Volume 9, Number 4 (July 2022):3595-3603, doi:10.15243/jdmlm.2022.094.3595 ISSN: 2339-076X (p); 2502-2458 (e), www.jdmlm.ub.ac.id
Open Access 3595 Research Article
Utilizing fine coal waste as a topsoil substitute on mine reclamation
Wahyu Sriningsih1*, Iskandar2, Dyah Tjahyandari Suryaningtyas2
1 Graduate Program of Soil Agrotechnology, Faculty of Agriculture, IPB University. Jl. Meranti, Dramaga, 16680 Bogor, West Java, Indonesia.
2 Department of Soil Science and Land Resource, Faculty of Agriculture, IPB University, Jl. Meranti, Dramaga, 16680 Bogor, West Java, Indonesia.
*corresponding author: [email protected]
Abstract Article history:
Received 2 March 2022 Accepted 30 April 2022 Published 1 July 2022
Topsoil in post-mined land generally has a low fertility level. Its availability is not always in sufficient quantities to meet minimal needs for mine reclamation, so substitute materials and ameliorants are needed to increase its quantity and quality. Fine coal and fly ash-bottom ash (FABA) are wastes expected to reduce the demand for topsoil and, at the same time, may improve topsoil quality. This study aimed to examine the application of fine coal as a topsoil substitution and its effect on changes in the chemical properties of topsoil and the growth of jabon (Anthocephalus chinensis).
The study was conducted in a greenhouse with a completely randomized design model with two factors. The first factor was fine coal with four levels of 0, 10, 20, and 50% from the topsoil (w w-1), and the second factor was FABA with three levels of 0, 500, 1000 g 15 kg-1 of growing media. The jabon plant was grown for 24 weeks. The results showed that up to 50%
fine coal could be used as a topsoil substitution. The interaction of fine coal and FABA increase pH, organic C, total N, cation exchange capacity, available P, base saturation, exchangeable cations, and micronutrients, and reduce the amount of exchangeable Al in the soil. FABA with a dose of 1000 g 15 kg-1 of growing media and 50% fine coal was the best treatment to increase the growth of the jabon plant.
Keywords:
Anthocephalus chinensis FABA
fine coal waste mine reclamation post-mined land soil ameliorant
To cite this article: Sriningsih, W., Iskandar, I. and Suryaningtyas, D.T. 2022.Utilizing fine coal as a topsoil substitute on mine reclamation. Journal of Degraded and Mining Lands Management 9(4):3595-3603, doi:10.15243/jdmlm.2022.094.3595.
Introduction
Coal mining in Indonesia is mostly carried out using an open-pit mining system. The mining process begins with clearing the land surface, which is cleaning the land from trees or vegetation in the area to be mined.
After that, the topsoil is stripped and collected to a safe place from erosion. Overburden or waste rock is excavated to obtain mining materials (Ta’in and Suhandi, 2001). This mining process results in changes in the landscape, including the formation of deep post- mining pits and overburdened material. Mining companies with mining authorization permits must carry out reclamation by returning mining land for certain purposes. The regulation is written in the
Ministry of Energy and Mineral Resources No. 1827 of 2018, requiring companies holding IUP and IUPK to reclaim post-mining land. The stages of reclamation of post-mining land attached to the above regulations include land arrangement, revegetation, and maintenance activities. Land arrangement in reclamation activities is carried out by recontouring, regrading, and re-sloping post-mining holes. Mine pits are covered with various materials peeled off during the initial excavation of the mine pit. The surface of the landscaping results is covered again with the topsoil of a certain thickness which will act as a planting medium for revegetation plants. Topsoil is a mixture of soil material from horizons A, B, and sometimes horizon C from the initial opening soil at
Open Access 3596 land mining (Iskandar et al., 2019). Therefore, topsoil
is generally heterogeneous and has a low fertility level, characterized by low organic matter content and damaged soil structure (Subowo, 2011). In addition, some mining areas have difficulty obtaining topsoil because the original soil condition has a very thin solum (Iskandar, 2008). Solum is the effective soil depth for plant roots to develop properly (Risamasu, 2010). Soil with a thin solum cannot support the nutrient and water needs of plants. So for the success of revegetation activities, it is necessary to modify the planting media with various materials from mining waste, household waste, and construction debris (Ruiz et al., 2020) or can make it specifically by combining waste and tailings to meet a planting medium (Rodríguez et al., 2017).
The material that has the potential to be used as a substitute for topsoil in coal mining areas is fine coal.
Fine coal is a waste from the coal preparation process, consisting of classification, crushing, and blending.
Several processes must be carried out before coal is sent to consumers, called coal processing. The coal produced from the mining front is accommodated in a place called the stockpile, undergoing crushing and blending (Panjaitan, 2018). This process produces a lot of fine coal that does not pass the criteria to be marketed. PT. Arutmin Indonesia is one of the mining companies that produce fine coal of approximately 500 t year-1 and will continue to increase along with the increasing demand for coal. The utilization of fine coal in agriculture has not been widely carried out and has the potential to be used as a substitute for topsoil, which has a thin solum in mining areas. The fine coal has a pH of 3-6 (Vasquez et al., 2013), containing 58.4% ash content, 25% carbon, 3.8% aluminum, 1.4% calcium, 2.3% iron, 0.5% potassium, 0.4%
magnesium (Weiler et al., 2020). In the long term, it has very high stability and can reduce greenhouse gas emissions (Antwi et al., 2020), so it is expected to meet the quantity and quality of topsoil on post-coal mining land.
Another material expected to improve topsoil quality is fly ash-bottom ash (FABA), waste from burning coal from a steam power plant (PLTU).
Approximately 5% FABA is produced from coal combustion, consisting of 10-20% bottom ash and 80- 90% fly ash. PLTU Suralaya produces fly ash waste of 1,183 t day-1 and bottom ash of 295 t day-1 (Siagian, 2021). Meanwhile, the production of FABA produced by world power plants reaches almost 500 million tons annually (Ahmaruzzaman, 2009). FABA has a high pH (11.70) and contains Al2O3 7.36%, SiO2 27.7%, CaO 10.7%, MgO 4.85%, Fe2O3 11.5% and K2O 0.85% (Oklima et al., 2014). Some of these elements are needed by plants, so FABA is expected to improve the quality and additional sources of topsoil nutrients in mine reclamation activities.
The utilization of fine coal has been carried out by Filho et al. (2020), namely the application of fine
coal and topsoil with a ratio of 1:1, 2% malt waste, and 3% compost produced a good growing medium for growth Tef cereals (Eragrostis teff) in South Africa.
In addition, research by Firpo et al. (2021) combined fine coal waste and steel slag with a ratio of 19:1, 2%
rice husks, 3% mud (sludge) into a good growing medium for the growth of oats (Avena sativa), and corn (Zea mays) in Brazil. In a study by Herjuna (2011), the application of fly ash can increase soil pH, organic C, available P, and base cations such as exchangeable K, exchangeable Na, exchangeable Ca, and exchangeable Mg in the soil. Coal ash has an alkaline pH (8-11), can increase pH, and contains macronutrients P, K, Ca, Mg, and S and micronutrients Fe, Mn, Zn, and Cu (Park et al., 2012). In addition to increasing important nutrients for plants, coal ash can also increase soil pH (Gupta et al., 2012). In a study by Iskandar et al.
(2009), the application of coal ash can increase the availability of base cations in peat soils. The application of bottom ash to Inceptisol soils can also increase growth, production yield, and uptake of N, P, K, Ca, and Mg in mustard plants (Agustini et al., 2017).
The purpose of the research was to study the effect of fine coal as a topsoil substitute and FABA on changes in the chemical properties of topsoil and the growth of jabon plants.
Materials and Methods
The materials used include fine coal from PT. Arutmin Indonesia, FABA from PLTU Suralaya, and Ultisol material as topsoil simulation taken from the Nasional Land Office (BPN) demonstration plot in Setu village, Jasinga District, Bogor Regency. Ultisol material was taken compositely at a depth of ± 50 cm from the soil surface layer. Fine coal from PT. Arutmin Indonesia has a particle size distribution of <2 mm, 2-5 mm, and
>5 mm of 58%, 28%, and 14%, respectively, acidic reaction (pH 5.32), 47.30% C, 24.43% ash, and various amounts of chemical elements (Table 1). These characteristics are in line with that reported by Vasquez et al. (2013) that fine coal has a pH of 3-6, several macros and micronutrient contents needed by plants, namely Ca, Mg, Cu, Zn, Fe, and Mn, and C.
Table 1. Total chemical characteristics of fine coal from PT Arutmin Indonesia.
Parameter Value
pH 1:5 5.32
Ash content (%) 21.21
C (%) 47.30
CaO (%) 0.32
MgO (%) 0.45
Fe2O3 (%) 0.33
MnO (%) 0,01
CuO (ppm) 2.37
ZnO (ppm) 18.98
Open Access 3597 The chemical characteristics of FABA from PLTU
Suralaya, Banten are as follows: pH 11.28 for fly ash and 8.86 for bottom ash, contains high Al2O3 and SiO2, and several nutrients needed by plants such as Ca, Mg, K, and Fe (Table 2). These results are in line with that reported by Oklima et al. (2014) that FABA has an alkaline pH of 11.70 and contains Al2O3 7.36%, SiO2
27.7%, CaO 10.7%, MgO 4.85%, Fe2O3 11.5%, and K2O 0.85%.
Table 2. Chemical characteristics of total FABA from PLTU Suralaya, Banten.
Parameter Fly asha Bottom asha
pH 1:5 11.28 8.86
C (%) 4.56 2.85
SiO2 (%) 50.16 52.37
Al2O3 (%) 33.30 31.86
Fe2O3 (%) 0.95 0.27
CaO (%) 4.75 1.86
MgO (%) 0.86 0.54
SO3 (%) 0.54 0.12
Na2O (%) 0.24 0.07
K2O (%) 0.22 0.22
a Source: Quality test data of PT. Indonesia Power Suralaya 2021.
The experiment was carried out in a greenhouse in a factorial, completely randomized design with two factors. The first factor was a mixture of fine coal and soil consisting of four ratios (0:1; 1:9; 1:4; 1:1) or equivalent to (0, 10, 20, 50%), and the second factor was FABA with three doses (0, 500, 1000 g 15 kg-1 of growing media). Each treatment was replicated three times, so there were 36 experimental units. The planting medium used was 15 kg per polybag and used jabon seedlings (± three months old) as the test plant.
1.5 kg of cow manure compost was added and 75 g NPK 16:16:16 as basic fertilizer to improve the quality of the planting media. All materials were mixed homogeneously and incubated for one week. The measured vegetative parameters were plant height and stem diameter every one week for 24 weeks. Plant height was measured using a meter from the base of the stem, while stem diameter was measured using a caliper at 10 cm from the ground. At the harvesting time, the soil was taken compositely from the top, middle and bottom. Then all the leaves, stems, and roots were taken and put into a separate envelope. Soil samples from the greenhouse were air-dried and then sieved using 2 mm and 0.5 mm sieves, while plant samples were placed in an oven at 60 oC and ground and then ready for analysis.
Laboratory analyses
Fine coal was analyzed to determine the distribution of particle size, pH, ash content, and elements (C, Fe, Cu, Zn, Mn, Ca, and Mg). For soil materials, the parameters of soil chemical properties analyzed were pH, organic C (Walkley and Black method), total N
(Kjeldahl method), available P (Bray 1 method), cation exchange capacity (CEC), and exchangeable cations K, Na, Ca, Mg (extraction with NH4OAc pH 7), Al (extraction with KCl 1N), and micronutrients of Fe, Mn, Zn and Cu (extraction with DTPA). The plant chemical properties analyzed were ash content, Ca, Mg, K, total P, and total S. Soil and plant analysis referred to Juo (1978) and Eviati and Sulaeman (2009).
Statistical analyses
The data obtained were analyzed using variance (ANOVA) at a 95% confidence interval, and the treatment that had a significant effect was further tested using Duncan's Multiple Range Test (DMRT) 5% level with SPSS version 16.0.
Results and Discussion
Effect of fine coal and FABA on the chemical properties of topsoil
The addition of fine coal and FABA significantly increased soil pH, CEC and available P, while the combination of fine coal and FABA had a significant effect, and there was an interaction on soil exchangeable Al content and base saturation (BS). The application of FABA with a dose of 1000 g 15 kg-1 of growing media can increase the soil pH from 4.29 to 4.78, and the application of fine coal at a dose of 50%
can increase the soil pH from 4.43 to 4.67 (Figure 1a).
All doses of FABA treatments with no fine coal addition resulted in the highest soil exchangeable Al, while the lowest amount of exchangeable Al was obtained in the addition of fine coal at a dose of 50%
(B3) combined with all FABA treatments (Figure 1b).
The application of fine coal increased the available P content of the soil from 2.3 ppm (B0) to 17.20 ppm (B3) (Figure 2c). Application of fine coal with a dose of 50% (B3) was the best dose to increase the soil CEC from 16.54 cmol(+) kg-1 to 23.58 cmol(+) kg-1 (Figure 1d).
The combination of fine coal and FABA in B3F2 treatment was the best treatment to increase the percentage of soil BS, which was 89.61% (Figure 1e).
The higher the dose of fine coal and FABA given, the more it increased soil pH, available P, CEC, BS, and decreased soil exchangeable Al. Fine coal and FABA have alkaline pH and high Ca and Mg elements (Tables 1 and 2), thus affecting the increase in soil pH. The increase in soil pH occurs because alkaline cations, especially Ca2+ and Mg2+, replace H+ ions that cause acidity in soil colloids (Pathan et al., 2003). These results are in line with the research of Oklima et al.
(2014), which stated that the application of coal ash could increase soil pH from 5.8 to 8.0 in former copper and gold mining soils. Soil CEC and BS increased along with the increase of soil pH because it affected the amount of negative soil charge originating from the edges of the 1:1 octahedral and tetrahedral clay minerals (Khawmee et al., 2013). Increasing soil pH
Open Access 3598 can also reduce soil exchangeable Al because when the
pH approaches 5.0, a bond occurs between Al and OH to form Al(OH)3 as a precipitate (Simonsson, 2000).
Exchangeable Al contributes to the availability of P in the soil; as the exchangeable Al of the soil decreases and the available P in the soil increases. The available P in the soil increases because Al-dd, which initially binds to P to form Al-P, becomes bound to the
hydroxyl (Yan et al., 2014). The application of fine coal had a significant effect on the organic C content of the soil, and the application of a combination of fine coal and FABA had a significant effect on the increase in the total-N content of the soil. Fine coal addition increased the organic C content of the soil from 3.41%
(without fine coal) to 7.82% (50% fine coal dose) (Figure 2a).
Figure 1. Effect of fine coal and FABA on pH (a), exchangeable Al (b), available P (c), CEC (d), and BS (e) soil.
The numbers in the bar chart followed by the same letter are not significantly different at the 5% test level according to the DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA
with a dose of 0; 500; 1000 g 15 kg-1 of growing media.
Treatment of 0% fine coal (B0) combined with FABA treatment (F0, F1, F2) resulted in the lowest N content, while 50% fine coal treatment (B3) combined with FABA (F0, F1, F2) showed high N content (Figure
2b). It can be seen that the organic C and total N soil content increased with increasing doses of fine coal and FABA. Fine coal can increase soil organic C content because it contains higher C content, which is
Open Access 3599 47.30%, compared to fly ash (4.56%) and bottom ash
(2.85%). These results are in line with the research results of Weiler et al. (2020) that the use of brown coal waste can increase the organic C content of the
soil. In addition, the application of fine coal and FABA can increase the total N of the soil because it is suspected that the effect of increasing the pH in the soil after the application of fine coal and FABA.
Figure 2. Effect of fine coal and FABA on soil organic C (a) and total N (b) contents.
The numbers in the bar chart followed by the same letters are not significantly different at the 5% test level according to the DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA
with a dose of 0; 500; 1000 g 15 kg-1 of growing media.
Soil acidity greatly determines the diversity of microorganisms that will control the nitrification process (Zhou et al., 2019). According to De Boer and Kowalchuk (2001), an increase in pH in acid soils can increase nitrification and nitrate accumulation.
Nitrosomonas sp. is an autotrophic bacterium capable of nitrifying at an acid pH (Allison and Prosser, 1993).
The combination of fine coal and FABA had a significant effect on soil Ca and Mg levels, while FABA had a significant effect on soil K and Na levels.
The combination of fine coal and FABA could increase the Ca content of the soil from 3.84 cmol(+) kg-1 (B0F0) to 8.94 cmol(+) kg-1 (B3F2) (Figure 3a).
Figure 3. Effect of fine coal and FABA on soil Ca (a), Mg (b), K (c) and Na (d) contents. Numbers followed by the same letters in the same column are not significantly different at 5% DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA with doses of 0; 500; 1000 g 15 kg-1 of growing media.
The combination of fine coal and FABA can also increase the Mg content of the soil from 1.34 cmol(+) kg-1 (B0F0) to 8.47 cmol(+) kg-1 (B3F2) (Figure 3b).
The addition of fine coal and FABA can increase the exchangeable K and Na levels of the soil (Figures 3c and 3d). The addition of fine coal with a dose of 50%
Open Access 3600 can increase the K of the soil from 0.91 cmol(+) kg-1
to 1.25 cmol(+) kg-1 and the addition of FABA with a dose of 1000 g 15 kg-1 of growing media can increase the content of exchangeable Na soil from 0.39 cmol(+) kg-1 to 0.64 cmol(+) kg-1. The increase in soil base cations occurred along with the increase in the dose of fine coal and FABA. This is because fine coal and FABA contain Ca, Mg, K, and Na cations (Tables 1 and 2). This increase in soil cations also occurred because the addition of fine coal and FABA had increased the soil CEC (Figure 1d). The results of previous studies showed that FABA could increase base cations in the soil. The results of the research by Iskandar et al. (2009) showed that the application of fly ash could increase the availability of basa cations (Ca, Mg, K, Na) in peat soils. The research by Oklima et al. (2014) showed that the addition of FABA can increase exchangeable K, exchangeable Ca, and
exchangeable Na in acid soils. The combination of fine coal and FABA had a significant effect on increasing Mn, Cu, and Zn contents. In contrast, the addition of fine coal and FABA significantly affected soil Fe content. Fine coal treatment with a dose of 50% (B3) and FABA 1000 g 15 kg-1 of growing media (F2) was the best dose to increase soil Fe content (Figure 4a).
Treatment of fine coal with a dose of 50% (B3) combined with FABA (F0) is the best dose to increase soil Mn and Zn levels, which are 62.08 ppm and 5.79 ppm, respectively (Figures 4b and 4d). The combination treatment of fine coal with a dose of 10%
(B1) and FABA 1000 g 15 kg-1 of growing media (F2) was the best combination to increase soil Cu content (Figure 4c). The increase in micronutrients occurred along with the increase in the dose of fine coal and FABA.
Figure 4. Effect of fine coal and FABA on soil available Fe, (a), available Mn (b), available Cu (c) and available Zn (d) contents. Numbers followed by the same letters in the same column are not significantly different at the 5% DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA with a dose of
0; 500; 1000 g 15 kg-1 of growing media.
The increase in micronutrients in the soil was due to fine coal and FABA containing high Fe2O3. Namely 0.33% in fine coal, 0.95% in fly ash, and 0.27% in bottom ash and fine coal containing MnO 0.01%
(Tables 1 and 2). Previous research by Shen et al.
(2008) showed that coal ash could increase the availability of Fe, Zn, Cu, and Mn in Sandy soils in Shanghai, China.
Effect of fine coal and FABA on jabon plant growth The jabon plant growth was observed by measuring plant height and stem diameter from 1 to 24 weeks after planting (WAP). The addition of fine coal and FABA significantly affected the addition of plant height and stem diameter in jabon plants. The higher the dose of fine coal and FABA, the higher the plant
Open Access 3601 height and stem diameter. Plant height increased from
39.00 cm (F0) to 73.71 cm (F2), while stem diameter increased from 0.93 cm (F0) to 1.42 cm (F2), and 0.81 cm (B0) to 1.23. cm (B3) (Figure 5).
Figure 5. The plant height (a) and stem diameter (b) of jabon plants aged 1-24 weeks after planting (WAP) in each treatment. Numbers followed by the same letters in the same column are not significantly different at the 5% DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA with a dose of
0; 500; 1000 g 15 kg-1 of growing media.
Table 3. Effect of fine coal and FABA on nutrient uptake by leaves of jabon plants.
Treatment
Nutrient Uptake by Leaf
N K Ca S P Mg
...(g plant-1)...
Fine coal
B0 1.68 a 1.47 a 0.68 a 0.14 a 0.12 a 0.10 a
B1 1.96 a 1.42 a 0.80 a 0.18 a 0.14 a 0.12 ab
B2 1.73 a 1.23 a 0.69 a 0.15 a 0.12 a 0.12 ab
B3 1.86 a 1.40 a 0.83 a 0.18 a 0.14 a 0.16 b
FABA
F0 1.63 a 1.26 a 0.58 a 0.15 a 0.12 a 0.10 a
F1 1.53 a 1.16 a 0.59 a 0.13 a 0.10 a 0.09 a
F2 2.27 b 1.72 b 1.07 b 0.21 b 0.16 b 0.18 b
Notes: numbers followed by the same letters in the same column are not significantly different at the 5% DMRT test. B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA with a dose of 0; 500; 1000 g 15 kg-1 of growing media.
Figure 6. Plant growth (a) and root cross section (b) of jabonplants aged 24 week after planted in each treatment.
B0, B1, B2, B3 = fine coal with a dose of 0; 10%; 20%; 50%. F0, F1, F2 = FABA with a dose of 0; 500; 1000 g 15 kg-1 of growing media.
Open Access 3602 This increase in growth occurred because the addition
of fine coal and FABA had increased soil pH (Figure 1a), the availability of essential nutrients needed by plants (Figures 3 and 4), and leaf nutrient uptake (Table 3). The result of previous research by Park et al.
(2012) showed that FABA could also increase plant growth and nutrients. Nurmegawati et al. (2020) showed that bottom ash could increase Ca and Mg nutrients and plant growth. Good plant growth (Figure 6a) is also supported by good root development. Figure 6b shows that the roots of the jabon plant have increased compared to the control. The more fine coal and FABA were given, the more the number of plant roots and the better plant growth. Roots are plant organs that function to absorb nutrients from the soil and are one of the important factors in plant growth (Widiastuti et al., 2003). Absorption of plant nutrients can increase, followed by increased root growth in plants (Fageria et al., 2014).
Conclusion
Fine coal can be used as a topsoil substitute for up to 50% while still showing a good plant rate. The addition of fine coal and FABA can increase pH, C-organic, N- total, CEC, available P, base saturation, Ca, Mg, K, Na, Fe, Mn, Cu, and Zn, and reduce exchangeable Al.
Giving FABA with a dose of 1000 g 15 kg-1 of growing media and 50% fine coal is the best treatment to increase the growth of jabon plants.
Acknowledgements
The authors wish to thank the Center for Mine Reclamation Studies (Pusdi Reklatam), LPPM, IPB University for funding this study and to PT. Arutmin Indonesia for providing fine coal and PT. Indonesia Power for providing FABA.
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