## 2 Materials and Methods  
Two categories of biomass--dry and wet--are commonly distinguished by their state of matter [7]. Biomass is also identified as a product or production waste [7; 23; 24]. Table 1 presents kinds of biomass, used for pyrolysis, gasification, and co-combustion, in different regions of the world. Based on the literature analysis (Table 1), for our experimental research we chose the most typical kinds of biomass (Table 2) from the categories of wood biomass, agricultural biomass, oil and oilseed waste, shell and husk. They included pine sawdust, wheat straw, birch leaves, sunflower cake, and rapeseed oil. These components are available in most of the world's regions and can be replaced by a similar component, if necessary (e.g., wheat straw by rapeseed or rice straw). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Ultimate Analysis (wt \%)**} & \multicolumn{6}{c}{**Proximate Analysis (wt \%)**} \\ \cline{3-13}
**Biomass** & **Country** & \multicolumn{3}{c}{**C**} & **H** & **O** & **N** & **S** & **Moisture** & **Volatile** & **Fixed Carbon** & **Ash** & **Heat of Combination** & **Ref. ** \\ \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Biomass**} & \multirow{2}{*}{**Country**} & \multicolumn{6}{c}{**Ultimate Analysis (wt \%)**} & \multicolumn{6}{c}{**Proximate Analysis (wt \%)**} & \multirow{2}{*}{**Ref.**} \\ \cline{3-14}  & & & & & & & & & & & & \\ \cline{3-14}  & & & & & & & & & & & & & & \\ \hline \multicolumn{14}{c}{Shell and bulk} \\ \hline Nut shell (arcs) & India & 48.71 & 5.79 & 43.45 & 1.95 & 0.1 & 7.43 \(\pm\) 0.1 & 74.05 \(\pm\) 0.2 & 15.55 \(\pm\) 0.3 & 2.48 \(\pm\) 0.05 & 18.21 \(\pm\) 0 & [30] \\ Coscont shell & UK & 48.31 & 5.26 & 46.14 & 0.29 & 0 & 7.16 & 68.58 & 22.00 & 2.26 & – & [33] \\ Walnut shell & Ukraine & 51.56 & 5.66 & 48.44 & 1.98 & 0.11 & 4.1 & – & – & 0.41 \(\pm\) 0.11 & 16.79 \(\pm\) 0.08 & [32] \\ Pount shell & China & 49.8 & 5.8 & 43.7 & 0.6 & 0.1 & – & 84.1 & 14.5 & 14 & – & [37] \\ Palm kernel shell & UK & 50.1 & 6.24 & 42.16 & 1.50 & 0 & 6.70 & 67.52 & 22.13 & 3.65 & – & [33] \\ \hline \multicolumn{14}{c}{Other} \\ \hline Algae & China & 58.9 & 7.0 & 25.4 & 8.2 & 0.5 & 10 & 81 & 16 & 9 & – & [40] \\ Cotton stalk & India & 46.3 & 6.4 & 46.8 & 0.3 & 0.2 & 8.9 & 71 & 16.6 & 3.5 & 19.2 & [30] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._At present, the amount of coal processing waste (filter cakes) is the largest of all the accumulated industrial waste. The quantity of this waste is annually increasing by 700-800 million tons [41; 42]. Lack of efficient methods of disposing of such waste leads to enormous mounds (dozens or even hundreds of hectares) of coal [41; 42]. Coal processing waste is a mixture of fine coal particles (80-140 \(\upmu\)m) with water and surfactants [41]. Notably, these products cannot be exactly regarded as waste, as the content of carbon in them is on average 65%-75% (in a dry state). Producing composite liquid fuels from them by adding biomass, water, municipal solid waste, and other components is a promising way of increasing the efficiency of resource exploitation [43], optimizing the energy industry [17], and reducing the environmental pollution [18; 43]. Fuel slurries were produced in several stages. Biomass samples were dried at room temperature and then milled using a Pulverisette 14 rotary mill (FRITSCH GmbH - Milling and Sizing, Idar-Oberstein, Germany) with rotor speed of 6000-20,000 rpm. After milling, biomass was sieved through a sifter with a mesh size of 140 \(\upmu\)m, using a laboratory plansifter. After that, a thin layer of milled biomass was spread on the surface of a sheet of paper and left at room temperature for several days to equilibrate in atmospheric moisture. Biomass was not dried any more. In this study, we used coal flotation waste--filter cake in the initial wet state (as it is produced at coal washing plants)--as the main component of slurry fuels.