Greenhouse Gas Mitigation Potential Research Articles

Evaluation of a hierarchy of models reveals importance of substrate limitation for predicting carbon dioxide and methane exchange in restored wetlands

AbstractWetlands and flooded peatlands can sequester large amounts of carbon (C) and have high greenhouse gas mitigation potential. There is growing interest in financing wetland restoration using C markets; however, this requires careful accounting of both CO2and CH4exchange at the ecosystem scale. Here we present a new model, the PEPRMT model (Peatland Ecosystem Photosynthesis Respiration and Methane Transport), which consists of a hierarchy of biogeochemical models designed to estimate CO2and CH4exchange in restored managed wetlands. Empirical models using temperature and/or photosynthesis to predict respiration and CH4production were contrasted with a more process‐based model that simulated substrate‐limited respiration and CH4production using multiple carbon pools. Models were parameterized by using a model‐data fusion approach with multiple years of eddy covariance data collected in a recently restored wetland and a mature restored wetland. A third recently restored wetland site was used for model validation. During model validation, the process‐based model explained 70% of the variance in net ecosystem exchange of CO2(NEE) and 50% of the variance in CH4exchange. Not accounting for high respiration following restoration led to empirical models overestimating annual NEE by 33–51%. By employing a model‐data fusion approach we provide rigorous estimates of uncertainty in model predictions, accounting for uncertainty in data, model parameters, and model structure. The PEPRMT model is a valuable tool for understanding carbon cycling in restored wetlands and for application in carbon market‐funded wetland restoration, thereby advancing opportunity to counteract the vast degradation of wetlands and flooded peatlands.

Assessment of pathways to reduce CO2 emissions from passenger car fleets: Case study in Ireland

This study modelled the Passenger (PC) fleet and other categories of road transport in Ireland from 2015 to 2035 to assess the impact of current and potential greenhouse gas mitigation policies on CO2 emissions. Scenarios included the shift of purchasing towards diesel PCs over gasoline PCs. Scrappage rates were also calculated and applied to the fleet to predict future sales of PCs. Seven future policy scenarios were examined using different penetrations of PC sales for different vehicle technologies under current and alternative bio-fuel obligations. Tank to Wheel (T2W) tailpipe and Well to Wheel (W2W) CO2 emissions, and energy demand were modelled using COPERT 4v11.3 and a recently published W2W CO2 emissions model. A percentage reduction of conventional diesel and petrol vehicles, in different scenarios compared to a baseline scenario in the W2W model was applied to estimate the likely changes in T2W emissions at the tailpipe up to 2035. The results revealed that the biofuel policy scenario was insufficient in achieving a significant reduction of CO2 emissions. However, without a fixed reduction target for CO2 from the road transport sector, the success of policy scenarios in the long run is difficult to compare. The current Electric vehicle (EV) policy in Ireland is required to be implemented to reduce CO2 emissions by a significant level. Results also show that a similar achievement of CO2 emission reduction could be possible by using alternative vehicle technologies with higher abatement cost. However, as EV based policies have not been successful so far, Ireland may need to search for alternative pathways.

A comparative life cycle assessment highlighting the trade-offs of a liquid manure separator-composter in a Canadian dairy farm system

Greenhouse gas (GHG) emissions from enteric and manure management (MM) activities tend to dominate the carbon footprint of beef and milk production. In this study, a comparative life cycle assessment of dairy milk production (cradle-to-farm gate) was undertaken where the trade-offs of an automated composter-separator technology were contrasted to those of a conventional liquid manure storage system. A simulation of a dairy farm in Ontario, Canada was carried out using the process based manure-DeNitrification DeComposition (Manure-DNDC) model after it was calibrated to a comprehensive set of on-farm MM GHG emission measurements. Results indicated that the active composter system on this farm reduced the carbon footprint (CF) of milk production by 36% (from 1.92 to 1.23 kg CO2eq kg−1 fat-protein corrected milk). For the simulated dairy farm system with only liquid manure storage as a treatment option, the GHG emissions (mainly methane) from the manure storage tank contributed 56% of the carbon footprint, which surpassed the contribution from enteric methane emissions. On the other hand, for the dairy farm with the active composter system, GHG emissions from manure (34% of CF) and enteric emissions (31% of CF) were found to be nearly equivalent in terms of carbon footprint contribution. The composter system created other life cycle benefits (no need to import sand for bedding, increased soil carbon sequestration) and burdens (increased on-farm electricity demand for composter operation), however, the relative contributions of these additional trade-offs were small. Given these additional trade-offs were minor, the GHG mitigation potential of this manure composting technology is likely high in any region of application. In addition, the dairy system with the composter created only marginal problem shifting concerns in terms of the non-CF environmental impact categories considered. For the 146 lactating dairy cow system investigated, an estimated 1460 tCO2eq in life-cycle GHG emissions reduction can be achieved on an annual basis. The benefits of manure composter solutions should provide an impetus for jurisdictions to explore the development of climate policies that incentivize increased adoption rates of this important climate change mitigation opportunity.

Global warming potential and greenhouse gas emission under different soil nutrient management practices in soybean-wheat system of central India.

Soil nutrient management is a key component contributing to the greenhouse gas (GHG) flux and mitigation potential of agricultural production systems. However, the effect of soil nutrient management practices on GHG flux and global warming potential (GWP) is less understood in agricultural soils of India. The present study was conducted to compare three nutrient management systems practiced for nine consecutive years in a soybean-wheat cropping system in the Vertisols of India, in terms of GHG flux and GWP. The treatments were composed of 100% organic (ONM), 100% inorganic (NPK), and integrated nutrient management (INM) with 50% organic+50% inorganic inputs. The gas samples for GHGs (CO2, CH4, and N2O) were collected by static chamber method at about 15-day interval during 2012-13 growing season. The change in soil organic carbon (SOC) content was estimated in terms of the changes in SOC stock in the 0-15cm soil over the 9-year period covering 2004 to 2013. There was a net uptake of CH4 in all the treatments in both soybean and wheat crop seasons. The cumulative N2O and CO2 emissions were in the order of INM>ONM>NPK with significant difference between treatments (p<0.05) in both the crop seasons. The annual GWP, expressed in terms of CH4 and N2O emission, also followed the same trend and was estimated to be 1126, 1002, and 896kg CO2 eqha-1year-1 under INM, ONM, and NPK treatments, respectively. However, the change in SOC stock was significantly higher under ONM (1250kgha-1year-1) followed by INM (417kgha-1year-1) and least under NPK (198kgha-1year-1) treatment. The wheat equivalent yield was similar under ONM and INM treatments and was significantly lower under NPK treatment. Thus, the GWP per unit grain yield was lower under ONM followed by NPK and INM treatments and varied from 250, 261, and 307kg CO2 eqMg-1 grain yield under ONM, NPK, and INM treatments, respectively.

Energy efficiency improvement opportunities and associated greenhouse gas abatement costs for the residential sector

Despite improvements, the residential sector is one of most energy-intensive sectors in the world and is the third largest consumer of energy across Canada, and in Alberta in particular. This study investigates opportunities to improve energy efficiency and reduce greenhouse gas emissions (GHG) in the residential sector. A case study for Alberta is conducted. Energy modeling and scenario analyses are used to project future energy savings and greenhouse gas mitigation potential in the residential sector. Seventeen energy-saving options are identified in different residential subsectors, including space heating and cooling, water heating, appliances, and lighting. The long-term impacts (i.e., from 2013 to 2050) of these technologies in terms of energy savings and greenhouse gas mitigation potential are assessed using the Long-range Energy Alternative Planning model. For the evaluated options, more than 80% of GHG mitigation is achievable with negative GHG abatement cost. A GHG abatement cost curve is developed to assess the economic performance of various options. The results of the cost curve indicate that efficient lighting, efficient furnaces, and high efficiency appliances are the three areas in which the most GHG mitigation can be achieved at the lowest cost. The results provide invaluable insights to policy makers.

Greenhouse Gas Mitigation in Chinese Eco-Industrial Parks by Targeting Energy Infrastructure: A Vintage Stock Model.

Mitigating greenhouse gas (GHG) emissions in China's industrial sector is crucial for addressing climate change. We developed a vintage stock model to quantify the GHG mitigation potential and cost effectiveness in Chinese eco-industrial parks by targeting energy infrastructure with five key measures. The model, integrating energy efficiency assessments, GHG emission accounting, cost-effectiveness analyses, and scenario analyses, was applied to 548 units of energy infrastructure in 106 parks. The results indicate that two measures (shifting coal-fired boilers to natural gas-fired boilers and replacing coal-fired units with natural gas combined cycle units) present a substantial potential to mitigate GHGs (42%-46%) compared with the baseline scenario. The other three measures (installation of municipal solid waste-to-energy units, replacement of small-capacity coal-fired units with large units, and implementation of turbine retrofitting) present potential mitigation values of 6.7%, 0.3%, and 2.1%, respectively. In most cases, substantial economic benefits also can be achieved by GHG emission mitigation. An uncertainty analysis showed that enhancing the annual working time or serviceable lifetime levels could strengthen the GHG mitigation potential at a lower cost for all of the measures.

Mitigation impact of minimum tillage on CO2 and N2O emissions from a Mediterranean maize cropped soil under low-water input management

Reduced tillage might reduce greenhouse gas (GHG) emissions from cropped soils. However the topic is somehow still controversial, since lower CO2 emissions achieved through reduced soil mineralization might be offset by higher N2O losses from less disturbed soil, because of higher water filled pore space. This work aimed to clarify the potential GHG mitigation benefits of minimum tillage (MT), as opposed to mouldboard ploughing (CT), for Mediterranean maize cultivations under low water input management. To this end, soil CO2 and N2O fluxes were monitored at high time resolution by means of a newly developed automated system of closed static chambers coupled to a field gas photoacoustic detector. Relative to CT, cumulated CO2 emissions appeared significantly reduced in MT over three months after the autumn ploughing (by about 30%) and along the spring-summer cultivation (by about 28%), for similar maize yields. N2O emissions from MT showed restrained averaged values relative to CT (by 40% and 18% for fallow and maize periods, respectively); however differences might not be significant. For both treatments, N2O emission factors were lower than the 1% IPCC default value (0.40 and 0.28 for CT and MT, respectively), following the restrained irrigation water input along the drought period. Results indicate that MT reduced GHG emissions both (i) in the short-term, likely due to the increased decomposition of soil organic matter in the ploughed soil (CT), mainly concentrated within the first week after deep tillage; (ii) in the longer-term, likely through its capacity to constrain the daily soil temperature fluctuations in the drought periods along the spring-summer maize cultivation. At this stage, the low-water input management might have played a key role in mediating the response of N2O emissions to MT treatment.These findings suggest that minimum tillage could entail consistent GHG benefits under the drip irrigation management in Mediterranean croplands.

Net global warming potential and greenhouse gas intensity of conventional and conservation agriculture system in rainfed semi arid tropics of India

Agriculture has been considered as one of the contributors to greenhouse gas (GHG) emissions and it continues to increase with increase in crop production. Hence development of sustainable agro techniques with maximum crop production, and low global warming potential is need of the hour. Quantifying net global warming potential (NGWP) and greenhouse gas intensity (GHGI) of an agricultural activity is a method to assess the mitigation potential of the activity. But there is dearth of information on NGWP of conservation agriculture under rainfed conditions. Hence in this study two methods such as crop based (NGWPcrop) and soil based (NGWPsoil) were estimated from the data of the experiment initiated in 2009 in rainfed semiarid regions of Hyderabad, India with different tillage practices like conventional tillage (CT), reduced tillage (RT), zero tillage (ZT) and residue retention levels by harvesting at different heights which includes 0, 10 and 30 cm anchored residue in pigeonpea-castor systems. The results of the study revealed that under rainfed conditions CT recorded 24% higher yields over ZT, but CT and RT were on par with each other. However, the yield gap between the tillage treatments is narrowing down over 5 years of study. ZT and RT recorded 26 and 11% lower indirect GHG emissions (emissions from farm operations and input use) over CT, respectively. The percent contribution of CO2 eq. N2O emission is higher to total GHG emissions in both the crops. Both NGWPcrop, NGWPsoil, GHGIcrop, and GHGIsoil based were influenced by tillage and residue treatments. Further, castor grown on pigeonpea residue recorded 20% higher GHG emissions over pigeonpea grown on castor residues. The fuel consumption in ZT was reduced by 58% and 81% as compared to CT in pigeonpea and castor, respectively. Lower NGWP and GHGI based on crop and soil was observed with increase in crop residues and decrease in tillage intensity in both the crops. The results of the study indicate that, there is scope to reduce the NGWP emissions by reducing one tillage operation as in RT and increase in crop residue by harvesting at 10 and 30 cm height with minimal impact on the crop yields. However, the trade-off between higher yield and soil health versus GHG emissions should be considered while promoting conservation agriculture. The NGWPcrop estimation method indicated considerable benefits of residues to the soil and higher potential of GHG mitigation than by the NGWPsoil method and may overestimate the potential of GHG mitigation in agriculture system.

Greenhouse gas mitigation potential of shelterbelts: estimating farm-scale emission reductions using the Holos model

Shelterbelts provide an opportunity for carbon (C) sequestration and have the potential to mitigate agricultural greenhouse gas (GHG) emissions. However, the influence of shelterbelts on GHG emissi...

Nitrification Inhibitors: A Perspective tool to Mitigate Greenhouse Gas Emission from Rice Soils

Rice fields are significant contributors of greenhouse gases mainly methane and nitrous oxide to the atmosphere. Increasing concentrations of these greenhouse gases play significant role in changing atmospheric chemistry such as mean air temperature, rainfall pattern, drought, and flood frequency. Mitigation of greenhouse gases for achieving sustainable agriculture without affecting economical production is one the biggest challenge of twenty first century at national and global scale. On the basis of published scientific studies, we hereby assess the use of nitrification inhibitors for greenhouse gas mitigation from rice soil. Biologically oxidation of ammonium to nitrate is termed as nitrification and materials which suppress this process are known as nitrification inhibitors. Soil amendment by addition of certain nitrification inhibitors such as neem oil coated urea, nimin-coated urea; dicyandiamide, encapsulated calcium carbide, and hydroquinone reduce cumulative methane and nitrous oxide emission from rice. Firstly, these inhibitors reduce nitrous oxide emissions both directly by nitrification (by reducing NH4+ to NO3-) as well as indirectly by de-nitrification (by reducing NO3- availability in soil). Secondly, methane emission from rice soil can be reduced by enhancing methane oxidation and suppressing methane production and further by reducing the aerenchymal transportation through rice plant. Application of some of the nitrification inhibitors such as calcium carbide and encapsulated calcium carbide reduce methane production by releasing acetylene gas which helps in reducing the population of methanogenic microbes in the soil. Application of nitrification inhibitors also helps to maintain soil redox potential at higher level subsequently reducing cumulative methane emission from soil. Plant derived organic nitrification inhibitors (neem oil, neem cake, karanja seed extract) are eco-friendly and possess substantial greenhouse gas mitigation potential from rice. In the current scenario of global warming and environmental pollution, application of organic plant derived nitrification inhibitors is much needed for sustainable agriculture.

Soil CO2, CH4 and N2O emissions from production fields with planted and remnant hedgerows in the Fraser River Delta of British Columbia

Planting hedgerows on farm field edges can help mitigate greenhouse gas (GHG) emissions from agricultural landscapes by sequestering carbon (C) in woody biomass and in soil. Sequestration rates however, must be assessed in terms of their overall global warming potential (GWP) which must also consider GHG emissions. The objectives of this study were to (1) compare carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions from two types of hedgerows and adjacent annual agricultural production fields, and 2) better understand how climate, soil properties and plant species configurations affect hedgerow GHG emissions. At eight study sites in the lower Fraser River delta of British Columbia, we measured emissions from soil in both planted (P-Hedgerow) and remnant hedgerows (R-Hedgerow), as well as in adjacent annual crop production fields over 1 year using a closed-static chamber method. CO2 emissions were 59 % higher in P-Hedgerow than R-Hedgerow, yet there were no significant differences of relative emissions of CH4 and N2O. The environmental variables that explained the variation in emissions differed for the three GHGs. CO2 emissions were significantly correlated with soil temperature. CH4 and N2O and emissions were marginally significantly correlated with soil organic carbon (SOC) and soil water-filled pore space (WFPS), respectively. Emissions were not significantly correlated with hedgerow plant species diversity. While hedgerows sequester carbon in their woody biomass, we demonstrated that it is critical to measure hedgerow emissions to accurately ascertain their overall GHG mitigation potential. Our results show that there are no CO2e emission differences between the management options that plant new diverse hedgerows or conserve existing hedgerows.

Carbonation and deactivation kinetics of a mixed calcium oxide–copper oxide sorbent/oxygen carrier for post-combustion carbon dioxide capture

Removing carbon dioxide from industrial effluents via solid carbonate sorbents is a potential greenhouse gas mitigation strategy that can also produce hydrogen from the effluent in water gas shift reactors downstream. However, to regenerate the calcium oxide (from the carbonate) requires high temperature that is provided via an oxidation step. To avoid costly oxycombustion to regenerate the CaCO3, it is possible to use the heat generated during the reduction of copper oxide and manganese oxides as chemical looping agents. Unfortunately, sorbents sinter thereby and consequently the surface area drops in the regeneration step. A mixed CuO–CaO sorbent with 10% calcium aluminate binder lost 84% of its initial BET surface area during the first 100min on stream. Homogeneous calcium–copper–cement oxide sorbent deactivate to the 0.5 order with respect to the remaining surface area and a decay constant equal to 2.86min−1. An empirical equilibrium power law model characterizes the carbonation rate from 425°C to 665°C with 10% to 20% CO2 in a 45mm fixed bed. The apparent activation energies of the forward and reverse reaction are 220 and 120kJmol−1, respectively. In addition to sintering, the reaction rate of the regeneration step decreases with time on stream following a zero order process. We attributed this gradual irreversibility to increased crystallinity, reducing the diffusion rate of CO2 to the active carbonate phase. By integrating this resistance to the kinetic model, we are able to explain 99% of the variance in the gas profiles measured by a mass spectrometer.

Carbon Inputs from Miscanthus Displace Older Soil Organic Carbon Without Inducing Priming

The carbon (C) dynamics of a bioenergy system are key to correctly defining its viability as a sustainable alternative to conventional fossil fuel energy sources. Recent studies have quantified the greenhouse gas mitigation potential of these bioenergy crops, often concluding that C sequestration in soils plays a primary role in offsetting emissions through energy generation. Miscanthus is a particularly promising bioenergy crop and research has shown that soil C stocks can increase by more than 2 t C ha−1 yr−1. In this study, we use a stable isotope (13C) technique to trace the inputs and outputs from soils below a commercial Miscanthus plantation in Lincolnshire, UK, over the first 7 years of growth after conversion from a conventional arable crop. Results suggest that an unchanging total topsoil (0–30 cm) C stock is caused by Miscanthus additions displacing older soil organic matter. Further, using a comparison between bare soil plots (no new Miscanthus inputs) and undisturbed Miscanthus controls, soil respiration was seen to be unaffected through priming by fresh inputs or rhizosphere. The temperature sensitivity of old soil C was also seen to be very similar with and without the presence of live root biomass. Total soil respiration from control plots was dominated by Miscanthus-derived emissions with autotrophic respiration alone accounting for ∼50 % of CO2. Although total soil C stocks did not change significantly over time, the Miscanthus-derived soil C accumulated at a rate of 860 kg C ha−1 yr−1 over the top 30 cm. Ultimately, the results from this study indicate that soil C stocks below Miscanthus plantations do not necessarily increase during the first 7 years.

Integrating agronomic practices to reduce greenhouse gas emissions while increasing the economic return in a rice-based cropping system

The effective mitigation of greenhouse gas (GHG) emissions from crop cultivation requires an overall consideration, due to the trade-off relationship between GHGs and the mitigation measures sometimes undermining grain yields and economic returns. To explore the maximum potential of GHG mitigation without sacrificing economic returns, we investigated the GHG emissions, crop yields and economic returns over two years in three rice-cropping systems (rice–wheat, RW; rice–fava bean, RB; and rice–fallow, RF). Different N fertilization levels and straw incorporation methods were employed in each of the rice-cropping systems at the study site, in the Taihu Lake region (TLR) of China. Bean straw produced in the RB system was fermented aerobically before incorporation, while straws produced in the RW and RF systems were directly incorporated into the soils. Relative to the traditional RW system, methane emissions during the rice seasons were significantly reduced by 29–44% in the RB system; annual N inputs were reduced by 43%; annual nitrous oxide emissions for N fertilization treatments were decreased by 56–69%; and the average rice yield was increased by 5.2%. As a result, the GHG intensity (GHGI) was significantly reduced by 11–41%, and the annual net economic benefit (NEB) was increased by 22–94%. Compared with the RW system, the GHGI in the RF system was increased by 8–30% and the NEB was decreased by 3–33%. Considering the current rice/wheat production practices employed in the TLR, the GHGI could be reduced by 26% while the NEB could be improved by 23%, with an annual reduction in the N application rate (currently 525kgNha−1) by 20% and the conversion of the RW systems into RB systems that use straw fermentation. The results of this study suggest that high economic return and GHG mitigation could be simultaneously achieved by the integrated adoption of reasonable reduction in N application rates, the use of appropriate rice-cropping systems and by employing eco-friendly straw management.

Benefits of Low Carbon Development Strategies in Emerging Cities of Developing Country: a Case of Kathmandu

Kathmandu is one of the fastest growing cities in South Asia facing various challenges related to climate change, local pollutants emissions and energy security of supply. This study analysed the greenhouse gas mitigation potential in different economic sectors of the city by using Long-range Energy Planning (LEAP) frame work. It shows that the effect of implementing various low carbon development strategy options can reduce 35.2% of total greenhouse gas emission from energy use as compared to the base case scenario in 2030. This indicates the need for exploring the possibility of utilizing the global climate funds and adopting voluntary mechanisms for greenhouse gas mitigation. The estimated demand side technology investment cost of low carbon measures for different sectors ranges from less than USD 1/tonne CO2e for residential sector to USD 99/tonne CO2e for transport sector. The low carbon options also results co-benefits in terms of significant reduction in emission of local pollutants and improvement of energy security. As Government of Nepal has envisioned following low carbon economic development path on the long run, there is the need of establishment of regulatory framework, institutional framework and development of clear action plans for realizing the implementation of low carbon development strategy measures in the country.

Alternate Wetting and Drying of Rice Reduced CH4 Emissions but Triggered N2O Peaks in a Clayey Soil of Central Italy

Reducing CH4 and N2O emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying (AWD) irrigation is one promising practice that has been shown to reduce CH4 emissions. However, little is known about the impact of this practice on N2O emissions, in particular under Mediterranean climate. To close this knowledge gap, we assessed how AWD influenced grain yield, fluxes and annual budgets of CH4 and N2O emissions, and global warming potential (GWP) in Italian rice systems over a 2-year period. Overall, a larger GWP was observed under AWD, as a result of high N2O emissions which offset reductions in CH4 emissions. In the first year, with 70% water reduction, the yields were reduced by 33%, CH4 emissions decreased by 97%, while N2O emissions increased by more than 5-fold under AWD as compared to PF; in the second year, with a 40% water saving, the reductions of rice yields and CH4 emissions (13% and 11%, respectively) were not significant, but N2O fluxes more than doubled. The transition from anaerobic to aerobic soil conditions resulted in the highest N2O fluxes under AWD. The duration of flooding, transition to aerobic conditions, water level above the soil surface, and the relative timing between fertilization and flooding were the main drivers affecting greenhouse gas mitigation potential under AWD and should be carefully planned through site-specific management options.

Range and uncertainties in estimating delays in greenhouse gas mitigation potential of forest bioenergy sourced from Canadian forests

AbstractAccurately assessing the delay before the substitution of fossil fuel by forest bioenergy starts having a net beneficial impact on atmospheric CO2 is becoming important as the cost of delaying GHG emission reductions is increasingly being recognized. We documented the time to carbon (C) parity of forest bioenergy sourced from different feedstocks (harvest residues, salvaged trees, and green trees), typical of forest biomass production in Canada, used to replace three fossil fuel types (coal, oil, and natural gas) in heating or power generation. The time to C parity is defined as the time needed for the newly established bioenergy system to reach the cumulative C emissions of a fossil fuel, counterfactual system. Furthermore, we estimated an uncertainty period derived from the difference in C parity time between predefined best‐ and worst‐case scenarios, in which parameter values related to the supply chain and forest dynamics varied. The results indicate short‐to‐long ranking of C parity times for residues &lt; salvaged trees &lt; green trees and for substituting the less energy‐dense fossil fuels (coal &lt; oil &lt; natural gas). A sensitivity analysis indicated that silviculture and enhanced conversion efficiency, when occurring only in the bioenergy system, help reduce time to C parity. The uncertainty around the estimate of C parity time is generally small and inconsequential in the case of harvest residues but is generally large for the other feedstocks, indicating that meeting specific C parity time using feedstock other than residues is possible, but would require very specific conditions. Overall, the use of single parity time values to evaluate the performance of a particular feedstock in mitigating GHG emissions should be questioned given the importance of uncertainty as an inherent component of any bioenergy project.

Plant roots and GHG mitigation in native perennial bioenergy cropping systems

AbstractNative perennial bioenergy crops can mitigate greenhouse gases (GHG) by displacing fossil fuels with renewable energy and sequestering atmospheric carbon (C) in soil and roots. The relative contribution of root C to net GHG mitigation potential has not been compared in perennial bioenergy crops ranging in species diversity and N fertility. We measured root biomass, C, nitrogen (N), and soil organic carbon (SOC) in the upper 90 cm of soil for five native perennial bioenergy crops managed with and without N fertilizer. Bioenergy crops ranged in species composition and were annually harvested for 6 (one location) and 7 years (three locations) following the seeding year. Total root biomass was 84% greater in switchgrass (Panicum virgatum L.) and a four‐species grass polyculture compared to high‐diversity polycultures; the difference was driven by more biomass at shallow soil depth (0–30 cm). Total root C (0–90 cm) ranged from 3.7 Mg C ha−1 for a 12‐species mixture to 7.6 Mg C ha−1 for switchgrass. On average, standing root C accounted for 41% of net GHG mitigation potential. After accounting for farm and ethanol production emissions, net GHG mitigation potential from fossil fuel offsets and root C was greatest for switchgrass (−8.4 Mg CO2e ha−1 yr−1) and lowest for high‐diversity mixtures (−4.5 Mg CO2e ha−1 yr−1). Nitrogen fertilizer did not affect net GHG mitigation potential or the contribution of roots to GHG mitigation for any bioenergy crop. SOC did not change and therefore did not contribute to GHG mitigation potential. However, associations among SOC, root biomass, and root C : N ratio suggest greater long‐term C storage in diverse polycultures vs. switchgrass. Carbon pools in roots have a greater effect on net GHG mitigation than SOC in the short‐term, yet variation in root characteristics may alter patterns in long‐term C storage among bioenergy crops.

Assessment of alternative disposal methods to reduce greenhouse gas emissions from municipal solid waste in India.

Open dumping, the most commonly practiced method of solid waste disposal in Indian cities, creates serious environment and economic challenges, and also contributes significantly to greenhouse gas emissions. The present article attempts to analyse and identify economically effective ways to reduce greenhouse gas emissions from municipal solid waste. The article looks at the selection of appropriate methods for the control of methane emissions. Multivariate functional models are presented, based on theoretical considerations as well as the field measurements to forecast the greenhouse gas mitigation potential for all the methodologies under consideration. Economic feasibility is tested by calculating the unit cost of waste disposal for the respective disposal process. The purpose-built landfill system proposed by Yedla and Parikh has shown promise in controlling greenhouse gas and saving land. However, these studies show that aerobic composting offers the optimal method, both in terms of controlling greenhouse gas emissions and reducing costs, mainly by requiring less land than other methods.

Remanufacturing as a means for achieving low-carbon SMEs in Indonesia

Remanufacturing can reduce the energy intensity and associated greenhouse gas (GHG) emissions significantly and increase the eco-efficiency of product systems by utilizing recovered end-of-life parts. This paper presents the GHG mitigation potential of technically feasible remanufactured alternators in Indonesian small- and medium-sized enterprizes. Life cycle assessment approach and Weibull ++8 software have been used to calculate environmental and quality parameters. Since existing remanufactured alternators have not been found to meet the technical criterion for customers’ satisfaction, a number of alternative remanufacturing strategies have been explored to identify an option that has not only reduced GHG emissions but also has satisfied reliability, durability and warranty period criterion. Three improvement scenarios involving three different remanufacturing strategies were investigated in this case study, and yielded useful insights in order to come up with a technically feasible remanufacturing strategy for reducing a significant amount of GHG emissions. The improvement scenario III, which maximizes the use of used components, was found to offer technically and environmentally feasible remanufacturing solutions. Overall, this research has found that about 7207 t of CO2 -eq GHG emissions and 111.7 TJ embodied energy consumption could potentially be avoided if 10 % of alternators in Indonesian automobile sector are remanufactured using technically feasible remanufacturing strategy.