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Table 4

Economics of struvite production

Description
Low-cost reactor developed in Nepal (Etter et al. 2011)aContinuous up-flow reactor developed in this studya
1. Operation parameters 
Reactor operation Filtration & Manual Stirring Sedimentation + Filtration & No stirring 
Reactor capacity 500 L 500 L 
Cycles per day 8 D−1 Continuous (2hrs HRT-24 hrs) 
Struvite recovery efficiency 90% 81% 
Yearly struvite production (250 workdays) 1,400 kg 1,893 kg 
Molar Mg:P ratio 1.1 molMg·mol P−1 1.5 molMg·mol P−1 
2. Installation costs (based on inflation ratesb(based on current prices in India) 
Steel tank for reactor Rs.17,023 Rs. 30,000 
Additional tanks, fittings, pipes etc. Rs.31,537 Rs. 50,000 
Building Rs.33,867 Rs. 40,000 
Total Rs.82,427 Rs.1,20,000 
Operation duration 10 years 10 Years 
Amortisation (per annum) Rs.8,243 Rs.12,000 
Capital costs (12% per annum) Rs.990 Rs.1,440 
3. Expenses 
Amortisation and capital costs (per annum) Rs.5,150 Rs.13,440 
Labour charges (per annum) Rs.1,12,890 Rs.27,000c 
Bittern price (per annum) Rs.34,763 Rs.1,000–15,000d 
Total (per annum) Rs.1,52,803 Rs.41,440–55,440 
4. Revenue   
Sale of struvite (per annum) Rs.46,124e Rs.62,488e 
5. Profit (per annum) A loss of Rs.1,06,679 is incurred Operation can be performed without making a loss. Profit for sites with minimum transportation of bittern for a distance of 50 km and a maximum distance of 2,000 km is about Rs.21,048/- and Rs.7,048/- per annum respectively. 
Description
Low-cost reactor developed in Nepal (Etter et al. 2011)aContinuous up-flow reactor developed in this studya
1. Operation parameters 
Reactor operation Filtration & Manual Stirring Sedimentation + Filtration & No stirring 
Reactor capacity 500 L 500 L 
Cycles per day 8 D−1 Continuous (2hrs HRT-24 hrs) 
Struvite recovery efficiency 90% 81% 
Yearly struvite production (250 workdays) 1,400 kg 1,893 kg 
Molar Mg:P ratio 1.1 molMg·mol P−1 1.5 molMg·mol P−1 
2. Installation costs (based on inflation ratesb(based on current prices in India) 
Steel tank for reactor Rs.17,023 Rs. 30,000 
Additional tanks, fittings, pipes etc. Rs.31,537 Rs. 50,000 
Building Rs.33,867 Rs. 40,000 
Total Rs.82,427 Rs.1,20,000 
Operation duration 10 years 10 Years 
Amortisation (per annum) Rs.8,243 Rs.12,000 
Capital costs (12% per annum) Rs.990 Rs.1,440 
3. Expenses 
Amortisation and capital costs (per annum) Rs.5,150 Rs.13,440 
Labour charges (per annum) Rs.1,12,890 Rs.27,000c 
Bittern price (per annum) Rs.34,763 Rs.1,000–15,000d 
Total (per annum) Rs.1,52,803 Rs.41,440–55,440 
4. Revenue   
Sale of struvite (per annum) Rs.46,124e Rs.62,488e 
5. Profit (per annum) A loss of Rs.1,06,679 is incurred Operation can be performed without making a loss. Profit for sites with minimum transportation of bittern for a distance of 50 km and a maximum distance of 2,000 km is about Rs.21,048/- and Rs.7,048/- per annum respectively. 

aAll financial costs are given in Indian Rupees. Nepali rupee is converted using 1NRs = 0.63 INRs.

bBased on total inflation rate of 79.19% from 2011 to 2020 in India has been considered for calculations.

cLabour charges for two days per week @Rs.300 D−1 for 45 weeks.

dBittern transportation price @ Rs.3 per ton/km for transporting 1.5 ton of bittern (distance taken for calculation minimum: 50 km @ Rs.1,000/- and maximum 2,000 km @ Rs.15,000/- per annum).

eStruvite price worked out for India based on current fertiliser rate using linear regression Rs.33.01 kg−1.

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