Greenhouse gas emissions from green waste composting windrow

A review on the main affecting factors of greenhouse gases emission in constructed wetlands

This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.

Abstract. This paper summarizes currently available data on greenhouse gas (GHG) emissions from African natural ecosystems and agricultural lands. The available data are used to synthesize current understanding of the drivers of change in GHG emissions, outline the knowledge gaps, and suggest future directions and strategies for GHG emission research. GHG emission data were collected from 75 studies conducted in 22 countries (n = 244) in sub-Saharan Africa (SSA). Carbon dioxide (CO2) emissions were by far the largest contributor to GHG emissions and global warming potential (GWP) in SSA natural terrestrial systems. CO2 emissions ranged from 3.3 to 57.0 Mg CO2 ha−1 yr−1, methane (CH4) emissions ranged from −4.8 to 3.5 kg ha−1 yr−1 (−0.16 to 0.12 Mg CO2 equivalent (eq.) ha−1 yr−1), and nitrous oxide (N2O) emissions ranged from −0.1 to 13.7 kg ha−1 yr−1 (−0.03 to 4.1 Mg CO2 eq. ha−1 yr−1). Soil physical and chemical properties, rewetting, vegetation type, forest management, and land-use changes were all found to be important factors affecting soil GHG emissions from natural terrestrial systems. In aquatic systems, CO2 was the largest contributor to total GHG emissions, ranging from 5.7 to 232.0 Mg CO2 ha−1 yr−1, followed by −26.3 to 2741.9 kg CH4 ha−1 yr−1 (−0.89 to 93.2 Mg CO2 eq. ha−1 yr−1) and 0.2 to 3.5 kg N2O ha−1 yr−1 (0.06 to 1.0 Mg CO2 eq. ha−1 yr−1). Rates of all GHG emissions from aquatic systems were affected by type, location, hydrological characteristics, and water quality. In croplands, soil GHG emissions were also dominated by CO2, ranging from 1.7 to 141.2 Mg CO2 ha−1 yr−1, with −1.3 to 66.7 kg CH4 ha−1 yr−1 (−0.04 to 2.3 Mg CO2 eq. ha−1 yr−1) and 0.05 to 112.0 kg N2O ha−1 yr−1 (0.015 to 33.4 Mg CO2 eq. ha−1 yr−1). N2O emission factors (EFs) ranged from 0.01 to 4.1 %. Incorporation of crop residues or manure with inorganic fertilizers invariably resulted in significant changes in GHG emissions, but results were inconsistent as the magnitude and direction of changes were differed by gas. Soil GHG emissions from vegetable gardens ranged from 73.3 to 132.0 Mg CO2 ha−1 yr−1 and 53.4 to 177.6 kg N2O ha−1 yr−1 (15.9 to 52.9 Mg CO2 eq. ha−1 yr−1) and N2O EFs ranged from 3 to 4 %. Soil CO2 and N2O emissions from agroforestry were 38.6 Mg CO2 ha−1 yr−1 and 0.2 to 26.7 kg N2O ha−1 yr−1 (0.06 to 8.0 Mg CO2 eq. ha−1 yr−1), respectively. Improving fallow with nitrogen (N)-fixing trees led to increased CO2 and N2O emissions compared to conventional croplands. The type and quality of plant residue in the fallow is an important control on how CO2 and N2O emissions are affected. Throughout agricultural lands, N2O emissions slowly increased with N inputs below 150 kg N ha−1 yr−1 and increased exponentially with N application rates up to 300 kg N ha−1 yr−1. The lowest yield-scaled N2O emissions were reported with N application rates ranging between 100 and 150 kg N ha−1. Overall, total CO2 eq. emissions from SSA natural ecosystems and agricultural lands were 56.9 ± 12.7 × 109 Mg CO2 eq. yr−1 with natural ecosystems and agricultural lands contributing 76.3 and 23.7 %, respectively. Additional GHG emission measurements are urgently required to reduce uncertainty on annual GHG emissions from the different land uses and identify major control factors and mitigation options for low-emission development. A common strategy for addressing this data gap may include identifying priorities for data acquisition, utilizing appropriate technologies, and involving international networks and collaboration.

دراینمقاله،میزانو ارزش انتشارگازهایگلخانه‌ای اکسید‌نیتروس(N2O) و دی‌اکسید‌کربن(CO2)حاصلازتولید حبوبات منتخب ایران (شامل نخود، لوبیا و عدس) با استفاده از مدل GHGE،برایسالزراعی91-90برآورد شده است.نتایج نشان‌داد که استان‌هایفارسوبوشهر، به‌ترتیبباتولیدسالانه271/79 و 004/0 تنN2O، بیشترینوکمترینمیزانتولیدگاز گلخانه‌ایN2Oرا دارامی‌باشند. همچنین استان‌هایلرستانوبوشهر نیز به‌ترتیب باتولیدسالانه83/10327 و33/1‌تنCO2،بیشترینوکمترینمیزانتولیدگاز گلخانه‌ایCO2را به‌خود اختصاص داده‌اند. مجموعهزینه‌هایزیست‌محیطی انتشار گازهای گلخانه‌ای N2O و CO2 کلکشورنیزحدود705/32‌میلیاردریالبرآوردگردید. باتوجهبه یافته‌ها، مدیریت کودهای نیتروژنه مصرفی در مزارعوتوسعهسیاست‌کاهشمیزانانتشاربه‌همراه مالیات زیست‌محیطی انتشار گازهای گلخانه‌ای بر سطوح مختلف تولید پیشنهاد شده ‌است. واژه‌های کلیدی: اکسید‌نیتروس، دی‌اکسید‌کربن، حبوبات، گازهای گلخانه‌ای

Agricultural greenhouse gas (GHG) emissions contribute approximately 12% to total global anthropogenic GHG emissions. Cereals (rice, wheat, and maize) are the largest source of human calories, and it is estimated that world cereal production must increase by 1.3% annually to 2025 to meet growing demand. Sustainable intensification of cereal production systems will require maintaining high yields while reducing environmental costs. We conducted a meta‐analysis (57 published studies consisting of 62 study sites and 328 observations) to test the hypothesis that the global warming potential (GWP) of CH4 and N2O emissions from rice, wheat, and maize, when expressed per ton of grain (yield‐scaled GWP), is similar, and that the lowest value for each cereal is achieved at near optimal yields. Results show that the GWP of CH4 and N2O emissions from rice (3757 kg CO2 eq ha−1 season−1) was higher than wheat (662 kg CO2 eq ha−1 season−1) and maize (1399 kg CO2 eq ha−1 season−1). The yield‐scaled GWP of rice was about four times higher (657 kg CO2 eq Mg−1) than wheat (166 kg CO2 eq Mg−1) and maize (185 kg CO2 eq Mg−1). Across cereals, the lowest yield‐scaled GWP values were achieved at 92% of maximal yield and were about twice as high for rice (279 kg CO2 eq Mg−1) than wheat (102 kg CO2 eq Mg−1) or maize (140 kg CO2 eq Mg−1), suggesting greater mitigation opportunities for rice systems. In rice, wheat and maize, 0.68%, 1.21%, and 1.06% of N applied was emitted as N2O, respectively. In rice systems, there was no correlation between CH4 emissions and N rate. In addition, when evaluating issues related to food security and environmental sustainability, other factors including cultural significance, the provisioning of ecosystem services, and human health and well‐being must also be considered.

Studies on the sustainability of crop production systems should consider both the carbon (C) footprint and the crop yield. Knowledge is urgently needed to estimate the C cost of maize (Zea mays L.) production in a continuous monoculture or in rotation with a leguminous crop, the popular rotation system in North America. In this study, we used a 19-year field experiment with maize under different levels of synthetic N treatments in a continuous culture or rotation with forage legume (Alfalfa or red clover; Medicago sativa L./Trifolium pratense L.) or soybean (Glycine max L. Merr) to assess the sustainability of maize production systems by estimating total greenhouse gas (GHG) emissions (kg CO2 eq ha−1) and the equivalent C cost of yield or C footprint (kg CO2 eq kg−1 grain). High N application increased both total GHG emissions and the C footprint across all the rotation systems. Compared to continuous maize monoculture (MM), maize following forage (alfalfa or red clover; FM) or grain (soybean; SM) legumes was estimated to generate greater total GHG emissions, however both FM and SM had a lower C footprint across all N levels due to increased productivity. When compared to MM treated with 100 kg N ha−1, maize treated with 100 kg N ha−1, following a forage legume resulted in a 5 % increase in total GHG emissions while reducing the C footprint by 17 %. Similarly, in 18 out of the 19-year period, maize treated with 100 kg N ha−1, following soybean (SM) had a minimal effect on total GHG emissions (1 %), but reduced the C footprint by 8 %. Compared to the conventional MM with the 200 kg N ha−1 treatment, FM with the 100 kg N ha−1 treatment had 40 % lower total GHG emissions and 46 % lower C footprint. Maize with 100 kg N ha−1 following soybean had a 42 % lower total GHG emissions and 41 % lower C footprint than MM treated with 200 kg N ha−1. Clearly, there was a trade-off among total GHG emissions, C footprint and yield, and yield and GHG emissions or C footprint not linearly related. Our data indicate that maize production with 100 kg N ha−1 in rotation with forage or grain legumes can maintain high productivity while reducing GHG emissions and the C footprint when compared to a continuous maize cropping system with 200 kg N ha−1.

Aims: To evaluate GHG emissions from two common manure management practices in Cameroon; windrow composting and Open-air dumping with and without the addition of wood shavings. Study design: The research employed a controlled experimental design with a comparative approach. Place and Duration of Study: Waste-to-resource project site and project laboratory of the Department of Environmental Science of the University of Buea, Cameroon between February and March 2023. Methodology: Fresh pig manure was treated in four configurations: 100% manure subjected to windrow composting, 100% manure subjected to open-air dumping, 90:10% manure: wood shavings subjected to windrow composting, and 90: 10% manure: wood shavings subjected to open-air dumping. Gas samples were collected every next morning at 10:00 AM over a period of 40 days using the static flux chamber method, and analyzed for CH₄, N₂O, and CO₂ emissions using gas chromatography. Results: Results showed that adding wood shavings significantly reduced CH₄ and N₂O emissions across both composting and open-air dumping systems. CH₄ emissions were highest in stockpiled 100% manure (2.152 ± 1.741 mg CH₄ m² min⁻¹) and lowest in composted manure with wood shavings (0.085 ± 0.179 mg CH₄ m² min⁻¹). N₂O emissions followed a similar trend, with the highest emissions (131.3 ± 90.4 mg N₂O m² min⁻¹) recorded in stockpiled 100% manure, compared to the lowest (35.25 ± 43.50 mg N₂O m² min⁻¹) in stockpiled manure with wood shavings. CO₂ emissions were higher in treatments with wood shavings, particularly in composting (159.2 ± 70.8 mg CO₂ m² min⁻¹). Further statistical analyses confirmed significant differences in GHG emissions among the different treatments, with windrow composting consistently outperforming Open-air dumping in reducing CH₄ and N₂O emissions. Conclusion: The study concluded that wood shavings addition and windrow composting practices significantly reduced GHG emissions from pig manure management in tropical settings.

Carbon footprint of different agricultural systems in China estimated by different evaluation metrics

In Northern China, vegetables are usually grown in solar greenhouses using intensive fertilization and cultivation, which produces significant greenhouse gas (GHG) emissions to the atmosphere. In this study, the nitrous oxide (N2O) emissions from 12 solar greenhouses with different fertilization practices (without manure application (SG); with chicken (SG‐CM) or swine (SG‐SM) manure application) were measured in the southern Loess Plateau of China during the summer fallow (35–61 days) in 2013 and 2014. The daily N2O fluxes varied over the ranges of 0.002–0.041, 0.014–12.58, and 0.005–8.41 mg N m−2 h−1 with averages of 0.037, 0.81, and 1.70 mg N m−2 h−1 in the SG, SG‐CM, and SG‐SM greenhouses, respectively, and the total N2O emissions were 1.17, 12.0, and 16.0 kg N ha−1, respectively. Significantly high peak N2O emissions were observed at the beginning of the summer fallow and after manure application, accounting for more than 80% of the total N2O emissions. The management practices of polythene removal, greenhouse enclosure for a week, and tillage also significantly increased the N2O daily fluxes and total emissions. Linear regression analyses showed that soil moisture and manure application were the main factors controlling the N2O emissions during summer fallow, followed by the residual mineral N in the soil. The results indicated that solar greenhouses cause high N2O emissions during summer fallow and farmers should use appropriate measures to mitigate these emissions. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

انتشار گازهای گلخانه‌ای و اثرات آن بر گرمایش جهانی یکی از چالش‌های جدی کشورهای توسعه‌یافته و درحال‌توسعه محسوب می‌شود. بر اساس پیمان کیوتو، کشورهای مختلف موظف به محاسبه و اعلام میزان انتشار گازهای گلخانه‌ای شدند. بررسی میزان انتشار گازهای گلخانه‌ای کشورهای مختلف این امکان را فراهم می‌آورد تا ضمن ارائه تصویری از سهم کشورها در تولید گازهای گلخانه‌ای، جایگاه ایران نیز در این مجموعه مشخص شود. این مقاله تلاش دارد تا میزان و ارزش انتشار گازهای گلخانه‌ای اکسید نیتروس (N2O) و دی‌اکسید کربن (CO2) حاصل از دانه های روغنی تولیدی منتخب در ایران (سویا، کلزا، ذرت دانه ای و سایر دانه های روغنی) را با استفاده از مدل GHGE، برای سال زراعی 91-90 برآورد نماید. نتایج نشان داد استان‌های خوزستان و زنجان به ترتیب، با تولید سالانه 49/341 و 004/0 تن، بیش ترین و کم ترین میزان تولید گاز گلخانه‌ای N2O را در سطح کشور دارا می‌باشند. همچنین استان‌های گلستان و هرمزگان نیز به ترتیب، با تولید سالانه 47/7841 و 24/0 تن دی‌اکسید کربن بیش ترین و کم ترین میزان تولید گاز گلخانه‌ای CO2 را به خود اختصاص داده‌اند. مجموع هزینه‌های انتشار گازهای گلخانه‌ای N2O و CO2 کل کشور نیز حدود 331/27 میلیارد ریال برآورد گردید. باتوجه به یافته ها، اصلاح و تغییر شیوه‌های مدیریتی کشاورزی نسبت به سطح زیرکشت محصولات زراعی، مدیریت و افزایش کارایی کودهای ازته مصرفی در مزارع و توسعه سیاست‌های کاهش میزان انتشار به‌همراه مالیات زیست-محیطی انتشار گازهای گلخانه ای به سیاست‌گذاران این عرصه پیشنهاد شد.

Carbon footprint of a winter wheat-summer maize cropping system under straw and plastic film mulching in the Loess Plateau of China

Mitigation of ammonia, nitrous oxide and methane emissions during solid waste composting with different additives: A meta-analysis

In order to explore the characteristics of N2O emissions from winter wheat fields in the Loess Plateau under different farming methods and nitrogen levels, the dynamic changes in N2O emissions from rain-fed winter wheat fields were quantified using static box-gas chromatography. Winter wheat 'Xiaoyan22' was used as the material, and a two-factor split area design was adopted. The conventional tillage (CT), straw incorporated into soil (SM), and flat film mulching (FM) were assigned as the main plot, and three nitrogen fertilizer rates (no nitrogen fertilization, 20% nitrogen reduction (144 kg·hm-2), and conventional nitrogen application (180 kg·hm-2)) were assigned as a split plot. Taking CT as a control, the effects of FM and SM on soil N2O emissions under different nitrogen rates were assessed. Furthermore, the correlation between relevant environmental factors and N2O emission flux were analyzed, and N2 emissions were estimated using empirical formulas. The results showed the following:the N2O emissions from the soil of each nitrogen treatment occurred within 20 days, and N2O emission flux peaked within two weeks post-fertilization. The average N2O flux, the total N2O emissions, and the global warming potential of N2O were 1.92-22.75 μg·(m2·h)-1, 0.10-0.46 kg·hm-2, and 26.72-122.15 kg·hm-2, respectively. The N2O emission coefficient of fertilizer nitrogen was 0.05%-0.28%. The total N2 emissions ranged from 0.70-1.82 kg·hm-2. The N fertilization and film mulching significantly increased the N2O emission flux (P<0.05) and the cumulative N2O emissions (P<0.05); however, SM marginally reduced the total N2O emissions. The N2O emission coefficient and global warming potential of fertilizer nitrogen under FM were significantly higher than those under CT and SM (P<0.05). The N2O emissions without nitrogen treatment were only significantly positively correlated with soil water-filled pore spaces (WFPS) (P<0.05); the N2O emissions in the N fertilization condition were significantly positively correlated with WFPS, ω(NO3--N), ω(NH4+-N), and 0-5 cm soil layer temperature (P<0.05). Overall, under the condition of no fertilization, water was the main factor to control the nitrogen transformation and soil N2O emission; nevertheless, under the N fertilization condition, both nitrification and denitrification contributed to the N2O emissions in the rain-fed winter wheat fields. Film mulching practice and nitrogen application markedly increased the N2O emissions, fertilizer nitrogen emission coefficient, and global warming potential in the rain-fed winter wheat fields. Nonetheless, straw incorporated into the soil resulted in a marginal reduction in N2O emissions.

Sheepfolds represent significant hot spot sources of greenhouse gases (GHG) in semi-arid grassland regions, such as Inner Mongolia in China. However, the annual contribution of sheepfolds to regional GHG emissions is still unknown. In order to quantify its annual contribution, we conducted measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes at two sheepfold sites in the Baiyinxile administrative region of Inner Mongolia for 1 year, using static opaque chamber and gas chromatography methods. Our data show that, at an annual scale, both sheepfolds functioned as net sources of CO2, CH4 and N2O. Temperatures primarily determined the seasonal pattern of CO2 emission; 60–84% of the CO2 flux variation could be explained by temperature changes. High rates of net CH4 emissions from sheepfold soils were only observed when animals (sheep and goats) were present. While nitrous oxide emissions were also stimulated by the presence of animals, pulses of N2O emissions were also be related to rainfall and spring-thaw events. The total annual cumulative GHG emissions in CO2 equivalents (CO2: 1; CH4: 25; and N2O: 298) were quantified as 87.4 ± 18.4 t ha−1 for the sheepfold that was used during the non-grazing period (i.e., winter sheepfold) and 136.7 ± 15.9 t ha−1 used during the grazing period (i.e., summer sheepfold). Of the annual total GHG emissions, CH4 release accounted for approximately 1% of emissions, while CO2 and N2O emissions contributed to approximately 59% and 40%, respectively. The total GHG emission factor (CO2 + CH4 + N2O) per animal for the sheepfolds investigated in this study was 30.3 kg CO2 eq yr−1 head−1, which translates to 0.3, 18.8 and 11.2 kg CO2 eq yr−1 head−1 for CH4, CO2 and N2O, respectively. Sheepfolds accounted for approximately 34% of overall N2O emissions in the Baiyinxile administrative region, a typical steppe region within Inner Mongolia. The contribution of sheepfolds to the regional CO2 or CH4 exchange is marginal.

The influence of ozone pollution on CO2, CH4, and N2O emissions from a Chinese subtropical rice–wheat rotation system under free-air O3 exposure