# Insights into PCDD/Fs and PAHs in Biomass Boilers Envisaging Risks of Ash Use as Fertilizers
## 3 Experimental Part
### Conformity of PCDD/Fs and PAHs in Ashes with the Proposed Limits for Fertilizers
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**BFB1**} & \multicolumn{2}{c}{**BFB3**} & \multicolumn{2}{c}{**GF**} \\
**mg/kg** & \multicolumn{2}{c}{**Ash Blends**} & \multicolumn{2}{c}{**Ash Blends**} & \multicolumn{2}{c}{**Ash Blends**} \\  & **BA** & **FA** & **BA** & **FA** & **BA** & **FA** \\ \hline NaP & 0.016 & 1.727 & ND(0.005) & 0.776 & 0.060 & 2.338 \\ Acy & ND(0.005) 1 & 0.075 & 0.008 & 0.100 & ND(0.005) & 0.066 \\ Ace & ND(0.005) & 0.006 & ND(0.005) & 0.006 & 0.006 & ND(0.005) \\ FL & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ Phe & 0.009 & 0.163 & 0.011 & 0.232 & ND(0.005) & 0.061 \\ Ant & ND(0.005) & 0.006 & ND(0.005) & 0.011 & ND(0.005) & ND(0.005) \\ Flut & ND(0.005) & 0.025 & 0.005 & 0.171 & ND(0.005) & 0.023 \\ Pyr & ND(0.005) & 0.020 & ND(0.005) & 0.181 & ND(0.005) & 0.022 \\ BaA * & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ Chry * & ND(0.005) & ND(0.005) & ND(0.005) & 0.006 & ND(0.005) & ND(0.005) \\ BbFA * & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ BkFA * & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ BaP ** & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ Daha ** & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ BghiP & ND(0.005) & ND(0.005) & ND(0.005) & 0.006 & ND(0.005) & ND(0.005) \\ IP * & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) & ND(0.005) \\ \(\Sigma_{16}\) PAH MB 2 & 0.060 & 2.045 & 0.057 & 1.507 & 0.101 & 2.539 \\ LB/UB 2 & 0.02/0.10 & 1.90/2.07 & 0.02/0.09 & 1.49/1.52 & 0.07/0.14 & 2.51/2.57 \\ \hline \(\Sigma\) 7 Carc. MB & 0.018 & 0.018 & 0.018 & 0.021 & 0.018 & 0.018 \\ LB/UB & 0/0.04 & 0.004 & 0.0/0.04 & 0.006/0.04 & 0.0/0.04 & 0.0/0.04 \\ \hline BaP-EQ US-EPA 3 MB & 0.006 & 0.006 & 0.006 & 0.006 & 0.006 & 0.006 \\ BaP-EQ N\&L 4 MB & 0.016 & 0.018 & 0.016 & 0.018 & 0.016 & 0.019 \\ \hline \hline \end{tabular} Notes. – carcinogenic 2 B, **—**–carcinogenic 2 A, **—**–carcinogenic 1. 1 ND—non-detected, (EQL)—Estimated Quantification Level. 2 IB—Lower-Bound (ND = 0), MB—Medium-Bound (ND = EQ/2), UB—Upper Bound (ND = EQL). 3[101], 4 [98], BA—bottom ash (Table 3), FA—fly ash (Table 3).  
\end{table} 
Table 8: PAHs, BaP-EQs of biomass ash blends, in dry base. used, for example, involving statistical approaches, although this would require a deep knowledge of characteristic distribution of congeners/compounds, for each matrix/source based in data analysis. While there are no specifications, the MB attribution to ND appears to be an acceptable choice as a mid-term approach. Similar to the control of PCDDs/Fs in food, the less conservative (LB) or more precautionary (UB) results should be included in reports, as well as criteria for differences between LB and UB. Research activities and risk assessment works should also observe these critical issues, so that experimental results may represent valuable sources of data to support regulation activities and protect the environment and human life. Although contents of CI, C and PAHs in ashes are important for PCDD/Fs formation, other mechanisms may be important, such as the presence of precursors and pre-existing PCDD/Fs. Thus, neither C, CI or any other parameter, should be assumed as pre-indicators for PCDD/Fs analysis. This analysis of PCDD/Fs must be mandatory and the same applies for dl-PCBs already incorporated in TEQs, or other highly toxic POPs. However, a balance between frequency of measurements and the cost of monitoring requirements need to be considered. One option might be the use of accredited effect-based bioassays used for monitoring PCDD/Fs, such as DRCALUX or CALUX(r) Bioassay, which are considerably cheaper. The selectivity of these assays for dioxin-like compounds and interference of PAHs can be overcome by appropriate clean-up, and by this can be used for soils and sediments [250] and ashes [251].