Economic Efficiency of Investment in Lettuce Production Using Organic Fertilizer from Aquaculture Waste

This study evaluated the effects of application rates of two biocomposts derived from fishery waste, produced with and without biochar, on lettuce growth and assessed the economic feasibility of small-scale lettuce production using these materials. A completely randomized 2 × 4 factorial design was used, comprising two biocompost types (with and without biochar) and four application rates (0, 25, 50, and 100 g per 2 kg of soil), with four replicates per treatment. Lettuce growth was evaluated over 30 days based on plant weight and length, aboveground biomass and length, root weight and length, and dry matter content. Application rate significantly affected total plant weight and length, aboveground biomass and length, and root length (p < 0.05). The 100 g rate resulted in the highest mean total plant weight (208.85 g) and aboveground biomass (167.31 g), representing increases of 207.8% and 248.3%, respectively, compared with the untreated control. Mean aboveground length was also greatest at this rate (20.13 cm), whereas root length was greatest at 25 g (25.73 cm). Biocompost type significantly affected root weight and dry matter content, with higher mean values in the treatment without biochar (24.61 g and 88.33%, respectively) than in the treatment with biochar (18.71 g and 86.73%, respectively). The economic analysis, based on lettuce production in a 96 m2 greenhouse, indicated that the project was economically feasible, with an Equivalent Annual Uniform Value (EAUV) of US$545.67, a Profitability Index of 1.86, and a Benefit–Cost Ratio of 1.50. Sensitivity analysis showed that the selling price of lettuce was the main determinant of project profitability, accounting for 99.5% of the modeled variation in Net Present Value. These findings indicate that fishery waste-derived biocomposts have potential for lettuce production, while economic success depends strongly on maintaining favorable market prices.