Emissions of carbon dioxide, methane and nitrous oxide from soil receiving urban wastewater for maize (Zea mays L.) cultivation

Methane emissions along biomethane and biogas supply chains are underestimated

Methane and nitrous oxide emissions from flooded rice fields as affected by water and straw management between rice crops

Ratoon rice (RR) is a practice that involves achieving a second crop originating from the stubble left after the previous main rice crop (MR) harvest. There has been little previous study on methane (CH 4 ) and nitrous oxide (N 2 O) emissions from ratoon paddy fields. A 3‐year field experiment was conducted to simultaneously measure CH 4 and N 2 O emissions from traditional single rice (SR) and MR + RR fields in Sichuan Province, southwest China. The CH 4 and N 2 O flux peaks were earlier for MR than SR. The CH 4 emissions from the RR season accounted for 8–30% of total emissions from MR + RR. Compared with SR, MR + RR increased seasonal CH 4 emissions by 3–15%. Correlation analysis showed that the seasonal variation of CH 4 fluxes for MR + RR was significantly related to soil redox potential (Eh). The proportion of emitted N 2 O from RR to MR + RR was 11–42%. The average cumulative N 2 O emissions from MR and MR + RR were increased by 49 and 110% relative to those from SR plots across the 3 years, respectively. The global warming potential (GWP) of RR occupied 10–27% of MR + RR. The GWP of MR + RR was 7–62% higher than that of SR, and it was chiefly dependent on the contribution of CH 4 emissions, despite the greater increase in N 2 O emissions. Grain yield in RR was 11–18% of that in MR + RR. MR + RR significantly increased rice yield by 19%, but the yield‐scaled GWP was comparable to SR. Our results suggest that MR + RR increases the amount of CH 4 and N 2 O emissions from rice paddy fields and rice grain yield. The yield gaps of ratoon rice would be narrowed by optimizing field management practices to realize sustainable rice production under future climate change conditions. The CH 4 and N 2 O emission peaks of ratoon rice were earlier than those of single rice. The CH 4 and N 2 O emissions from ratoon rice fields were significantly higher than from single rice fields. Ratoon rice significantly increased yield and GWP compared to single rice. No significant difference in yield‐scaled GWP was observed between ratoon rice and single rice. Highlights The CH 2 and N 2 O emission peaks of ratoon rice were earlier than those of single rice. The CH 4 and N 2 O emissions from ratoon rice fields were significantly higher than from single rice fields. Ratoon rice significantly increased yield and GWP compared to single rice. No significant difference in yield‐scaled GWP was observed between ratoon rice and single rice.

There is a lack of information regarding carbon dioxide (CO), methane (CH), and nitrous oxide (NO) emissions from pasture soils and the effects of grazing. The objective of this study was to quantify greenhouse gas (GHG) fluxes from pasture soils grazed with cow-calf pairs managed with different stocking rates and densities. The central hypothesis was that irrigated low-density stocking systems (SysB) would result in greater GHG emissions from pasture soils than nonirrigated high-density stocking systems (SysA) and grazing-exclusion (GRE) pasture sites. The nonirrigated high-density stocking systems consisted of 120 cow-calf pairs rotating on a total of 120 ha (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). The irrigated low-density stocking systems consisted of 64 cow-calf pairs rotating on a total of 26 ha of pasture (stocking rate 2.5 cows/ha, stocking density 32,700 kg BW/ha, rest period of 18 to 30 d). Both systems consisted of mixed cool-season grass-legume pastures. Static chambers were randomly placed for collection of CO, CH, and NO samples. Soil temperature (ST), ambient temperature (temperature inside the chamber; AT), and soil water content (WC) were monitored and considered explanatory variables for GHG emissions. GHG fluxes were monitored for 3 yr (2011 to 2013) at the beginning (P1) and at the end (P2) of the grazing season, always postgrazing. Paddock was the experimental unit (3 pseudoreplicates per treatment), and chambers (30 chambers per paddock) were considered multiple measurements of each experimental unit. A completely randomized design considered the term year × period as a repeated measure and chamber nested within paddock and treatment as the random term. Generally, SysB had greater CO emissions than SysA and GRE pasture sites across years and periods ( < 0.01). Soil temperature, AT, and WC had effects on CO emissions. Methane and NO emissions were observed from pasture sites of the 3 systems, but the effect of grazing was not constantly significant for CH and NO emissions. In addition, ST, AT, and WC did not conclusively explain CH and NO emissions. No clear trade-offs between GHG were observed; generally, GHG emissions increased from 2011 to 2013, which was likely associated with weather conditions, such as higher daily temperature and precipitation events. The central hypothesis that SysB would result in greater GHG emissions from pasture soils than SysA and GRE was not confirmed.

The science is clear. When debating emissions, consider your goals. Biological emissions from agriculture (methane and nitrous oxide) make up almost half New Zealand’s total greenhouse gas emissions, so their importance relative to carbon dioxide is of particular policy interest. Motu Economic and Public Policy Research brought together a group of New Zealand climate change and agriculture specialists to respond to questions posed by the Parliamentary Commissioner for the Environment on the science. The paper finds that the overriding need to reduce carbon dioxide emissions is scientifically uncontentious. For the climate to stabilise, net carbon dioxide emissions must ultimately be cut to zero. There is debate about whether, when and how much action to take on other gases. Some scientists advocate a comprehensive multi-gas approach, arguing that will be more cost-effective. It may already be too late to limit warming to two degrees without mitigating agricultural greenhouse gases. Others advocate a focus on carbon dioxide or on all long-lived gases (including nitrous oxide), with concerted mitigation of methane (a short-lived gas) only once carbon dioxide emissions are falling sustainably towards zero. There is support for ‘easy wins’ on all gases, but it is unclear how easy it is for New Zealand to reduce total nitrous oxide and methane emissions while maintaining production. The report summarises current and emerging options, and discusses methods to calculate methane and nitrous oxide emissions at the paddock, farm, regional and national scale. Finally, the report considers metrics used for comparison between gases, focusing on Global Warming Potential (GWP) and Global Temperture change Potential (GTP). The authors reached a consensus that the ‘right’ value depends on the policy goal and could change substantially over time; and if the main policy goal is to cost-effectively limit global average warming to two degrees above pre-industrial levels, then the value of methane should be less than the GWP100 value of 28 until global carbon dioxide emissions have begun to decline steadily towards zero. There is no agreement beyond this on the best value to use; the arguments reflect judgments about politics, economics, and the intersection of policy and science.

Biological emissions from agriculture (methane and nitrous oxide) make up almost half New Zealand’s total greenhouse gas emissions, so their importance relative to carbon dioxide is of particular policy interest. Motu Economic and Public Policy Research brought together a group of New Zealand climate change and agriculture specialists to respond to questions posed by the Parliamentary Commissioner for the Environment on the science. The paper finds that the overriding need to reduce carbon dioxide emissions is scientifically uncontentious. For the climate to stabilise, net carbon dioxide emissions must ultimately be cut to zero. There is debate about whether, when and how much action to take on other gases. Some scientists advocate a comprehensive multi-gas approach, arguing that will be more cost-effective. It may already be too late to limit warming to two degrees without mitigating agricultural greenhouse gases. Others advocate a focus on carbon dioxide or on all long-lived gases (including nitrous oxide), with concerted mitigation of methane (a short-lived gas) only once carbon dioxide emissions are falling sustainably towards zero. There is support for ‘easy wins’ on all gases, but it is unclear how easy it is for New Zealand to reduce total nitrous oxide and methane emissions while maintaining production. The report summarises current and emerging options, and discusses methods to calculate methane and nitrous oxide emissions at the paddock, farm, regional and national scale. Finally, the report considers metrics used for comparison between gases, focusing on Global Warming Potential (GWP) and Global Temperture change Potential (GTP). The authors reached a consensus that the ‘right’ value depends on the policy goal and could change substantially over time; and if the main policy goal is to cost-effectively limit global average warming to two degrees above pre-industrial levels, then the value of methane should be less than the GWP100 value of 28 until global carbon dioxide emissions have begun to decline steadily towards zero. There is no agreement beyond this on the best value to use; the arguments reflect judgments about politics, economics, and the intersection of policy and science.

No one can deny the progression and innovation in the aviation transportation collected at national and international level. But the accountancy of the impact of air transportation on environmental degradation is naive and emerging trend of the current era. The air transportation versus environment is the key contribution to the literature that is solely conducted for Pakistan first time in this context. The objective of this research is to compute the impact of air transportation on carbon dioxide emissions, nitrous emissions and methane emissions separately in the three models by applying ARDL bound test approach during 1990 to 2017. The result depicts significant and positive relation of air transportation (carriage) to carbon dioxide emissions (0.77), nitrous emissions (0.20) and methane emissions (0.38) in long-run. The short-run results infer that the air transportation (passenger) has significantly positive relation to carbon dioxide emissions (0.278), nitrous emissions (0.207), and methane emissions (0.080). The econometric outcomes show the significant and direct relation to transportation (both passenger and cargo) to carbon dioxide, methane, and nitrous oxide emissions in short and long-run. Moreover, per capita GDP, population density, and energy demand also significantly affect the environment showing significant and positive coefficients to all three categories (carbon dioxide, methane, and nitrous oxide) of emission. In case of Pakistan, FDI and trade for this duration didn’t significantly contribute to the CO2, NO2, and methane emissions. Since the last decade the economic issues of Pakistan like terrorism, political instability, energy crises, and poor management along with the worst performance by tertiary sectors have severely hit the economy, and as a result, the FDI and trade sector has tormented in a substantial proportion. Finally, pairwise Granger causation also supports the short and long-run consequences. The outcomes suggested that the fuel-efficient energy use and technological diversification in the transportation sector are essential to mitigate the degrading environmental emissions.

The study of the effects of different fertilization treatments on soil methane (CH4) and nitrous oxide (N2O) emissions in rice-vegetable rotation systems is of great significance to supplement the research gap on greenhouse gas emissions in tropical regions of China. In this study, four fertilization treatments were set up during the pepper season:phosphorus and potassium fertilizer application (PK); nitrogen, phosphorus, and potassium (NPK) application; half application of nitrogen, phosphorus, and potassium plus half application of organic fertilizer (NPK+M); and application of organic fertilizer (M). There was no fertilizer application during the following early rice season. The objective of our study was to investigate the rules of CH4 and N2O emissions under different fertilization treatments in the pepper growth season, and the effects of different fertilization treatments in the pepper growth season on rice yield, and CH4 and N2O emissions in the following early rice growth season. The close static chamber-gas chromatography method was applied to determine soil CH4 and N2O emissions. We measured crop yield, estimated global warming potential (GWP), and calculated greenhouse gas emission intensity (GHGI). Our results showed that:① the cumulative CH4 emission under the four fertilization treatments ranged between 0.9 kg·hm-2 to 2.7 kg·hm-2 during the pepper growth season and between 5.5 kg·hm-2 to 8.4 kg·hm-2 during the early rice growth season. Compared with NPK, NPK+M and M reduced the cumulative CH4 emission in the pepper growth season by 35.3% and 7.6%, respectively; however, NPK+M and M increased the cumulative CH4 emission in the early rice season by 37.5% and 55.1%, respectively. There was a significant difference in cumulative CH4 emission between M and NPK in the early rice growth season. ② The cumulative N2O emission under the four fertilization treatments varied from 0.5 kg·hm-2 to 3.0 kg·hm-2 in the pepper growth season and from 0.3 kg·hm-2 to 0.5 kg·hm-2 in the early rice growth season. The cumulative N2O emission was significantly decreased by 33.7% in NPK+M and by 16.0% in M, compared with that in NPK. In the early rice growth season, the cumulative N2O emission was decreased by 23.5% by NPK+M but was increased by 9.1% by M. There was no significant difference in the cumulative N2O emission among the four fertilization treatments. ③ The yields of pepper and early rice under the four fertilization treatments were 3055.6-37722.5 kg·hm-2 and 5850.9-6994.4 kg·hm-2, respectively. Compared with that in NPK, NPK+M and M significantly increased pepper yield. The GWP under the four fertilization treatments in the pepper-early rice rotation system varied from 508.0 kg·hm-2 to 1864.4 kg·hm-2. Compared with NPK, NPK+M significantly decreased GWP by 25.7% and M insignificantly decreased GWP by 5.7%. The pepper growth season with the four fertilization treatments contributed to 69.2%-78.1% of the total GWP, and N2O contributed to 77.3%-85.3% of the total GWP. The GHGI ranged between 0.03 kg·kg-1 and 0.09 kg·kg-1 in the pepper growth season and between 0.04 kg·kg-1 and 0.24 kg·kg-1 in the early rice growth season. Compared with that in NPK, both M and NPK+M significantly reduced the GHGI by 71.5% and 54.7%, respectively, in the pepper growth season. In the early rice season, NPK+M significantly decreased the GHGI by 44.0%, but M non-significantly decreased the GHGI by 20.8%. The peak in N2O emission in the tropical pepper-early rice rotation system appeared after fertilization, and N2O emissions primarily occurred in the pepper growth season. However, CH4 emission was mainly concentrated in the early rice season. Considering the overall enhancing effects on crop yield and mitigation of greenhouse gas emissions, the co-application of chemical and organic fertilizers (NPK+M) can be recommended as an optimal fertilization practice to mitigate greenhouse gas emissions and maintain crop yield in pepper-rice rotation systems of Hainan, China.

Under intensive vegetable production, increased productivity is primarily considered for selecting better water management and irrigation intensity in upland soils. Soil water potential at −30 kPa (field capacity) for red pepper (Capsicum annum L.) production, which is the optimum moisture potential for plants, is recommended for Korean upland soils to maximize fruit yield; however its impact on greenhouse gas (GHG) emissions have not yet been considered. In this study, red pepper was cultivated under two soil water potentials at −30 and −50 kPa by drip irrigation control in two different textured soils (clay and sandy loams). Nitrous oxide (N2O) and methane (CH4) emissions were simultaneously investigated during the cultivation period. Results indicated N2O was the main GHG and contributed to approximate 97–9% of the total global warming potential (GWP), though the extent of its contribution varied depending on soil texture and soil moisture control with emitted CH4 being negligible throughout the investigation period. Between the treatments, soil moisture control at −50 kPa was effective in reducing the emissions of the two GHGs and also increased red pepper productivity in both clay loam and sandy loam soils. Comparing the gross GWP per unit pepper fruit yield between the treatments, maintaining soil water potential at −50 kPa by controlled irrigation led to a 50% reduction of GWP per unit pepper fruit yield. Therefore, drip irrigation control to lower soil water potential at −50 than −30 kPa is recommended to obtain high crop yield and reduce GWP per unit red pepper fruit yield for red pepper production in Korea.

A study on the effect of organic fertilizer (cow manure) on carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions in a paddy field was conducted. Suphanburi 1 rice varieties were planted in a double-crop organic rice field at Pathum Thani Rice Research Center, Pathum Thani Province, Thailand. The study was categorized into 4 sets of experiments as follows: 1) control, without added fertilizer, 2) addition of organic fertilizer (cow manure) at 3.13 t·ha-1, 3) addition of organic fertilizer at 9.38 t·ha-1 and 4) addition of organic fertilizer at 12.50 t·ha-1. The study showed that the set with the addition of organic fertilizer at 12.50 t·ha-1 had the highest emissions rate of methane at an average rate of 4.94 mg·m-2 d. Lower methane emissions were found in the sets with added organic fertilizer at 9.38 t·ha-1 and in the control set without added fertilizer and the set with added organic fertilizer at 3.13 t·ha-1, with an average emission rate of 3.08, 1.77 and 1.49 mg·m-2·d, respectively. The differences in the methane emissions of all of the sets are statistically significant, (P<0.05). Compared to the other sets, the carbon dioxide emissions were highest in the set with added organic fertilizer at 9.38 t·ha-1, at an average rate of 380.55 mg·m-2·d. The rates were lower in the set with added organic fertilizer at 3.13 t·ha-1, the control set without added fertilizer, and the set with the addition of organic fertilizer at 12.50 t·ha-1, with emission rates of 325.24, 253.92 and 198.16 mg·m-2 d, respectively. However, these results had no significant difference. Meanwhile, the nitrous oxide emissions during the growing season of the rice were the highest in the set with the addition of organic fertilizer at 9.38 t·ha-1, which had an average rate of 1.41 mg·m-2·d. The rate was lower in the control set without added fertilizer, the set with added organic fertilizer at 3.13 t·ha-1, and the set with added organic fertilizer at 12.50 t·ha-1 with average emissions rates of 1.10, 1.40 and 0.60 mg·m-2·d, respectively.

Since 1750, the year that commonly marks the start of the Industrial Revolution, the atmospheric concentrations of carbon dioxide, methane and nitrous oxide have risen about 40 %, 150 % and 20 %, respectively, above the pre-industrial levels due to human activity (IPCC (2013) Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the IPCC 5th Assessment Report, IPCC, Cambridge, United Kingdom and New York, NY, USA). These elevated greenhouse gas concentrations are held responsible for climate change, which has detrimental effects on the global ecosystem. The treatment of municipal wastewater entails the emission of greenhouse gases. The emission of carbon dioxide and the extent to which it contributes to the increased atmospheric greenhouse gas concentrations is well understood. The origins of methane and nitrous oxide, both potent greenhouse gases with a global warming potential of respectively 34 and 298 CO2 equivalents over a 100 year time horizon, are far less understood. This lack of insight hampers the mitigation of these emissions. The present thesis discusses the emission of nitrous oxide and methane from municipal wastewater treatment plants. The final goal is to come up with guidelines to mitigate these emissions in order to decrease the climate footprint of wastewater treatment. This requires insight into the extent of the emissions and into the relationships between the emissions on the one hand and the plant’s operational conditions on the other hand. This work fulfils the need for decent emission data by providing long-term, online emission data from a covered wastewater treatment plant that resulted in the most precise and accurate emission estimate from a full-scale plant to date. Given the importance of reliable data, particular attention is paid to sampling techniques (dissolved methane) and sampling strategies (nitrous oxide).

Identifying rice varieties for mitigating methane and nitrous oxide emissions under intermittent irrigation

A three-year experiment of annual methane and nitrous oxide emissions from the subtropical permanently flooded rice paddy fields of China: Emission factor, temperature sensitivity and fertilizer nitrogen effect

Based on the rice-vegetable crop rotation model, in-situ measurements of nitrous oxide (N2O) and methane (CH4) emissions were conducted in double-cropping rice fields in Hainan to determine the impact of coconut chaff biochar on greenhouse gas emissions. The experiment involved four treatments:conventional farming fertilization (CON), nitrogen fertilizer combined with 20 t ·hm-2 biochar (B1), nitrogen fertilizer combined with 40 t ·hm-2 biochar (B2), and no nitrogen fertilizer, as the control (CK). The N2O and CH4 emissions were measured using static chamber-gas chromatography during the two paddy seasons, and the global warming potential (GWP) and greenhouse gas intensity (GHGI) were also estimated. The results show that N2O emission dynamics during the early rice season are closely related to the mineral nitrogen content of the soil. The N2O is emitted at the rice seedling and tillering stages after fertilization. The cumulative N2O emission during the early rice season was 0.18-0.76 kg ·hm-2. Compared with the CON treatment, the biochar treatments reduced N2O by 18%-43%, and the B2 treatment resulted in a significant reduction. The addition of biochar may promote the reduction of N2O at the early rice seedling stage and increase N2O emissions by improving the soil NO3--N content at the early rice tillering stage. During the late rice season, N2O is emitted during the heading and maturity stages, and the cumulative N2O emission was 0.17-0.34 kg ·hm-2. The B1 treatment reduced emissions by 37%, and B2 increased emission by only 3%, which is not a significant difference. The peak of CH4 emissions from rice fields appeared in the late phase of the early rice season and prophase of the late rice season. The cumulative emission of CH4 in the early rice season was 3.11-14.87 kg ·hm-2. Compared with CON, the CK treatment increased emission by 39%. The biochar treatment may increase soil aeration and limit the ability of CH4 production in the early rice season, as B1 and B2 treatments reduced CH4 emissions by 28% and 71%. The cumulative CH4 emission in late rice season was 53.1-146.3 kg ·hm-2, and the emission dynamics were significantly positively correlated with NH4+-N content. CK and B1 treatments increased CH4 emissions by 52% and 99%, respectively compared with CON, and the B2 treatment significantly increased CH4 emissions by 176%. Compared with CON, the B1 and B2 treatments increased the yield by 12.0% and 14.3% when applied in the early rice season and by 7.6% and 0.4% when applied in the late rice season, respectively. Due to the increased methane emissions in the late rice season, biochar amendment increased the GWP of the double-cropping rice field, in which the high amount of biochar reached a significant level; different amounts of biochar had no significant effect on the GHGI of the double-cropping rice field. Thus, the application of coconut chaff biochar for the reduction of greenhouse gas emission, from rice fields in hot areas, requires further research.

To understand methane (CH4) and nitrous oxide (N2O) emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years (from late 2002 to early 2005) in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a, non-rice season (PF), a rice-wheat rotation system (RW) and a rice-rapeseed rotation system (RR) in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3+/-52.1 and 215.0+/-45.4 kg CH4 hm(-2) during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5+/-0.6 kg N2O hm(-2) yr(-1). The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential (GWP). Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period (ca. 58%, P >RR approximate to RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.