Greenhouse Gases and Ammonia Emissions from Organic Mixed Crop-Dairy Systems: A Critical Review of Mitigation Options

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.

All material supplied via Jukuri is protected by copyright and other intellectual property rights. Duplication or sale, in electronic or print form, of any part of the repository collections is prohibited. Making electronic or print copies of the material is permitted only for your own personal use or for educational purposes. For other purposes, this article may be used in accordance with the publisher's terms. There may be differences between this version and the publisher's version. You are advised to cite the publisher's version. This is an electronic reprint of the original article. This reprint may differ from the original in pagination and typographic detail.

Management of livestock manure may recycle nutrients and decrease greenhouse gas (GHG) and ammonia (NH3) emissions. The objectives were to ascertain effects of environmental conditions and turning on methane (CH4), nitrous oxide (N2O), and NH3 emissions and if treatment with 8.5 g of dicyandiamide (DCD), a denitrification agent, altered GHG emissions. Manure and bedding were collected from feedlot pens and used to construct 3 piles (~1.9 m3 volume) each in winter (WI) and spring (SP). WI piles were turned once, and SP piles were turned twice. Methane, N2O, and NH3 emissions were collected. Methane and N2O flux measurements were collected from SP piles using a static chamber (3.7m L x 2.2m W x 0.9m H). Initial dry matter and nitrogen contents were 33.2 and 30.0% and 20.1 and 17.7 g/kg in WI and SP piles, respectively. Average ambient temperatures and wind speeds were 0.3oC and 10.7oC and 1.76 m/s and 1.97 m/s during WI and SP, respectively. Internal temperatures reached 51±3.9oC on d 4–11 and gradually decreased. Normalized CH4 averaged 2.19 mg٠s٠m-4 and N2O emissions averaged 0.84 mg٠s٠m-4, and were not different between the WI and SP piles. Turning did not affect CH4 emissions from WI piles, but were 55% greater (P < 0.05) when SP piles were turned a second time. Emissions of N2O increased 51% when WI and SP piles were turned (P < 0.05). Ammonia emissions were 83.5% greater from WI piles due to their higher initial concentrations of NH4+-N (2.21 vs. 1.11 g/kg; P < 0.05). Turning did not influence CH4 and N2O fluxes. Addition of DCD at pile formation appears to decrease N2O emissions and fluxes 3 and 10 d later. Turning management and season impacted overall CH4, N2O, and NH3 emissions. Fine-tuning manure handling and management during different seasons may effectively reduce GHG and NH3 emissions.

Liquid manure storages are an important source of greenhouse gases (GHG) on dairy farms. Methane (CH4) and nitrous oxide (N2O) are the predominant GHGs, while ammonia (NH3) is an indirect source of N2O. Addition of acid to manure has shown promising emission reductions, however, cost of acidification may be unfeasible for farmers. Fully cleaning storages has also shown to reduce CH4, due to removal of inoculating effects of residual manure (“inoculum”) on fresh manure (FM). However, complete removal of inoculum is practically impossible on large farms, thus acidifying only the inoculum may reduce GHGs without requiring acidification of all FM. This study aimed to quantify the effect of acidified inoculum on CH4, N2O and NH3 emissions from stored manure and quantify the changes in methanogen abundance and activity. Emissions were measured from six 10.6 m3 storages filled with 20% inoculum (1-yr-old manure) and 80% FM. Inoculum was treated in three ways: untreated (control); previously acidified (1-yr prior); and newly acidified with 70% H2SO4 (1.1 L m-3 manure). The CH4 and N2O emissions were continuously measured from June – November using tunable diode trace gas analyzers coupled with venturi air flow systems. The NH3 emissions were measured at 24-h intervals 3 × weekly using acid traps. The activity and abundance of methanogens were quantified by targeting the Methyl Coenzyme M Reductase A (mcrA) gene and transcript which encodes a subunit of the key enzyme that catalyzes the final step of methanogenesis. Bacterial abundance was quantified by targeting the bacterial 16S rRNA gene. Quantifications were performed using quantitative real-time PCR. CH4 emissions were reduced by 77% using newly acidified inoculum and 38% using previously acidified inoculum, compared to the control with untreated inoculum (36.1 g CH4 m-2). Significant treatment reductions in mcrA gene and transcript abundance suggest that CH4 reductions were caused by disruption of methanogen activity. NH3 and N2O emissions were reduced by 33% and 73% using acidified inoculum and 23% and 50% using previously acidified inoculum, respectively, compared to the control. Results suggest that lower acid rates and acidifying less frequently may still have good treatment effects while minimizing cost.

The objective of this study was to determine the effect of diet CP levels on nitrous oxide (N2O), ammonia (NH3), and methane (CH4) emissions from 1) cattle housed in confined settings and 2) cattle manure following surface application to incubated soils. Twelve 500-kg Holstein steers were fed diets containing 10% CP (10CP) and 13% CP (13CP). The experimental design was a 2 × 2 Latin square conducted during two 20-d periods. Diets were fed for 14 d before each measurement period to allow for diet acclimation. Steers were housed in environmentally controlled rooms allowing for continuous emission measures of N2O, NH3, and CH4. At the end of the second period, manure was collected and surface applied to incubated soils to verify potential NH3 and N2O emissions. To assess emissions from incubated soils, 2 experiments were set up with 3 replicates each: Exp. 1, in which soil fertilization was based on manure mass (496 g of manure), and Exp. 2, in which soil fertilization was based on manure N content (targeted at 170 kg N/ha). Manure emissions were monitored for 7 d. Steers fed 13CP diets had increased daily NH3 emissions when compared to steers fed 10CP diets (32.36 vs. 11.82 ± 1.10 g NH3/d, respectively; P < 0.01). Daily N2O emissions from steers fed 13CP and 10CP diets were significantly different only during Period 1 (0.82 vs. 0.31 ± 0.24 g N2O/d; P = 0.04). Steers fed the 10CP diet had greater N2O emissions per unit of N consumed than steers fed the 13CP diet (9.73 vs. 4.26 ± 1.71 mg N2O/g N intake; P = 0.01). Diet CP levels did not affect enteric CH4 production from steers. In terms of soil emissions, different CP levels did not affect NH3, N2O, or CH4 emissions when soil fertilization was based on manure mass. However, NH3 emissions were reduced when manure from steers fed the 10CP diet was applied to soil based on N content. Ammonia emissions decreased during the 7-d incubation period. Conversely, N2O emissions increased over the period. Our results indicated that management of diet CP levels of confined finishing steers mitigates NH3 emissions from steers but does not affect enteric CH4. In addition, results suggested that soil characteristics might be as important as manure N content to generate NH3 and greenhouse gases from soils receiving manure fertilization.

Manure treatment such as anaerobic digestion and solid-liquid separation has shown a potential to abate greenhouse gas (GHG) emissions, but few studies have considered GHG emissions from both storage and field application regarding crop yield. In this study, four different organic fertilizers were studied: untreated cattle manure (CA); digestate of cattle manure anaerobically co-digested with grass-clover (DD); a liquid fraction from the separation of DD (LF); and a liquid fraction derived from a biogas desulfurization biofilter enriched with sulfur and ammonium (NS). The CH4, N2O and NH3 emissions during storage of CA, DD and LF between August and November 2020 (11 weeks) were quantified. Storage continued until April 2021 when these materials, as well as the NS fertilizer and a mineral NKS fertilizer, were applied at a rate of 100 kg total N ha−1 to spring barley. N2O emissions and soil mineral N content were monitored during the growing season. Overall, CH4 emissions during storage were the main source of GHG emissions independent of treatments, accounting for 85 %, 40 % and 11 % of total GHG emissions (based on field application of 100 kg ha−1 total N) from treatments CA, DD and LF, respectively. Anaerobic digestion and separation significantly reduced CH4 emissions during storage due to the diminished content of degradable organic matter available for methanogens. The N2O emissions from treatments CA, DD, and LF during storage were not significantly different. Treatments DD and LF emitted more NH3 than CA during storage, presumably because of higher pH and ammonium content. In the field experiment, the dilute solution of NS emitted the most N2O, while emissions from treatments CA, DD and LF were comparable. Yield-scaled GHG emissions for treatments CA, DD, LF and NS during both periods of storage and field were 44.4, 17.1, 8.5 and 24.3 kg CO2 eq hkg−1 grain yield, respectively. Anaerobic digestion with or without separation were thus effective strategies for the mitigation of GHG emissions from cattle manure in this study. Yields and nitrogen use efficiencies of the processed manure materials were not significantly different from those observed with the same N application rate as inorganic fertilizer, and hence anaerobic digestion with or without separation were promising GHG mitigation strategies.

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

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.

Application of N fertilizers and special land management practices during agricultural production could have significant implication in influencing the air quality. In this study, field experiments were established at different research sites in Louisiana to evaluate the emission of ammonia (NH3), greenhouse gases (GHG), and fine particulates from sugarcane cultivation and harvesting. Specifically, this study was planned to (i) evaluate the effect of different N sources (urea and urea ammonium nitrate) and residue management schemes (residue burned, RB; and residue retained, RR) on NH3 and GHG emissions, (ii) characterize the chemical and morphological characteristics of fine particles generated during sugarcane harvesting operations (regular harvesting, RH; ground burn, GB; standing burn, SB; and combine harvesting, CH), and (iii) evaluate the micrometeorological study of NH3 flux above sugarcane crop canopy. Ammonia (NH3) and greenhouse gas samples were collected through active and passive chamber methods, respectively, following N application in the field. Then those NH3 and GHG samples were analyzed using ion chromatography (IC) and gas chromatography, respectively. Organic/elemental carbon, water soluble species, elemental species, and morphological features were determined using thermal carbon analyzer, ion chromatography, inductively-coupled plasma-optical emission spectroscopy, and scanning electron microscopy, respectively. Volatile organic carbon and polycyclic aromatic hydrocarbons were analyzed using gas chromatography-mass spectroscopy. Bi-directional NH3 emission was obtained from two installed denuders (at 10 ft and 18 ft) equipped with meteorological tower in the sugarcane field and the captured NH3 was analyzed in IC. Field experiments showed that urea treatment produced almost 2.8 times and 1.6 times higher NH3 and N2O, respectively, as compared to UAN plots. However, N had little effect on CH4 and N2O emissions. Overall, majority of total NH3 and N2O emission was observed within 3-4 weeks after N application in the field. On the other hand, residue retained treatment resulted significantly higher NH3, N2O, and CH4 emissions as compared to RB treatments over the years. Ammonia and N2O emissions were highly correlated with water filled pore space (%), but higher correlation was found in 2012 due to higher rainfall received within 3 weeks of N application. Particulates released during different sugarcane harvesting operations showed that carbonaceous compounds contributed about 30-70% of the total particle mass. Ammonia was the major cation found in the burning particulates (GB and SB) and showed high correlation with SO42- ions. Overall, organic carbon, major ionic species, elemental species were significantly higher in GB particles than SB particles. Low molecular

Responses of CH4, N2O, and NH3 emissions to different slurry pH values of 5.5–10.0: Characteristics and mechanisms

Greenhouse gas and ammonia emissions and mitigation options from livestock production in peri-urban agriculture: Beijing – A case study

The dependence of oil production in the Gulf Cooperation Council (GCC) region may have environmental consequences. This research explores the nonlinear effects of oil rents and the economic growth of six GCC countries on their per capita CO2, CH4, N2O, and Greenhouse Gas (GHG) emissions, considering spatial linkages through 1980–2014. We apply fixed effects (FE) and corroborate the spatial dependency in all estimated pollution models. Spatial Durbin model (SDM) is utilized to estimate the direct and spillover effects. We find the inverted U-shaped relationship of economic growth with CO2, CH4, N2O and GHG emissions, and of oil rents with CH4 and GHG emissions. Monotonic positive effects of oil rents on CO2 emissions and U-shaped relationship between oil rents and N2O emissions are also found. Urbanization has positive effect on the CO2, CH4 and GHG emissions and has negative effect on N2O emissions. Financial market development (FMD) has negative effects on all types of investigated emissions. Foreign direct investment (FDI) has negative effects on CO2 and N2O emissions. Energy use has positive effects on CO2 and N2O emissions. Further, the neighboring spillover effects of economic growth, oil rents, urbanization, FDI, energy use and FMD are found statistically significant for some investigated emissions. Hence, oil rents, energy use, urbanization and economic growth are responsible for environmental degradation of home and neighboring countries in the GCC region, and we recommend implementing tighter laws to protect the environment.

Methane, nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment

Ammonia (NH3) and greenhouse gas (GHG) emissions are substantial contributors to C and N loss in composting. Lignite can increase N retention by absorbing N H 4 + and NH3. However, the effects of co-composting on NH3 and GHG emissions in view of closing nutrient cycle are still poorly investigated. In the study, poultry litter was composted without (CK) or with lignite (T1) or dewatered lignite (T2), and their respective composts N H 4 + Com_CK, Com_T1, and Com_T2) were tested in a soil incubation to assess NH3 and GHG emission during composting and following soil utilization. The cumulative NH3 flux in T1 and T2 were reduced by 39.3% and 50.2%, while N2O emissions were increased by 7.5 and 15.6 times, relative to CK. The total GHG emission in T2 was reduced by 16.8% compared to CK. Lignite addition significantly increased nitrification and denitrification as evidenced by the increased abundances of amoA, amoB, nirK, and nirS. The increased reduction on NH3 emission by dewatered lignite could be attributed to reduced pH and enhanced cation exchangeable capacity than lignite. The increased N2O was related to enhanced nitrification and denitrification. In the soil incubation experiment, compost addition reduced NH3 emission by 72%∼83% while increased emissions of CO2 and N2O by 306%∼740% and 208%∼454%, compared with urea. Com_T2 strongly reduced NH3 and GHG emissions after soil amendment compared to Com_CK. Overall, dewatered lignite, as an effective additive, exhibits great potential to simultaneously mitigate NH3 and GHG secondary pollution during composting and subsequent utilization of manure composts.

There is hot debate about whether grassland-based livestock production can be climate-smart or not. Greenhouse gas (GHG) emissions from livestock (primarily from enteric methane [CH4] and manure CH4 and nitrous oxide [N2O]) stand vis-&amp;#224;-vis vegetation CO2 uptake and soil carbon sequestration. In sub-Saharan Africa (SSA), livestock are a precious good that ensures the livelihoods of millions of people, which often belong to marginalized groups such as pastoralists. To protect their animals from predation and theft, livestock are secured in overnight enclosures (&amp;#8220;bomas&amp;#8221; in Kiswahili), which form the center of many pastoral settlements. However, in these enclosures manure accumulates for months or even years, making them a potential hotspot for GHG emissions. Here, we present the first year-long measurements of GHG emissions from active and inactive (abandoned) bomas from an African rangeland at the ILRI Kapiti Research Station in Kenya.We found that active bomas were continuous sources for CO2, CH4 and N2O emissions, with flux peaks of up to 1940 mg&amp;#160;CO2-C&amp;#160;m&amp;#8209;2&amp;#160;h&amp;#8209;1, 1600 &amp;#956;g&amp;#160;N2O-N&amp;#160;m&amp;#8209;2&amp;#160;h&amp;#8209;1 , and 6690 &amp;#956;g&amp;#160;CH4-C&amp;#160;m&amp;#8209;2&amp;#160;h&amp;#8209;1. Even after their abandonment, fluxes from bomas continued to be elevated compared to savanna soil background emissions for all GHGs. When calculated over a full year and put in context with manure deposition rates into the bomas (GHG emission factors), we found that 12.6 &amp;#177; 5.3 % manure-C was emitted as CO2, 2.4 &amp;#177; 0.4 % manure-N was emitted as N2O, and 0.5 &amp;#177; 0.1 % manure-C was emitted as CH4. GHG emissions from active bomas were not affected by rainfall seasonality or temperature, presumably because the moisture content of the fresh manure was always high due to urine input, and because temperature did not vary much during the year. In abandoned bomas, GHG emissions were driven by rainfall events that triggered emission pulses, leading to higher emissions during the wet season.The high N2O and CH4 emissions we found have implications for global GHG inventories, which currently do not have a category for overnight livestock enclosures and therefore do not account for these emissions. Furthermore, hotspots for GHG emissions such as these livestock enclosures need to be included to assess the full GHG budget of pastoral livestock systems and to develop management interventions for low-emission livestock production in developing countries.