Accounting for forest carbon pool dynamics in product carbon footprints: Challenges and opportunities

Modification and loss of forests due to natural and anthropogenic disturbance contribute an estimated 20% of annual greenhouse gas (GHG) emissions worldwide. Although forest carbon pool modeling rarely suggests a ‘carbon neutral’ flux profile, the life cycle assessment community and associated product carbon footprint protocols have struggled to account for the GHG emissions associated with forestry, specifically, and land use generally. Principally, this is due to underdeveloped linkages between life cycle inventory (LCI) modeling for wood and forest carbon modeling for a full range of forest types and harvest practices, as well as a lack of transparency in globalized forest supply chains. In this paper, through a comparative study of U.S. and Chinese coated freesheet paper, we develop the initial foundations for a methodology that rescales IPCC methods from the national to the product level, with reference to the approaches in three international product carbon footprint protocols. Due to differences in geographic origin of the wood fiber, the results for two scenarios are highly divergent. This suggests that both wood LCI models and the protocols need further development to capture the range of spatial and temporal dimensions for supply chains (and the associated land use change and modification) for specific product systems. The paper concludes by outlining opportunities to measure and reduce uncertainty in accounting for net emissions of biogenic carbon from forestland, where timber is harvested for consumer products.     

The evolution of city-scale GHG emissions inventory methods: A systematic review

The capacity of cities to act on climate change mitigation is essential to fulfil the Paris Agreement target. In order to do so, cities should establish an effective climate policy which requires, as a first step, a complete greenhouse gas (GHG) emissions inventory. The accurate city-scale GHG inventory enables cities to develop, implement and track climate solution measures, mainly those related to transportation. The compilation of a city-scale GHG inventory requires a standardized method and up-to-date activity data. This systematic review critically examines 40 articles over the past 20 years to (1) identify city-scale GHG inventory methods being applied worldwide, (2) evaluate how these methods are evolving, (3) elaborate how emissions from transport sector are being estimated, and (4) determine what data types and sources of transport-related data are being used. The review was limited to articles that addressed the process of compilation of a GHG inventory. The results demonstrate that city-scale GHG inventory methods evolved from the Intergovernmental Panel on Climate Change (IPCC) Guidelines to a variety of GHG accounting methods that offer levels of complexity to estimate city-scale emissions. Although GHG inventory methods for city-scale have advanced over the years, almost one third of the articles reviewed were focused on the proposal of a GHG inventory framework, adjusting current methods to each city's reality or proposing new ones. The majority of the cities analysed lack local transport-related data to measure GHG emissions based on the bottom-up approach. Yet, more than 40% of the articles managed to deliver the bottom-up inventory using a diversity of data types and sources. This review shows that there is still a path to achieve a globally compatible method. This would require a joint effort between researchers and city authorities to make international protocols more compliant to each city's data availability along with the improvement of cities data collection.     

Greenhouse gas emissions from two hydroelectric reservoirs in Mediterranean region

Water reservoirs are used for many purposes, such as water supply, irrigation, flood mitigation, and hydroelectric energy generation. Although hydroelectric energy is considered “green,” many studies show that the construction of a reservoir enhances greenhouse gas (GHG) emissions at the transformed area. These emissions, mainly of CO₂, CH₄, and N₂O gases, depend on the age of the reservoir, landscape and soil composition, fauna and flora remnants of the impounded area, climatic conditions, and basin runoffs. Consequently, GHG emissions significantly vary between reservoirs and depending on local specificities. Several studies have investigated GHG emissions from reservoirs around the world, focusing mainly on reservoirs located in cold regions, temperate regions, and tropical regions. Research is lacking for reservoirs in Mediterranean countries, like Greece, and similar regions. This work initially assesses the net GHG emissions of a newly created reservoir (Ilarion est. 2012) in Western Macedonia, Greece. The methodology for net GHG emission calculation was based on the use of literature data concerning pre-impoundment emission factors and local specificities of the reservoir (terrain type, canopy cover), as well as on the 2-year measurement data that were collected using a “static floating chamber.” Furthermore, in this work, the gross GHG emissions of an older, in-line reservoir (Polyfytos est. 1974) were also calculated, based on 2-year measurement data. The results show that the global warming potential (GWP) of the reservoirs is dictated by methane emissions; it minimizes during winter and spring and maximizes during summer and autumn. Hydroelectric energy production at Ilarion Reservoir results in 32 to 97 times less total CO₂ equivalent emissions in comparison to fossil fuels, while at Polyfytos Reservoir only 8 to 24 times less (based on gross emissions). It appears that the impact of a reservoir’s morphology on GHG emissions is more significant than that of a reservoir’s age.     

Greenhouse gas emission inventory for Senegal, 1991

The first greenhouse gas (GHG) emission estimates for Senegal, for the year 1991, were produced according to the draft IPCC/OECD guidelines for national inventories of GHGs. Despite certain discrepancies, nonavailability of data, the quality of some of the data collected, and the methodology, the estimates provide a provisional basis for Senegal to fulfill its obligations under the UN Framework Convention on Climate Change. This inventory reveals that GHG emissions in Senegal, like those in many developing countries, can mainly be attributed to the use of biomass for energy, land-use change and forestry, and savanna burning. Taking into account the direct global warming potential of the main GHGs (CO₂, CH₄, and N₂O), Senegal's emissions are estimated at 17.6 Tg ECO₂. The major gases emitted are CO₂ (61% of GHG emissions), followed by CH₄ (35%) and N₂O (4%). Energy accounts for 45% of total emissions (12% from fossil energy and 33% from traditional biomass energy); land-use change and forests, 18%; agriculture, 24%; waste, 12%; and industry, 1%.     

Urban form and spatial structure as determinants of per capita greenhouse gas emissions considering possible endogeneity and compensation behaviors

Modifying the form and spatial structure of cities through urban planning can be an effective means to reduce greenhouse gas (GHG) emissions in cities. The supporters of the Compact City Approach to urban sustainability propose dense and centralized urban systems. In the case of population density, they argue that it promotes displacements of foot and public transport, and that typical apartments of compact fabrics require less energy than single-family dwellings. Therefore, high density should lead to low GHG emissions. During the last decade this association has been questioned because: a) there may be compensatory behaviors (more energy consumption and more GHG emissions in mobility and housing during weekends and holidays, and b) the fact of not considering the effects of the endogeneity associated with self-selection. In this paper, we analyze population density as a determinant of mobility and residential GHG emissions in Gran Concepción (Chile) using multivariate regression models. The results obtained indicate that density does not exert a significant impact on GHG emissions in mobility and housing. It is income differences that mostly explain individual GHG emissions variability. This calls into question the possible effectiveness of compactness policies in regional, cultural and climatic contexts different from those of the US and Europe and are excessively oriented towards the maintenance and increase of density in urban centers and slowing down the expansion of suburban neighborhoods.     

Availability of disaggregated greenhouse gas emissions from beef cattle production: A systematic review

Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO₂e) ‘carbon footprint’ per unit output. The 100-year Global Warming Potential (GWP₁₀₀) is the most commonly used CO₂e metric, but others have also been proposed, and there is no universal reason to prefer GWP₁₀₀ over alternative metrics. The weightings assigned to non-CO₂ GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH₄) and nitrous oxide (N₂O), rather than CO₂. This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO₂e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP₁₀₀ CO₂e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO₂e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP₁₀₀ non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP₁₀₀), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO₂e footprints.     

Consequential life cycle assessment of automotive material substitution: Replacing steel with aluminum in production of north American vehicles

The substitution of aluminum for steel in vehicle body and closure components is a common strategy for reducing fuel consumption. In order to assess the greenhouse gas (GHG) consequences of this decision, the system must be examined using a life cycle approach. Furthermore, attributional life cycle assessment (ALCA) does not suffice for a number of reasons, including the fact that ALCA does not model the incremental system and that allocating the benefits of recycling inhibits the modelling of system-wide consequences caused by the decision studied. This study thus uses a consequential life cycle assessment (CLCA) framework. We examine the physical and economic processes that guide the North American light-duty vehicle fleet from its initial state in 2012 to a state in 2050. Industry projections are used to model the production and use phases. The system is expanded to include the scrap and material markets. This generates new insights regarding the environmental consequences of changes in scrap generation and recycling in automotive material substitution. The method is applied to the fleet in order to forecast if and when aluminum intensification constitutes net GHG reduction under various conditions. Using baseline parameter values compiled from public and industry data; we calculate a GHG payback period of 25 years, i.e. before a net reduction in emissions relative to a no change counterfactual is achieved. A local sensitivity analysis is performed, showing that the net GHG reduction may be achieved in a period as short as 12 years, or never be achieved at all. A global sensitivity analysis is performed using Monte Carlo simulation, where 16% of trials never reach a net reduction in GHG emissions. We also estimate which parameters contribute the most to variance in the model outcomes. The material replacement coefficient, or the amount of aluminum it takes to functionally replace one kilogram of steel, is the top contributor to the variance (29.8%). Overall, the results are most sensitive to parameters governing the amount of mass that can be replaced by each kilogram of additional aluminum, the GHG intensity of additional aluminum production, and the response of the aluminum scrap and material markets to additional aluminum scrap generation. We conclude that given the current lack of understanding of key parameters and their underlying uncertainties, it is not possible to definitively state that substituting aluminum for steel results in a net reduction in GHG emissions from a fleet of vehicles.     

Dynamical Allocation Method of Emission Rights of Pollutants by Viability Constraints Under Tychastic Uncertainty

This study proposes a method of dynamic decentralization by constraints and its associated software. It can be used to allocate pollutant emissions rights among the different polluters such that they achieve both given global and local emission thresholds not to be transgressed. Knowing the maximum growth rates of polluting emissions of each polluter in the worst case, this method provides the rule of a dynamic allocation of pollutant emissions rights as well as the required initial emissions of each polluters assuring that, whatever the growth rates of the emissions below the maximum growth rates, the resulting emissions will be, both globally and locally, under their thresholds. These guaranteed initial emissions supply each polluter with a measure of risk insurance. This problem, formulated as a “tychastic” regulated system with viability constraints, is solved with mathematical and algorithmic tools of viability theory and numerical results obtained by a dedicated software are presented.     

Modeling lifetime greenhouse gas emissions associated with materials for various end-of-life treatments

This research has developed mathematical models for computing lifetime greenhouse gas (GHG) emissions associated with materials. The models include embodied carbon (EC) emissions from the manufacture of materials, and GHG emissions from incineration, or landfill gas (LFG) production from landfill disposal of the material beyond their service lives. The models are applicable to all materials; however, their applications here are demonstrated for the lumber from a residential building with 50- and 100-year service lives, and with incineration, landfill, and deconstruction as end-of-life treatments. This paper introduces a new metric for lifetime GHG emissions associated with materials termed “Global Warming Impact of Materials (GWIM).” The GWIM is subdivided into two portions: (i) productive portion (GWIM_p) that includes the materials’ emissions until the service life of the facility and (ii) non-productive portion (GWIM_np) which includes the materials’ GHG emissions beyond the service life until they are eliminated from the atmosphere. In place of the current, static, EC measurements (kgCO₂e or MTCO₂e), this model reports the GWIMs in units of kgCO₂e-years or MTCO₂e-years, which includes the effects of “time of use” of a facility. Using the models, this paper has computed GHG reductions by deconstruction, with material recoveries of 30%, 50%, and 70% at demolition for reuse, recycle, or repurpose. A 70% material recovery, after a 50-year service life of the building, affected a savings of 47% and 52% if the remaining 30% debris was incinerated or landfilled respectively. All of the values computed using models checked out with manual calculations.     

北京市废弃物处理温室气体排放特征

基于《2006年IPCC国家温室气体清单指南》推荐的方法,结合《省级温室气体清单编制指南（试行）》和《城市温室气体核算工具指南》的部分数据与核算范围,针对固体废弃物填埋、焚烧和废水处理等过程,核算了北京市2005-2014年废弃物处理过程中温室气体总排放量。结果表明：2005-2014年北京市废弃物处理过程温室气体总排放量呈逐渐上升趋势,2014年温室气体总排放量比2005年增长98%。10年间,固体废弃物填埋过程一直是最主要的温室气体排放源,到2014年排放量达到最大,为416.3×10⁴t二氧化碳当量（CO₂e）。废弃物填埋、废水处理和废弃物焚烧过程占总排放量的比例分别为78.5%（CO₂e质量分数,下同）、13.5%和8%。结合已有研究,系统优化国内7个典型城市废弃物处理温室气体排放因子,核算7个城市排放情况,并对比分析了北京市排放情况。     

Kyoto commitments: macro and micro insights on trading and the Clean Development Mechanism

The purpose of this paper is twofold. First, we raise some issues related to the expected dimension of the carbon market. This analysis is based on a survey of model results on the implementation of the Kyoto goal with and without reliance on emissions trading. In particular, we consider both the emissions and the financial implications associated with different trading scenarios. Transfers related to international GHG trading might be equivalent to a 400% increase in foreign direct investment to countries with economies in transition. A closer look at the GHG reductions expected from the developing world also suggests that global models may be overly optimistic in their assessment of the contribution of flexibility mechanisms in meeting the Kyoto emission goals. OECD countries may need to rely more on domestic policies to reduce their emissions than what has so far been projected by global models. Second, we use a simple microeconomic model to test the potential contribution of typical power generation technologies in the context of the Clean Development Mechanism. Projects that are defined as additional in terms of the environment but already profitable can bring about significant results at a relatively low price of certified emission reductions. To assume that the contribution of the CDM will come close to what is projected by global models (both for prices and quantities) is to assume that such projects could be credited under the CDM. This revised version was published online in July 2006 with corrections to the Cover Date.     

Review of PSR framework and development of a DPSIR model to assess greenhouse effect in Taiwan

In dealing with the complex issues of greenhouse gas (GHG) emission and climate change mitigation, many interrelated factors such as cost, level of technology development, supply and demand of energy, structure of industry, and expenditures on research and development exist. Using indicators to monitor environmental impacts and evaluate the efficacies of policies and regulations has been practiced for a long time, and it can serve as a useful tool for decision making and for comparison between different countries. Although numerous indicators have been developed for relevant subjects, integrated approaches that consider individual changes, dynamic interaction, and multi-dimensions of indicators are scarce. This paper aimed to develop a Driving Force-Pressure-State-Impact-Response (DPSIR) framework to assess the problems. This DPSIR model is mainly related to energy consumption, environmental impacts, and policy responses. The objectives of the paper were: (1) conduct a literature review on the indicators that have been used in GHG-related studies; (2) develop a DPSIR model that incorporates GHG-related indicators and evaluate their relationships using a cause?Ceffect chain of GHG emission; and (3) develop a calculative method that can be used to explain the dynamic correlation among the interdependent indicators. Taiwan is a significant source of global GHG emissions. A case study, using the developed framework and Taiwan??s actual data of the past two decades, was conducted. The results indicate that regulatory strategies for pollution control are inadequate in terms of ensuring environmental quality, and the nature does not have the capability to revert the impacts from the existing level of pollution.     

Estimation of green house gas emissions from Koteshwar hydropower reservoir,India

The emissions of greenhouse gas (GHG) from soils are of significant importance for global warming. The biological and physico-chemical characteristics of soil affect the GHG emissions from soils of different land use types. Methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) production rates from six forest and agricultural soil types in the Koteshwar hydropower reservoir catchments located in the Uttarakhand, India, were estimated and their relations with physico-chemical characteristics of soils were examined. The samples of different land use types were flooded and incubated under anaerobic condition at 30 °C for 60 days. The cumulative GHG production rates in reservoir catchment are found as 1.52 ± 0.26, 0.13 ± 0.02, and 0.0004 ± 0.0001 μg g soil^?1 day^?1 for CO₂, CH₄, and N₂O, respectively, which is lower than global reservoirs located in the same eco-region. The significant positive correlation between CO₂ productions and labile organic carbon (LOC), CH₄ and C/N ratio, while N₂O and N/P ratio, while pH of soils is negatively correlated, conforms their key role in GHG emissions. Carbon available as LOC in the reservoir catchment is found as 3–14% of the total ?C” available in soils and 0–23% is retained in the soil after the completion of incubation. The key objective of this study to signify the C, N, and P ratios, LOC, and pH with GHG production rate by creating an incubation experiment (as in the case of benthic soil/sediment) in the lab for 60 days. In summary, the results suggest that carbon, as LOC were more sensitive indicators for CO₂ emissions and significant C, N, and P ratios, affects the GHG emissions. This study is useful for the hydropower industry to know the GHG production rates after the construction of reservoir so that its effect could be minimized by taking care of catchment area treatment plan.     

Integrated Assessment of Swiss GHG Mitigation Policies After 2012

The residential sector presents a great potential for greenhouse gases (GHG) mitigation. We perform an integrated assessment of different mitigation policies for Switzerland focusing on the residential sector. We analyze the case of pure incentive taxes and technical regulations. For our analysis, we have coupled a general equilibrium model with a Swiss residential energy model. We find that a progressive GHG tax of more than 200 USD2000/tCO₂ eq is necessary to reach a target of 50% reduction of GHG emissions in 2050. Finally, we also find that efficiency-based technical regulations provide limited additional abatement incentives.     

Meat,Dairy and Climate Change: Assessing the Long-Term Mitigation Potential of Alternative Agri-Food Consumption Patterns in Canada

We use a newly developed model of the entire Canadian energy system (TIMES-Canada) to assess the climate change mitigation potential of different agri-food consumption patterns in Canada. For this, our model has been extended by disaggregating the agricultural demand sector into individual agri-food demands to allow for a more in-depth analysis. Besides a business-as-usual (baseline) scenario, we have constructed four different agri-food scenarios to assess the viability of reducing Canadian meat and dairy consumption in order to diminish Canada’s agricultural sector energy consumption and greenhouse gas (GHG) emissions. Our policy scenarios progressively restrict the consumption of different meat and dairy agricultural products until the year 2030. Our results suggest that the implementation of a meat and dairy consumption reduction policy would lead to a 10 to 40 % reduction in agricultural GHG emissions, depending on the severity of the scenario. This translates to a 1 to 3 % decrease in total Canadian GHG emissions by the year 2030. Besides these environmental benefits, health benefits associated with a reduction in meat and dairy consumption (as inferred from other studies) are presented as an additional source of motivation for implementing such a policy in Canada.     

Environmental impact analysis for the construction of subway stations: Comparison between open-excavation and underground-excavation scheme

The excessive environmental impacts from the construction of subway infrastructure have become a concern for operators who are keen on continuing to lower the environmental footprint, but the factors affecting the impacts are yet to be fully identified. Excavation scheme is the governing factor in subway construction, not only because it prescribes the ensuing construction procedures, but it also epitomizes the design philosophy towards the interaction between the subway structure and city environment. In this paper, a comparative assessment is made among the fifteen mid-point environmental impacts from the two major excavation schemes in subway construction, i.e. the open-excavation (OE) and underground-excavation (UE) scheme. The case station provides a perfect example for such a comparison as it consists of both OE and UE section at the same buried depth. GHG emissions are identified as the largest contributor after normalization. However, GHG emissions are not representative for the overall impacts. The UE section is responsible for more impacts per area than that of OE section in all the investigated categories. The gap between the two sections is attributable to the extra reinforcement procedures that protect the surrounding infrastructure from adverse settlement. Though the underground environment limits the use of construction machines, the UE construction involves more on-site impacts because it requires 11.79 times the labor used in the OE section. Based on the results, the adaptability of the two methods was discussed, considering the life-cycle performance and their interaction with the city environment.     

Biofuel use assessments in Africa: Implications for greenhouse gas emissions and mitigation strategies

The energy balances of most African countries suggest that biofuels (woodfuel, crop and wood residues, and dung) constitute the largest share of total energy consumption (up to 97% in some sub-Saharan Africa countries). There is, however, an increasing scarcity of woodfuel (fuelwood and charcoal), the major biofuel, and a feared increase in greenhouse gas (GHG) emissions associated with biofuel combustion. The extent of GHG emissions is estimated from biofuel consumption levels that are in turn based on methodologies that might be inaccurate. A questionnaire, supplemented by informal interviews, are used to collect data, yielding information regarding end-uses, technologies used, scale of consumption, determinants of fuel consumption, and interfuel substitution (among other parameters). The survey revealed that cooking is the major end-use, with other common uses, such as space and water heating. Improved stoves that provide better combustion efficiency and, thus, reduce woodfuel consumption have not been widely disseminated and are associated with higher methane emissions than open fires. More than 90% of the households in Africa use open fires. Consumption is presented as per capita for households and as products and quantity of fuel in the small scale industries, commercial, and public sectors. Among the determinants for biofuel consumption are affordability, availability of the fuel, and interfuel substitutions. Flaws in estimating biofuel consumption yield large uncertainties in GHG emissions, with implications for the development of policies on energy planning and environmental protection. However, the application of scenarios can guide policy formulation.     

A comparison of emission calculations using different modeled indicators with 1-year online measurements

The overall measurement of farm level greenhouse gas (GHG) emissions in dairy production is not feasible, from either an engineering or administrative point of view. Instead, computational model systems are used to generate emission inventories, demanding a validation by measurement data. This paper tests the GHG calculation of the dairy farm-level optimization model DAIRYDYN, including methane (CH₄) from enteric fermentation and managed manure. The model involves four emission calculation procedures (indicators), differing in the aggregation level of relevant input variables. The corresponding emission factors used by the indicators range from default per cow (activity level) emissions up to emission factors based on feed intake, manure amount, and milk production intensity. For validation of the CH₄ accounting of the model, 1-year CH₄ measurements of an experimental free-stall dairy farm in Germany are compared to model simulation results. An advantage of this interdisciplinary study is given by the correspondence of the model parameterization and simulation horizon with the experimental farm’s characteristics and measurement period. The results clarify that modeled emission inventories (2,898, 4,637, 4,247, and 3,600 kg CO₂-eq. cow^?1 year^?1) lead to more or less good approximations of online measurements (average 3,845 kg CO₂-eq. cow^?1 year^?1 (±275 owing to manure management)) depending on the indicator utilized. The more farm-specific characteristics are used by the GHG indicator; the lower is the bias of the modeled emissions. Results underline that an accurate emission calculation procedure should capture differences in energy intake, owing to milk production intensity as well as manure storage time. Despite the differences between indicator estimates, the deviation of modeled GHGs using detailed indicators in DAIRYDYN from on-farm measurements is relatively low (between ?6.4 % and 10.5 %), compared with findings from the literature.     

A dynamic analysis of the global warming potential associated with air conditioning at a city scale: an empirical study in Shenzhen,China

Heating, ventilation and air conditioning (HVAC) systems are a major source of energy consumption in buildings, directly and indirectly contributing to greenhouse gas (GHG) emissions. In the urban environment, and depending on local climatic conditions, air conditioning units attribute to these high energy demands. This study analyzes the use of residential air conditioning units and their associated global warming potential (GWP) between 2005 and 2030 for the city of Shenzhen, a fast-growing megacity located in Southern China. A life cycle assessment approach was adopted to quantify the GWP impacts which arise from both direct (refrigerant release) and indirect (energy consumption) sources, in combination with a materials flow analysis approach. The results show that the total GWP (expressed as carbon dioxide equivalents, CO₂ eq.) from residential air conditioning systems increased from 2.2 ± 0.2 to 5.1 ± 0.4 million tonnes (Mt) CO₂ eq. between 2005 and 2017, with energy consumption and refrigerant release contributing to 72.5% and 27.5% of the total demands, respectively. Immediate measures are required to restrict refrigerant release and reduce the energy consumption of air conditioning units, to help mitigate the predicted additional total emissions of 36.4 Mt. CO₂ eq. potentially released between 2018 and 2030. This amount equals to approximately New Zealand's national CO₂ emissions in 2017. The findings proposed in this study targets air conditioning units to reduce the GWP emissions in cities, and provide useful data references and insights for local authorities to incentivise measures for improving building energy efficiency management and performance.