# Application of Fly Ash as an Adsorbent for Removal of Air and Water Pollutants
## 2 Global Overview of Fly Ash  
### China  
China is a populous country with high electricity consumption per capita. Coal is one of the main energy sources in China, accounting for 70% of the total energy consumption from 1978 to 2009 [36]. China is the largest coal mining and consuming country in the world, and it has surpassed Japan to become the world's largest coal-importing country in 2008 [36]. China consumed more than 3 billion tons of coals in 2010 [37], and most cities in northern China use coal-fired heating in the winter. Figure 2 shows the coal consumption of China compared with other countries and its relationship with Gross Domestic Product (GDP). China clearly is dependent on energy from coal. However, burning coal produces FA in the air that causes environmental problems such as acid rain, fog and haze, and heavy metal pollution [38; 39; 40]. Solving the problem of FA pollutant from burning coal would be a great contribution to environmental and human health.  
Figure 3 shows the production and utilization rate of FA from 2001 to 2015 and the degree of utilization of FA in different cities of China in 2010. The annual output of FA is huge in China. At the end of 2015, about 580 million tons of FA were produced, accounting for about 77% of the global FA production [41]. FA utilization in China increased after 2004 and reached about 70% in 2015 (Figure 3a), which is closely related to the rapid development of China's economy and technology. However, different statistical offices have different estimates of the utilization rate of fly ash in China. For example, Greenpeace [41] estimated the utilization rate to be only 30%. Regardless of the value, the utilization rate of FA in China is very high. According to statistics, the global average utilization rate of FA is about 25% [42]. Other researchers reported that the utilization rate of FA is about 67% [43]. The utilization rate of FA in different cities in China is shown in Figure 3b. The utilization rate of fly ash in eastern China is clearly higher than in western China, due to the large market for FA in the east [37]. The specific utilization of FA is shown in Table 1. Although there are many ways to utilize FA in China, few technologically advanced products use FA. If processes involving FA are not strictly controlled, they can cause secondary pollution [37].  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Item** & **Specific Utilization** \\ \hline Building materials & Cement, fly ash bricks, fly ash ceramics, fly ash blocks, concrete, mortar \\ Road construction & Embankments, pavement bases and pavement \\  & Structure backfill, construction backfill, filling in low-lying areas and \\ Backfill & wastelands, filling mines, filling coal mining subsidence areas, building materials for pits, tidal marshes \\ Agriculture & Soil improvement, fertilizer production, land reclamation \\ Recycling useful raw materials & Hollow microspheres, Al\({}_{2}\)O\({}_{3}\), Fe\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\), carbon granules \\ \hline \hline \end{tabular}
\end{table}
Table 1: Specific utilization of fly ash in China.  
Figure 2: Comparison of coal consumption in China with other important coal consuming countries (**a**); and relationship between coal consumption and GDP in China (**b**) (reproduced with permission from [36], Elsevier, 2018).