Effect of tricarboxylic acid cycle regulators on the formation of humic substance during composting: The performance in labile and refractory materials

The aims of this study are to reveal the roles of tricarboxylic acid (TCA) cycle regulators in reducing CO₂ emission and promoting humic substance (HS) formation during composting with different materials. The results showed that the addition of adenosine tri-phosphate (ATP) or malonic acid (MA) reduced CO₂ emission during chicken manure composting. However, only the addition of MA reduced CO₂ emission during lawn waste and garden waste composting. In addition, both of the two inhibitors promoted HS formation, especially for ATP. Structural equation models further confirmed that ATP and MA reduced CO₂ emission by inhibiting the decomposition of amino acid by microorganisms. Meanwhile, ATP promoted the conversion of amino acid and soluble sugars to HS, while MA only promoted the conversion of soluble sugars to HS. In summary, this study provides a theoretical basis for the application of inhibitors to reduce CO₂ emission and promote HS formation during composting.

Potential of tri-reforming process and membrane technology for improving ammonia production and CO2 reduction

In this work, a tri-reforming process was coupled with a membrane separation unit to enhance efficiency of ammonia (NH₃) synthesis process in terms of CO₂ emission, NH₃ production, and NO_x emission. Primary and secondary reformers were replaced by a tri-reforming process, while a Perovskite membrane was applied to separate nitrogen (N₂) from oxygen (O₂). A conventional NH₃ synthesis process and the proposed process were simulated by Aspen-Hysys and compared in order to investigate the performance of the proposed sterategy. The simulation results indicated that when temperature increased and pressure decreased, conversion of hydrocarbons and H₂/CO ratio were improved from 1.73 to 2.54, which resulted in an increase in NH₃ production by 27 %, and a decrease in CO₂ emission rate from 1192 kg/h to approximately 1 kg/h. The proposed sterategy was optimized in terms of different parameters e.g., temperature and pressure. Optimum reaction pressure and temperature were determined to be between 1 and 10 bar and 500-800 °C, respectively. The results of the study revealed that the proposed strategy not only removed amine and methanol sweeteners which reduce the operational costs of the process, but also decreased the NO_x content from 8220 ppm to almost 10 ppm.

Relationship between CO2 emissions and soil properties of differently tilled soils

Different tillage technologies have different effects on CO₂ emissions from soil. Unfortunately, little information exists about the impact of different types of tillage as compared with no-tillage, and the main controls. The aim of this research is to determine the relationship between physicomechanical, chemical and biological properties of soil and CO₂ emissions from differently tilled soils under the climatic conditions of central Lithuania before and after autumn tillage. The studies were conducted in 2009-2012 and 2014 at the Experimental Station of Aleksandras Stulginskis University in Central Lithuania. Different tillage technologies were applied: deep ploughing at 23-25 cm depth (DP); shallow ploughing at 12-15 cm depth (SP); deep cultivation with a cultivator at 25-27 cm depth (DC); shallow cultivation with a disc harrow at 12-15 cm depth (SC); and no-tillage (NT). The correlation of physicomechanical, chemical and biological soil properties with CO₂ emissions was determined. During all the experimental period total CO₂ emissions from soil in DP, SP, DC, SC and NT technologies were respectively 6.05, 4.25, 4.97, 4.42, 3.94 μmol m^-2 s^-1 before autumn soil tillage and 29.88, 22.50, 16.73, 13.72, 10.00 μmol m^-2 s^-1 after autumn tillage. Negative correlation between soil temperature and CO₂ emissions before the autumn tillage from soil was evidenced (r = -0.98). A strong negative correlation between soil respiration and total soil porosity was observed. Correlation between aeration soil porosity and CO₂ emissions was strong. After autumn tillage, the strongest correlations were found between soil penetration resistance and respiration in the upper (r = -0.75) and deeper (r = -0.71) layers. In autumn, a significant strong correlation (r = 0.78) between soil respiration and aeration porosity was obtained in the upper soil layer under ploughing or cultivation. This study revealed that CO₂ emissions were significantly higher immediately after autumn ploughing technologies compared to deep and shallow cultivation and no-tillage.

Decomposition of maize stover varies with maize type and stover management strategies: A microcosm study on a Black soil (Mollisol) in northeast China

Crop residue decomposition has an important impact on soil organic carbon (SOC) sequestration and CO₂ emission. Residue quality and management strategies are two important factors regulating decomposition process and SOC mineralization and greenhouse gas emission. In this study, a microcosm experiment in field condition was conducted on a silty loam (a Black soil) in Northeast China to investigate stover decomposition and soil CO₂ emission characteristics as influenced by different crop cultivars and stover field incorporation methods. Stover from two popular maize cultivars Xianyu335 (XY) and Liangyu99 (LY) were applied in two modes (soil surface application vs soil incorporation) at a rate of 11 t ha^-1, and CO₂ efflux was monitored during the decomposition duration of 144 days. The structural transformation of carbon functional groups in maize stover were evaluated using solid state ¹³C-CPMAS NMR and elemental analysis techniques. Results showed that up to 71.7%∼86.9% (weight basis) of C and N in soil-incorporated stover was decomposed during the study period, which was significantly greater than the losses (32.8%∼55.3%) of C or N from the surface-applied stover for both maize cultivars; decomposition rates of main C functional groups were significantly higher in soil incorporation (71.1%∼88.8%) than in surface application (20.9%∼60.2%) systems. The concentrations of SOC, total N, available N, and microbial biomass C and N in soil were also higher with stover incorporation than surface application. Stover incorporation resulted in a notably lower CO₂ emission rate and accumulative CO₂ efflux (53.9-55.4 mol m^-2) during the stover decomposition compared with surface application (57.4-67.0 mol m^-2). Between the two maize cultivars, the LY stover showed a higher decomposition rate and greater capacity for SOC sequestration when incorporated into soil. The LY stover induced higher (16.8%) CO₂ emission than XY when applied on soil surface, but no significant difference was found between the two cultivars when incorporated into soil. The results suggested that cultivar selection and stover management strategies have great potential in reducing soil CO₂ emission while improving soil biochemical properties. Incorporating the LY stover into soil rather than surface mulching could enhance SOC sequestration and reduce CO₂ emission.

CO2 fluxes from aquaculture ponds of a tropical wetland: Potential of multiple lime treatment in reduction of CO2 emission

Partial pressure of CO₂ in water [pCO₂(water)] and air-water CO₂ flux were estimated in two aquaculture ponds (one received no lime treatment (NTP) and in the other lime treatment was performed (LTP) four times a year) every month throughout an annual cycle, situated in East Kolkata Wetlands, a Ramsar Site in eastern India. It was hypothesized that lime treatment can potentially lower the pCO₂(water) in aquaculture ponds and hence make these aquatic bodies sinks for CO₂. The results portrayed that NTP acted as a source of CO₂ throughout the year (annual mean: 1929 ± 1397 μmol m^-2 h^-1), whereas, LTP acted as CO₂ sinks post lime addition (monthly mean ranged from -366 ± 16 to -449 ± 32 μmol m^-2 h^-1), though the effect of lime addition was found to diminish by the next month and it acted as source for CO₂ in the months when no lime treatment was done (LTP annual mean: 1010 ± 1617 μmol m^-2 h^-1). Lime treatment increased the pH level and reduced the turbidity which facilitated optimum photosynthesis and the productivity increased rapidly. Beyond the critical pH value of 8.9-9.0, the pCO₂(water) values became under-saturated with respect to atmospheric CO₂ concentration. The effect of lime treatment was not found to prevail in the following months as a steady source of sewage from the Kolkata metropolis which feeds these aquaculture constantly bring in a huge carbon source both in inorganic and organic form. As soon as the flocculation effect of the lime dies off, the water column starts becoming turbid again which aids in converting the system into a net heterotrophic one from a net autotrophic. Based on the results we could successfully accept our hypothesis that lime treatment can not only reduce the CO₂ emission but also make the system a CO₂ sink.

Net N2O production from soil particle size fractions and its response to changing temperature

Previous studies demonstrated that finer soil particles have smaller rates of CO₂ emission but larger Q₁₀ values (the proportionate increase in the rate for a warming of 10 °C) than coarser particles. However, it has not been tested whether there is a regular pattern for rates and Q₁₀ for N₂O emission (net production) across soil particle size fractions, considering the known positive correlation between soil CO₂ and N₂O emissions. A short-term incubation study with different soil particle fractions was conducted for soils from a grassland, a forest, an upland (including organic manure (OM) and chemical nitrogen, phosphorus, and potassium fertilizers (NPK) treatments), and a paddy (including manure plus chemical fertilizer (MNPK) and NPK treatments) under a series of increasing and decreasing temperatures between 5 °C and 30 °C with 5 °C intervals. For all the soils, net N₂O production per unit mass of soil N was smaller from the silt (2-50 μm) fraction than from the sand (>50 μm) and clay (<2 μm) fractions. In paddy soils, Q₁₀ for net N₂O production was highest from the clay fraction. In contrast, Q₁₀ was highest in the sand fraction for the grassland soil. In the upland and paddy soils, the rates of net N₂O production were higher in OM or MNPK treatment than in their corresponding NPK treatment, but Q₁₀ values were similar between the manure and NPK treatments. The net N₂O production rates positively correlated with CO₂ emission across all soil samples, and this was also the case for their Q₁₀ values. Q₁₀ values for net N₂O production averaged 8% lower than those for CO₂ emissions. In conclusion, the net N₂O production rates appear to be the smallest from the silt fraction.

Carbon footprint of fertilizer technologies

The work discussed the necessity to evaluate the environmental effect - i.e. carbon footprint (CF), of N-containing fertilizers when including their production, transportation and use. For that purpose, life cycle assessment (LCA) methodology was involved. The LCA-based CF concerned model fertilizer technology determined with the consideration of greenhouse gases assimilation during fertilizer-induced vegetation, as compared to non-treated crops system. According to the available data, the inclusion of CO₂ assimilation by plants via photosynthesis in balance sheet offsets 87.6% of the CF from the biomass consumption. Thus, the new approach to LCA along with the analysis of life cycle costs would provide more reliable determination of the fee amount charged to European fertilizer manufacturers. The approach might be further developed for various products for plant treatment. Also, the verification of similar fertilizer technologies in different installations is expected to identify bottlenecks in terms of the ecological, technical and economic evaluation.

Engineering Microorganisms for Enhanced CO2 Sequestration

Microbial CO₂ sequestration not only provides a green and sustainable approach for ameliorating global warming but also simultaneously produces biofuels and chemicals. However, the efficiency of microbial CO₂ fixation is still very low. In addition, concomitant microbial CO₂ emission decreases the carbon yield of desired chemicals. To address these issues, strategies including engineering CO₂-fixing pathways and energy-harvesting systems have been developed to improve the efficiency of CO₂ fixation in autotrophic and heterotrophic microorganisms. Furthermore, metabolic pathways and energy metabolism can be rewired to reduce microbial CO₂ emissions and increase the carbon yield of value-added products. This review highlights the potential of biotechnology to promote microbial CO₂ sequestration and provides guidance for the broader use of microorganisms as attractive carbon sinks.

Estimation of CO2 emissions from heavy-duty vehicles in Korea and potential for reduction based on scenario analysis

Estimations of CO₂ emissions and the potential to reduce heavy-duty vehicles in Korea under different reduction scenarios are presented in this paper. Technologically achievable CO₂ reduction rates are applied to four scenarios: the business as usual (BAU) scenario, mild scenario, normal scenario, and aggressive scenario. In estimating CO₂ emissions, a simulation model based on longitudinal vehicle dynamics was used in cooperation with average vehicle mileage traveled and the number of registered Korean heavy-duty vehicles. In the BAU scenario, which is the reference scenario, 30.82 million tons of CO₂ will be emitted in 2030, and CO₂ emissions will be reduced by 2.1%, 4%, and 5%, respectively, in mild, normal, and aggressive scenarios. In 2040, the reduction effects of these scenarios will be 5.7%, 10.9%, and 15.8%, respectively. These results indicate the range of available potential reduction of CO₂ by technical improvements or the CO₂ emission regulation of heavy-duty vehicles in Korea.

The impact of electricity consumption on CO2 emission, carbon footprint, water footprint and ecological footprint: The role of hydropower in an emerging economy

The primary objective of this paper is to investigate the isolated impacts of hydroelectricity consumption on the environment in Malaysia as an emerging economy. We use four different measures of environmental degradation including ecological footprint, carbon footprint, water footprint and CO₂ emission as target variables, while controlling for GDP, GDP square and urbanization for the period 1971 to 2016. A recently introduced unit root test with breaks is utilized to examine the stationarity of the series and the bounds testing approach to cointegration is used to probe the long run relationships between the variables. VECM Granger causality technique is employed to examine the long-run causal dynamics between the variables. Sensitivity analysis is conducted by further including fossil fuels in the equations. The results show evidence of an inverted U-shaped relationship between environmental degradation and real GDP. Hydroelectricity is found to significantly reduce environmental degradation while urbanization is also not particularly harmful on the environment apart from its effect on air pollution. The VECM Granger causality results show evidence of unidirectional causality running from hydroelectricity and fossil fuels consumption to all measures of environmental degradation and real GDP per capita. There is evidence of feedback hypothesis between real GDP to all environmental degradation indices. The inclusion of fossil fuel did not change the behavior of hydroelectricity on the environment but fossil fuels significantly increase water footprint.

The influence of biopreparations on the reduction of energy consumption and CO2 emissions in shallow and deep soil tillage

The application of innovation in agriculture technologies is very important for increasing the efficiency of agricultural production, ensuring the high productivity of plants, production quality, farm profitability, the positive balance of used energy, and the requirements of environmental protection. Therefore, it is a scientific problem that solid and soil surfaces covered with plant residue have a negative impact on the work, traction resistance, energy consumption, and environmental pollution of tillage machines. The objective of this work was to determine the dependence of the reduction of energy consumption and CO₂ gas emissions on different biopreparations. Experimental research was carried out in a control (SC1) and seven different biopreparations using scenarios (SC2-SC8) using bacterial and non-bacterial biopreparations in different consistencies (with essential and mineral oils, extracts of various grasses and sea algae, phosphorus, potassium, humic and gibberellic acids, copper, zinc, manganese, iron, and calcium), estimating discing and plowing as the energy consumption parameters of shallow and deep soil tillage machines, respectively. CO₂ emissions were determined by evaluating soil characteristics (such as hardness, total porosity and density). Meteorological conditions such average daily temperatures (2015-20.3 °C; 2016-16.90 °C) and precipitations (2015-6.9 mm; 2016-114.9 mm) during the month strongly influenced different results in 2015 and 2016. Substantial differences between the averages of energy consumption identified in approximately 62% of biological preparation combinations created usage scenarios. Experimental research established that crop field treatments with biological preparations at the beginning of vegetation could reduce the energy consumption of shallow tillage machines by up to approximately 23%, whereas the energy consumption of deep tillage could be reduced by up to approximately 19.2% compared with the control treatment. The experimental research results reveal the reduction of CO₂ emissions in shallow tillage to approximately 20.14% (and that in deep tillage to approximately 19.16%) when works were performed by different biological preparation usage scenarios. This experimental research demonstrates the efficient use of the special adaptation of a new biotechnological method for the reduction of the energy consumption and CO₂ gas emissions of agricultural machinery.

What is the probability of achieving the carbon dioxide emission targets of the Paris Agreement? Evidence from the top ten emitters

This study predicts the probabilities of achieving the carbon dioxide (CO₂) emission targets set by the Paris Agreement and the Intended Nationally Determined Contribution (INDC) of the top ten CO₂ emitters (TTCE). The TTCE are China, USA, India, Russia, Japan, Germany, South Korea, Iran, Saudi Arabia and Indonesia based on their emission trends over 1991-2015 period. The methods of trend extrapolation and back propagation (BP) neural networks are used in this paper to overcome the weakness of multiple linear regression (MLR) and the assumptions of the environmental Kuznets curve (EKC). The results show that the model performs well and has high predictive accuracy. The volume of the CO₂ emissions by the TTCE in 2030 is predicted to increase by 26.5-36.5%, compared with 2005. According to different trends of economic growth, energy consumption, and changes in share of renewable energy, the results show that China, India and Russia will achieve their INDC targets in some scenarios, whereas there will be a shortfall in achieving targets by USA, Japan, Germany, and South Korea. In particular, the carbon reduction situations of Saudi Arabia, Iran and Indonesia are quite severe. Moreover, the results show that there is no common trend that can be used as a suitable benchmark for every country for the implementation of carbon reductions targets of the Paris Agreement and their INDC goals. Finally, there are signs of improvement of the equality of carbon emissions based on the analysis of the Gini coefficient.

The economic impact of agricultural pollutions in Iran, spatial distance function approach

Pollution has increased in Iran in the last two decades due to agricultural activities. Pollutions are released into the atmosphere and thereafter pollute water and soil resources. Therefore, it is important to develop models that can estimate the economic value of these Pollutions. For this purpose, a Spatial Output Distance Function was used in the present study to estimate the shadow price of carbon dioxide emission and water salinity in spatial and temporal dimensions. This method can be used as a new method to estimate the value of externalities. In this study, the data of provinces in Iran during 1995-2014 were used. The results showed that the total shadow price of agricultural Pollutions was equal to 42.54 dollars per unit. In addition, the effects due to the adjacency of regions to each other led to the transfer of pollution and its externalities were equal to 26.3 dollars per unit of pollution. This finding refers to the importance of considering the spatial dimension when analyzing the shadow price of pollutions caused by production. Thus, internalizing the damage caused by pollutions based on the adjacency of regions to each other can increase the efficiency of the production environment.

Upgraded biogas from municipal solid waste for natural gas substitution and CO2 reduction--a case study of Austria, Italy, and Spain

Biogas is rich in methane and can be further purified through biogas upgrading technologies, presenting a viable alternative to natural gas. Landfills and anaerobic digestors treating municipal solid waste are a large source of such biogas. They therefore offer an attractive opportunity to tap into this potential source of natural gas while at the same time minimizing the global warming impact resulting from methane emissions in waste management schemes (WMS) and fossil fuel consumption reduction. This study looks at the current municipal solid waste flows of Spain, Italy, and Austria over one year (2009), in order to determine how much biogas is generated. Then it examines how much natural gas could be substituted by using four different biogas upgrading technologies. Based on current waste generation rates, exploratory but realistic WMS were created for each country in order to maximize biogas production and potential for natural gas substitution. It was found that the potential substitution of natural gas by biogas resulting from the current WMS seems rather insignificant: 0.2% for Austria, 0.6% for Italy and 0.3% for Spain. However, if the WMS is redesigned to maximize biogas production, these figures can increase to 0.7% for Austria, 1% for Italy and 2% for Spain. Furthermore, the potential CO2 reduction as a consequence of capturing the biogas and replacing fossil fuel can result in up to a 93% reduction of the annual national waste greenhouse gas emissions of Spain and Italy.

Performance analysis of CO(2) emissions and energy efficiency of metal industries in China

Nonferrous metal industries play an important role in China's national economy and are some of the country's largest energy consumers. To better understand the nature of CO(2) emissions from these industries and to further move towards low-carbon development in this industry sector, this study investigates the CO(2) emissions of 12 nonferrous metal industries from 2003 to 2010 based on their life-cycle assessments. It then classifies these industries into four "emission-efficiency" types through cluster analysis. The results show that (1) the industrial economy and energy consumption of China's nonferrous metal industries have grown rapidly, although their recent energy consumption rate shows a declining trend. (2) The copper, aluminum, zinc, lead, and magnesium industries, classified as high-emission industries, are the main contributors of CO(2) emissions. The results have implications for policy decisions that aim to enhance energy efficiency, particularly for promoting the transformation of low-efficiency industries to high-efficiency ones. The study also highlights the important role of policy development in technological innovations, optimization, and upgrades, the reduction of coal proportion in energy consumption, and the advancement of new energy sources.

Influence of pyrolysis temperature on composted sewage sludge biochar priming effect in a loamy soil

Biochar is a carbon-rich solid product obtained by the pyrolysis of organic materials. The carbon stability of biochar allows that it can be applied to soil for long-term carbon storage. This carbon stability is greatly influenced by the pyrolysis temperature and the raw material used for biochar production. The aim of the present work is to study the soil carbon sequestration after the application of biochar from sewage sludge (SL) pyrolysis at two different temperatures (400 and 600 °C). For this purpose, soil CO2 emissions were measured for 80 d in an incubation experiment after soil amendment with the SL and each biochar at a dosage of 8 wt%. Biochar reduced the CO2 emissions during incubation between 11% and 32% relative to the SL treatment. The CO2 data were fit to a dual exponential model, and the CO2 emissions were simulated at different times (1, 5 and 10 yr). Additionally, the kinetics of the CO2 evolution from SL, two biochar samples, soil and amended soil were well fit to a dual first-order kinetic model with correlation coefficients greater than 0.93. The simulation of CO2 emissions from the soil by applying the proposed double first-order kinetic model (kg CO2-C ha(-1)) showed a reduction of CO2 emissions between 301 and 932 kg CO2-C ha(-1)with respect to the direct application of raw sewage sludge after 10 yr.