby waste can easily escape by wind or rain and floods during monsoon seasons. This study suggests that dumpsites present near watershed areas and coastline should be considered as a priority to reduce plastic waste. There are 973 such dumpsites spread over 42 provinces that can act as major contributor to marine plastic pollution due to their proximity to water bodies. Table 2 depicts the provinces in Thailand with the total number of dumpsites in each province. Figure 3 represents the provinces in Thailand. The highlighted provinces should be considered as a priority due to their geographical location.
Table 2

Dumpsite location in Thailand (A) province on map (B) number of dumpsites

A

Province

B

A

Province

B

A

Province

B

A

Province

B

1

Bangkok

21

Loei

43

40

Phatthalung

14

59

Samut Songkhram

2

Amnat Charoen

22

Lopburi

33

41

Phayao

59

60

Saraburi

7

3

Ang Thong

23

Mae Hong Son

107

42

Phetchabun

38

61

Satun

8

4

Bueng Kan

24

24

Maha Sarakham

11

43

Phetchaburi

11

62

Sing Buri

4

5

Buri Ram

44

25

Mukdahan

13

44

Phichit

14

63

Si Sa Ket

49

6

Chachoengsao

10

26

Nakhon Nayok

3

45

Phitsanulok

21

64

Songkhla

21

7

Chai Nat

7

27

Nakhon Pathom

4

46

Phrae

40

65

Sukhothai

7

8

Chaiyaphum

94

28

Nakhon Phanom

37

47

Phra Nakhon Si Ayutthaya

11

66

Suphan Buri

23

9

Chanthaburi

8

29

Nakhon Ratchasima

90

48

Phuket

67

Surat Thani

40

10

Chiang Mai

126

30

Nakhon Sawan

17

49

Prachin Buri

22

68

Surin

14

11

Chiang Rai

72

31

Nakhon Si Thammarat

30

50

Prachuap Khiri Khan

19

69

Tak

20

12

Chon Buri

20

32

Nan

42

51

Ranong

13

70

Trang

13

13

Chumphon

15

33

Narathiwat

21

52

Ratchaburi

9

71

Trat

15

14

Kalasin

46

34

Nong Bua Lam Phu

46

53

Rayong

12

72

Ubon

Ratchathani

69

15

Kamphaeng Phet

13

35

Nong Khai

16

54

Roi Et

54

73

Udon Thani

94

16

Kanchanaburi

49

36

Nonthaburi

55

Sa Kaeo

9

74

Uthai Thani

2

17

Khon Kaen

173

37

Pathum Thani

4

56

Sakon Nakhon

22

75

Uttaradit

37

18

Krabi

22

38

Pattani

42

57

Samut Prakan

76

Yala

2

19

Lampang

191

39

Phangnga

11

58

Samut Sakhon

3

77

Yasothon

38

Fig. 3

Provinces in Thailand

These dumpsites are closest to water bodies where the effect of monsoon season or fast blowing oceanic winds is strongest. Hence, it is necessary to reduce the amount of plastic waste in these dumpsites to control marine plastic pollution. As discussed earlier, the waste present in the dumpsites is open and above ground level meaning it is much easier to extract waste here than from dumpsites than landfills. Therefore, processing waste at dumpsites is more pragmatic and attractive than landfills.

Co-fuelling in cement industry

Production of cement is an energy intensive process and demand for cement is expected to grow hand-in-hand with the growing economy and urban centres. Cement industries typically use solid fuel in their kilns and rely heavily on coal to generate heat and meet their energy demand. In this study, it is suggested to co-fuel plastic waste from dumpsites and landfills along with coal, which will reduce the dependence on of cement industries on coal.

Plastic waste treatment

Plastic waste segregated from the dumpsites can be treated either by waste-to-energy (WTE) or waste-to-material (WTM). For the mixed plastic waste recovered from dumpsites and landfills, WTE is the preferred form of plastic waste treatment due to the presence of mixed plastic waste. Although according to waste management hierarchy WTM stands above WTE, WTE is a more attractive option in case of plastic waste treatment for waste recovered from dumpsites and landfills. Cement industries can utilise the very crude form of this waste, which does not require sophisticated waste pre-processing.

For WTM, waste recovered from landfills or dumpsites must go through extensive purification and treatment processes to recover a high-quality product, which can be used to produce recyclable material. Moreover, during the waste analysis it was observed that most plastic waste is made up of single-use shopping bags or packaging material, which are made from low-density polyethylene (LDPE). These plastics are also known as single-use plastics and can only be incinerated. Therefore, plastic waste reclaimed from landfills or dumpsites is more suited for WTE. With simple techniques and processes, the waste present at the dumpsites and landfills can simply be converted into solid recovered fuel for cement kilns.

Waste to energy

Energy generated from waste incineration can be utilised either in the form of heat, i.e., waste-to-heat (WTH) where energy is directly utilised in the form of heat, or in the form of waste-to-energy (WTE) where heat generated from combustion is utilised to produce electricity using boilers.

Fuel is fed in cement kilns where incineration takes place and the heat generated from incineration is directly transferred to the raw material for cement production to produce clinker. A cement kiln can attain typically high average efficiencies of 75% and higher [17]. When compared to a cement kiln, energy losses during heat transfer in a traditional WTE plant are much higher as the number of sites where heat transfer takes place are much higher. Therefore, a typical WTE plant can reach an average efficiency of 13% [18], which is much lower than a cement kiln. Some of the latest and state of the art WTE in Denmark are able to an efficiency of 27% [19]. Hence, a cement kiln will be able to utilise energy from waste much more efficiently when compared to a WTE plant, due to the significant difference in their efficiencies.

This study, therefore, suggests that WTH plants, such as cement industries, are well suited to utilise the energy from plastic waste incineration. Table 3, represents a tabular comparative analysis between cement industry and a waste to energy plant.
Table 3

Tabular comparison between cement kiln and WTE plants

 

Cement industry

WTE

Heat losses

Less heat losses, limited moving parts implies less frictional resistance

More heat losses, more moving parts and interfaces for heat exchange implies more friction resistance

Efficiency

74%

13%

End-products

No solid waste generation

Air emissions are controlled by pre-installed pollution control devices

Ash from waste and coal combustion

Air pollution control devices have to be installed to control the emissions

Economic Policies

No subsidies for waste co-fuelling in cement industries

WTE are given subsidies in the form of feed-in tariffs

Feed-in-tariffs are divided in two categories, i.e., variable feed-in tariffs and fixed feed-in tariffs

End products from waste incineration

Incineration of plastic waste generates end products like ash and emissions. Ash from plastic waste combustion may contain harmful contaminants, such as heavy metals, that are difficult to dispose of. The temperatures inside cement kilns can reach up to 2000 °C [20]. Due to such high temperature, the raw material for cement production turns into molten state. However, when plastic waste is incinerated in the cement kiln the ashes produced from fuel combustion react with molten clinker material and become a part of it [21]. Therefore, the composition of the finished end product of the clinker material contains a portion of combusted waste and the ash produced from it. In the cement process, contents of raw material are monitored to compensate for the addition of ashes from raw materials to achieve the desired product properties.

Another aspect that must be looked into during plastic waste incineration is the generation of dioxins. Due to the long residence time and high temperature in cement kilns, the lime present in the raw material acts as a scrubber to curb emissions. As the exit gases reach dioxin formation temperatures ranging between 200 and 400 °C, the exit gas is quenched in the conditioning towers where temperatures are lowered and dedusting of gas is effectively carried out. This reduces the residence time of exit gases keeping them out of the dioxin forming temperature range thereby reducing the likelihood of dioxin formation. Moreover, chlorine emissions from raw material in cement production far outweigh the chlorine emissions from plastic waste.

The percentage of chlorine content in the cement clinker can have a typical value of 0.1% w/w [22], which is much lower than the chlorine content of the plastic waste. The typical composition of plastic can have 2.5% of chlorine in it [23]. However, the weight of clinker is much higher than the weight of plastic waste in the kiln. Therefore, chlorine emissions released from combusting plastic waste are marginal when compared to what is released by raw material for cement production. In addition, the range for dioxins and furans formation lies between of 250 and 450 °C. As the extreme temperatures inside the kiln and steady conditions are maintained the formation of dioxins and furans are controlled easily [24]. In addition, to that the majority of chloride is released from PVC plastics, which are typically separated from the waste streams due to higher density and ease of recyclability.

Therefore, if plastic waste is utilised in a cement kiln there is no solid waste generated or harmful emissions released. Moreover, there is no need for modification in pollution control devices or the firing process of the kiln. This gives the cement industry technical superiority over traditional WTE plants where modifications in existing emission control devices may be required while using plastic waste for co-fuelling.

Due to these qualities, cement kilns are able to utilise many different forms of waste streams including plastic waste, wood waste, dried sewage sludge, tyres, biomass, etc. Hence, cement kilns can be a superior form of waste disposal method for different forms of waste, requiring minimal modifications in the production process and allowing waste to be utilised for efficient energy generation.

Policies in Thailand

Much like other developing countries, Thailand is shifting its policies to reduce waste generation and setting targets to reduce dependence on fossil fuels to fulfil its energy requirements. According to the Alternative Energy Development Plan (AEDP) 2012–2021 [25], Thailand wishes to generate 25% of total energy demand from alternative energy sources. This includes 400 MW of electricity generation from MSW incineration by 2021, requiring an increase from 66 MW in 2014. To reach this goal, the government is providing subsidies and incentives to promote WTE plants. These subsidies are given in the form of feed-in tariffs, where plants are divided into two broad categories based on their capacity, small power provider (SPP) if it is more than 10 MW and very small power provider (VSPP) if less than 10 MW. VSPP is further divided into three categories ranging from less than 1 MW, between 1–3 MW and 3–10 MW. There are three categories for feed-in tariffs namely, feed-in-tariff (F): fixed feed-in tariffs, feed-in-tariff (V): variable feed-in tariffs, which is fixed based on the investment cost of raw materials used for power generation, varying with time. The third, feed-in-tariff premium, is a special tariff given to the southern border provinces of Yala, Pattani, Narathiwat and Chana, Thepha, Saba-Yoi and Na-Thawi.

Apart from direct feed-in-tariffs support, these plants are also receiving project subsidies and financial support in the form of Energy Service Company (ESCO) fund. Due to policy inclination of government towards WTE plants, it is difficult for WTH plants to effectively utilise MSW as fuel.

Waste pre-processing

Wastes from dumpsites or landfills are not typically suitable to be used as fuel in cement kilns due to the presence of unwanted material as discussed in Sect. 3.1. To make it more suitable, the waste has to go through various pre-processing steps which increases the calorific value of the fuel and removes other unwanted material like metals, which are recyclable in nature, or ceramics, which may not add value to the cement production process.

Each step involved in pre-processing increases the calorific value of waste while removing unwanted material. Typical steps involved in waste pre-processing are shown in Fig. 4. Pre-processing of waste can be divided into two categories by current practice, i.e., pre-processing at dumpsites and pre-processing at material recovery facilities.
Fig. 4

Waste pre-processing

As the waste passes through different steps, the concentration of plastic increases. Only 42% of plastic waste is present at the dumpsites and as it is processed through a trommel screen the concentration of plastic waste increases to 60% in dry solid waste, while in rejected waste it remains around 19%. With further processing, metals are also removed at a material recovery facility. Although metals are only 0.76% in trommel processed waste, they are removed from waste because they can cause damage to the cement production process and reduce the quality of the final product. Additionally, metals are incombustible in nature and can easily be recycled.

Calorific value of waste present at the dumpsite can reach up to 16.74 GJ/tonne. As the waste is processed the calorific value of the final product increases to 18.84 GJ/tonne. Once the waste is excavated from the dumpsite and processed through a trommel screen, the calorific value increases up to 17.58 GJ/tonne. Trommel reject waste, which is largely composed of soil, has 4.18 GJ/tonne of calorific value, which is much less in comparison. Although the calorific value of clean plastic free from moisture and other impurities can reach up to 30 GJ/tonne, the value can only reach up to 18.84 GJ/tonne due to the presence of foreign materials and moisture in dumpsite plastics. The final product having 80% plastic waste is used as fuel in cement kiln, with a typical plastic-to-coal ratio being 5%, though it can be higher if larger volumes of recovered plastics are made available. Figure 5 shows the changes in calorific value of waste as it is processed to produce RDF.
Fig. 5

Calorific value comparison

Energy recovery potential of plastic waste

Waste in dumpsites and landfills are one of the biggest untapped sources of energy. The amount of waste accumulated in waste storage facilities have reached such an extensive level that it can be used as a constant source of fuel for WTE or WTH plants. As discussed in previous sections, plastic waste has a significant amount of calorific value in it and the concentration of plastic waste in dumpsites and landfills is suitably large enough to use as fuel. The energy generation potential from waste in dumpsites and landfills is, therefore, significant. From Table 4, it can be seen that waste accumulated in dumpsites and landfills can be used to generate up to 3868.27 PJ and 3588.05 PJ of energy, respectively. Such a large source of energy can be easily extracted and processed to further increase energy generation, while reclaiming recyclable materials in the process.
Table 4

Energy recovery potential

Location of waste

Million tonnes

GJ/tonne

PJ (106 GJ)

Amount of waste

Net calorific value

Energy recovery potential

Raw MSW (per year)

25.24

4

100.96

Dumpsites accumulated waste

231.08

16.74

3868.27

Landfills accumulated waste

214.34

16.74

3588.05

Trommel processed (per year/trommel)

0.019

17.58

0.341

Material recovery facility (final processed waste)

0.124

18.84

2.35

With the simple trommel screen processing, waste from a dumpsite can be processed to generate 0.341 PJ of energy. Using a trommel screen is one of the primary steps that can be taken while extracting waste from dumpsites or a landfill, as the inorganic soil content is removed from waste. Once, the waste is passed to a material recovery facility, the energy generation potential is further increased to 2.35 PJ. When compared to raw MSW, where calorific value of waste only remains at 4 GJ/tonne, the energy recovery potential is also notably smaller and remains only at 100.96 PJ. This is due to the presence of high organic waste in raw MSW containing a large moisture content. If 1000 trommel screens were to work all year round, it would require more than 12 years to process all the waste from dumpsites and more than 11 years to process all waste at landfills. Still, a significantly large amount of waste would be left at dumpsites, but considering the fact that most of trommel rejected waste is inorganic soil, it poses no harmful effects to the surrounding area nor does it add to marine pollution.

Hence, the significant energy generation potential of waste in landfills and dumpsites makes it a highly appealing choice for solid recovered fuel.

Challenges in co-fuelling

As discussed in previous sections, co-fuelling of plastic waste in the cement industry is an attractive option to treat plastic waste without producing end products such as ash or air emissions. But, much like any other treatment method there are challenges involved in co-fuelling.

Due to the lack of source segregation in Thailand, the waste available for co-fuelling is mixed with foreign materials. This decreases the quality of solid recovered fuel and increases the complexity and cost of pre-processing, which further reduces the attractiveness of plastic waste reclaimed from dumpsites and landfills as fuel for the cement industry. Although WTH plants are technically superior to WTE plants, the Thai government’s inclination to increase the dependence on alternative fuels for electricity generation results in policies which provide support to WTE plants. As the policies are more inclined towards WTE plants, the economic benefits for WTH plants or the cement industry remain limited. Also, it becomes difficult to monitor these plants due to the lack of regulations for WTH plants for emission control, solid waste disposal, and raw material usage. As there are no regulations and monitory bodies to regulate the plants, the attractiveness of having a WTH plant reduces among local bodies.

Waste utilisation is still a socially undesirable choice. As it was perceived during the case studies, dumpsites may be limited to a maximum operation time of 8 h/day by inhabitants living around the dumpsites due to noise pollution and stench created by dumpsite operations. Due to such limitations, it becomes challenging for a waste recovery plant to operate under optimum conditions to ensure consistent feed supply.

The challenges involved with WTH plants make it a less appealing solution for plastic waste treatment and with the government’s inclination towards WTE, it is difficult for operators to valorise plastic waste. Moreover, with the social acceptability of waste utilisation still being an unsavoury idea to locals, it becomes difficult for the WTH industry to procure a high-quality waste feed. Some of these challenges can be common for both WTE and WTH plants, but without the required support from governing bodies, the survival of WTH plants can be very difficult.

Conclusions

This study clearly shows that reducing plastic waste from dumpsites and landfills can play an important role in reducing marine plastic pollution from land-based activities in Thailand. It is recommended that dumpsites which are located in the provinces near river shed areas or along the coastline of Thailand should be considered as priority to reduce marine plastic pollution. Waste accumulated in dumpsites and landfills can be used to generate 3868.27 PJ and 3588.05 PJ of energy, respectively. If recovered, this energy waste can be utilised as a fuel in cement kilns thus reducing the amount of waste in dumpsites and landfills. The study suggests that cement industries can be utilised as a sustainable sink for plastic waste to reduce marine plastic pollution in Thailand.

Notes

Acknowledgements

The authors are grateful to Asian Institute of Technology and Ecocycle, Siam City Cement Company for providing the support and opportunity to carry out this study and highly appreciate the Pollution Control Department of Thailand for providing us with necessary data.

Supplementary material

42768_2019_27_MOESM1_ESM.jpeg (482 kb)
Supplementary material 1 (JPEG 483 kb)
42768_2019_27_MOESM2_ESM.jpeg (634 kb)
Supplementary material 2 (JPEG 634 kb)

References

  1. 1.
    Geyer R, Jambeck J, Law KL. Production, use, and fate of all plastics ever made. Sci Adv. 2017;3(e1700782):1–5.Google Scholar
  2. 2.
    Jambeck JR, Geyer R, Wicox C, et al. Plastic waste inputs from land into the ocean. Science. 2015;347(6223):768–71.CrossRefGoogle Scholar
  3. 3.
    Munari C, Infantini V, Scoponi M, et al. Microplastics in the sediments of Terra Nova Bay (Ross Sea, Antarctica). Mar Pollut Bull. 2017;122(1–2):161–5.CrossRefGoogle Scholar
  4. 4.
    Verma R, Vinoda KS, Papireddy M, et al. Toxic pollutants from plastic waste—a review. Procedia Environ Sci. 2016;35(2016):701–8.CrossRefGoogle Scholar
  5. 5.
    Conservancy Ocean. Stemming the tide: land-based strategies for a plastic—free ocean. New York: Mckinsey Center; 2017.Google Scholar
  6. 6.
    World Bank Group. What a waste 2.0. Washington: World Bank Organisation; 2018.Google Scholar
  7. 7.
    Bangkok Post. What Thailand needs to do to kick its plastic addiction. Bangkok. 2018. [Online] https://www.bangkokpost.com/opinion/opinion/1587290/what-thailand-needs-to-do-to-kick-its-plastic-addiction. Accessed 2019.
  8. 8.
    Pollution Control Department. Booklet on Thailand state of pollution. Bangkok: Ministry of Natural Resources and Environment; 2018.Google Scholar
  9. 9.
    Pollution Control Department. Booklet on Thailand state of pollution 2018. Bangkok: Ministry of Natural Resources and Environment; 2019.Google Scholar
  10. 10.
    Styllis G. Thailand falling behind in global battle with plastic waste. 2018. [Online]. https://asia.nikkei.com/Economy/Thailand-falling-behind-in-global-battle-with-plastic-waste. Accessed 2019.
  11. 11.
    Royal Thai Embassy. Thailand will ban three plastics this year. Royal Thai Embassy, 2019. [Online] https://thaiembdc.org/2019/04/29/thailand-will-ban-three-plastics-this-year/. Accessed 2019.
  12. 12.
    Saveyn H, Eder P, Ramsay M, et al. Towards a better exploitation of the technical potential of waste-to-energy. Seville: European Commission; 2016.Google Scholar
  13. 13.
    Giacovelli C. Single-use plastic: a roadmap for sustainability. Nairobi: UNEP; 2018.Google Scholar
  14. 14.
    Theulen J. Cement kilns: a ready made waste to energy solution? 2015. [Online]. https://waste-management-world.com/a/cement-kilns-a-ready-made-waste-to-energy-solution. Accessed 01 Dec 2015.
  15. 15.
    Sharma M, McBean E. A methodology for solid waste characterization based on diminishing marginal returns. Waste Manag. 2007;27(3):337–44.CrossRefGoogle Scholar
  16. 16.
    EPA. RCRA Waste Sampling Draft Technical Guidance. Washington: Office of Solid Waste, EPA; 2002.Google Scholar
  17. 17.
    Rand T, Haukohl J, Marxen U. Municipal solid waste incineration: a decision maker’s guide. Washington, DC: The World Bank; 2000.Google Scholar
  18. 18.
    Maria FD, Contini S, Bidini G, et al. Energetic efficiency of an existing waste to energy power plant. Energy Procedia. 2016;101:1175–1182.CrossRefGoogle Scholar
  19. 19.
    Norman T. Maximising electrical efficiency at waste to energy plants; 2011. [Online] https://waste-management-world.com/a/maximising-electrical-efficiency-at-waste-to-energy-plants. Accessed 2019.
  20. 20.
    Arad S. Thermal analysis of the rotary kiln through FEA. In: 2nd international conference on applied and computational mathematics (ICAM'13), Vouliagmeni, Greece; 2013. ISSN: 2227-4588.Google Scholar
  21. 21.
    Baidya R, Ghosh SK, Parlikar UV. Sustainability of cement kiln co-processing of wastes in India: a pilot study. Environ Technol. 2017;38:1650–1659.  https://doi.org/10.1080/09593330.2017.1293738.CrossRefGoogle Scholar
  22. 22.
    Pachitsas S. Control of HCl emission from cement plants. Lyngby: Denmark Technical University; 2018.Google Scholar
  23. 23.
    Penque A. Examination of chlorides in municipal solid waste to energy combustion residue: origins, fate and potential for treatment. New York: Columbia University; 2007.Google Scholar
  24. 24.
    GTZ-Holcim Public Private Partnership. Guidelines on co-processing waste materials in cement production. Bonn: GTZ; 2006.Google Scholar
  25. 25.
    Thailand Board of Investment. Thailand Alternative Energy. Bangkok: Thailand Board of Investment; 2015.Google Scholar

Copyright information

© Zhejiang University Press 2019

Authors and Affiliations

  1. 1.Department of Energy, Environment and Climate Change, School of Environment, Resources and DevelopmentAsian Institute of TechnologyKhlong LuangThailand
  2. 2.Ecocycle, Siam City Cement CompanyBangkokThailand

Personalised recommendations