# Waste-to-Energy Process to Recover Dangerous Pollutants in an Environmental Protected Area
## 2 Materials and Methods
### Energy Balance Assessment  
An energy balance of the waste is carried out throughout the period of extraction from the lagoon, in order to know the consumed energy when the process of using the waste in  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **2015** & **2016** & **2017** & **2018** & **Total** \\ \hline Weight of fuel (t) & 12,509.48 & 34,337.54 & 26,823.15 & 25,410.78 & 99,080.95 \\ \hline Percentage of waste (\%) & 57.56 & 45.77 & 38.52 & 35.41 & 42.64 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Fuel transported to the cement factories and percentage of the lagoon waste.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Weight of the Fuel Transported (ft\({}_{\text{fuel}}\))**} \\ \hline
**Cement Plants** & **2015** & **2016** & **2017** & **2018** & **Total** \\ \hline Bunol & 8182.20 & 17,475.84 & 8274.18 & 9264.54 & 43,196.76 \\ \hline Gador & 2613.06 & 11,291.06 & 13,488.81 & 10,032.14 & 37,425.07 \\ \hline Mataporquera & 622.28 & 1065.86 & 2480.44 & 1885.50 & 6054.08 \\ \hline Carboneras & 698.34 & 2765.42 & 1259.30 & 1015.94 & 5739.00 \\ \hline Oural & 0.00 & 0.00 & 568.48 & 2960.94 & 3529.42 \\ \hline Jerez & 326.00 & 1415.40 & 0.00 & 0.00 & 1741.40 \\ \hline Albox & 67.60 & 183.74 & 211.56 & 251.72 & 714.62 \\ \hline Sagunto & 0.00 & 0.00 & 540.38 & 0.00 & 540.38 \\ \hline Villaluenga & 0.00 & 140.22 & 0.00 & 0.00 & 140.22 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Weight of the fuel transported.  
a cement industry as fuel (_Consumed energy\({}_{w2f}\)_) is carried (Equation (1), in kWh/t). This balance takes into account the gross energy provided by the waste (\(E_{gross}\)), the energy from the extraction of the waste (\(E_{extr}\)), the energy in the transport--both from the lagoon to the treatment plant (\(E_{t1}\)) and from the treatment plant to each of the cement industries (\(E_{t2}\))--and the treatment energy to convert the waste into fuel (\(E_{tr}\)). The energy gross is the energy used in the cement manufacturing process.  
\[Consumed\ energy_{w2f}=E_{gross}\ +(E_{extr}+E_{t1}+E_{tr}+E_{t2}) \tag{1}\]  
With regard to the energy balance in cases where the waste is taken directly to the hazardous waste incinerator (_Consumed energy\({}_{ncincinration}\)_), the energy from the extraction of the waste and the transport energy from the lagoon to the incinerator (\(E_{t}\)) will be taken into account, so that the consumed energy in this case is calculated using Equation (2). Incineration facilities are comprised of a rotary kiln, with an energy production that is used only onsite for internally proposed uses, so there is no external energy use. For this reason, energy production in this facility outside the limit of the system is not considered in the present study. Incineration facilities are the unique in Spain because they can burn hazardous waste with this kind of composition.  
\[Consumed\ energy_{ncineration}=E_{petcoke}+\left(E_{gross}\ +\ E_{extr}+E_{t}\right) \tag{2}\]  
In another case, petroleum coke is used as fuel in cement industry kilns, while waste is being eliminated without any use in the hazardous waste incinerator. In this case, waste to fuel the lagoon is a replacement for petroleum coke. The energy of the waste (\(E_{gross}\)) fed into the cement kilns has to be the same energy as the energy of the coke (\(E_{coke}\)) it replaces, as reflected in Equation (3):  
\[E_{coke}=E_{gross} \tag{3}\]  
Equation (4) shows the difference between the two case studies, and Figure 4 shows it graphically.  
\[Consumed\ energy_{(ncineration\ -\ w2f)}\ =E_{coke}+\ E_{t}-E_{t1}-E_{tr}-E_{t2} \tag{4}\]  
Figure 4: Graphical representation of the two alternatives (kWh/twaste).  
Therefore, the case with the best energy efficiency is the waste-to-fuel case if the result of Equation (4) is positive; if negative, it would mean that the best energy efficiency case is the incineration case.