# Thermogravimetric Study of Refuse Derived Fuel Produced from Municipal Solid Waste of Kazakhstan
## 1 Introduction  
The waste management strategy of developed European Union countries employs following steps such as prevention, reuse, recycling, energy recovery and disposal [1]. Such preventive measures across EU countries have led to a significant decrease of landfilling municipal solid waste (MSW) and increase of waste recycling. An alternative to landfilling is the waste to energy (WtE) technology, which has also significantly increased with effective waste management strategies. Considering local state, in Kazakhstan, roughly 4.3 million tons of MSW was produced in 2018, and this quantity is expected to increase to 7 M tons by 2030 [2, 3]. Even though some elements of the waste management practices have been implemented in Kazakhstan, including source separation of recyclables (plastics and cardboards) and battery and electronic waste containers, the disposal of MSW in sanitary landfills is still dominates in major cities [4]. The current capital city of Kazakhstan, Nur-Sultan city (previously named as Astana city) has been growing continuously since the capital city was transferred from Almaty city in 1998 [5]. Only in the time interval of 1998-2019, the population of Nur-Sultan city has increased from 327,000 to 1,078,000 and based on this dynamics, a further increase of city's population is anticipated [5]. In 2018, around 1300 tons of MSW is generated per day in the capital city Nur-Sultan, with recycling rate of 13%. The composition of the MSW depends on the country and the applied waste management schemes, and the variationsin the MSW can be significant [6]. A detailed composition of Nur-Sultan's MSW obtained during the sampling campaigns is plotted in Figure 1.  
The production of solid refuse derived fuel (RDF) from MSW can be considered as potential alternative source of fossil fuels, which can be utilized in the existing power plants [7]. RDF, as stated by [PERSON] et al. [8], typically consist of mixed plastic, mixed paper, textiles, and wood fractions. [PERSON] et al. [9], on the other hand observed that RDF consisted of 75% of paper and 25% plastics. Comparable compounds of RDF were also reported by [PERSON] et al. (1995). According to the [PERSON] et al., [10] the potential share of solid RDF in MSW of Nur-Sultan city was around 10% and has calorific values of around 20 to 23 MJ/kg. In comparison, the RDF investigated in Turkey consisted of 17% of papers, 17% of all types of plastic and remaining 66% were textile fraction [11]. Moreover, [PERSON] et al. [12] observed that RDF composed of 26% all type of papers, 20% of plastics, 3% of textile, and 6.2% of wood/rubber or leather materials. Typical plastics in solid RDF consists of polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and low and high density plastics (LDPE andHDPE, respectively) [13]. Mixed paper typically includes packaging paper, cardboard, tetra pack, newspapers, while the textile was made of general clothes. The development of WtE technology particularly with co-firing option of solid RDF with coal in combined heat and power (CHP) plants is an optimal combustion solution [14; 15; 16]. In the cold regions, such as Kazakhstan, co-firing of solid RDF can be easily justified due to high energy demand for district heating in most cities of the country [17]. In addition, co-firing of RDF with coal also reduces the landfilling areas for MSW disposal and transportation of coal, which in turn would further mitigate greenhouse gas (GHG) emissions [18; 19]. Other advantages of co-firing solid RDF and coal are that retrofitting an existing power plants (PP) does not involve high capital costs and can be flexible to switch to coal-fired when biomass or MSW supplies are unavailable [19]. Co-firing also helps to control NOx and SOx emissions [16], as low sulfur RDF tend to reduce SOx emissions, and high moisture content of RDF decreases the flame temperature, thereby reducing NOx formation [16].