Application of Coal Ash to Postmine Land for Prevention of Soil Erosion in Coal Mine in Indonesia: Utilization of Fly Ash and Bottom Ash

Abstract

The increase in the number of coal-fired power plants with the increase in coal production and its consumption has caused the problem of the treatment of a large amount of coal ash in Indonesia. In the past studies, coal ash was applied to postmine land with the aim of improving soil conditions for plant growth; however, heavy rain in the tropical climate may cause soil erosion with the change in soil conditions. This study presents the effects of application of coal ash to postmine land on soil erosion by performing the artificial rainfall test as well as physical testing. The results indicate that the risk of soil erosion can be reduced significantly by applying the coal ash which consists of more than 85% of sand to topsoil in the postmine land at the mixing ratio of over 30%. Additionally, they reveal that not only fine fractions but also microporous structures in coal ash enhance water retention capacity by retaining water in the structure, leading to the prevention of soil erosion. Thus, the risk of soil erosion can be reduced by applying coal ash to topsoil in consideration of soil composition and microporous structure of coal ash.

Effects of pH-Induced Changes in Soil Physical Characteristics on the Development of Soil Water Erosion

“…The simulated soils were prepared by mixing decomposed granite produced by Gulin Kita-Kyu Co., Ltd. and Kyushu bentonite produced by Shinagawa Yogyo Co., Ltd. after screening based on soil texture. It was measured at a post-mining site in A coal mine in Indonesia, where topsoil was placed soon after excavation (Table 1) [20]. The measurement was conducted at 6 points at the site, and the soil samples were supplied to sieving test to understand the soil texture.…”

“…The measured pH of rainwater at the post-mining site showed pH = 5.6-6.0. The experimental conditions were set by reference to a past study [20]. The rainfall intensity was adjusted to 80 mm/hour using the hydraulic head, the water content of the simulated soils was 15%, the slope angle was 35 deg., and the annual rainfall was 3000 mm/year [23][24][25][26]; these annual rainfall and rainfall intensity values reflect those observed in Indonesia.…”

Application of a mixture of fly ash and topsoil for rehabilitation in open-pit coal mines in South East Asian countries

“…In order to secure the amount of topsoil, fly ash (FA), which is considered industrial waste after thermal electric power generation with coal was mixed in topsoil in the past research (Hamanaka et al 2014). The amount of topsoil was successfully increased by mixing FA in topsoil without soil erosion by rainfall (Gorman et al 2000, Matsumoto et al 2016. Although FA has been utilized with the aim of increasing the amount of topsoil in several cases, the effects of metals in FA and the high alkalinity are concerned in terms of the inhibition of plant growth (Mahlaba et al 2012, Cheng 2003.…”

“…Topsoil was prepared by mixing the decomposed granite produced by the Gulin Kita-Kyu Co., Ltd., and the Kyushu Bentonite produced by the Shinagawa Yogyo Co., Ltd. based on the soil composition which was reported in post-mine land in open-pit coal mine in Indonesia (Matsumoto et al 2016). The soils were classified as sand, silt, and clay after screening, followed by the preparation of the topsoil.…”

Effect of Different Types of Fly Ash on Properties of Asphalt Mixtures

“…Globally, almost one billion tonnes of fly ash is generated annually [7] and its landfilling represents a significant environmental problem. As a material with pozzolanic activity, fly ash has been widely used in a variety of applications such as concrete, soil improvement, and road construction, namely, for embankments and both unbound and bound subbase and base layers [8][9][10][11][12].…”