# Life Cycle Assessment of Different Waste Lubrication Oil Management Options in Serbia
## 3 Methodology
### Life Cycle Assessment  
The environmental impact of different scenarios is estimated with the life cycle assessment (LCA) method (ISO 14040:2006 and ISO 14044:2006), which (according to the European Commission (COM (2003; 302)) is currently the best framework for assessing the potential environmental impacts of products. The LCA's main goal is to identify which waste management system (see description of the scenarios in Section 3.2) is the most or least environmentally advantageous. The present study assumes that the primary function of the scenarios considered is waste treatment, and the functional unit is defined as 1000 kg of waste lubricant oil. The modeling follows the cut-off system model approach [41], which assumes that the waste carries no upstream environmental burden into the waste management system [42]; in other words, waste is available burden-free to the waste treatment process and only impacts associated with its collection and transportation are accounted for. In each scenario, it is assumed that the average distance between collection centres and waste treatment facility is 100 km and that the waste lubricating oil is transported by road using a lorry of 16-32 metric tons gross vehicle weight. The foreground system was modeled using secondary data. The foreground data, consisting of material and energy flows associated with five different re-refining technologies (ReR1-ReR5), are available from Fehrenbach [40]. The data on emissions from hazardous waste incinerator (relevant to Inc1 and Inc2) are available from [43] and are applicable to modern incineration practices in Europe. In Inc1, it was assumed that the net thermal and electric energy generated would amount to 25.82 MJ/kg and 2.44 MJ/kg, respectively [43]. Rotary kiln emissions for CemK were compiled from the inventory data of the works of [PERSON], [PERSON] et al. [8] and the research data of [PERSON] [40]. It is assumed that the heat generated from the burning of WLO (40 MJ/kg of WLO) [40] can substitute the same amount of heat from petroleum coke burning, which is the primary source of energy in the Serbian cement factories. The background system (up- and downstream processes) was modelled with generic or average life cycle inventory (LCI) datasets available from the ecoinvent 3.7. LCI database [41]. Most of the waste treatment processes considered in this study are multifunctional, i.e., they produce several co-products (materials and/or energy). The problem of multifunctionality [44] is solved by the substitution method, which is suitable for waste management systems because the generated co-products can be produced using alternative methods and processes [8]. In ReR1-ReR5, a portion of the co-products produced (as specified in [40]) is used to meet the energy requirements of the process itself, and only the surplus is supplied \begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & & \begin{tabular}{l} **Burning in** \\ **Cement** \\ **Kilns** \\ \end{tabular} & \begin{tabular}{l} **Re-Refining** \\ **(ReR1 to** \\ **ReR5)** \\ \end{tabular} & \
\begin{tabular}{l} **Burning in HWI** \\ **with Energy** \\ **Recovery** \\ **(Inc1)** \\ \end{tabular} &
\begin{tabular}{l} **Burning in HWI** \\ **without Energy** \\ **Recovery (Inc2)** \\ \end{tabular} \\ \hline Scenario 1 & t & 7777 & 26,602 & & \\ Scenario 2 & t & 7777 & 13,301 & 13,301 & \\ Scenario 3 & t & 7777 & 8867 & 8867 & 8867 \\ Scenario 4 & t & 5967 & 9470 & 9470 & 9470 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Different WLO treatment scenarios considered in this study. to the market. Table 9 summarizes the main co-products from the analysed waste treatment processes, the avoided processes, and their respective LCI datasets. The life cycle environmental impacts of the different waste management processes were estimated with the ReCiPe 2016 (H) method, which considers impacts within 18 midpoint and 22 endpoint impact categories [45].