CO2-eq Year Research Articles

Exploring compost production potential and its economic benefits and greenhouse gas mitigation in Addis Ababa, Ethiopia

The increasing amount of municipal organic waste (MOW) and human excreta (HE) has led to socio-economic and environmental challenges in the cities of developing countries. This study estimated MOW and HE, compost production potential from MOW and HE, and compost application potential for urban agriculture fertilization, economic benefits, soil carbon sequestration, and greenhouse gas (GHG) mitigation in Addis Ababa, Ethiopia, for the period 2025–2050. MOW was forecasted using the Holt-Winters forecasting model. HE was estimated using the daily average rate of HE generation. The compost production potential was estimated using the forecasted MOW and HE. Compost fertilization was determined by considering compost nitrogen (N), phosphorus (P), and potassium (K) and the fertilizer requirements of cereals and vegetables. The economic benefits of compost were determined by considering the price of compost-equivalent urea, NPS, and potassium chloride fertilizers. The mitigation of GHG emissions from compost application was estimated using the IPCC Tier 1 method. The forecasted quantities of MOW, HE, and compost for 2050 are 301, 462, and 343 Gg, respectively. The compost could supply 5 Gg of N and 2.2 Gg of P in 2050, sufficient to fertilize 14,129 ha of vegetable fields. The economic benefits of using compost as a substitute for synthetic fertilizers could reach 10 million USD in 2050. Compost production and application could offset the total GHG emissions of Addis Ababa by 13.1 % (10,241Gg CO2-eq year−1) in 2050. The application of compost generated from MOW and HE in Addis Ababa can substitute synthetic fertilizers, provide economic benefits, and mitigate GHG emissions.

Degassing of greenhouse gases from groundwater under different irrigation methods: A neglected carbon source in agriculture

The degassing potential of supersaturated dissolved greenhouse gases (N2O, CO2, and CH4) in groundwater has often been overlooked as a source of emissions in irrigated agriculture. Quantifying the degassing potential and investigating measures are essential for agricultural carbon mitigation. This study estimated for the first time the direct greenhouse gas degassing potential from groundwater under different irrigation methods and explored mitigation strategies in the Guanzhong Basin, Northwest China. The results revealed that while short-term degassing potential from groundwater irrigation exceeds that reported for global inland waters and fertilized soils, the interannual degassing potential (13,819–52,163 t CO2-eq year−1) represents only 0.3–1.1 % of annual emissions from regional agricultural soils. The degassing potential exhibited a trend of over-surface drip irrigation (ODI) > surface drip irrigation (DI) > subsurface drip irrigation (SDI) > flood irrigation (FI) under equivalent irrigation volumes. Notably, SDI emerges as a promising strategy for concurrent water conservation and greenhouse gas mitigation. Switching from over-surface and surface drip irrigation to subsurface drip irrigation yields a reduction of 60.8 % and 46.3 % in carbon emissions per cubic meter of water saved, respectively. This study provides valuable insights for the development of sustainable irrigation practices and emphasizes the importance of integrating groundwater degassing potential into agricultural carbon budgets and emission mitigation strategies.

Life cycle assessment of the production of an extruded dog food in Brazil

Sustainability is the current focus of the scientific community, governments, and companies in various market segments, such as pet food. Pet food production has increased rapidly in recent years, with a trend toward the development of environmentally friendly products and processes. The first step in creating strategies for mitigating environmental impacts is to assess key points in manufacturing processes. Given this, this study aimed to perform a life cycle assessment (LCA) to estimate the environmental impacts associated with the formulation, production, and distribution phases of an extruded dog food produced in Brazil. System boundaries were from cradle-to-gate, encompassing extraction of raw materials, transportation, processing, production, packaging, and distribution. Estimates were based on the amount of food required to meet the energy requirements for maintenance of a 10 kg dog (functional unit = 2.59 MJ day−1, reference flow = 177.3 g day−1). Environmental impacts were calculated by the environmental footprint method (EF 3.0 v. 1.00) using SimaPro software (v. 9.1.1.1). Product ingredients and packaging materials were modeled under Brazilian conditions using ecoinvent 3.7.1 and Agri-footprint 5.0 databases. Data regarding transportation, processing, distribution, electric and thermal power generation, water usage, and waste generation were obtained from the company's records (2019–2020). In this study, as expected, formulation was the most relevant factor, accounting for 70%–90% of the total environmental impacts. The main impact categories were terrestrial and marine eutrophication, acidification, particulate matter, and climate change (80% of total impacts). Production of the evaluated dog food was associated with the emission of 88.73 kg CO2 eq year−1 or 1.37 kg CO2 eq kg−1 distributed food. The use of animal meals (poultry by-product meal and meat and bone meal) and vegetable by-products (wheat bran and rice bran) contributed to reducing environmental impacts. Therefore, in this study, ingredient selection was considered the most important factor in mitigating the environmental impacts of pet foods. As the overall impact of the formulation depends on data on the use stage, such as nutrient excretion after consumption, future studies should adopt a cradle-to-grave approach for a better comprehension of the feasibility of applying animal and vegetable by-products in the eco-design of pet food products.

Elevated CO2 does not necessarily enhance greenhouse gas emissions from rice paddies

Elevated atmospheric carbon dioxide (eCO2) greatly impacts greenhouse gas (GHG) emissions of CH4 and N2O from rice fields. Although eCO2 generally stimulates GHG emissions in the short term (<5 years) experiments, the responses to long-term (≥10 years) eCO2 remain poorly known. Here we show, through a series of experiments and meta-analysis, that the eCO2 does not necessarily increase CH4 and N2O emissions from rice paddies. In an experiment of free-air CO2 enrichment for 13–15 years, CH4 and N2O emissions were decreased by 11–54% and 33–54%, respectively. The decline of CH4 emissions was related to the reduction of CH4 production and enhancement of CH4 oxidation via raising soil Eh and soil-water interface [O2] under eCO2. Moreover, the eCO2 significantly decreased NH4+-N content, suggesting a reduction of soil nitrification and thereby N2O emissions. A meta-analysis showed that CH4 and N2O emissions were stimulated under short-term eCO2 while reduced under long-term eCO2. The eCO2-induced increase in yield and biomass and the ratio of mcrA genes/pmoA genes declined with eCO2 duration, indicating an eCO2-stimulation of methanogenesis lower than that of methanotrophy over time by fewer increased substrates. Upscaling the results of meta-analysis, the eCO2-induced global paddy CH4 and N2O emissions shifted from an increase (+0.17 Pg CO2-eq year−1) in the short term into a decrease (−0.11 Pg CO2-eq year−1) in the long term. Our findings suggest that the effect of eCO2 on GHG emissions changes over time, and this should be considered in future climate change research.

Techno-economic evaluation of bioenergy production from anaerobic digestion of by-products from ethanol flex plants

Ethanol production implies in by-products generation, mainly vinasse and stillage, respectively generated from sugarcane and corn ethanol production in flex plants. Both by-products require efficient treatment routes to avoid environmental side-effects to support energy recovery. Accordingly, the aim of this study was to evaluate the techno-economic potential of bioenergy (electric and thermal energy) production from the anaerobic digestion (AD) of vinasse and stillage. Three scenarios were defined: (a) Scenario 1, AD of vinasse; (b) Scenario 2, AD of stillage; and (c) Scenario 3, AD of vinasse and stillage in an integrated process. From the results, the methane production was estimated at 3.8 × 106 m3 year−1 considering the AD of stillage and vinasse in Scenario 3. The electricity and thermal energy generation was estimated as 14.61 GWh year−1 and 1.37 × 105 GJ year−1, respectively. This energy would mitigate 1096.05 and 7659.27 ton CO2eq year−1 when replacing fossil fuel energy. The profitability analysis indicated a positive net present value in the scenarios evaluated, however, the highest value was achieved for Scenario 3 (7,890,407.44 USD). For the integrated process, an internal return rate of 86.87% and a payback of 0.68 year were observed. The sensitivity analysis showed that the project profitability is highly dependent on electricity and thermal energy selling prices. In conclusion, AD demonstrated to be a feasible alternative for vinasse and stillage management in an integrated process, being a sustainable technology to the circular economy transition and energy matrix decarbonization.

Annual greenhouse gas emissions from sheepfolds and cattle sheds

AbstractLivestock sheds are local and regional hotspots of greenhouse gases (GHG) emissions, but only very few studies analyse the intensities of GHG emissions from this source. The objective of this study was to quantify annual CH4, CO2 and N2O emissions from inside and outside of sheepfolds and summer cattle sheds in a typical agro‐pastoral ecotone using static chamber technique. Both sheepfolds and cattle shed functioned as huge net sources of CH4 and N2O at annual scale. Animal presence increased CH4, CO2 and N2O effluxes for up to 1100 times compared to the animal sheds without animals. N2O emissions boosted for 160%–280% during and after rainfall and spring‐thaw events. The CH4 and CO2 fluxes increased exponentially with faeces temperature for the outside sheepfold and summer cattle shed. The annual GHG emissions from both sheepfolds and summer cattle shed were 56 t CO2 equivalents ha−1, of which N2O contributed to 94%. Sheepfold dominated the total GHG emissions from animal sheds and accounted for 83% of the annual GHG flux. Annual emission on a per animal basis was 15, 0.2 and 28 kg CO2 eq year−1 sheep−1 and 26, 10 and 140 kg CO2 eq year−1 cattle−1 for N2O, CH4 and CO2, respectively. The annual N2O emissions from animal sheds were 70–250 times larger than nearby grassland soils, which were also net sink for atmospheric CH4. Concluding, animal sheds are very intensive local hotspots of GHG emissions, which should be considered at the local and regional scales.

Carbon and nitrogen footprints accounting of peanut and peanut oil production in China

The peanut sector has significant potential for decreasing greenhouse gas (GHG) emissions and reactive nitrogen (Nr) loss from agricultural production activity in China. This study calculated the carbon (C) and nitrgen (N) emissions of the peanut sector in China by jointly using the carbon footprint (CF) and nitrogen footprint (NF) methods based on the national statistical data from 2008 to 2017. The results showed that the average area-based CF (CFa) and NF (NFa) of peanut cropping in China were 1912.58 kg CO2-eq ha−1 and 41.19 kg N-eq ha−1, respectively. The average yield-based CF (CFy) and NF (NFy) of peanut oil reached 1.38 kg CO2-eq kg−1 and 28.23 g N-eq kg−1, respectively. The CFa of the peanut cropping subsystem in China increased from 2008 to 2017, while the NFa presented a reduction feature during 2009–2011 and during 2015–2017. Based on the results above, the total GHG emissions and Nr losses caused by the peanut sector in China were estimated to reach average values of 8.33 million tons (Mt) CO2-eq year−1 and 0.15 Mt N-eq year−1, respectively, during 2009–2017. Moreover, peanut cropping in Fujian showed the highest CF and NF, while that in Anhui and Chongqing presented the lowest CF and NF, implying that optimizing peanut layout in China would be of significant importance to developing the peanut sector with fewer environmental consequences. Fertilizer production and application were continuously the largest sources of CF and NF in the peanut sector in China, which should be given more attention for reducing the environmental consequences in the future. This study provides policy guidance for clean production in peanut industrial chain in the China.

Characteristics of greenhouse gas emissions from rice paddy fields in South Korea under climate change scenario RCP-8.5 using the DNDC model

Understanding the greenhouse gas (GHG) emission from rice paddy fields is essential to come up with appropriate countermeasure in response to global warming. However, GHG emissions from paddy fields in South Korea are not well characterized. The objectives of this study were to estimate the carbon dioxide (CO2) and methane (CH4) emissions from rice paddy fields in South Korea, under the Representative Concentration Pathway 8.5 (RCP-8.5) climate change scenario using the DNDC (i.e., DeNitrification-DeComposition) model at 1-km2 resolution. The performance of the model was verified with field data collected using a closed chamber, which supports the application of the model to South Korea. Both the model predictions and field measurements showed that most (> 95%) GHG emissions occur in the cropping period, between April and October. As a baseline (assuming no climate change), the national sums of the CO2 and CH4 emissions for the 2020s and 2090s were estimated to be 5.8 × 106 and 6.0 × 106 t CO2-equivalents (CO2-eq) year–1 for CO2 and 6.4 × 106 and 6.6 × 106 t CO2-eq year–1 for CH4, respectively, indicating no significant changes over 80 years. Under RCP-8.5, in the 2090s, CH4 emissions were predicted to increase by 10.7 × 106 and 14.9 × 106 t CO2-eq year–1, for a 10- or 30-cm tillage depth, respectively. However, the CO2 emissions gradually decreased with rising temperatures, due to reduced root respiration. Deep tillage increased the emissions of both GHGs, with a more pronounced effect for CH4 than CO2. Intermittent drainage in the middle of the cropping season can attenuate the CH4 emissions from paddy fields. The findings of this work will aid in developing nationwide policies on agricultural land management in the face of climate change.

Design Aspects, Energy Consumption Evaluation, and Offset for Drinking Water Treatment Operation

Drinking water treatment, wastewater treatment, and water distribution are energy-intensive processes. The goal of this study was to design the unit processes of an existing drinking water treatment plant (DWTP), evaluate the associated energy consumption, and then offset it using solar photovoltaics (PVs) to reduce carbon emissions. The selected DWTP, situated in the southwestern United States, utilizes coagulation, flocculation, sedimentation, filtration, and chlorination to treat 3.94 m3 of local river water per second. Based on the energy consumption determined for each unit process (validated using the plant’s data) and the plant’s available landholding, the DWTP was sized for solar PV (as a modeling study) using the system advisor model. Total operational energy consumption was estimated to be 56.3 MWh day−1 for the DWTP including water distribution pumps, whereas energy consumption for the DWTP excluding water distribution pumps was 2661 kWh day−1. The results showed that the largest consumers of energy—after the water distribution pumps (158.1 Wh m−3)—were the processes of coagulation (1.95 Wh m−3) and flocculation (1.93 Wh m−3). A 500 kW PV system was found to be sufficient to offset the energy consumption of the water treatment only operations, for a net present value of $0.24 million. The net reduction in carbon emissions due to the PV-based design was found to be 450 and 240 metric tons CO2-eq year−1 with and without battery storage, respectively. This methodology can be applied to other existing DWTPs for design and assessment of energy consumption and use of renewables.

Water -energy -carbon nexus approach for sustainable large-scale drinking water treatment operation

Sustainability of energy and water are inextricably linked with each other. Over-utilization/degradation of these resources may occur due to changing climate, growing population, and increasing pollution including carbon emissions due to the burning of fossil fuels. Drinking water treatment is essential for safeguarding public health; however, it is an energy-intensive process. The purpose of the current study is to study the energy -water -carbon nexus of a large-scale drinking water treatment plant (DWTP) that treats 1 Mm3 of raw Colorado River water per day by using direct filtration process and utilizes fossil fuel as energy source. Energy consumption of each treatment process was determined and then validated against DWTP data. Energy intensity was found for the processes of ozonation (19.6 Wh m−3), coagulation (1.3 Wh m−3), flocculation (1.22 Wh m−3), filtration (1.24 Wh m−3), the sodium hypochlorite generation system (31.7 Wh m−3), chlorination feed pumps (1.27 Wh m−3), and residual management (0.07 Wh m−3). Further, a modeling study was conducted to offset the energy consumption of the DWTP and thus reduce carbon emissions, by utilizing PV system, considering both the existing land-holdings of the plant and cost-effectiveness of the PV system. Comparison of PV system performance and the effects of incentives and electric rates on cost effectiveness were analyzed for the locations of Nevada, New York and Massachusetts. Net reduction in carbon emissions was estimated in the range of 980–11000 and 480–5200 metric tons CO₂eq year−1, by using PV with and without battery storage, respectively.

An Analysis of Energy Consumption and the Use of Renewables for a Small Drinking Water Treatment Plant

One of the pressing issues currently faced by the water industry is incorporating sustainability considerations into design practice and reducing the carbon emissions of energy-intensive processes. Water treatment, an indispensable step for safeguarding public health, is an energy-intensive process. The purpose of this study was to analyze the energy consumption of an existing drinking water treatment plant (DWTP), then conduct a modeling study for using photovoltaics (PVs) to offset that energy consumption, and thus reduce emissions. The selected plant, located in southwestern United States, treats 0.425 m3 of groundwater per second by utilizing the processes of coagulation, filtration, and disinfection. Based on the energy consumption individually determined for each unit process (validated using the DWTP’s data), the DWTP was sized for PVs (as a modeling study). The results showed that the dependency of a DWTP on the traditional electric grid could be greatly reduced by the use of PVs. The largest consumption of energy was associated with the pumping operations, corresponding to 150.6 Wh m−3 for the booster pumps to covey water to the storage tanks, while the energy intensity of the water treatment units was found to be 3.1 Wh m−3. A PV system with a 1.5 MW capacity with battery storage (30 MWh) was found to have a positive net present value and a levelized cost of electricity of 3.1 cents kWh−1. A net reduction in the carbon emissions was found as 950 and 570 metric tons of CO2-eq year−1 due to the PV-based design, with and without battery storage, respectively.

Effects on Greenhouse Gas (CH4, CO2, N2O) Emissions of Conversion from Over-Mature Forest to Secondary Forest and Korean Pine Plantation in Northeast China

This study aimed to evaluate the seasonal variations of Greenhouse Gas fluxes (CH4, CO2, and N2O), Greenhouse Gas (GHG) emissions, and Global Warming Potential (GWP) over the extent of the regions and understand the controlling factors. CH4, CO2, and N2O fluxes were measured along with their environmental variables from the over-mature forest, Korean pine plantation, and five 60-year-old natural secondary forests in mountainous regions in Northeast China from May 2015 to April 2016. The results revealed that secondary forests, except for Betula platyphylla forest, significantly increased CH4 absorption by 19.6% to 51.0% and 32.6% to 67.0% compared with over-mature forest (OMF) and Korean pine plantation (KPP). Five secondary forests significantly increased CO2 flux by 32.9% to 78.6% and 14.1% to 53.4% compared with OMF and KPP, respectively. According to the annual statistics, the N2O fluxes had significant differences among seven forest types and decreased in the following order: mixed deciduous forest (MDF) &gt; OMF &gt; KPP &gt; Populous davidiana forest (PDF) &gt; hardwood forest (HWF) &gt; Mongolian oak forest (MOF) &gt; Betula platyphylla forest (BPF). The CH4 absorption and CO2 emission peaks occurred in summer, while the peak N2O fluxes occurred in spring. Stepwise multiple linear regression showed that CH4 and CO2 fluxes from soils were strongly influenced by air and soil temperature, soil volumetric water content (SVWC), nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), and soil organic carbon (SOC) across the whole year. Air temperature, SVWC, pH, NO3−-N, and NH4+-N were the dominant factors controlling N2O fluxes from OMF and five secondary forests (except for BPF). No significant relationships were observed between these environmental factors and N2O fluxes from KPP and BPF. Additionally, the total cumulative CH4, CO2, and N2O fluxes were –13.37 t CH4 year−1, 41,608.96 t CO2 year−1, and 3.24 t N2O year−1, and the total cumulative GWP were 42,151.87 t CO2 eq year−1 through the whole year in seven forest types at the Maoershan Ecosystem Research Station in Northeast China. For the annual GWP per hectare, secondary forests and KPP averaged a higher GWP by 33.7%–80.1% and 17.9% compared with OMF. This indicates that the effects of early human activities have not been completely eliminated in the middle stage of KPP and secondary forests.

Greenhouse gas fluxes and mitigation potential for managed lands in the Russian Federation

This work aims to assess the dynamics of net greenhouse gas (GHG) emissions and removals, as well as analyse the mitigation potential for managed lands in Russia, the country’s contributions to global GHG fluxes and global mitigation in agriculture, forestry and other land use required under the goals of the United Nations Framework Convention on Climate Change 21st Conference of the Parties (Paris Agreement). Russia is the fifth-largest GHG emitter in the world, yet information on its ecosystem-based emissions and related mitigation potential remains insufficient. In order to estimate annual GHG emissions and removals, the adapted methodologies and parameters of the Intergovernmental Panel on Climate Change’s (IPCC) methodological reports were applied. Managed land in Russia exhibits a steady trend of increasing net GHG absorption from 1990 to 2016, reaching an absorption value of 553 Mt carbon dioxide (CO2-eq) in 2016 (compensating for about 4.6% of the current global net GHG emission from land use) from a net loss of 343 Mt CO2-eq in 1990 due to the decrease in forest harvesting rates and reduction in the organic and mineral fertilisation of croplands. The results obtained in our work are in accordance with the carbon fluxes (per hectare) of other countries, taking into account similarities and differences in climatic conditions. The total mitigation potential of managed land in Russia is estimated at about 545–940 Mt CO2-eq year−1, which may compensate for an additional 4.5–7.8% of current global net GHG emissions from land use. Major mitigation measures in Russia comprise sustainable land management activities, such as land protection from fires, insect outbreaks and other natural disturbances, the reduction of carbon losses due to harvesting and wood production, the replacement of existing extensive agricultural management with intense farming, the prevention of soil erosion, reforestation and reclamation activities. Our research demonstrates that implementing these activities can provide general insights into land mitigation strategies and affect land management in other countries, particularly in the former Union of Soviet Socialist Republics. On the global scale mitigation recommendations informed by our study include improved forest management, reforestation, cropland nutrient management and wetland restoration.

Greenhouse gas emissions from a semi-arid tropical reservoir in northeastern Brazil

We estimated carbon dioxide (CO2) and methane (CH4) emissions by diffusion, ebullition, and degassing in turbines from a semi-arid hydropower reservoir in northeastern Brazil. Sampling sites were allocated within the littoral and deeper waters of one embayment, the main-stream, and at turbines. Annual carbon emissions were estimated at 2.3 × 105 ± 7.45 × 104 t C year−1, or in CO2-equivalents (CO2-eq) at 1.33 × 106 ± 4.5 × 105 t CO2-eq year−1. Diffusion across the water surface was the main pathway accounting for 96% of total carbon emissions. Ebullition was limited to littoral areas. A slight accumulation of CO2, but not of CH4, in bottom waters close to the turbines inlet led to degassing emissions about 8 × 103 t C year−1. Emissions in littoral areas were higher than in main-stream and contribute to 40% of the total carbon. Carbon (C) emissions per electricity generated, at 60% of installed capacity, is 0.05 t C-CO2-eq MWh−1. The ratio increases to 0.09 t C-CO2 MWh−1, equating 80% of the emissions from natural gas and 40% of diesel or coal power plants. Retention time and benthic metabolism were identified as main drivers for carbon emissions in littoral areas, while water column mixing and rapid water flow are important factors preventing CH4 accumulation and loss by degassing. Our results indicate that Itaparica Reservoir, located in the semi-arid region of Northeastern Brazil, acts as a source of GHGs. Management measurements are needed to prevent emissions to raise in the future.

Estimation of greenhouse gas emissions from sewer pipeline system

The aim of this study was to estimate the total greenhouse gas (GHG) emissions generated from whole life cycle stages of a sewer pipeline system and suggest the strategies to mitigate GHG emissions from the system. The process-based life cycle assessment (LCA) with a city-scale inventory database of a sewer pipeline system was conducted. The GHG emissions (direct, indirect, and embodied) generated from a sewer pipeline system in Daejeon Metropolitan City (DMC), South Korea, were estimated for a case study. The potential improvement actions which can mitigate GHG emissions were evaluated through a scenario analysis based on a sensitivity analysis. The amount of GHG emissions varied with the size (150, 300, 450, 700, and 900 mm) and materials (polyvinyl chloride (PVC), polyethylene (PE), concrete, and cast iron) of the pipeline. Pipes with smaller diameter emitted less GHG, and the concrete pipe generated lower amount of GHG than pipes made from other materials. The case study demonstrated that the operation (OP) stage (3.67 × 104 t CO2eq year−1, 64.9%) is the most significant for total GHG emissions (5.65 × 104 t CO2eq year−1) because a huge amount of CH4 (3.51 × 104 t CO2eq year−1) can be generated at the stage due to biofilm reaction in the inner surface of pipeline. Mitigation of CH4 emissions by reducing hydraulic retention time (HRT), optimizing surface area-to-volume (A/V) ratio of pipes, and lowering biofilm reaction during the OP stage could be effective ways to reduce total GHG emissions from the sewer pipeline system. For the rehabilitation of sewer pipeline system in DMC, the use of small diameter pipe, combination of pipe materials, and periodic maintenance activities are suggested as suitable strategies that could mitigate GHG emissions. This study demonstrated the usability and appropriateness of the process-based LCA providing effective GHG mitigation strategies at a city-scale sewer pipeline system. The results obtained from this study could be applied to the development of comprehensive models which can precisely estimate all GHG emissions generated from sewer pipeline and other urban environmental systems.

Global warming potential of drained and undrained peatlands in estonia: A synthesis

We estimated the global warming potential of Estonian peatlands (transitional fens and ombrotrophic bogs) based on greenhouse gases (GHG) CO2, CH4, and N2O and carbon (C) accrual in biomass, and the effects of drainage on these processes. Data were derived from a review of the literature of boreal peatlands. Areal estimates of peatland types were multiplied with the values of the interquartile range of literature-derived GHG fluxes. The effect of drainage and radiative forcing of Estonian peatlands were also evaluated. Annual emission of CO2, CH4, and N2O is estimated to be 278 to 1,056×103 of CO2 equivalent (eq), of which CO2 makes up 22 to 44%, CH4 53 to 73%, and N2O 3 to 5%. The annual efflux is 419 to 676×103 CO2 eq year−1 from drained peatlands, and 2141 to 380×103 CO2 eq year−1 from the undrained peatlands. The annual loss of C from peatlands is estimated to be 38 to 86 tons C×103 year−1. Thus due to drainage, Estonia’s transitional fens and ombrotrophic bogs have gone from being sinks to sources of C.

Mitigation of global greenhouse gas emissions from waste: conclusions and strategies from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Working Group III (Mitigation)

Greenhouse gas (GHG) emissions from post-consumer waste and wastewater are a small contributor (about 3%) to total global anthropogenic GHG emissions. Emissions for 2004-2005 totalled 1.4 Gt CO2-eq year(-1) relative to total emissions from all sectors of 49 Gt CO2-eq year(-1) [including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and F-gases normalized according to their 100-year global warming potentials (GWP)]. The CH4 from landfills and wastewater collectively accounted for about 90% of waste sector emissions, or about 18% of global anthropogenic methane emissions (which were about 14% of the global total in 2004). Wastewater N2O and CO2 from the incineration of waste containing fossil carbon (plastics; synthetic textiles) are minor sources. Due to the wide range of mature technologies that can mitigate GHG emissions from waste and provide public health, environmental protection, and sustainable development co-benefits, existing waste management practices can provide effective mitigation of GHG emissions from this sector. Current mitigation technologies include landfill gas recovery, improved landfill practices, and engineered wastewater management. In addition, significant GHG generation is avoided through controlled composting, state-of-the-art incineration, and expanded sanitation coverage. Reduced waste generation and the exploitation of energy from waste (landfill gas, incineration, anaerobic digester biogas) produce an indirect reduction of GHG emissions through the conservation of raw materials, improved energy and resource efficiency, and fossil fuel avoidance. Flexible strategies and financial incentives can expand waste management options to achieve GHG mitigation goals; local technology decisions are influenced by a variety of factors such as waste quantity and characteristics, cost and financing issues, infrastructure requirements including available land area, collection and transport considerations, and regulatory constraints. Existing studies on mitigation potentials and costs for the waste sector tend to focus on landfill CH4 as the baseline. The commercial recovery of landfill CH4 as a source of renewable energy has been practised at full scale since 1975 and currently exceeds 105 Mt CO2-eq year(-1). Although landfill CH4 emissions from developed countries have been largely stabilized, emissions from developing countries are increasing as more controlled (anaerobic) landfilling practices are implemented; these emissions could be reduced by accelerating the introduction of engineered gas recovery, increasing rates of waste minimization and recycling, and implementing alternative waste management strategies provided they are affordable, effective, and sustainable. Aided by Kyoto mechanisms such as the Clean Development Mechanism (CDM) and Joint Implementation (JI), the total global economic mitigation potential for reducing waste sector emissions in 2030 is estimated to be > 1000 Mt CO2-eq (or 70% of estimated emissions) at costs below 100 US$ t(-1) CO2-eq year(-1). An estimated 20-30% of projected emissions for 2030 can be reduced at negative cost and 30-50% at costs < 20 US$ t(-) CO2-eq year(-1). As landfills produce CH4 for several decades, incineration and composting are complementary mitigation measures to landfill gas recovery in the short- to medium-term--at the present time, there are > 130 Mt waste year(-1) incinerated at more than 600 plants. Current uncertainties with respect to emissions and mitigation potentials could be reduced by more consistent national definitions, coordinated international data collection, standardized data analysis, field validation of models, and consistent application of life-cycle assessment tools inclusive of fossil fuel offsets.

Quantifying the Reduction of Greenhouse Gas Emissions as a Resultof Composting Dairy and Beef Cattle Manure

Greenhouse gas emissions from the agricultural sector can be reduced through implementation of improved management practices. For example, the choice of manure storage method should be based on environmental decision criteria, as well as production capacity. In this study, greenhouse gas emissions from three methods of storing dairy and beef cattle manure were compared during the summer period. The emissions of CH4 ,N 2O and CO2 from manure stored as slurry, stockpile, and compost were measured using a flowthrough closed chamber. The largest combined N2O–CH4 emissions in CO2 equivalent were observed from the slurry storage, followed by the stockpile and lastly the passively aerated compost. This ranking was governed by CH4 emissions in relation to the degree of aerobic conditions within the manure. The radiative forcing in CO2 equivalent from the stockpiled manure was 1.46 times higher than from the compost for both types of cattle manure. It was almost twice as high from the dairy cattle manure slurry and four to seven times higher from the beef cattle manure slurry than from the compost. The potential reduction of GHG was estimated, by extrapolating the results of the study to all of Canada. By composting all the cattle manure stored as slurry and stockpile, a reduction of 0.70 Tg CO2-eq year � 1 would be achieved. Similarly, by collecting and burning CH4 emissions from existing slurry facilities, a reduction of 0.76 Tg CO2eq year � 1 would be achieved. New CH4 emission factors were estimated based on these results and incorporated into the IPCC methodology. For North-America under cool conditions, the CH4 emission factors would be 45 kg CH4 hd � 1 year � 1 for dairy cattle manure rather than 36 kg CH4 hd � 1 year � 1 , and 3k g CH 4 hd � 1 year � 1 for beef cattle manure rather than 1 kg CH4 hd � 1 year � 1 .