GHG Emissions from an Aquaculture System of Freshwater Fish with Hydroponic Plants

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1 GHG Emissions from an Aquaculture System of Freshwater Fish with Hydroponic Plants Kumiko Ohgaki 1, Yoko Oki 2, Atsushi Inaba 3 1 Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Japan 2 Graduate School of Environmental and Life Science, Okayama University, 3-1-1Tsushima-naka, Kita-ku, Okayama-shi, Japan 3 Department of Environmental and Energy Chemistry, Faculty of Engineering, Kogakuin University, Nishi-shinjuku,Shinjuku-ku, Tokyo, Japan Corresponding author. ohgaki.k.aa@m.titech.ac.jp ABSTRACT In this study, the GHG emissions of the farmed fish willow shiner (called Honmoroko in Japanese) were calculated including the GHG emissions for reforming the rice field to the aquaculture pond and expendable materials consumption on their production as well as the GHG emissions caused by energy on their production. Furthermore, the nitrous oxide (N2O) volatilization from an aquaculture pond was estimated. As the results, the GHG emissions for the production of willow shiner were calculated as 3.62 t-co2e/t, which was correspond to 1,447 g-co2e/m 2 /year, and the direct volatilization of N2O was also estimated to be 572 g-co2e/ m2/ year. Nutritive salts removal experiment shows that SunPatiens flower has enough potential to remove inorganic nitrogen in the aquaculture pond. In other words, an aquaculture system with hydroponic plants has a capacity to make a clearance of N2O from the aquaculture pond. Keywords: GHG emission, aquaculture, cyprinoid fish, willow shiner, hydroponic plant, absorptive removal, nitrous oxide, volatilization 1. Introduction There are many studies on the calculation of the GHG emissions for food, which are however calculated only for their production processes using the data of energy and expendable materials consumption. In this study, the GHG emission of the farmed fish willow shiner (called Honmoroko in Japanese) is calculated including the GHG emissions for reforming the rice field to the aquaculture pond and expendable materials consumption on their production. However, it is significant to know the direct volatilization potential of N 2 O from the aquaculture pond caused by non-consumed feed and waste (ammonia and feces) of fish, moreover, the removal potential of inorganic nitrogen by hydroponic plant cultivated in aquaculture pond is also important to reduce the GHG emissions. 2. GHG emission of willow shiner Figure 1. System boundary In this study the amount of GHG emission for the farming of willow shiner is calculated including initial investment to reform the rice field to the aquaculture pond. The system boundary is illustrated in Figure 1. As water supply system differs according to farming region and area, it is excluded from the system. The materials used for reforming rice field, aquaculture instruments, consumable goods, commercial fish feed, power consumption, hatching goods and storage materials are included in a system boundary. In order to obtain the amount of consumption of materials and energy, the balance of payment was used which is shown in a Tutorial Manual No.9 - Honmoroko Farming Technology-published by Saitama Prefectural Agriculture and Forestry Research Center Fisheries Research Insti- 920

2 Source: Organization for Regional Industrial Academic Cooperation, Tottori University Figure 2. Examples of reformed rice fields in western Japan tute. Additional interviews were performed in the Fisheries Research Institute in Saitama Prefecture and Honmoroko Farming Manual by Kusatsu city in Shiga Prefecture was also used as supplements for the GHG calculation. The rice field reform is performed shown in the figure 2 which are examples in Tottori Prefecture. The cm water depth is needed by digging a bit deeper the rice field and raise on the ridge. Waterproof sheets are laid on the ridge as shown in Figure 2. The amount of the GHG emission into units of CO 2 equivalent (CO 2 e) is calculated according to the aquaculture schedule of the Table kg willow shiner per 1,000m 2 (10a) reformed rice field was produced in a year. To calculate the GHG emission of the willow shiner farming, the official secondary data for Japanese Carbon Footprint Program are used firstly as the CO 2 e emission factors and then the 3EID data (2000) derived from I/O analysis for Japan are used secondly. Table 2 shows the amount of consumption for durable /expendable materi- Table 1. Aquaculture schedule Table 2. The used primary unit and calculated GHG emissions (CO 2 e) 921

3 Table 3. The actual GHG emission of fishes considering wastage rate thought to be smaller than the GHG emissions of other farmed fishes shown in table3. als and energy to produce willow shiner per 1,000m 2 pond in a year and their CO 2 e emission factors. Furthermore, Table 2 shows also the calculation results of GHG emissions (CO 2 e) per 1,000m 2 pond per year. The amount of durable materials per year was obtained by dividing the whole weights by the years using them. As the result, the CO 2 e emission for the production of willow shiner is 1.447t- CO 2 e/1,000m 2, which correspond to 3.62t- CO 2 e /t-willow shiner. It is almost the same as those for other farmed fishes. However, as the edible part of willow shiner is 100%, while those of other fishes are about 50%, the actual GHG emission of willow shiner is 3. Estimation of the GHG emission including Nitrous oxide (N 2 O) from the aquaculture pond 670kg of fish feed, shown in Table2, was fed in the 1,000m 2 pond to produce 400kg of willow shiner per year. Non-consumed feed and waste (feces and ammonia) from fish are in the pond. The CO 2 emissions caused by them do not need to be counted, because the fish feed was produced by some plant and wild fish meal of phytoplankton origin, they are thought to be carbon-neutral. Moreover, the emission of CH 4 caused by nonconsumed feed and waste from fish is negligible, because oxygen is always supplied by aeration in the pond for fish. However, we have to count the emission of N 2 O caused by protein included in fish feed, because the global warming potential of N 2 O is higher than CO 2. As mentioned above, 670 kg fish feed was fed in the pond, which has 45.1kg of nitrogen because the 3 kind of commercial feeds shown in Table 4 were used. On the other hand, 400 kg of willow shiner has 11.2 kg nitrogen because the protein ratio of willow shiner is 17.5% according to the data of Standard Tables of Food Composition in Japan (2010) and nitrogen ratio of protein is 16% by nitrogen-protein conversion factor. It means Table 4. Ingredient labeling of commercial feed 33.9kg of nitrogen was discharged into pond a year, which is the difference between 45.1kg contained in feed and 11.2kg of willow shiner. Almost no research has been conducted to quantify N2O emission on aquatic production. Ahn et al. quantified the annual N 2 O emissions of 12 wastewater treatment plants across the United States and found that the N 2 O emission can be as high as 1.80% of influent nitrogen. Using this ratio, the CO 2 equivalent emission (CO 2 e) of N 2 O for the production of willow shiner is calculated as follows. Global warming potential 298 is compliant with the (AR4). 33,900 g = 610g-N 610 g 44/14 = 1,917 g-n 2 O 1,917 g-n 2 O/ 1000m 2 / year = 1.92 g-n 2 O/ m 2 / year = 572 g-co 2 e/ m 2 / year Adding this to the CO 2 emission, the total GHG emission (CO 2 e) for the production of willow shiner is calculated. 1, = 2,019 g-co 2 e/ m 2 / year 922

4 Around 2,000 g-co 2 e/ m 2 / year are totally emitted for the production of willow shiner. But it is very rough estimation because the conversion ratio of influent nitrogen to N 2 O, i.e. 1.8%, was estimated by the studies of wastewater treatment plants which were probably different from aquaculture conditions. 4. An absorptive removal experiment of the inorganic nitrogen by hydroponic plants in a similar condition to an aquaculture pond Table5. Nitrogen absorption rate by the hydroponic plant (SunPatiens) Hydroponic plants can absorb and remove the inorganic nitrogen in water. The potential to reduce the GHG emission from willow shiner aquaculture pond introducing hydroponic culture in the pond was estimated using the data of the following experiments by SunPatiens Salmon (Impatiens hybrid) flower, which showed the high absorption potential of nutrients in the water. Hydroponic pots of SunPatiens and plant-free pot were prepared in small pools without aeration, which was called as Pool condition. Hydroponic pots of SunPatiens and plant-free pot were prepared with aeration condition, which was called as Aeration condition. It was the very similar condition to willow shiner aquaculture pond. 10% Hoagland s solution was used as nutrient (NH 4 -N: 10mg/L, NO 3 -N: 10mg/L, etc.). Every week 10L 10% Hoagland s nutrient solution was exchanged. Experimental period was for 7 weeks from 28 th June to 11 th August, but 5 th week it was 6 days to be exchanged the 10% Hoagland s solution and 7 th week it was 3 days to be exchanged it (44 days), because Sun- Patiens salmon absorbed nutrient completely before 7 th day in these weeks. Table 5 shows Nitrogen absorption rate by SunPatiens Salmon. Aeration condition is similar to willow shiner pond. Mean absorption rate of total nitrogen (ammonium nitrogen and nitrate nitrogen) is 423mg/m 2 /day. Figure 3 shows Nitrogen concentration changes of Hoagland s nutrient solution, that an ammonium nitrogen concentration decreased more rapidly on the aeration condition plant-free pot than pool condition plant-free pot, and furthermore, the nitrate nitrogen concentration on the aeration condition plant-free pot was higher than pool condition plant-free pot.it is considered that aeration accelerate the nitrification and volatilization of ammonia. The 423mg/m 2 /day might be over estimation because the ammonia volatilization is included. However, figure 3 also shows SunPatiens Salmon absorbed the nutrient of 10l Hoagland s solution in a few days. As the period become progressively shorter in accordance with the biomass growth of the SunPatiens, and as expected the rate of absorption becomes larger, it would be used as the reasonable average value 423mg/m 2 /day. In the case of the mean absorption rate of total nitrogen i.e. 423mg/m 2 /day, one plant has the absorption potential of 76g /m 2 /180days. It means that 33,900g-N can be removed by 446 plants in 180 days. 923

5 Figure 3 Nitrogen concentration changes of Hoagland s nutrient solution 5. Conclusion A GHG emission for the production of farmed willow shiner in reformed rice field in Japan is around 2,000 g-co 2 e/ m 2 / year. It will be 3-4 times larger than the GHG emission of rice production of 728g CO 2 e/m 2 /year in Japan, which is calculated using 1.35kgCO 2 e/kg-rice by the carbon footprint secondary data (B-J301001) and 539kg-rice /1000m 2 /year by the averaged rice annual crop (2013) of Japan. The result shows the GHG emission caused by electricity consumption is the largest in willow shiner farming. The power is consumed for the aeration which is essential to freshwater aquaculture. The development of aeration technology which consumes little power is needed. The second largest emission source is fish feed. The fish feed production process of less GHG emissions should be developed, which might be the process using food waste. In this paper, the absorptive removal potential of inorganic nitrogen by hydroponic flower, SunPatiens Salmon was estimated. The 33,900g-N, which was discharged in 1,000 m 2 pond for 400kg production of willow shiner in 180days, could be removed by 446 plants. As SunPatiens has the purifying effect of the aquaculture pond, the higher density fish farming can be achieved which could lead the less GHG aquaculture per the production volume. Acknowledgment: This work was supported by JSPS KAKENHI (Grant-in Aid for Challenging Exploratory Research ) 6. References Ahn, J. H., Kim S., Park, H., Rahm, B., Pagilla, K. and Chandran K.(2010). N2O Emissions from Activated Sludge Processes, : Results of a National Monitoring Survey in the United States. Environmental Science & Technology, 44, Doi: /es903845y Ajinomoto Co., Inc. Environmental and Safety Department (2010). Food-related material CO2 emission factor database activity/environment/pdf/2010/lcco2.pdf 924

6 Hu, Z., Lee, J.W., Chandran, K., Kim, S. and Khanal, S.K.(2012). Nitrous Oxide (N2O) Emission from Aquaculture: A Review. Environmental Science & Technology, 46, Doi: /es300110x Ministry of Agriculture, Forestry and Fisheries General contact of government statistics (2014) f (1) Science and Technology Council Subcommittee resource survey (2010) component/b_menu/shingi/toushin/ icsfiles/afieldfile/2011/05/30/ _10.pdf, Item No

7 This paper is from: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector 8-10 October San Francisco Rita Schenck and Douglas Huizenga, Editors American Center for Life Cycle Assessment

8 The full proceedings document can be found here: It should be cited as: Schenck, R., Huizenga, D. (Eds.), Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector (LCA Food 2014), 8-10 October 2014, San Francisco, USA. ACLCA, Vashon, WA, USA. Questions and comments can be addressed to: ISBN: