Assessing greenhouse gas emissions in Cuban agricultural soils: Implications for climate change and rice (Oryza sativa L.) production

Assessing the impact of greenhouse gas (GHG) emissions on agricultural soils is crucial for ensuring food production sustainability in the global effort to combat climate change. The present study delves to comprehensively assess GHG emissions in Cuba's agricultural soil and analyze its implications for rice production and climate change because of its rich agriculture cultivation tradition and diverse agro-ecological zones from the period of 1990-2022. In this research, based on Autoregressive Distributed Lag (ARDL) approach the empirical findings depicts that in short run, a positive and significant impact of 1.60 percent % in Cuba's rice production. The higher amount of atmospheric carbon dioxide (CO2) levels improves photosynthesis, and stimulates the growth of rice plants, resulting in greater grain yields. On the other hand, rice production index raising GHG emissions from agriculture by 0.35 % in the short run. Furthermore, a significant and positive impact on rice production is found in relation to the farm machinery i.e., 3.1 %. Conversely, an adverse and significant impact of land quality was observed on rice production i.e., -5.5 %. The reliability of models was confirmed by CUSUM and CUSUM square plot. Diagnostic tests ensure the absence of serial correlation and heteroscedasticity in the models. Additionally, the forecasting results are obtained from the three machine learning models i.e. feed forward neural network (FFNN), support vector machines (SVM) and adaptive boosting technique (Adaboost). Through the % MAPE criterion, it is evident that FFNN has achieved high precision (91 %). Based on the empirical findings, the study proposed the adoption of sustainable agricultural practices and incentives should be given to the farmers so that future generations inherit a world that is sustainable, and healthy.

Enhanced anaerobic oxidation of methane with the coexistence of iron oxides and sulfate fertilizer in paddy soil

Iron oxides and sulfate are usually abundant in paddy soil, but their role in reducing methane emissions is little known. In this work, paddy soil was anaerobically cultivated with ferrihydrite and sulfate for 380 days. An activity assay, inhibition experiment, and microbial analysis were conducted to evaluate the microbial activity, possible pathways, and community structure, respectively. The results showed that anaerobic oxidation of methane (AOM) was active in the paddy soil. The AOM activity was much higher with ferrihydrite than sulfate, and an extra 10% of AOM activity was stimulated when ferrihydrite and sulfate coexisted. The microbial community was highly similar to the duplicates but totally different with different electron acceptors. The microbial abundance and diversity decreased due to the oligotrophic condition, but mcrA-carrying archaea increased 2-3 times after 380 days. Both the microbial community and the inhibition experiment implied that there was an intersection between iron and sulfur cycles. A "cryptic sulfur cycle" might link the two cycles, in which sulfate was quickly regenerated by iron oxides, and it might contribute 33% of AOM in the tested paddy soil. Complex links between methane, iron, and sulfur geochemical cycles occur in paddy soil, which may be significant in reducing methane emissions from rice fields.

Impact of smallholder cattle farms on the environment: a study

With increasing evidence of global warming, the pressure is building to limit greenhouse gas emission from many human activities including dairy production systems. In this context, the present study was conducted to estimate the carbon footprint (CF) of cattle milk produced in the Hisar district of Haryana, India. The data about feeding practices, crops grown, manure management systems, etc. was collected through personal interviews with cattle-rearing rural male farmers chosen through multistep random sampling. The life cycle assessment (LCA) methodology was adopted to estimate carbon footprint, with the system boundary being "Cradle to farm gate." The latest methodologies prescribed by the IPCC were used to estimate GHG emissions using the tier-2 approach. The current study has presented a detailed and recent GHG inventory from smallholder cattle farms at the village level. On the basis of the inventory analysis, a simplified life cycle-based analysis is used in order to quantify the carbon footprint of fat- and protein-corrected milk (FPCM). The carbon footprint of cattle milk was estimated at 2.13 kg CO₂-eq/kilogram FPCM. Enteric fermentation was the most potent contributor to GHG, contributing around 35.5% of the total emissions, followed by manure management (13.8%) and soil management (8.2%). Further studies to accurately estimate carbon footprint are advocated besides suggesting ways to reduce GHG emissions and using efficient production technologies.

GHG Monitoring Project for the Global Stocktake 2023: implications of the COP26 Japan Pavilion seminar

During the 2021 Glasgow Climate Change Conference (COP26), a hybrid seminar event "Greenhouse gas (GHG) Monitoring Project for the Global Stocktake 2023" was held at the COP26 Japan Pavilion on 2nd of November 2011. The participants presented and discussed science-based GHG monitoring approaches in support of the Global Stocktake. This report summarizes the five research talks given at the event.

N2O emissions from decomposing crop residues are strongly linked to their initial soluble fraction and early C mineralization

The emission of nitrous oxide (N₂O), a strong greenhouse gas, during crop residue decomposition in the soil can offset the benefits of residue recycling. The IPCC inventory considers agricultural N₂O emissions proportional to the amount of nitrogen (N) added by residues to soils. However, N₂O involves several emission pathways driven directly by the form of N returned and indirectly by changes in the soil induced by decomposition. We investigated the decomposition factors related to N₂O emissions under controlled conditions. Residues of sugar beet (SUB), wheat (WHT), rape seed (RAS), potato (POT), pea (PEA), mustard (MUS), red clover (RC), alfalfa (ALF), and miscanthus (MIS), varying by maturity at the time of collection, were incubated in two soils (GRI and SLU) at 15 °C with a water-filled pore space of 60%. The residues contained a wide proportion range of water-soluble components, components soluble in neutral detergent (SOL-NDS), hemicellulose, cellulose, and lignin. Their composition drastically influenced the dynamics of C mineralization and soil ammonium and nitrate and was correlated with N₂O flux dynamics. The net cumulative N₂O emitted after 60 days originated mostly from MUS (4828 ± 892 g N-N₂O ha^-1), SUB (2818 ± 314 g N-N₂O ha^-1) and RC (2567 ± 1245 g N-N₂O ha^-1); the other residue treatments had much lower emissions (<200 g N-N₂O ha^-1). For the first time N₂O emissions could be explained only by the residue content in the SOL-NDS, according to an exponential relationship. Residues with a high SOL-NDS (>25% DM) were also non-senescent and promoted high N₂O emissions (representing 1-5% of applied N), likely directly by nitrification and indirectly by denitrification in microbial hotspots. Crop residue quality appears to be valuable information for accurately predicting N₂O emissions and objectively weighing their other potential benefits to agriculture and the environment.

The impact of a seasonal change in loading rate on the nitrous oxide emissions at the WWTP of a tourist region

Nitrous oxide (N₂O) is a powerful greenhouse gas (GHG) whose production and emission must be minimised from wastewater treatment plants (WWTPs) to avoid undesirable impacts to climate change and the ozone layer. WWTPs operated in tourist regions undergo large seasonal changes to the influent loading rates of organic matter, nitrogen and phosphorus, which operators must respond to by changing their operational conditions. This study examines the impact of a change in low to high season on the N₂O emissions of an activated sludge WWTP in a well-known tourist region in the Algarve, Portugal. While literature studies have suggested that increases in the nitrogen and organic loading rates can promote increased N₂O emissions, we have found higher N₂O emissions in the low season (7.4% kgN₂O-N·kgNH₄-N^-1), where these loading rates were lower. It was found that the impact of accompanying operational changes to the WWTP outweighed any change caused by the increased loading rate, where the aeration rate showed a significant correlation with N₂O emission dynamics. The location of the N₂O fluxes observed as well as the dissolved vs gaseous N₂O levels suggested that the hydroxylamine oxidation pathway was likely to be of higher relevance towards N₂O production as compared to nitrifier denitrification. This study contributes towards the understanding of operational factors impacting N₂O emissions at full-scale WWTPs and potential mitigation strategies.

Regulating CH4, N2O, and NO emissions from an alkaline paddy field under rice-wheat rotation with controlled release N fertilizer

Controlled release fertilizer (CRF) has been shown to increase crop yield and N use efficiency (NUE) compared with traditional chemical fertilizer (TF). However, few studies examined the effects of CRF on CH₄, N₂O, and NO emissions simultaneously in alkaline paddy fields under rice-wheat rotation. In the present study, we conducted a 2-year field experiment to compare the effects of different CRF application strategies on these gas emissions with those of TF and explored the effects of CRF on global warming potential (GWP), crop yields, and greenhouse gas emission intensity (GHGI). Results showed that CRF can reduce 0.98-14.3%, 13.3-21.1%, and 8.22-16.3% of CH₄, N₂O, and NO emissions, respectively, in the studied alkaline paddy field. CRF reduce CH₄ emission probably by regulating soil NH₄⁺ concentration. CRF reduce N₂O and NO emissions probably by regulating inorganic N content in the studied alkaline paddy soil. CRF had the same effect on annual crop yield as TF, especially when CRF was applied twice in each season and had the same N application rate as TF. Annual crop yields and the agronomic efficiency of N (AE_N) increased by 8.24% and 21.6%, respectively. On the average of the two rice-wheat rotation cycles, GHGI significantly decreased by up to 14.1% after the application of CRF as relative to that after the application of TF (P < 0.05). These results suggest that CRF is an environment-friendly N fertilization strategy for mitigating GWP and ensuring high crop yield in an alkaline paddy field under rice-wheat rotation.

Fuel consumption and air emissions in one of the world's largest commercial fisheries

The little information available on fuel consumption and emissions by high seas tuna fisheries indicates that the global tuna fleet may have consumed about 2.5 Mt of fuel in 2009, resulting in the production of about 9 Mt of CO2-equivalent greenhouse gases (GHGs), i.e., about 4.5-5% of the global fishing fleet emissions. We developed a model of annual fuel consumption for the large-scale purse seiners operating in the western Indian Ocean as a function of fishing effort, strategy, and vessel characteristics based on an original and unique data set of more than 4300 bunkering operations that spanned the period 2013-2019. We used the model to estimate the total fuel consumption and associated GHG and SO2 emissions of the Indian Ocean purse seine fishery between 1981 and 2019. Our results showed that the energetic performance of this fishery was characterized by strong interannual variability over the last four decades. This resulted from a combination of variations in tuna abundance but also changes in catchability and fishing strategy. In recent years, the increased targeting of schools associated with fish aggregating devices in response to market incentives combined with the IOTC management measure implemented to rebuild the stock of yellowfin tuna has strongly modified the productivity and spatio-temporal patterns of purse seine fishing. This had effects on fuel consumption and air pollutant emissions. Over the period 2015 to 2019, the purse seine fishery, including its support vessel component, annually consumed about 160,000 t of fuel and emitted 590,000 t of CO2-eq GHG. Furthermore, our results showed that air pollutant emissions can be significantly reduced when limits in fuel composition are imposed. In 2015, SO2 air pollution exceeded 1500 t, but successive implementation of sulphur limits in the Indian Ocean purse seine fishery in 2016 and 2018 have almost eliminated this pollution. Our findings highlight the need for a routine monitoring of fuel consumption with standardized methods to better assess the determinants of fuel consumption in fisheries and the air pollutants they emit in the atmosphere.

Development of a mobile platform for monitoring gaseous, particulate, and greenhouse gas (GHG) pollutants

The Michigan Pollution Assessment Laboratory (MPAL) is a mobile air quality monitoring platform designed to measure conventional, toxic, and greenhouse gas (GHG) air pollutants. The spatially and temporally resolved data collected can be used for multiple purposes, such as mapping spatial patterns and identifying peaks. The truck-based platform includes instrumentation for 11 gaseous pollutants and for particulate matter (PM), size distribution (7 nm to 20 μm), PM₁₀, black and brown carbon, and trace metals. MPAL is equipped with meteorological instruments, a high-accuracy GPS, forward and reverse cameras, and a data logging and display system. We selected commercially available instrumentation based on sensitivity, response time, and robustness. The vehicle's power system allows ~ 6.5 h of continuous operation with all instruments operating. This article details the design, construction, and evaluation of MPAL and summarizes data collected in its first year (March 2019 to March 2020) of operation. We completed a series of runs on 84 days in Detroit, Michigan, an area with a diverse set of traffic, industrial, and commercial emission sources, and collected 265,816 1-s observations (excluding collocations, zero checks, and other quality assurance measurements). Using data from these runs as well as special tests, we present results of performance evaluations that examined the response time, PM losses, and wind measurements and compare results to stationary regulatory monitoring data. We highlight key issues and provide practical solutions to help evaluate and resolve these issues and share many lessons learned in developing and using a mobile platform.

Impact of COVID-19 outbreak measures of lockdown on the Italian Carbon Footprint

Stringent lockdown measures implemented in Italy to mitigate the spread of COVID-19 are generating unprecedented economic impacts. However, the environmental consequences associated with the temporary shutdown and recovery of industrial and commercial activities are still not fully understood. Using the well-known carbon footprint (CF) indicator, this paper provides a comprehensive estimation of environmental effects due to the COVID-19 outbreak lockdown measures in Italy. Our aim was to quantify the CF associated with the consumption of energy by any economic activity and region in Italy during the lockdown, and then compare these environmental burdens with the CF calculated for analogous periods from 2015 to 2019 (~March and April). Complementarily, we also conducted a scenario analysis to estimate the post-lockdown CF impact in Italy. A consumption-based approach was applied according to the principles of the established Life Cycle Assessment method. The CF was therefore quantified as a sum of direct and indirect greenhouse gases (GHGs) released from domestically produced and imported energy metabolism flows, excluding the exports. Our findings indicate that the CF in the lockdown period is ~-20% lower than the mean CF calculated for the past. This means avoided GHGs in between ~5.6 and ~10.6 Mt CO₂e. Results further suggest that a tendency occurs towards higher impact savings in the Northern regions, on average ~230 kt CO₂e of GHGs avoided by province (against ~110-130 kt CO₂e in central and Southern provinces). Not surprisingly, these are the utmost industrialized areas of Italy and have been the ones mostly affected by the outbreak. Despite our CF estimates are not free of uncertainties, our research offers quantitative insights to start understanding the magnitude generated by such an exceptional lockdown event in Italy on climate change, and to complement current scientific efforts investigating the relationships between air pollution and the spread of COVID-19.

Can information and communication technology reduce CO2 emission? A quantile regression analysis

By employing China's provincial panel data covering period 2001-2016, the present study empirically investigates the impact of ICT on CO₂ emission intensity. Specifically, this paper utilizes Internet penetration and mobile phone penetration as proxies to measure ICT respectively and employs quantile regression method to estimate the benchmark model at five quantiles (0.1, 0.25, 0.5, 0.75, and 0.9). It is demonstrated that Internet penetration at the national level has a significant negative effect on the CO₂ emission intensity for all quantiles. In addition, Internet penetration has a significant negative effect on CO₂ emission intensity at all quantiles except for 0.1 quantile for China's eastern provinces and has a significant negative effect on CO₂ emission intensity at all quantiles for China's central provinces, whereas Internet penetration has no significant negative impact on CO₂ emission intensity at all quantiles for China's western provinces. By comparison, the reduction effect of Internet penetration on CO₂ emission intensity in China's eastern and central provinces is more obvious and in contrast with the reduction effect of Internet penetration on CO₂ emission intensity in China's eastern provinces, it is greater in China's central provinces. Finally, the impact of mobile phone penetration on CO₂ emission intensity is generally consistent with the impact of Internet penetration. This study provides further evidence that developing countries can simultaneously achieve economic development and reduce carbon emissions through ICT.

Revealing the environmental pollution in nexus of aviation transportation in SAARC region

The environmental degradation has put serious concern among the nations at global level, yet contented measures are still lagged behind the prospective outcomes. This study is aimed at analyzing the existence of "aviation transportation Kuznets curve" together with "environmental Kuznets curve" in perspective of greenhouse gas (GHG) emissions for the SAARC region during 1980 to 2018. The panel unit root test summary applied to panel data indicates the first difference order while panel fisher cointegration shows long-run association among the considered variables. The econometric results by fully modified least square (FMOLS) validate the existence of "inverted U-shaped" Kuznets curve for environment as (EKC) and aviation transported carriage (ATC) while "U shaped" aviation transported passenger (ATP) is observed in context to greenhouse gas (GHG). In addition, the dynamic ordinary least square (DOLS) exhibits "inverted U shaped" for aviation transportation while GDP has an increasing trend of "U-shaped" curve. The pairwise Dumitrescu-Hurlin panel causality shows unidirectional association from economic growth, trade openness, and aviation sector to greenhouse gas (GHG) emissions. Therefore, it is an urgent need of the hour for the SAARC region to consider the sustainability of the environment by key sector. This analysis suggests that SAARC nations must focus on exploiting renewable energy means along with implementing fuel-saving traveler and merchandise expertise that thoroughly cuts the diesel fuel.

The link between nitrous oxide emissions, microbial community profile and function from three full-scale WWTPs

Few attempts have been made in previous studies to link the microbial community structure and function with nitrous oxide (N₂O) emissions at full-scale wastewater treatment plants (WWTPs). In this work, high-throughput sequencing and reverse transcriptase-qPCR (RT-qPCR) was applied to activated sludge samples from three WWTPs for two seasonal periods (winter and summer) and linked with the N₂O emissions and wastewater characteristics. The total N₂O emissions ranged from 7.2 to 937.0 g N-N₂O/day, which corresponds to an emission factor of 0.001 to 0.280% of the influent NH₄-N being emitted as N₂O. Those emissions were related to the abundance of Nitrotoga, Candidatus Microthrix and Rhodobacter genera, which were favored by higher dissolved oxygen (DO) and nitrate (NO₃^-) concentrations in the activated sludge tanks. Furthermore, a relationship between the nirK gene expression and N₂O emissions was verified. Detected N₂O emission peaks were associated with different process events, related to aeration transition periods, that occurred during the regular operation of the plants, which could be potentially associated to increased emissions of the WWTP. The design of mitigation strategies, such as optimizing the aeration regime, is therefore important to avoid process events that lead to those N₂O emissions peaks. Furthermore, this study also demonstrates the importance of assessing the gene expression of nosZ clade II, since its high abundance in WWTPs could be an important key to reduce the N₂O emissions.

Impact of the treatment of NH3 emissions from pig farms on greenhouse gas emissions. Quantitative assessment from the literature data

In order to limit ammonia (NH₃) emissions from pig farms, various air cleaning solutions are widely applied. However, the literature data report that these systems (chemical scrubbers, bioscrubbers and biofilters) can be both inefficient and promote nitrous oxide (N₂O) production. As air cleaning technologies should not contribute to secondary trace gases that may have a stronger environmental impact than the raw gas compounds themselves, the objective of this study was to quantify the effect of NH₃ treatment in pig farms on greenhouse gas (GHG) emissions. GHGs (carbon dioxide, methane and nitrous oxide) emitted at the outlet of three different cleaning systems ("chemical scrubber", "bioscrubber" and "bioscrubber + denitrification step") were assessed and compared with the emissions generated by the exhaust air with "no treatment". The calculations show that the chemical scrubber has no effect whereas biological treatments can increase GHG emissions. The use of bioscrubbers alone for NH₃ removal can remain acceptable provided that less than 3% of the NH₃ entering the apparatus is converted into N₂O. In such cases, a maximum increase of 1.9% in GHG emissions could be obtained. Conversely, the addition of a denitrification step to a bioscrubber must be avoided. Increases in overall GHG emissions of up to 25.8% were calculated but more significant increases could occur. With regard to GHG emissions, it is concluded that the use of a chemical scrubber is more suitable than a bioscrubber to treat exhaust air from pig farms.

Linking climate change mitigation and coastal eutrophication management through biogas technology: Evidence from a new Danish bioenergy concept

The interest in sustainable bioenergy solutions has gained great importance in Europe due to the need to reduce GHG emissions and to meet environmental policy targets, not least for the protection of groundwater and surface water quality. In the Municipality of Solrød in Denmark, a novel bioenergy concept for anaerobic co-digestion of food industry residues, manure and beach-cast seaweed has been developed and tested in order to quantify the potential for synergies between climate change mitigation and coastal eutrophication management in the Køge Bay catchment. The biogas plant, currently under construction, was designed to handle an annual input of up to 200,000 t of biomass based on four main fractions: pectin wastes, carrageenan wastes, manure and beach-cast seaweed. This paper describes how this bioenergy concept can contribute to strengthening the linkages between climate change mitigation strategies and Water Framework Directive (WFD) action planning. Our assessments of the projected biogas plant indicate an annual reduction of GHG emissions of approx. 40,000 t CO2 equivalents, corresponding to approx. 1/3 of current total GHG emissions in the Municipality of Solrød. In addition, nitrogen and phosphorous loads to Køge Bay are estimated to be reduced by approx. 63 t yr.(-1) and 9 tyr.(-1), respectively, contributing to the achievement of more than 70% of the nutrient reduction target set for Køge Bay in the first WFD river basin management plan. This study shows that anaerobic co-digestion of the specific food industry residues, pig manure and beach-cast seaweed is feasible and that there is a very significant, cost-effective GHG and nutrient loading mitigation potential for this bioenergy concept. Our research demonstrates how an integrated planning process where considerations about the total environment are integrated into the design and decision processes can support the development of this kind of holistic bioenergy solutions.

Effects of temperature on nitrous oxide (N2O) emission from intensive aquaculture system

This study examines the effects of temperature on nitrous oxide (N2O) emissions in a bench-scale intensive aquaculture system rearing Koi fish. The water temperature varied from 15 to 24 °C at interval of 3 °C. Both volumetric and specific rate for nitrification and denitrification declined as the temperature decreased. The concentrations of ammonia and nitrite, however, were lower than the inhibitory level for Koi fish regardless of temperature. The effects of temperature on N2O emissions were significant, with the emission rate and emission factor increasing from 1.11 to 1.82 mg N2O-N/d and 0.49 to 0.94 mg N2O-N/kg fish as the temperature decreased from 24 to 15 °C. A global map of N2O emission from aquaculture was established by using the N2O emission factor depending on temperature. This study demonstrates that N2O emission from aquaculture is strongly dependent on regional water temperatures as well as on fish production.

Implications of a consumer-based perspective for the estimation of GHG emissions. The illustrative case of Luxembourg

The Kyoto protocol has established an accounting system for national greenhouse gas (GHG) emissions according to a geographic criterion (producer perspective), such as that proposed by the IPCC guidelines for national GHG inventories. However, the representativeness of this approach is still being debated, because the role of final consumers (consumer perspective) is not considered in the emission allocation system. This paper explores the usefulness of a hybrid analysis, including input-output (IO) and process inventory data, as a complementary tool for estimating and allocating national GHG emissions according to both consumer- and producer-based perspectives. We assess the historical GHG impact profile (from 1995 to 2009) of Luxembourg, which is taken as a case study. The country's net consumption over time is estimated to generate about 28,700 Gg CO2e/year on average. Compared to the conventional IPCC inventory, the IO-based framework typically shows much higher emission estimations. This relevant discrepancy is mainly due to the different points of view obtained from the hybrid model, in particular with regard to the contribution of imported goods and services. Detailing the GHG inventory by economic activity and considering a wider system boundary make the hybrid IO method advantageous as compared to the IPCC approach, but its effective implementation is still limited by the relatively complex modeling system, as well as the lack of coordination and scarce availability of datasets at the national level.

Life cycle assessment of first-generation biofuels using a nitrogen crop model

This paper presents an alternative approach to assess the impacts of biofuel production using a method integrating the simulated values of a new semi-empirical model at the crop production stage within a life cycle assessment (LCA). This new approach enabled us to capture some of the effects that climatic conditions and crop management have on soil nitrous oxide (N₂O) emissions, crop yields and other nitrogen (N) losses. This analysis considered the whole system to produce 1 MJ of biofuel (bioethanol from wheat and biodiesel from rapeseed). Non-renewable energy use, global warming potential (GWP), acidification, eutrophication and land competition are considered as potential environmental impacts. Different co-products were handled by system expansion. The aim of this study was (i) to evaluate the variability due to site-specific conditions of climate and fertiliser management of the LCA of two different products: biodiesel from rapeseed and bioethanol from wheat produced in the Basque Country (Northern Spain), and (ii) to improve the estimations of the LCA impacts due to N losses (N₂O, NO₃, NH₃), normally estimated with unspecific emission factors (EFs), that contribute to the impact categories analysed in the LCA of biofuels at local scale. Using biodiesel and bioethanol derived from rapeseed and wheat instead of conventional diesel and gasoline, respectively, would reduce non-renewable energy dependence (-55%) and GWP (-40%), on average, but would increase eutrophication (42 times more potential). An uncertainty analysis for GWP impact showed that the variability associated with the prediction of the major contributor to global warming potential (soil N₂O) can significantly affect the results from the LCA. Therefore the use of a model to account for local factors will improve the precision of the assessment and reduce the uncertainty associated with the convenience of the use of biofuels.

Energy consumption, greenhouse gas emissions and assessment of sustainability index in corn agroecosystems of Iran

The objectives of this study were to assess the energy flow, greenhouse gas (GHG) emission, global warming potential (GWP) and sustainability of corn production systems in Kermanshah province, western Iran. The data were collected from 70 corn agroecosystems which were selected based on randomly sampled method in the summer of 2011. The results indicated that total input and output energy were 50,485 and 134,946 MJ ha(-1), respectively. The highest share of total input energy in corn production systems was recorded for N fertilizer, electricity power and diesel fuel with 35, 25 and 20%, respectively. Energy use efficiency and energy productivity were 2.67 and 0.18 kg MJ(-1), respectively. Also agrochemical energy ratio was estimated as 40%. Applying chemical inputs produced the following emissions of greenhouse gases: 2994.66 kg CO2, 31.58 kg N2O and 3.82 kg CH4 per hectare. Hence, total GWP was 12,864.84 kg Co2eq ha(-1) in corn production systems. In terms of CO2 equivalents 23% of the GWPs came from CO2, 76% from N2O, and 1% from CH4. In this study input and output C equivalents per total GHG and Biomass production were 3508.59 and 10,696.34 kg Cha(-1). Net carbon and sustainability indexes in corn production systems were 7187.75 kg Cha(-1) and 2.05. Accordingly, efficient use of energy is essential to reduce the greenhouse gas emissions and environmental impact in corn agroecosystems.

Effects of biochar and other amendments on the physical properties and greenhouse gas emissions of an artificially degraded soil

Short and long-term impacts of biochar on soil properties under field conditions are poorly understood. In addition, there is a lack of field reports of the impacts of biochar on soil physical properties, gaseous emissions and C stability, particularly in comparison with other amendments. Thus, three amendments - biochar produced from oak at 650°C, humic acid (HA) and water treatment residual - (WTR) were added to a scalped silty-loam soil @ 0.5% (w/w) in triplicated plots under soybean. Over the 4-month active growing season, all amendments significantly increased soil pH, but the effect of biochar was the greatest. Biochar significantly increased soil-C by 7%, increased sub-nanopore surface area by 15% and reduced soil bulk density by 13% compared to control. However, only WTR amendment significantly increased soil nanopore surface area by 23% relative to the control. While total cumulative CH4 and CO2 emissions were not significantly affected by any amendment, cumulative N2O emission was significantly decreased in the biochar-amended soil (by 92%) compared to control over the growing period. Considering both the total gas emissions and the C removed from the atmosphere as crop growth and C added to the soil, WTR and HA resulted in net soil C losses and biochar as a soil C gain. However, all amendments reduced the global warming potential (GWP) of the soil and biochar addition even produced a net negative GWP effect. The short observation period, low application rate and high intra-treatment variation resulted in fewer significant effects of the amendments on the physicochemical properties of the soils than one might expect indicating further possible experimentation altering these variables. However, there was clear evidence of amendment-soil interaction processes affecting both soil properties and gaseous emissions, particularly for biochar, that might lead to greater changes with additional field emplacement time.