CHAPTER 10: Economic analysis
10.4 CONCLUSIONS
Commercially available organic fertilizers have a wide variety of nutrient compositions, as do the products produced from each urine treatment method investigated in this work. A commercial fertilizer with a comparable nitrogen content could be found for each UBF regardless of the urine treatment method used. Therefore, theoretically, there is a market for all the UBFs produced, however, the market size for the fertilizers produced may not result in the highest profitability for the same volume of feed urine to the process.
Treatment methods that incorporated RO had the lowest energy requirements, followed by FC, and AD processes had the highest energy requirements. An RO-EFC process with 95% water removal required 2.8 times less energy than if FC had been used alone and 3.4 times less energy than AD to concentrate the same volume of feed urine. Converting the energy requirements to a kWh kg-N-1 recovered improved the comparative energy requirements of FC and AD as these typically have higher nitrogen recovery (96% and 90% N recovery, respectively) compared to RO-EFC (77% N recovery).
Niche fertilizers are more valuable than bulk fertilizers and can be sold for more than R8 292 kg-N-1 compared to R68.7 kg-N-1 for bulk fertilizers. Based on the estimated niche fertilizer market of 140 L per week, the UBF produced using RO-EFC had the highest gross value of R73 000 (produced from 7 500 L of feed urine). This converts to a gross value of R9 700 m-3 feed urine. However, if the niche fertilizer market is larger (2 000 L per week for example) the RO fertilizer would have the highest gross value (R304 000) whilst the RO-EFC fertilizer’s gross value would remain at R69 800. This analysis only considers gross value and does not account for the cost of production. The UBF produced using RO-EFC or AD would be the most practical for bulk sale as these two treatment methods would have the lowest transportation costs (as they have the highest N-content). For example, to supply 1000 kg of N, 2.8 tons of commercial fertilizer are required and only 7.5 m3 of UBF is produced using RO-EFC compared to 51 m3 of the UBF produced using RO-only with a 70% water removal. The net cost of decreased transportation costs versus increased operational costs to further reduce the fertilizer volume requires additional analysis though, especially considering the capital costs that would be required for the RO-EFC process. In addition, the volume of urine that needs to be collected and treated to meet agricultural requirements is significant. Wide-spread urine collection would be required. At this stage, the business model favors producing UBFs for the niche liquid fertilizer market.
This research showed the technical feasibility of concentrating stabilized urine using a suite of different treatment technologies. In general, the final choice of treatment method will depend on several factors and not only the gross product value. These include the product end-use (ornamental plants versus edible crops), plant nutrient requirements and desired nutrient ratios, and the method of urine collection (plumbed versus free-standing systems) as well as the scale of treatment required (toilet, building,
centralized). A detailed economic analysis comparing multiple different system boundary options would likely yield different preferred treatment options for each scenario.
Further testing using a pilot-scale plant is necessary to obtain more accurate operational costs (energy requirements, product transportation costs, nutrient recovery, water removal, and practicality of operation) that can be used to determine a net profit rather than gross sales value. Future work should investigate fertilizer licensing and ensuring the product meets local fertilizer regulations. A detailed market analysis should also be conducted of the different potential fertilizer products. A comparison of capital and operating expenses for each treatment method is also required to determine the financial feasibility of each treatment method.
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