## 2 Methodology
### Life Cycle Input and Output Data for Each Biosolids Production Process
#### 2.2.2 Lagoon Storage  
The inputs and outputs for Lagoon Storage are presented in Table 3. In the Lagoon Storage case, mechanical dewatering with a belt filter press occurs first (Figure 1), which includes similar inputs and outputs as the Air-Drying scenario: dewatering electricity, polymer and water, and the wastewater to be treated. The slight differences in inputs are a result of different amounts of solids at this beginning stage in the process. After dewatering, it is assumed that the biosolids (22% total solids content) are transported by a diesel-powered dump truck 2000 feet to the lagoons. The dump truck places the biosolids next to the lagoons, where a front-end loader then distributes the biosolids in the lagoon. The lagoons were assumed to be constructed using clay and a 40 mil. High-density polyethylene (HDPE) liner. The quantities of clay and HDPE were determined by sizing the lagoons based on the volume of biosolids requiring storage. The lagoon was assumed to have a clay layer with a thickness of 0.5 feet, a biosolids depth of 5 feet, and a freeboard (additional wall height) of 2 feet. The soil excavated for the lagoons was assumed to have a useful purpose on the site, such as building berms, so no off-site soil transportation was included. After two years of storage, the biosolids were removed using a front-end loader and transported 500 feet to the Air-Drying pad. Once at the pad, the biosolids were formed into small windows and mixed periodically for about ten weeks. The biosolids were then transported to their final destination. The quantity of diesel fuel used in the process was estimated using the assumed distances, use time, and the equipment manufacturers' information. With respect to outputs from the process, the biogenic emissions from the lagoons were estimated based on a study that examined the emissions produced by rectangular stockpiles of biosolids [23] along with the assumed quantities of biosolids and lagoon storage times. The one- to three-year-old lagoon emissions rates (CO\({}_{2}\) flux = 3.92 kg CO\({}_{2}\) eq/m\({}^{2}\) month, \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Unit** & **Ecoinvent Item/Comments** \\ \hline Inputs & & & \\ \hline Dewatering electricity & 20,895 & kWh & Electricity, medium voltage, at grid \\ \hline Dewatering polymer & 1368 & kg & Acrylonitrile, market \\ \hline Dewatering water & 2496 & kg & Tap water, at user \\ \hline Wastewater to be treated & 3531 & kg & Treatment, sewage, unpolluted, at wastewater \\ \hline Diesel fuel & 528 & kg & Diesel, at regional storage \\ \hline Clay & 54,244 & kg & Clay, market \\ \hline HPDE liner & 230 & kg & HDPE resin E \\ \hline Asphalt & 53,150 & kg & Asphalt 1  \\ \hline Transportation of biosolids & 48,664 & tkm & Transport, lorry 16–32 t, EURO3 \\ \hline Outputs & & & \\ \hline CO\({}_{2}\), biogenic & 207,370 & kg & Carbon dioxide \\ \hline CH\({}_{4}\), biogenic & 1926 & kg & Methane \\ \hline N\({}_{2}\)O, biogenic & 885 & kg & Nitro oxide \\ \hline CO\({}_{2}\), fuel combustion & 3720 & kg & Carbon dioxide \\ \hline \hline \end{tabular}  
* a \(=1\) kg of asphalt, which includes 0.1 kg of hot bitumen adhesive compound; 0.9 kg of gravel, crushed; and 0.0013 kWh of diesel burned in machine.  
\end{table} 
Table 3: Inputs and outputs for Lagoon Storage Plus Air Drying LCA. CH\({}_{4}\) flux = 0.8 kg CO\({}_{2}\) eq/m\({}^{2}\) month, and N\({}_{2}\)O flux = 3.75 kg CO\({}_{2}\) eq/m\({}^{2}\) month) reported by [PERSON] et al. [23] were used to represent half of the first year of storage, the second year of storage, and the two months used for removing the biosolids from the lagoons. The <1-year-old lagoon emissions (CO\({}_{2}\) flux = 2.75 kg CO\({}_{2}\) eq/m\({}^{2}\) month, CH\({}_{4}\) flux = 0.1 kg CO\({}_{2}\) eq/m\({}^{2}\) month, and N\({}_{2}\)O flux = 5.55 kg CO\({}_{2}\) eq/m\({}^{2}\) month) reported in [23] were used to represent the lagoon during six months of filling time and half of the first year of storage.