Waste Reuse for Building Material, Beijing , China. Beijing , China

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1 216 International Conference on Energy Development and Environmental Protection (EDEP 216) ISBN: Effect of Nitrification Inhibitor Addition on H 2 S and NH 3 Emissions During Kitchen Waste Composting Hong-Yu ZHANG 1,a,*, Jun GU 1,b, Guo-Xue LI 2,c, Wen-Tao CAI 1,d 1 Beijing Building Materials Academy of Science Research/State Key Laboratory of Solid Waste Reuse for Building Material, Beijing 141, China 2 College of Resource and Environmental Science, China Agriculture University, Beijing 1193, China a zhyycj6688@163.com, b gujun@bbma.com.cn, c ligx@cau.edu.cn, d @qq.com * Corresponding author Keywords: Kitchen Waste, Composting, Nitrification Inhibitor, H 2 S, NH 3. Abstract. NH 3 and H 2 S emissions play an important role in the total odor emission during kitchen waste composting. In order to reduce odor emission, this study designed experiments to investigate the effects of nitrification inhibitor addition on H 2 S and NH 3 emissions during kitchen waste composting. All experiments were performed in simulated composting device. The results showed that the addition of NaNO 3 and ammonium molybdate can effectively restrain H 2 S emissions, while adding NaNO 2 not only failed to restrain the H 2 S emission but increased the emission concentration. NaNO 3 can be used as the first choice to control the H 2 S emission. The addition of nitrification inhibitors increased the ph of compost materials, from this the NH 3 emission was increased during kitchen waste composting. In kitchen waste composting process, once adding nitrification inhibitors to reduce the H 2 S emission, it is bound to be the same time to strengthen the emission reduction measures of NH 3. Introduction Aerobic composting technology can not only realize the harmless and reduction of kitchen waste, but also the production of organic fertilizer can improve soil structure and increase the yield of crops. At the same time to alleviate the problem of shortage of fertilizer resources in China [1-6]. However, due to improper control of raw materials, ventilation, etc. the anaerobic zone in aerobic composting reactor can produce [7,8].The concentration of emissions of NH 3 and H 2 S are very high in kitchen waste composting, and play an important role in the total odor emission for composting [9]. So it is very important to reduce the emissions of H 2 S and NH 3 in the kitchen waste composting, and so as to improve the nutrient content of composting product and reduce the odor pollution in composting process. In recent years, many researches are focus on the reduction of NH 3 emission during kitchen waste composting. The NH 3 reduction measures include adding magnesium salt, calcium salt or regulation C/N ratio of composting material [1-12]. At present, there is little research on H 2 S reduction during kitchen waste composting. Previous studies pay more attention to H 2 S reduction in organic waste anaerobic fermentation process, mainly through the addition of

2 hematite, magnesium oxide, nitrite sodium and sodium molybdate and chemical reagents to restrain H 2 S generation [13,14]. Previous studies have shown that it can reduce the H 2 S emission by inhibiting the competition of sulfate reducing bacteria. The anti nitrification bacteria have obvious competitive inhibition on sulfate reducing bacteria. In this study, the effect of nitrification inhibitor addition on H 2 S and NH 3 emissions during kitchen waste composting were investigated. This study provides an important reference to the choice of odor control material during kitchen waste composting. Materials and Methods Raw Materials and Treatments Design Kitchen waste was collected from a separate collection system in south Beijing. The chopped cornstalk (with a length of 2-5 cm) used as the bulking agent was obtained from the Shangzhuang experiment station, China Agricultural University, and the addition proportion is 1% (wet weight) during kitchen waste composting. In this study, four experiments were conducted with different inhibitors, and all nitrification inhibitors were added to 1% of the total nitrogen content of compost materials. The composting period is 3 days. Composting piles were turned once a week. Gas samples were collected once a day at three sampling ports on top of the vessels throughout the experiment. The characters of the raw materials and the detailed design of experiments were shown in Table 1. Table 1. Characters of the raw materials for different treatments. Treatments TN[%] a TS[%] Moisture content[%] Nitrification inhibitors ±1.4 b ±2. NaNO ±3.2 NaNO ±1.7 Nmmonium molybdate a : total sulfur; b : Not added. A series of 6-L composting vessels were used in this research to simulate the forced aeration system. The design and operation of the vessels has been described in detail elsewhere [15]. The vessels were controlled by the C-LGX program, which enables aeration to be controlled automatically by time or inside temperature. Aeration consisted of pumping ambient air into the reactor continuously. The temperature in the vessel will be recorded by this program. Analysis Method H 2 S was analyzed daily using a portable biogas analyzer (Biogas Check, Geotech, UK). The ammonia (NH 3 ) was determined by boric acid titration. The TKN and TS were determined by elemental analyzer. The moisture content was determined by drying the samples at 15 until the weight was constant.

3 Results and Discussion Changes of Temperature and ph The change of temperature in composting process is illustrated in Fig.1. From figure 1a can be seen, and has similar temperature change trend, the temperatures for three treatments were up to 55 degrees or more on the third day, and at this temperature were maintained for 11, 1 and 11 days, respectively. All treatments achieved the harmless specification requirements. The treatment adding NaNO 2 had a significant inhibitory effect on the composting process, and the inhibition lasted for a week, so that this treatment delayed into the high temperature period. One-way analysis of variance showed a difference among the four treatments for temperature (P<.5). Fig.1b is the change of the ph value of the four treatments with the composting time, it can be seen that adding NaNO 3 () and NaNO 2 () increased the ph value of the compost material, the ph values of 2 kinds of compost materials were 7 and 7.2 respectively, and the ph value of compost raw materials was 6. Adding ammonium molybdate does not affect the ph value of composting materials. With the composting, the ph value of each treatment showed a significant upward trend, the ph values of and all higher than the other two treatments, and the ph value of slightly higher than in the whole composting process. Temperature/ o C Ambient ph value a 6 4 b Figure 1. Changes of temperature and ph value of different treatments during composting. Productions of H 2 S The H 2 S concentration and cumulative emissions are shown in Fig.2 for different treatments. The emission concentration pattern of H 2 S is presented in Fig.2a, and the H 2 S emissions with the similar trends for all treatments. In the early stage of composting, the concentrations of H 2 S were low. With the advance of compost, the organic matter decomposition consumes a large amount of oxygen. The emission concentrations of H 2 S were rapidly increased due to the shortage of oxygen. The emission of H 2 S concentrations reached the peak value at the 7th day for all treatments. Compared with the control, the addition of NaNO 3 () and ammonium molybdate () can effectively restrain H 2 S emissions, while adding NaNO 2 () not only failed to restrain the H 2 S emission but increased the emission concentration. This is contrary to the conclusion that addition NaNO 2 can effectively inhibit the activity of sulfate reducing bacteria and reduce the emission of H 2 S.

4 Fig.2b shows the cumulative emissions of H 2 S for all four treatments. The cumulative emissions of H 2 S reached 571.2, 211.9, and 322.2mg kg -1 (DM) for,, and, respectively. Compared with control, the cumulative emissions of H 2 S for and decreased by 43.6% and 62.9% respectively, while increased by 29.8%, Therefore, NaNO 3 can be used as the first choice to control the H 2 S emission. One-way analysis of variance showed a significant difference among the four treatments for H 2 S emission (P=.). H2S/mg m a Cumulative H 2S/mg kg -1 DM Figure 2. Changes of hydrogen sulfide concentration and cumulative of different treatments during composting b Productions of NH 3 The NH 3 concentration and cumulative emissions are shown in Fig. 3 for different treatments. Fig.3a shows the emission concentration pattern of H 2 S, the NH 3 reached 2 emission peaks on the 8th and 15th day for all treatments. This is mainly due to the turning artificial for the composting material on the 7th and 14 th day, the aerobic environment of the reactor is greatly improved by turning over, the oxygen is added in time, and the compost material is fully mixed again. The organic matter decomposed rapidly, and then released a large number of NH 3. The decomposition of organic matter in the waste was stable, and the emission of NH 3 was decreased and tended to zero after 2d composting. Fig.3b shows the cumulative emissions of NH 3 for all treatments. The cumulative emissions of NH 3 reached , , and mg kg -1 (DM) for,, and T3, respectively. Compared with control, NH 3 emissions were increased in different degrees after adding nitrification inhibitors for all treatments. This is mainly because the ph value of compost material was obviously improved after adding nitrification inhibitors, which caused the high concentration of NH 3 emission. Although the addition of ammonium molybdate did not significantly improve the ph value of composting materials, but ammonium molybdate easily thermal dissociation, so the overall emission of NH 3 higher than and. It is found that adding nitrification inhibitors will increase ammonia emissions in the process of kitchen waste composting. One-way analysis of variance showed a significant difference among the four treatments for NH 3 emission (P=.).

5 NH3/mg m a Cumulative NH 3/mg kg -1 DM b Figure 3. Changes of ammonia concentration and cumulative of different treatments during composting. Conclusion (1) Addition of NaNO 3 and ammonium molybdate can effectively restrain H 2 S emissions, while adding NaNO 2 not only failed to restrain the H 2 S emission but increased the emission concentration. NaNO 3 can be used as the first choice to control the H 2 S emission. (2) The addition of nitrification inhibitors increased the ph of compost materials, from this the NH 3 emission was increased during kitchen waste composting. (3) In kitchen waste composting process, once adding nitrification inhibitors to reduce the H 2 S emission, it is bound to be the same time to strengthen the emission reduction measures of NH 3. Acknowledgements This study was financially supported by Beijing Natural Science Foundation (NO.81445), and supported by the country 12th Five-Year Plan to support science and technology projects (212BAD14B3, 212BAD14B16). References [1]X.F.Li, Y.Zhao, G.C.Du, et al. Chinese J. of Environ. Engineering, Vol.3 (29), p [2]Z.H.Zhao, C. J.Jin, P.Zhang, et al. Chinese J. of Environ. Engineering, 3 (29) [3]M.Raut, W.S.Prince, J.Bhattacharyya, et al. Bioresource Technol. 99 (28) [4] Y.Xiao, G. M.Zeng, H.Y.Zhao, et al. Bioresource Technol. 1 (29) [5] J.Nair and K.Okamitsu. Waste Manage. 3 (21) [6]M.K.Jukka, A.Mona, H. K. Merj, et al. Bioresource Technol. 12 (211) [7]G.D'Imporzano, F.Crivelli, F. Adani. Sci. of the Total Environ. 42 (28) [8]J.L.Domingo, M.Nadal. Environ. International, 35 (29) [9] HY. Zhang. Beijing: China Agricultural University, 212. [1]L.M. Ren, F.Schuchardt, Y. J. Shen, et al. Waste Manage. 3 (21)

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