# Biomass District Heating Systems Based on Agriculture Residues
## 5 Discussion  
In this paper a methodology for the evaluation at regional level of the implantation of BioDH systems based on renewable biomass forestry and agricultural residues is presented. This methodology has been applied, as case study, to the continental region of Spain in order to evaluate the potential of a BioDH network in this region and how it is influenced by considering agriculture and forest biomass. From the analysis is derived that for this region, and under the current local agriculture residues production, the profitability is not highly improved with the use of available resource of agricultural biomass. This is mainly due to the reduced availability of agriculture biomass that combined with exploitation costs of agriculture biomass not significantly lower than the forest biomass costs results in only a slight increase of Internal Rate of Return in most of the municipalities analyzed. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Inhabitants** & \begin{tabular}{c} **Number of** \\ **Villages** \\ \end{tabular} & **Users** & \begin{tabular}{c} **Invest** \\ **MG** \\ \end{tabular} & \begin{tabular}{c} **Required** \\ **Biomas (t)** \\ \end{tabular} & \begin{tabular}{c} **Available** \\ **Foresal** \\ **Biomass** \\ \end{tabular} & \
\begin{tabular}{c} **Available** \\ **Foresal** \\ **Only** \\ \end{tabular} &
\begin{tabular}{c} **IRR (\%)** \\ **Savings (t)** \\ \end{tabular} \\ \hline \(\textless{2}\) k & 131 & 228 k & 635 & 1019 k & 197 k & 9.87 k & 4.73 & 4.72 & 779 k \\ \(\textless{5}\) k & 294 & 858 k & 2372 & 3759 k & 452 k & 22.67 k & 4.37 & 4.44 & 2907 k \\ \(\textgreater{5}\) k & 76 & 1100 k & 1252 & 2202 k & 138 k & 9.88 k & 3.86 & 3.92 & 1720 k \\ Total & 501 & 1584 k & 4260 & 6980 k & 787 k & 42.42 k & 4.32 & 4.36 & 5406 k \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Main characteristics of the municipalities under study and the expected impact of BioDH. Therefore, for the region selected, as long as there is not a situation in which a greater amount of biomass resources are available or one in which the reuse of agricultural biomass is for some reason of a considerably lower cost, from the direct analysis of mean values it could be concluded that BioDH systems based on the combination of both resources do not provide clear benefits compared to only forest biomass. In other regions, with different patterns of agriculture production and renewable forestry biomass resources, different results would arise with the application of methodology. However, the methodology and analysis has identified a relevant number of municipalities where the integration results in values of _IRR_ above 10% operating only with local biomass resource. These values for an infrastructure investment can be high enough for BioDH deployment in these municipalities. In addition, in most of the villages under analysis there is an increase of the profitability with both fuel sources. If BioDH systems were implanted in them the combination of both biomass fuel sources would extend the availability of biomass resource of the municipalities for future scenarios. Besides with an increase of profitability, small but positive, there are additional positive impacts in the local economy. New economic activity and jobs can be created both in the agriculture and in the collection and exploitation of the biomass [27]. Any case, special attention must be paid to additional issues associate to the use of biomass multifuel. On one hand, different fuels should be stored in isolated places of other types of fuel, which would mean an increase in storage costs [28] with an increase of the complexity in the management of the storage and fuel preparation. On the other hand, special attention must be paid to the boiler selection and biomass fuel mixes preparation for an adequate performance as with several types of biomass there will be different combustion characteristics and fuel geometries (chips, pellets, etc.) [29].