Hydroelectric Energy

**229**

**Chapter 14**

**Abstract**

Production

metals and the toxicity PAHs of MSW.

hydrocarbons, hydrochar

**1. Introduction**

Formation and Transformation

of Typical Pollutant from MSW

by Hydrothermal Carbonization

An unprecedented increase in municipal solid waste (MSW) is increasingly attractive in response to waste-to-energy. MSW pretreatment is an essential step due to the inherent properties of MSW. Hydrothermal carbonization (HTC) offers an efficient approach for converting MSW into carbonaceous hydrochars. In this chapter, the formation and transformation of heavy metals and polycyclic aromatic hydrocarbons (PAHs) during HTC of MSW were determined. The results indicated that HTC can homogenize the density and size of MSW and also increase carbon content. Moreover, the concentrations of heavy metals in the leachates of the hydrochars were lower than the United States Environmental Protection Agency (US EPA) maximum limits. Compared to MSW, the concentrations of Cr, Cd, Hg, and Zn in the hydrochars were low and the concentrations of Pb, As, Ni, and Cu were high. The concentrations of PAHs in the hydrochars increased with increasing temperature in the range of 1298.71–177698.20 μg/kg, which were much higher than that in MSW, except for H-160. The dominant PAH rings in MSW and the hydrochars were four-ring PAHs and three-ring PAHs, respectively. These findings suggest that 180°C is an appropriate hydrothermal temperature to reduce heavy

**Keywords:** biomass, waste-to-energy, fuel quality, heavy metals, polycyclic aromatic

At present, municipal solid waste (MSW) generated in daily life is the major waste in the urban management, which consists of food waste, plastics, paper, garden waste, textiles, stone, glass, etc. [1]. An unprecedented increase in the amount of MSW is observed in all over the world, especially for the populous development countries, such as India and China due to the population growth, rapid urbanization, and industrialization [2, 3]. It is reported that about 1.70–1.90 billion metric tons per year of MSW is produced in the world [4]. In China, the MSW delivering quantity had grown to 0.20 billion metric tons in 2016 [5]. It is estimated that China

towards Biofuel Hydrochar

*Wentao Jiao, Nana Peng and Zhengang Liu*

## **Chapter 14**
