## 5 Results and Discussion  
The results of measurements of the performance and emission parameters of the heat source for the different types of burners (average heat output (kW), thermal efficiency (%), CO production (mg.m\({}^{-3}\)), NOx production (mg.m\({}^{-3}\)), organic gaseous carbon (OGC)production (mg.m\({}^{-3}\)), and particulate matter (PM) production (mg.m\({}^{-3}\)) are shown in Table 1.  
The average heat output of the rotary burner was higher than the heat output of the retort burner by approximately 1.5 kW, but the thermal efficiency of combustion was a little lower, namely by approximately 1%. This could be caused by our novel construction, which could be optimized for greater thermal efficiency in the future, but the achieved combustion efficiency values are close to those of other similar heat sources in a rotary burner [26]. Typical time courses of the heat output of the heat source in retort and rotary burners from our experiments are shown in Figure 6. The time course of the retort burner was more constant-stable and reached values of between 12.5 and 13.5 kW during the experiments. In contrast, the heat output of the rotary burner varied during the experiments, with values of between 11.5 and 16 kW. This variation was caused by the changing amounts of burial and burning wood pellets in the combustion space--at one moment there was little burning fuel and at the next more. It was manifested in the obvious fluctuations in the temperature of the flue gases, a change in the heat removed through the hot-water heat exchanger, and subsequently also in the production of emissions. This problem could be solved by changing the method of dosing fuel into the burner space--a more continuous supply of pellets in smaller and more frequent doses. The long response time between the change in heat output and the subsequent supply of fuel can also be a problem. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Burner Type** & \begin{tabular}{c} **Measurement** \\ **Number** \\ \end{tabular} & \begin{tabular}{c} **Heat Output** \\ **(kW)** \\ \end{tabular} & \begin{tabular}{c} **Thermal Efficiency (\%)** \\ \end{tabular} & \begin{tabular}{c} **CO** \\ **(mg.m\({}^{-3}\))** \\ \end{tabular} & \begin{tabular}{c} **NOx** \\ **(mg.m\({}^{-3}\))** \\ \end{tabular} & \
\begin{tabular}{c} **OGC** \\ **(mg.m\({}^{-3}\))** \\ \end{tabular} &
\begin{tabular}{c} **PM** \\ **(mg.m\({}^{-3}\))** \\ \end{tabular} \\ \hline \multirow{3}{*}{**Rotary**} & 1. & 14.56 & 85.61 & 854.4 & 211.1 & 15.92 & 82.4 \\  & 2. & 15.01 & 86.15 & 759.3 & 214.6 & 14.74 & 67.6 \\  & 3. & 14.92 & 86.01 & 748.6 & 202.9 & 15.07 & 77.2 \\  & Avg. & 14.83 & 85.92 & 787.43 & 215.53 & 15.24 & 75.73 \\ \hline \multirow{3}{*}{**Retort**} & 1. & 13.52 & 87.88 & 918.3 & 196.3 & 18.41 & 47.9 \\  & 2. & 13.13 & 87.12 & 1283.2 & 191 & 21.36 & 51.5 \\ \cline{1-1}  & 3. & 13.27 & 86.91 & 1301.6 & 187.3 & 19.62 & 57.6 \\ \cline{1-1}  & Avg. & 13.31 & 87.3 & 1167.7 & 191.53 & 19.79 & 52.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of measurements of performance and emission parameters of heat source for different types of burners. Figure 6: Typical time courses of heat output of heat source in different types burners from experiments. Figure 7 shows the typical time courses of CO emissions from the same heat source in both rotary and retort burners during the experiments. The characteristics of these time courses are very similar to the time courses of the heat output--CO production from the retort burner was more stable, not changing much over time and reaching values of around 1000-1400 mg.m\({}^{-3}\)\({}_{10\%\;\Omega}\). CO production during use of the rotary burner was much more variable and reached values of from 100 to 5000 mg.m\({}^{-3}\)\({}_{10\%\;\Omega}\). This was related to variable fuel metering as well as uneven heat output. Paradoxically, the average CO production was lower for the rotary burner by approximately one third, namely by 380 mg.m\({}^{-3}\)\({}_{10\%\;\Omega}\).