Global Temperature Change Potential Research Articles

Are single global warming potential impact assessments adequate for carbon footprints of agri-food systems?

The vast majority of agri-food climate-based sustainability analyses use global warming potential (GWP100) as an impact assessment, usually in isolation; however, in recent years, discussions have criticised the ‘across-the-board’ application of GWP100 in Life Cycle Assessments (LCAs), particularly of food systems which generate large amounts of methane (CH4) and considered whether reporting additional and/or alternative metrics may be more applicable to certain circumstances or research questions (e.g. Global Temperature Change Potential (GTP)). This paper reports a largescale sensitivity analysis using a pasture-based beef production system (a high producer of CH4 emissions) as an exemplar to compare various climatatic impact assessments: CO2-equivalents using GWP100 and GTP100, and ‘CO2-warming-equivalents’ using ‘GWP Star’, or GWP*. The inventory for this system was compiled using data from the UK Research and Innovation National Capability, the North Wyke Farm Platform, in Devon, SW England. LCAs can have an important bearing on: (i) policymakers’ decisions; (ii) farmer management decisions; (iii) consumers’ purchasing habits; and (iv) wider perceptions of whether certain activities can be considered ‘sustainable’ or not; it is, therefore, the responsibility of LCA practitioners and scientists to ensure that subjective decisions are tested as robustly as possible through appropriate sensitivity and uncertainty analyses. We demonstrate herein that the choice of climate impact assessment has dramatic effects on interpretation, with GWP100 and GTP100 producing substantially different results due to their different treatments of CH4 in the context of carbon dioxide (CO2) equivalents. Given its dynamic nature and previously proven strong correspondence with climate models, out of the three assessments covered, GWP* provides the most complete coverage of the temporal evolution of temperature change for different greenhouse gas emissions. We extend previous discussions on the limitations of static emission metrics and encourage LCA practitioners to consider due care and attention where additional information or dynamic approaches may prove superior, scientifically speaking, particularly in cases of decision support.

The Role of Renewable-Derived Plastics in the Analysis of Waste Management Schemes: A Time-Dependent Carbon Cycle Assessment

Carbon capture and storage (CCS) is an essential greenhouse gas removal (GGR) technology used to achieve negative emissions in bioenergy plants using biomass feedstock (Bio-CCS). In this study, the climate mitigation potential of a novel GGR technology consisting in the production of renewable-derived plastics from municipal solid waste (MSW) refuse has been evaluated. This novel GGR technology allows for carbon storage, for variable periods, in stable materials (plastics), and thus overcomes the technical limitations of CCS. A time-dependent carbon cycle assessment has been conducted based on the Absolute Global surface Temperature change Potential (AGTP) metric. This new method to assess carbon emissions is presented against a traditional life cycle assessment (LCA). The production of renewable-derived plastics proves to be an effective GGR technology for both landfill- and incineration-dominant countries in Europe. The results obtained encourage the implementation of renewable-derived plastics in Integrated Assessment Models (IAMs) to assess their global potential in forecasting scenarios to achieve the ambitious climate change targets set in the European Union. Thanks to this study, a novel approach toward a green and sustainable economy has been established. This study will help to fill the gaps between bioenergy and renewable materials production.

Theoretical Investigation on Hydrogen Abstraction Reactions of Sulfur Compounds HSX(O)H and CH3SX(O)H (X = C, S) by OH Radicals

The kinetic and mechanistic investigation of oxidation reactions of HSC(O)H, HSS(O)H, CH3SC(O)H, and CH3SS(O)H by OH radicals is performed extensively with the help of theoretical calculations. The potential energy profiles for the titled reactions are constructed at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level. Two isomers, cis and trans, are observed for both HSC(O)H and HSS(O)H molecules. Reaction enthalpies and reaction Gibbs free energies are calculated employing the M06-2X/aug-cc-pVTZ method. The kinetic study uses canonical variational transition state theory and small-curvature tunneling in the temperature range of 210–350 K. CVT/SCT rate coefficients are utilized for calculating branching ratios. The atmospheric lifetime of HSC(O)H is computed to be 26.76 h, 3.51 h for HSS(O)H, 1.55 years for CH3SC(O)H, and 18.20 h for CH3SS(O)H. The global warming potential (GWP) and global temperature change potential (GTP) of CH3SC(O)H are found to be significant, while cis-HSC(O)H, trans-HSC(O)H, cis-HSS(O)H, trans-HSS(O)H, and CH3SS(O)H have negligible GWPs and GTPs.

Global temperature goals should determine the time horizons for greenhouse gas emission metrics

Emission metrics, a crucial tool in setting effective exchange rates between greenhouse gases, currently require an arbitrary choice of time horizon. Here, we propose a novel framework to calculate the time horizon that aligns with scenarios achieving a specific temperature goal. We analyze the Intergovernmental Panel on Climate Change Special Report on Global Warming of 1.5 °C Scenario Database to find that time horizons aligning with the 1.5 °C and 2 °C global warming goals of the Paris Agreement are 24 [90% prediction interval: 7, 41] and 58 [90% PI: 41, 74] years, respectively. We then use these time horizons to quantify time-dependent emission metrics for methane. We find that the Global Warming Potential (GWP) values that align with the 1.5 °C and 2 °C goals are GWP1.5 °C = 75 [90% PI: 54, 107] and GWP2 °C = 42 [90% PI: 35, 54]. For the Global Temperature change Potential (GTP) they are GTP1.5 °C = 41 [90% PI: 16, 102] and GTP2 °C = 9 [90% PI: 7, 16]. The most commonly used time horizon, 100 years, underestimates methane’s GWP and GTP by 34% and 38%, respectively, relative to the values we calculate that align with the 2 °C goal and by 63% and 87%, respectively, relative to the 1.5 °C goal. To best align emission metrics with the Paris Agreement 1.5 °C goal, we recommend a 24 year time horizon, using 2045 as the endpoint time, with its associated GWP1.5 °C = 75 and GTP1.5 °C = 41.

Temperature change and mitigation potential of Indian cement industry

Cement is one of the highest energy-consuming and emission generating industries around the world. To reduce greenhouse emissions, several mitigation measures have been proposed, and their effectiveness is estimated. However, estimates of the global temperature change potential of the cement industry have seldom been performed. Hence, in this study, we propose a new framework that estimates CO2 emissions and other seven pollutants to estimate temperature change potential from the cement industry. The underlying framework uses system dynamics, where the effectiveness of four mitigation measures, i.e., a shift in demand, newer methodologies to produce clinker, use of energy efficiency improvements, and implementation of renewable energy, are explored. The results indicate that renewable sources of energy show highest mitigation potential. The cement industry has contributed to an increase in 2 mK temperature since 1990, which is likely to grow up to 14.8 mK by 2050 if no mitigation measures are applied. Energy efficiency improvements by extensions of perform achieve and trade scheme can reduce 0.33 mK from the Indian cement industry. This paper provides a unique opportunity for estimating temperature influence of the cement industry, which can be further implemented for other countries.

Climate co-benefits of air quality and clean energy policy in India

Sustainable development goals connect policies addressing air quality and energy efficiency with complementary benefits for climate mitigation. However, a typically fragmented approach across these domains hinders effectiveness in addressing short-lived climate forcers (SLCFs)—including methane, carbon monoxide, non-methane volatile organic compounds and black carbon—to supplement CO2 mitigation. Here, to support policy coordination in India, we assess climate co-benefits of air quality and clean energy policies, using multiple metrics (global warming and temperature change potentials). We estimate an emission reduction potential of −0.1 to −1.8 GtCO2e yr−1 in 2030. The largest benefits accrue from residential clean energy policy (biomass cooking) and air pollution regulation (curbing brick production and agricultural residue burning emissions), which cut black carbon. In the next 1–2 decades (using global warming potential—GWP20), emission reduction potentials of warming SLCFs exceed those of CO2, which is not evident on longer timescales. Concurrently, policies in the electricity generation and transport sectors reduce cooling SLCFs (SO2 and NOx), potentially unmasking 0.1–2.4 GtCO2e yr−1. Integrating these interventions into national climate policies can strengthen both climate action and sustainability. The crucial impact of black carbon suggests that it should be included in the international climate accord. Climate-oriented goals in air quality and clean energy policies can substantially reduce greenhouse gas emissions, particularly if shifting to biomass cooking and addressing emissions from brick production and agricultural residue burning.

Climate Metrics for C1-C4 Hydrofluorocarbons (HFCs).

Hydrofluorocarbons (HFCs) are potent greenhouse gases that are potential substitutes for ozone depleting substances. The Kigali amendment lists 17 HFCs that are currently in commercial use to be regulated under the Montreal Protocol. Future commercial applications may explore the use of other HFCs, most of which currently lack an evaluation of their climate metrics. In this work, atmospheric lifetimes, radiative efficiencies (REs), global warming potentials (GWPs), and global temperature change potentials (GTPs) for all saturated HFCs with fewer than 5 carbon atoms are estimated to help guide future usage and policy decisions. Atmospheric lifetimes were estimated using a structure activity relationship (SAR) for OH radical reactivity and estimated O(1D) reactivity. Radiative metrics were obtained using theoretically calculated infrared absorption spectra that were presented in a previous work. Calculations for some additional HFCs not included in the previous work were performed in this work. The HFCs display unique infrared spectra with strong absorption in the Earth's atmospheric infrared window region, primarily due to the C-F stretching vibration. Results from this study show that the HFC global atmospheric lifetimes and REs are dependent upon their H atom content and molecular structure. Therefore, the HFC radiative metric evaluation requires a case-by-case evaluation. A thorough experimental evaluation of a targeted HFC's atmospheric lifetime and climate metrics is always highly recommended. However, in cases where it is experimentally difficult to separate isomers, the new results from this study should help guide the experiments, as well as provide relevant climate metrics with uncertainties and policy relevant data.

Global warming impacts of nitrogen use in agriculture: an assessment for India since 1960

ABSTRACT Global warming impacts of N use in Indian agriculture since 1960 was estimated for 20- and 100-year time scales using equation-based empirical method. During 2014, total Warming in terms of global temperature change potential (GTP) for a 20-year time scale (GTP20) was assessed as 217.31 ± 17.74 Tg CO2e, and for a 100-year time scale (GTP100) was 217.78 ± 17.78 Tg CO2e. N2O contributed 90% and 99%of the GTP20 and GTP100, respectively. Total cooling impacts were 94.86 ± 7.75 and 50.36 ± 4.11 Tg CO2e on GTP20 and GTP100, respectively. Aerosols of NH3 and NOx, NOx-induced O3 and CH4 alteration, and N-induced C sequestration contributed 41, 6 and 51%, respectively, to GTP20, however, N-induced C sequestration contributed about 99% to GTP100. Net warming impacts were 122.45 ± 10.00 and 167.42 ± 13.67 Tg CO2e on GTP20 and GTP100, respectively. Net warming impacts were lowered by 10% and 1% compared to total warming, and 37% and 23% compared to warming caused by N2O alone, for GTP20 and GTP100, respectively. Usually, to estimate the global warming impacts of N use in agriculture, the warming effects of only N2O emission are considered. However, both warming and cooling impacts should be considered to capture the net impacts of N use in agriculture on climate change.

Global warming potential and absolute global temperature change potential from carbon dioxide and methane fluxes as indicators of regional sustainability – A case study of Jämtland, Sweden

Abstract This study presents a regional model showing the balance of carbon dioxide and methane fluxes in the Swedish county Jamtland, applying a Global Warming Potential 20-year time horizon (GWP20) to meet the Paris agreement horizon and regional policy goals. The results clearly show the necessity to take both anthropogenic and non-anthropogenic emissions into consideration in analyses to be able to make proper priorities in future action strategies. The total annual impact from Jamtland calculated as carbon dioxide equivalents (CO2eq) is an uptake of 2.4 Mton (19 ton per capita). Jamtland shows large annual uptakes in forests (12.7 Mton CO2), but also large emissions of methane (80 kton corresponding to 6.7 Mton CO2eq), mainly from lakes, mires and ruminants. Anthropogenic carbon Greenhous gas emissions are dominated by transportation, working machines and consumption (mainly imported indirect emissions). As a complement to GWP also the Absolute Global Temperature Change Potential (AGTP) as degree K response, is presented per sector and total for Jamtland County, for yearly emissions (as a pulse) and continuous emissions over 200 years. A yearly pulse from Jamtland gives a temperature response of about 0 K after 10 years and about −4 μK (cooling effect) after about 50 years). Using both GWP and AGTP as indicators improves the possibilities to find ways how to optimize regional climate policies to reduce global warming until a specific year. Strategies and action plans should be developed focusing on the following: - Reduced regional transportation and consumption activity. - Increased (prioritized) use of renewable fuels for working machines in forestry and agriculture, as well as for heavy trucks. - Evaluate the potential to reduce emissions of methane from wetlands and mires. - Increase/optimize carbon dioxide assimilation in forests.

Climate impact of Finnish air pollutants and greenhouse gases using multiple emission metrics

Abstract. We present a case study where emission metric values from different studies are applied to estimate global and Arctic temperature impacts of emissions from a northern European country. This study assesses the climate impact of Finnish air pollutants and greenhouse gas emissions from 2000 to 2010, as well as future emissions until 2030. We consider both emission pulses and emission scenarios. The pollutants included are SO2, NOx, NH3, non-methane volatile organic compound (NMVOC), black carbon (BC), organic carbon (OC), CO, CO2, CH4 and N2O, and our study is the first one for Finland to include all of them in one coherent dataset. These pollutants have different atmospheric lifetimes and influence the climate differently; hence, we look at different climate metrics and time horizons. The study uses the global warming potential (GWP and GWP*), the global temperature change potential (GTP) and the regional temperature change potential (RTP) with different timescales for estimating the climate impacts by species and sectors globally and in the Arctic. We compare the climate impacts of emissions occurring in winter and summer. This assessment is an example of how the climate impact of emissions from small countries and sources can be estimated, as it is challenging to use climate models to study the climate effect of national policies in a multi-pollutant situation. Our methods are applicable to other countries and regions and present a practical tool to analyze the climate impacts in multiple dimensions, such as assessing different sectors and mitigation measures. While our study focuses on short-lived climate forcers, we found that the CO2 emissions have the most significant climate impact, and the significance increases over longer time horizons. In the short term, emissions of especially CH4 and BC played an important role as well. The warming impact of BC emissions is enhanced during winter. Many metric choices are available, but our findings hold for most choices.

Prospect and potential of biomass power to mitigate climate change: A case study in India

Biomass has often been regarded as a promising renewable energy resource to mitigate climate change. However, what will be the impact on global surface temperature if biomass replace fossil fuel remain unclear. This paper, through a case study in Uttar Pradesh, India address this issue by assessing biomass resource potential to reduce fossil fuel demand and mitigate climate change. Impact of biomass power related GHG emissions on global surface temperature is estimated using the Absolute Global Temperature change Potential (AGTP) climate metric. Uttar Pradesh can produce 71 Mt surplus biomass annually, equivalent to 7298 MW power. Power density of biomass range between 0.10 and 0.25 Wm-2. Significant amount of GHG emissions reduction is possible if biomass replace fossil fuel as a power source in the region. Annual GHG emissions associated with 1 MWh of power derived from coal, natural gas and biomass would cause 4.10 × 10−7, 2.40 × 10−7 and 1.25 × 10−7 mK rise in global surface temperature, 100 years after an initial emission, indicating potential of biomass power to mitigate climate change. Variation in spatio-temporal distribution and low power density could be delimiting factors in large-scale deployment of biomass power.

Life cycle assessment (LCA) of an alkali-activated binary concrete based on natural volcanic pozzolan: A comparative analysis to OPC concrete

This article evaluates, through a life cycle assessment (LCA), the GWP (Global Warming Potential) and GTP (Global Temperature Change Potential) of an alkali-activated binary concrete (AABC) based on natural volcanic pozzolan from Colombia (NP) (70%) and granulated blast furnace slag (GBFS) (30%). A NaOH and Na2SiO3 solution was used as alkaline activator. The results obtained demonstrate the possibility of producing an AABC of “normal strength”, with an equal or even higher compressive strength than the OPC concrete, designed and produced in an equivalent manner to the AABC, and a clear environmental advantage as its carbon footprint (GWP) is 44.7% lower (AABC = 210.90 kg CO2 eq/m3 vs. OPC = 381.17 kg CO2 eq/m3). These results are viewed as an important contribution towards the adoption and standardization of the production methods (on an industrial scale) of low carbon footprint alkali-activated concrete in the foreseeable future in countries with soils mostly deriving from volcanic ashes like Colombia.

Integrating impacts on climate change and biodiversity from forest harvest in Norway

Forest ecosystems provide a variety of services, from climate regulation to biodiversity conservation. Temporary land cover variations such as those related to forest management can contribute to climate change through both biogeochemical (carbon, warming) and biophysical (albedo, cooling) mechanisms. As global rising demand for biomass for energy and materials can contribute to biodiversity losses, there is an evident need for integrated assessments of climate and biodiversity impacts to investigate possible trade-offs and synergies. We explore the integration of impacts on climate change and biodiversity from forest harvest for three case studies based on forest plantations in Norway. We focus on impacts from land disturbance after clear-cutting using three plots of one ha each of homogeneous forest in two ecoregions in Norway involving three different tree species: spruce, pine and birch. We use existing ecoregion specific characterization factors (CFs) to quantify occupation, short-term and long-term transformation impacts of land use on biodiversity loss for five taxonomic groups: mammals, birds, amphibians, reptiles and plants at regional and global level. For climate change impacts, we quantify the contributions of CO2 fluxes and changes in albedo. We estimate CFs for two complementary climate metrics, namely global warming potential (GWP) and global temperature change potential (GTP) for time horizons of 20 and 100 years and quantify impacts in CO2 equivalents. We pursue the integration of impacts on climate and biodiversity from a time perspective: very short (GWP20 and land occupation), medium (GWP100 and land transformation within 100 years) and long (GTP100 and land transformation after 100 years). We find CFs from −0.21 to 1.6 kg CO2-eq./kg CO2 for carbon emissions, and from −0.03 to −1.4 kg CO2-eq./kg CO2 for albedo changes, while net characterized impacts range from −44.8 t CO2-eq./ha (GTP100, spruce) to 93.25 t CO2-eq./ha (GWP20, spruce). Damages to biodiversity range from 4.76 * 10−13 to 6.24 * 10−8 global species eq. lost per ton of carbon harvested. Our results reinforce the notion that spatially and temporally explicit analyses are vital when assessing life-cycle impacts from land derived products. We show that the existing set of multiple and complementary indicators for climate change and biodiversity impacts can be integrated into a common framework to better inform about the complex heterogeneities of the forest ecosystem response to disturbances. We argue for a more frequent consideration of integrated impacts on biodiversity and climate change from forestry operations to better highlight possible co-benefits or adverse side-effects of forest management strategies.

Evaluating climate change mitigation potential of hydrochars: compounding insights from three different indicators

AbstractWe employed life cycle assessment to evaluate the use of hydrochars, prospective soil conditioners produced from biowaste using hydrothermal carbonization, as an approach to improving agriculture while using carbon present in the biowaste. We considered six different crops (barley, wheat, sugar beet, fava bean, onion, and lucerne) and two different countries (Spain and Germany), and used three different indicators of climate change: global warming potential (GWP), global temperature change potential (GTP), and climate tipping potential (CTP). We found that although climate change benefits (GWP) from just sequestration and temporary storage of carbon are sufficient to outweigh impacts stemming from hydrochar production and transportation to the field, even greater benefits stem from replacing climate‐inefficient biowaste management treatment options, like composting in Spain. By contrast, hydrochar addition to soil is not a good approach to improving agriculture in countries where incineration with energy recovery is the dominant treatment option for biowaste, like in Germany. Relatively small, but statistically significant differences in impact scores (ISs) were found between crops. Although these conclusions remained the same in our study, potential benefits from replacing composting were smaller in the GTP approach, which due to its long‐term perspective gives less weight to short‐lived greenhouse gases (GHGs) like methane. Using CTP as indicator, we also found that there is a risk of contributing to crossing of a short‐term climatic target, the tipping point corresponding to an atmospheric GHG concentration of 450 ppm CO2 equivalents, unless hydrochar stability in the soil is optimized. Our results highlight the need for considering complementary perspectives that different climate change indicators offer, and overall provide a foundation for assessing climate change mitigation potential of hydrochars used in agriculture.

Climate change impact of livestock CH4 emission in India: Global temperature change potential (GTP) and surface temperature response

Two climate metrics, Global surface Temperature Change Potential (GTP) and the Absolute GTP (AGTP) are used for studying the global surface temperature impact of CH4 emission from livestock in India. The impact on global surface temperature is estimated for 20 and 100 year time frames due to CH4 emission. The results show that the CH4 emission from livestock, worked out to 15.3 Tg in 2012. In terms of climate metrics GTP of livestock-related CH4 emission in India in 2012 were 1030 Tg CO2e (GTP20) and 62 Tg CO2e (GTP100) at the 20 and 100 year time horizon, respectively. The study also illustrates that livestock-related CH4 emissions in India can cause a surface temperature increase of up to 0.7mK and 0.036mK over the 20 and 100 year time periods, respectively. The surface temperature response to a year of Indian livestock emission peaks at 0.9mK in the year 2021 (9 years after the time of emission). The AGTP gives important information in terms of temperature change due to annual CH4 emissions, which is useful when comparing policies that address multiple gases.

Emission metrics for quantifying regional climate impacts of aviation

Abstract. This study examines the impacts of emissions from aviation in six source regions on global and regional temperatures. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation and calculate the global and regional emission metrics global warming potential (GWP), global temperature change potential (GTP) and absolute regional temperature change potential (ARTP). The GWPs and GTPs vary by a factor of 2–4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: the temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify temperature change in four broad latitude bands following 1 year of emissions from present-day aviation, including CO2. Aviation over North America and Europe causes the largest net warming impact in all latitude bands, reflecting the higher air traffic activity in these regions. Contrail cirrus gives the largest warming contribution in the short term, but remain important at about 15 % of the CO2 impact in several regions even after 100 years. Our results also illustrate both the short- and long-term impacts of CO2: while CO2 becomes dominant on longer timescales, it also gives a notable warming contribution already 20 years after the emission. Our emission metrics can be further used to estimate regional temperature change under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept.

Accounting for the climate–carbon feedback in emission metrics

Abstract. Most emission metrics have previously been inconsistently estimated by including the climate–carbon feedback for the reference gas (i.e. CO2) but not the other species (e.g. CH4). In the fifth assessment report of the IPCC, a first attempt was made to consistently account for the climate–carbon feedback in emission metrics. This attempt was based on only one study, and therefore the IPCC concluded that more research was needed. Here, we carry out this research. First, using the simple Earth system model OSCAR v2.2, we establish a new impulse response function for the climate–carbon feedback. Second, we use this impulse response function to provide new estimates for the two most common metrics: global warming potential (GWP) and global temperature-change potential (GTP). We find that, when the climate–carbon feedback is correctly accounted for, the emission metrics of non-CO2 species increase, but in most cases not as much as initially indicated by IPCC. We also find that, when the feedback is removed for both the reference and studied species, these relative metric values only have modest changes compared to when the feedback is included (absolute metrics change more markedly). Including or excluding the climate–carbon feedback ultimately depends on the user's goal, but consistency should be ensured in either case.

Global temperature change potential of nitrogen use in agriculture: A 50-year assessment

Nitrogen (N) use in agriculture substantially alters global N cycle with the short- and long-term effects on global warming and climate change. It increases emission of nitrous oxide, which contributes 6.2%, while carbon dioxide and methane contribute 76% and 16%, respectively of the global warming. However, N causes cooling due to emission of NOx, which alters concentrations of tropospheric ozone and methane. NOx and NH3 also form aerosols with considerable cooling effects. We studied global temperature change potential (GTP) of N use in agriculture. The GTP due to N2O was 396.67 and 1168.32 Tg CO2e on a 20-year (GTP20) and 439.94 and 1295.78 Tg CO2e on 100-year scale (GTP100) during years 1961 and 2010, respectively. Cooling effects due to N use were 92.14 and 271.39 Tg CO2e (GTP20) and 15.21 and 44.80 Tg CO2e (GTP100) during 1961 and 2010, respectively. Net GTP20 was 369.44 and 1088.15 Tg CO2e and net GTP100 was 429.17 and 1264.06 Tg CO2e during 1961 and 2010, respectively. Thus net GTP20 is lower by 6.9% and GTP100 by 2.4% compared to the GTP considering N2O emission alone. The study shows that both warming and cooling effects should be considered to estimate the GTP of N use.

Life-cycle assessment of a biogas power plant with application of different climate metrics and inclusion of near-term climate forcers

This study assesses the environmental sustainability of electricity production through anaerobic co-digestion of sewage sludge and organic wastes. The analysis relies on primary data from a biogas plant, supplemented with data from the literature. The climate impact assessment includes emissions of near-term climate forcers (NTCFs) like ozone precursors and aerosols, which are frequently overlooked in Life Cycle Assessment (LCA), and the application of a suite of different emission metrics, based on either the Global Warming Potential (GWP) or the Global Temperature change Potential (GTP) with a time horizon (TH) of 20 or 100 years. The environmental performances of the biogas system are benchmarked against a conventional fossil fuel system. We also investigate the sensitivity of the system to critical parameters and provide five different scenarios in a sensitivity analysis. Hotspots are the management of the digestate (mainly due to the open storage) and methane (CH4) losses during the anaerobic co-digestion. Results are sensitive to the type of climate metric used. The impacts range from 52 up to 116 g CO2-eq./MJ electricity when using GTP100 and GWP20, respectively. This difference is mostly due to the varying contribution from CH4 emissions. The influence of NTCFs is about 6% for GWP100 (worst case), and grows up to 31% for GWP20 (best case). The biogas system has a lower performance than the fossil reference system for the acidification and particulate matter formation potentials. We argue for an active consideration of NTCFs in LCA and a critical reflection over the climate metrics to be used, as these aspects can significantly affect the final outcomes.

Climate impact assessment of willow energy from a landscape perspective: a Swedish case study

AbstractLocally produced bioenergy can decrease the dependency on imported fossil fuels in a region, while also being valuable for climate change mitigation. Short‐rotation coppice willow is a potentially high‐yielding energy crop that can be grown to supply a local energy facility. This study assessed the energy performance and climate impacts when establishing willow on current fallow land in a Swedish region with the purpose of supplying a bio‐based combined heat and power plant. Time‐dependent life cycle assessment (LCA) was combined with geographic information system (GIS) mapping to include spatial variation in terms of transport distance, initial soil organic carbon content, soil texture and yield. Two climate metrics were used [global warming potential (GWP) and absolute global temperature change potential (AGTP)], and the energy performance was determined by calculating the energy ratio (energy produced per unit of energy used). The results showed that when current fallow land in a Swedish region was used for willow energy, an average energy ratio of 30 MJ MJ−1 (including heat, power and flue gas condensation) was obtained and on average 84.3 Mg carbon per ha was sequestered in the soil during a 100‐year time frame (compared with the reference land use). The processes contributing most to the energy use during one willow rotation were the production and application of fertilizers (~40%), followed by harvest (~35%) and transport (~20%). The temperature response after 100 years of willow cultivation was −6·10−16 K MJ−1 heat, which is much lower compared with fossil coal and natural gas (70·10−16 K MJ−1 heat and 35·10−16 K MJ−1 heat, respectively). The combined GIS and time‐dependent LCA approach developed here can be a useful tool in systematic analysis of bioenergy production systems and related land use effects.