## 3 Results  
Table 3 summarizes the average amount of energy consumed and produced on lettuce farms. As seen below, diesel fuel and nitrogen, with approximate values of 38 and 24%, respectively, had the highest rate of consumption, while the labor force and seeds possessed the lowest energy consumptions, with contributions below 1%. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Impact Categories** & **Symbol** & **Unit of Measurement** \\ \hline Reduction of inorganic substance & AD & kg Sb eq \\ Acidification & AC & kg SO\({}_{2}\) eq \\ Eutrophication & EU & kg PO\({}_{4}\)\({}^{-}\) eq \\ Global warming & GW & kg CO\({}_{2}\) eq \({}^{\rm a}\) \\ Ozone layer defect & OD & kg CFC-11 eq \\ Human toxicity & HT & kg 1,4-DCB eq \({}^{\rm b}\) \\ Surface water toxicity & FAET & kg 1,4-DCB eq \({}^{\rm b}\) \\ Free water toxicity & MAET & kg 1,4-DCB eq \({}^{\rm b}\) \\ Soil toxicity & TE & kg 1,4-DCB eq \({}^{\rm b}\) \\ Phytochemical oxidation & Pho & kg C\({}_{2}\)H\({}_{4}\) eq \\ \hline \end{tabular} \({}^{\rm a}\) Considering 100 years. \({}^{\rm b}\) DCB = dichlorobenzene.  
\end{table} 
Table 2: Impact categories and unit of measurement of each section. Figure 2: The boundary of the lettuce production system in the field. Table 4 presents the energy indices and their contribution to lettuce production. The ER was 0.4, leading to the negative value for the NEG, indicating the low energy consumption efficiency in lettuce production. The share of direct energy in lettuce production is equal to 55%, and the share of indirect energy is equal to 45%. The environmental consequences of lettuce production were also analyzed in the region, and the results were reported for each impact category for one ton of lettuce in Table 5. The contribution of each consumption input is depicted in Figure 3 for the impact categories. One of the most important parts of the effect investigated in this study is the global warming potential. Global warming potential is a way to express the share of gases released from agricultural systems. In this study, the amount of global warming potential per ton of produced product is estimated to equal 96.01 kg of carbon dioxide equivalent. As can be seen when comparing the sections of the eutrophication effect, acidification, soil toxicity, surface water toxicity, and the global warming potential of pollution caused by direct farm emissions (caused by burning diesel fuel, using chemical and organic fertilizers, atmospheric decomposition of fertilizers, mixing product residues with soil, using chemical poisons, and human breathing) the latter had the largest values of the mentioned indicators. With respect to the effect of reducing inorganic substances, the most impact is related to the process of diesel fuel and nitrogen fertilizer. In terms of the effect of the ozone layer defect, the biggest effect is related to the pesticides. In the areas of human toxicity and surface water toxicity, the production process of pesticides and the use of agricultural machinery in the farm has the greatest effect. In the field of photochemical oxidation, the greatest effect is related to pesticides, nitrogen fertilizer and agricultural machinery. \begin{table}
\begin{tabular}{c c c c} \hline
**Index or Type of Energy** & **Unit** & **Average Value** & **Percent** \\ \hline Energy ratio & - & 0.4 & - \\ Energy productivity & kg/MJ & 17.28 & - \\ Specific energy & MJ/kg & 0.06 & - \\ NEG & MJ/ha & \(-\)29,922 & - \\ Direct energy & MJ/ha & 27,998.16 & 55.78 \\ Indirect energy & MJ/ha & 22,193 & 44.22 \\ Renewable energy & MJ/ha & 457.77 & 0.91 \\ Nonrenewable energy & MJ/ha & 49,733.39 & 99.09 \\ \hline \end{tabular}
\end{table} 
Table 4: Indicators and classification of energy types.