Study On The Characteristic And Reduction For Greenhouse Gases And Ammonia Emissions During The Storage Of Manure And Wastewater

Livestock manure management process is an important source of greenhouse gases(GHGs) and ammonia(NH3) emissions from agriculture. Among the manure management options, liquid/solid manure storage would be one important source of the GHGs and NH3 emissions, implying the high significant of studying the characteristic and mitigation techniques for GHGs and NH3 emission from manure storage process. Large amount of manure are produced in China, while little research are available about the gas emission characteristics from different manure sources. The GHGs and NH3 emission from pig manure(PM), dairy manure(DCM), beef cattle manure(BCM), layer manure(LM) and broilers manure(BM) were monitored using dynamic chamber method, aiming to compare the difference of gas emission characteristics among the five types of manure, also to elucidate the key factors causing the differences. After reviewing the researches about the gas emission and mitigation options from manure storage, acidification using sulfuric acid was chosen as a mitigation option to treat the raw slurry and biogas liquid from pig farm. For raw slurry, the slurry p H was 6.5 in control group(RCK), while the treatment group was acidified to 5.1(RT1) and 5.7(RT1); for biogas liquid, the p H was 7.85 in control group(BCK), while the treatment group was acidified to 5.7(BT1) and 6.5(BT2). The gas emission flux was monitored with dynamic chamber method during 75-day storage period, to compare the mitigation effect between raw slurry and biogas liquid. The main conclusions are as follows:Results of the gas emissions from different sources of manure storage showed that: for PM, DCM, BCM, LM, BM storage, the average daily gas emission rates were 3.40, 122.30, 41.47, 2.21, and 4.73 mg CH4 kg-1 d-1, respectively; 792.85, 652.65, 444.00, 1668.08, and 645.42 mg CO2 kg-1 d-1, respectively; 14.86, 0.95, 1.68, 67.21, and 19.80 mg NH3 kg-1 d-1, respectively; 0.33, 0.90, 0.94, 0.76 and 0.27 mg N2 O kg-1.d-1, respectively. The results indicated that C and N gas emissions from manure storage were influenced by manure characteristics. The total CO2-eq emissions from PM, DCM, BCM, LM, BM were 14.09, 281.98, 108.67, 20.18 and 15.81 g kg-1 during the 77 days of storage, respectively. The CO2-eq emission of DCM was the highest and was significantly higher than other manures(p<0.05), while the CO2-eq emission of PM was the lowest. The GHGs(CH4 + N2O) of LM was dominated by N2 O with contribution ratio of 76%, while the main GHGs contributor for DCM, BCM and BM were CH4, reaching 65% to 94%; and for PM, CH4 and N2 O equaled for the contribution. The study found that obvious differences occurred for the methane conversion factor(MCF) among the different manures during storage. The MCF of DCM was the highest, reaching 41.2% and MCF for BCM was 18.5%, both were obviously higher than the IPCC recommended value; while MCF of other manures were lower than the recommended value. The N2 O emission factors of the five types of manure were 0.002 ~ 0.013 kg N2O-N kg-1 N, which were comparable with the IPCC recommended value.Results of the gas emissions from acidified wastewater during the storage showed that: for raw slurry, the average daily gas emission rates for RCK, RT1 and RT2 were 32.2, 2.37 and 3.10 g CH4 m-3 d-1, 336.45, 23.36 and 29.79 mg N2 O m-3 d-1, 1.01,0.82 and 1.63 g NH3 m-3 d-1, 109.14, 99.66 and 110.55 g CO2 m-3 d-1, respectively; for biogas liquid, the average daily gas emission rates for BCK, BT1 and BT2 were 30.24, 0.86 and 0.63 g CH4 m-3 d-1, 2.54, 73.43 and 268.66 mg N2 O m-3 d-1, 8.02, 1.35 and 1.51 g NH3 m-3 d-1, 48.9, 44.3 and 44.0 g CO2 m-3 d-1, respectively. For biogas liquid, the acidification can significantly increase the CH4 and N2 O emissions, but NH3 can be reduced by 81% to 83%, and the NH4+ increased by 40% to 54% when compared with the control group. Based on 100-year global warming potential(GWP) for CH4 and N2 O, total GHGs(GHG = CH4 +N2O) emissions can be reduced by 91% to 92% with acidification for raw pig slurry, while being increased by 5 to 11 times with acidification for biogas liquid. The results show that the acidification of raw slurry can reduce GHG emissions significantly, while increase the GHG emissions in biogas liquid to some extent, but it helps to significantly reduce the NH3 emissions and reserve the N content in biogas liquid.