National inventory of N2O emissions from agriculture and waste sectors: Emission estimation and uncertainty analysis

One of the factors that make greenhouse gases important is that its contribution to climate change. They can absorb energy from infrared (IR) radiation and gas molecules are gained extra energy thereafter, molecules give up energy by emitting another infrared photon. This process causes trapping heat in the atmosphere. The increase in the temperature of the Earth causes climate change. Climate change began to become evident in the 18th century with the industrial revolution. When it comes day by day from the industrial revolution, a slight increase is observed every year in the average temperature of the world. International organizations are striving to prevent global warming and climate change and/or to reduce the most. Various agreements have been signed with the participation of the states. The first climate change agreement The United Nations Framework Convention on Climate Change was held in Rio de Janeiro in 1992 with the participation of countries. The primary aim of this deal is to create a global response to climate change. Turkey had also signed the agreement in 2004. The United Nations subsequently signed the Kyoto Protocol. The difference between the treaties is that the legal procedures and processes are opened in the Kyoto Protocol. The latest agreement on these aims is the Paris Climate Change Agreement, signed by 195 countries. An important goal of the agreement is to ensure that global temperature increases are kept below 2 degrees until the end of the century. There are many types of greenhouse gases in the atmosphere and the heat holding capacities are different from each other. All greenhouse gases have a global warming potential that characterizes their ability to hold heat concerning CO2. For example, nitrous oxide is 298 equivalents of carbon dioxide while methane is calculated as 24 equivalents of carbon dioxide. The primary greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), water vapor (H2O), chlorofluorocarbons (CFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6). Countries calculate national greenhouse gas emission inventories, which are estimated to understand the effects of climate change. In addition, international agreements are being made with the participation of governments to prevent climate change. When calculating emissions of greenhouse gases, the Intergovernmental Panel on Climate Change (IPCC) has a guideline for the calculation method. There is also some software available. It seems that countries have also developed their own programs and/or methods to develop calculation methods for national emission calculations. In the calculation method of IPCC, Tier 1, Tier 2 and Tier 3 are separated for find out more representative results. In Tier 1, some parameters and input factors are country specific and emission factor are used as default values suggested by the IPCC. In Tier 2, the data and the emission factors that are used to calculate the national emissions are specific values. In Tier 3, more complex structures and models are used for emission calculations. After the calculation is made, the uncertainty analysis is performed to determine how certain the results are. In this context, emission uncertainty is usually calculated using the Monte Carlo methodology. The Monte Carlo method generates input and output probability distribution functions by iterating randomly using the probability distributions of the inputs. In this study, a greenhouse gas, N2O emissions were calculated and uncertainty analysis was performed. N2O emissions from managed soils, and waste sector were calculated for Turkey. The calculation method of IPCC Tier 1 was used. Uncertainty and sensitivity analysis were performed via @RISK programme. Emission factors, and input activity data had been obtained from previous studies, IPCC Guidelines, Turkey Statistical Institute. In addition, the data published by institutions such as the Ministry of Food, Agriculture and Livestock were also used. Indirect emission sources can produce emission in these processes by depositing in the atmosphere, leaching and runoff. In this study, both indirect and direct emission sources were calculated between 2011 and 2015. Calculated values of the United Nations Food and Agriculture Organization (FAO) and the Turkey Statistical Institute (TURKSTAT) were compared. The resulting from agricultural emissions were 54.44, 64.55, 66.79 Gg N2O/year for the FAO, TURKSTAT and our study respectively, in 2011. In the calculation of emissions from manure management, 0.47, 8.68, 9.11 Gg N2O/year were found respectively. It is estimated that the difference is high due to selected manure management systems. When the results of the burning of crop residue (agricultural waste) were compared, it was 0.25, 0.28, 0.29 Gg N2O/year respectively. Three results in this parameter appear to be consistent within themselves. In the waste sector, results compared with TURKSTAT data these were the amount of emissions resulting from the compost, wastewater treatment plant and compost. The amount of emissions from wastewater treatment plants were 6.25, 5.34 Gg N2O/year, the amount of emissions from compost 0.04 and 0.04 Gg N2O/year, respectively. The amount of emissions generated by open burning of waste were 0.01 and 0.01 Gg N2O/year, respectively. The amount of emission from the total waste sector was 6.30 Gg N2O/year in TURKSTAT and the calculated value in this study was 5.39 Gg N2O/year. When the total obtained values were examined in 2015, FAO 67.15, TURKSTAT 87.59 and 88.05 Gg N2O/year were found when managed soils (agricultural soils + manure management + open burning of crop residue) were calculated. Emissions from the waste sector (wastewater treatment plant + compost + open burning of waste) were calculated as TURKSTAT 6.84 for 2015 and 7.04 Gg N2O/year for this study. The difference arises from the difference in the results of wastewater emissions. In general, when the results are compared, the results obtained differences are less than 3% with the TURKSTAT data. On the other hand, according to the FAO data, it is seen that the differences have grown even more and have resulted in different results of about 30-35%. There was a difference between the results when FAO and TURKSTAT were compared. The reason for this difference is thought to be due to the different input data generated in the fertilizer management calculation mentioned above. In the calculations, the total values of direct and indirect emissions from agricultural and waste sector were calculated. Total direct and indirect emission amounts were 116.21 Gg N2O/year. In 2011, emission amounts are 34629.07 Gg CO2eq/year. The year of 2012 emissions amounts 125.05 Gg N2O/year and 37263.92 Gg CO2eq/year, the year 2013 values were 128.56 Gg N2O/year and 38311.22 Gg CO2eq/year. The values were 128.81 Gg N2O/year and 38385.46 Gg CO2eq/year for 2014. The calculated amounts of emissions were 130.27 Gg N2O/year and 38819.16 Gg CO2eq/year for 2015. The calculations made were compared to TURKSTAT and FAO data. In the estimated amounts of N2O emissions for the year 2011, the provinces with the highest total direct emissions were Konya, Ankara and Şanlıurfa. Calculated values were 5141, 3843 and 2476 tons/year, respectively. Konya, Ankara and Erzurum had the most indirect N2O emissions. Their calculated amounts were 1531, 968 and 791 tons/year in 2011, respectively. The amount of total emissions were calculated for cities in the year 2015, the highest direct emissions were from Konya, Ankara and Şanlıurfa. Calculated values were 6420, 4271 and 3239 N2O tons/year respectively. Compared with 2011, there were 25%, 11% and 16% increase in the emissions. Konya, Ankara and Erzurum had the most indirect N2O emissions of 1614, 914 and 755 tons/year in 2015, respectively. Compared to 2011, there were changes in the emissions of 5%, -5% and -4% respectively. When the total N2O emissions for 2015 were examined, FAO reported 67.151 TURKSTAT reported 87.592 and this study calculated 88.058 Gg N2O/year for managed soils (agricultural soils + manure management + open burning of agricultural residue). Emissions from the waste sector (wastewater treatment plant + compost + open burning of waste) were calculated as 7.049 Gg N2O/year for 2015. When compared with TURKSTAT estimation (6.843 Gg N2O/year), our emissions was slightly higher. Uncertainty analysis was performed using the Monte Carlo method with the @RISK program. Direct N2O emissions were estimated for managed soil, manure management, waste and total, with the uncertainty expressed as 95% confidence intervals. Total emission mean was 98.04 Gg N2O/yr with 95% confidence interval of (31.40-230.39). Emission from managed soil was 85.39 Gg N2O/yr with 95% confidence interval of (20.81-216.49). Emission from manure management was 14.38 Gg N2O/yr with 95% confidence interval of (3.62-35.78). Emission from waste sector was 7.29 Gg N2O/yr with 95% confidence interval of (2.01-15.75). 95% confidence interval for the total N2O emission estimate was given between -68% to 135%. According to the Spearman rank correlation coefficient for sensitivity analysis, emission factors were found as the most influencing inputs to emission calculations. These are EF1 emission factor for N2O emissions from N inputs and EF1fr the emission factor for N2O emissions from N inputs to flooded rice. Spearman rank correlation coefficients were 0.72 and 0.54 for EF1 and EF1fr, respectively. Another important parameter was the default N excretion rate (per 1000 kg animal mass).