A proposed framework for measuring direct and indirect carbon emissions in the operational phase of a construction project: a case study

ABSTRACT

The construction sector is one of the most significant contributors to the carbon footprint. Buildings are primarily responsible for emitting high levels of carbon throughout their entire life cycle, from construction to operation and disposal. Researchers have discussed carbon dioxide emissions from different references and ways of reduction and mitigation techniques to cease rising temperatures and global warming. The various sources of greenhouse emissions in the construction industry are discussed in this paper to understand their negative impact better. A framework is developed for the buildings’ operational phase. It is used to quantify that effect and physical properties to measurables to assist policymakers, stakeholders, and decision-makers in making better decisions and choices to reduce carbon emissions during the operation process. This framework aims to make it more flexible, easy to use for stakeholders, involves their feedback from the beginning of the process, and applies to the ground. Furthermore, a case study was applied to the Nile University operational phase to test the eligibility of the proposed framework in calculating the carbon emissions of a medium-scale building.

KEYWORDS:

• Carbon footprint
• carbon emissions
• construction industry
• operations phase
• case study

1. Introduction

The construction industry is known for being one of the most polluting industries worldwide. Buildings are among the top seven contributors to environmental emissions and resource depletion Sandanayake (2022). In 2018, the construction and building sectors accounted for 36% of energy use and 39% of energy and process-related carbon dioxide emissions. About 11 % of these emissions result from manufacturing building materials like cement and steel (United Nations Environment Programme (2019). Therefore, the construction industry is one of the most contributing sectors to carbon emissions Labaran et al., (2022). In Australia, for example, the construction industry accounted for about 9.5 Metric tons of carbon dioxide equivalent. (MT CO_2e) in 2013 Yu et al., (2017). Construction services also have 54.8 % embodied emissions that release the most significant quantities of carbon footprint Yu et al., (2017) as cited by Labaran et al., (2022). The accumulation of carbon in the atmosphere has led to a rise in temperature by more than one degree Celsius in the past 100 years Labaran et al., (2022). This will be worsened if no action is taken to alleviate the carbon emissions, as it could lead to a rise of 45 degrees Celsius Labaran et al., (2022). The increase in temperature leads to hazardous effects such as soil degradation, desertification, loss of agricultural land, reduced fresh water and acidification of oceans Rossati (2017).

It is essential to monitor the building through its life cycle and use sustainable practices to reduce GHG emissions emitted by constructing a building. A framework was proposed by The International Organisation for Standardization (ISO) called life-cycle assessment (LCA). The building life cycle is classified into four main stages: production, construction, use, and end-of-life (ISO 21,930:2017). The production is concerned with materials, where the Construction industry uses different materials such as concrete, bricks, steel, and timber. Concrete and steel are considered the most common choices for most projects Mohajerani et al., (2019). In addition, Asphalt is considered the most common material used for pavements Levenberg and Adam (2021). Cement is a major contributor to global carbon emissions, accounting for 8% of global emissions. Steel is also known for its high release of carbon. It consumes coal and coke energy in China, around 89.18% of the total energy consumption of the steel industry. It releases around 15% of the total national emissions of CO2 Xu et al., (2021). The construction phase is more concerned with the transportation and installation process. Transportation is a key factor in the construction process, where carbon emissions from Construction transportation range from 2.4% to 5.5% Seo et al., (2016).

The operational stage is considered the major contributor, with 85.4 percent of the total carbon emission, followed by the construction stage, with 12.6 percent of the total emissions. Peng and Wu (2016). The main categories to be considered are classified into:

1.1. Air conditioning/ventilation/heating

The need for air conditioning services is expanding with the increase in temperatures. The cooling services account for more than 10% of the global greenhouse emissions. Dong et al., (2021).

1.2. Electricity

Carbon emissions from residential and public buildings each accounted for 50% of the emissions from urban buildings. Electricity was the primary type of energy used, and carbon emissions from power use accounted for the largest proportion of the total, increasing from 77.38% to 81.6%. Huang et al., (2018).

1.3. Water usage

In 2005, 27 and 39 billion kWh were consumed to pump, treat, distribute, and clean the water used in the building sector. US Department of Energy, (2011) Water use for the operational phase of the building is greater than water use during the construction phase. This high consumption is due to leakage and water dripping from taps. Peng and Wu (2015).

1.4. Commuting

Transportation is one of the major contributors to greenhouse gas (GHG) emissions. Almost 20% of the firm’s footprint is due to employees commuting in personal cars and other public transportation. Peng and Wu (2015).

The end-of-life phase is concerned with the demolition of buildings, which can cause a significant waste of resources. Construction & demolition activities yield an incredible amount of waste that needs to be disposed of. In the US alone, the construction industry has around 136 Mt of waste per year Labaran et al., (2021). These effects can be reduced by salvaging, reusing and recycling materials that are still in good condition. It can also be reduced from the beginning of the designing phase by choosing sustainable materials. Another critical aspect to be considered is developing a well-studied waste management plan.

A framework is proposed to calculate and reduce carbon sources specified in the operational/use phase of construction, as it is considered both the major contributor to carbon emissions and the most challenging phase at which emissions can be reduced. Over the building’s lifetime, energy consumption is considered a major issue and contributor to the building’s carbon footprint. Energy is consumed mainly in the operational phase of the building, used in heating, cooling, water use, lighting, and ventilation. The difficulty lies in reducing carbon emissions while maintaining human comfort and space functionality.

The framework is developed and referred from the LCA process that is classified into five main points, the Scope definition at which everything is defined, whether as included or excluded, and the limitations that can be faced. Life cycle inventory (LCI) involves collecting and quantifying data, such as energy use, refrigerants, and water use. Life cycle impact assessment (LCIA) studies the environmental impact of the process used for better identification of reducing techniques. This is all followed by interpretation of results and uncertainties, as well as reporting the results to stakeholders (ISO 21,930:2017). While LCA is a valuable framework, some limitations must be considered, such as complexity and time-consuming steps, which do not give small organisations flexibility.

Moreover, due to this complexity, stakeholders are often not a part of the process as it has to be conducted by technical experts, which may lead to non-relevance of results to actual processes. Another limitation is data gathering and data quality. Some data acquired can be tough to obtain, which might lead to inaccuracy. The lack of standardisation can also act as a limitation as it becomes difficult to compare two results or have a basis due to the lack of global standards followed by this framework. To develop and fix the limitation found in the previous framework, The proposed framework is developed into 3 phases, questionnaire and collection of data, where energy-consuming processes are classified, and their data is collected separately and directly related to the next step of calculations to avoid the complexity. The next phase is calculations, in which data is quantified into numbers that can be measured. The main concern in developing this phase was making it more flexible for small organisations and easy for stakeholders to ensure it involves their input and feedback from the beginning. We had to guarantee the application of our framework on the ground, so the final phase is a list of recommendations and mitigation strategies that can be followed to reduce carbon emissions; it is also classified and separated based on the data gathered at the start as shown in Figure 1.

Figure 1. Main methodology diagram.

Read the detailed description of this figure

A flowchart of 3 steps; starts by taking a questionnaire, then calculations, and then applying mitigation strategies.

2. Literature review

Sizirici et al. (2021) studied the different carbon emission sources in the construction industry through different phases and the different searches done to reduce these effects. Therefore, this paper could guide the stakeholders in the early stages to better assess their materials and construction methods to decrease carbon emissions. Zainordin & Zahra, (2021) studied the factor contributing to carbon emissions in the construction industry by reviewing research done in the latest ten years to enhance the existing knowledge about this topic and its consequences. Ali et al., (2020) gave an overview of issues, impacts and mitigation actions that could be adopted in the building sectors to reduce and control CO₂ emissions. Toufani et al., (2019) examined the indirect and direct carbon emissions associated with the construction sector at national and global scales. Then, they highlighted the major elements that need a reduction in carbon emissions. Accordingly, this would help governments in managing and reducing their carbon footprints. Tabrizikahou and Nowotarski (2021) Mitigated the Energy Consumption and Carbon Emission in the building; an attempt has been made to review the existing methods, aiming to lower the consumption of energy and carbon emission in the construction buildings by optimising the construction processes, especially with the lean construction approach. Pandey et al. (2011) discussed the current different methods of estimating carbon footprint by illustrating examples to demonstrate different approaches for carbon footprint calculations. Estimated carbon emission during an office’s building cycle using Building information modelling (BIM) and Ecotect. It was beneficial in reducing the efforts of estimating carbon emissions from a building’s life cycle.

3. Methodology

In 2021, Decision makers can fully understand the different carbon emission sources and have an overview of reducing these emissions. Nevertheless, there is no adequate precise method for decision-makers to close the gap between physical output and measurable quantified carbon emission. Several researchers have addressed carbon footprint estimation and calculation through mathematical equations and models. However, to encourage stakeholders to take action, a list must be easy to understand, clear enough to follow, and flexible to be achieved in any building type. Thus, the authors proposed a framework that decision-makers on the ground could use to measure and minimise the carbon footprint of various constructions.

The framework is developed to guide decision-makers through a series of steps to reach mitigation strategies to decrease carbon footprint. The strength of the framework is in its flexibility. A wide variety of different users in the construction industry can use it. The framework is a model with parameters that helps translate each measurable’s physical properties into an associated footprint. It measures direct emissions, representing Greenhouse gas emissions from facilities/sources owned or controlled by a reporting company. As well as indirect emissions, which represent Greenhouse gas emissions from facilities/sources not owned or controlled by the reporting company, but for which the reporting company’s activities are responsible (Ex: electricity purchase).

3.1. Phase one: gathering data and information about your organisation

Phase one consists of a series of questions and data to be gathered in order to proceed to phase two.

3.1.1. Identify your organisation

The organisation’s data are gathered, such as its name, the building reported, the type of the building, the country in which the building is based, as well as the number of employees and the period of the report, as shown in Table 1.

Table 1. Organisation information.

Name of the organisation
Country of the organisation
The building number
The type of the building
Area per floor
Number of employees
Period of the report

3.1.2. Commuting data

Commuting data describes the vehicles that are either owned or controlled by the organisation. The fuel consumption is based on the type of fuel, amount of CO₂ per litre, type of car to identify its tank capacity (km/L), and total distance commuted by the vehicle (km), as shown in Table 2.

Table 2. Questionnaire and data gathering for commuting.

do the organisation own/control vehicles?			Yes
Specify the number of employees.
Specify the number of employees using the bus.
Number of buses/vans	Capacity:	21
Average distance commuted in one bus route (km)
Specify the number of vehicles owned by employees.
Specify the number of vehicles/private cars.

3.1.3. Water usage data

Data related to indoor water usage is gathered, such as bathrooms, swimming pools, and showers. Moreover, outdoor water usage, such as gardening, as shown in Table 3.

Table 3. Questionnaire and data gathering of water usage.

Specify if you have a swimming pool and showers	Yes
Specify if you water a garden.	No
Specify the number of employees.
Specify the number of janitors.
Specify the number of cleaning laps.
Specify the amount of water supplied.
Specify the amount of water treated and reused.
Specify the number of garden watering laps.

3.1.4. Energy efficiency

The main data gathered is the total consumption of electricity per year, measured in Kilowatt hours (kWh), as shown in Table 4.

Table 4. Questionnaire and data gathering of energy usage.

Specify total annual electricity consumption

3.1.5. Air conditioning/ventilation/heating

Data on refrigerants from air-conditioning and refrigeration units are gathered with the type of equipment and the type of refrigerant, as shown in Table 5.

Table 5. Questionnaire and data gathering of refrigerants.

do your organisation uses ACs/Heaters	Yes
Specify the type of equipment charged.
Specify the number of equipment charged.
Specify the type of refrigerant.
Specify the quantity of refrigerant.

3.2. Phase two: calculations of your carbon footprint

Phase two includes the variables asked in the questionnaire, their emission factors, and the result calculated. To calculate the GHG emissions, the main formula used to calculate GHG emissions is:

(1) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}(\mathrm{M}\mathrm{T}\mathrm{C}{\mathrm{O}}_2\mathrm{e})=\mathrm{A}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{i}\mathrm{t}\mathrm{y}\mathrm{D}\mathrm{a}\mathrm{t}\mathrm{a}(\mathrm{u}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{o}\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{i}\mathrm{t}\mathrm{y})\times \mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{F}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}$(1)

Where, activity data is associated with the consumption of any consumables of the organisation, such as electricity. The emission factor is the weight of a pollutant divided by a unit weight depending on the activity emitting the greenhouse gases; it is obtained from United Nations Framework Convention on Climate Change (UNFCCC) Greenhouse Gas Emissions Calculator UNFCCC (2021) and measured in Kg CO_2e/unit weight. The United Nations designed the greenhouse gas emissions calculator to assist countries in their reports agreed to be delivered under the Paris Agreement. It was designed with a simple and easy interface to allow stakeholders to use it, which follows the methodology in our framework proposal.

3.2.1. Commuting

The formula used to calculate gaseous fuel is:

(2) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{m}\mathrm{u}\mathrm{t}\mathrm{i}\mathrm{n}\mathrm{g}(\mathrm{M}\mathrm{T}\mathrm{C}{\mathrm{O}}_2\mathrm{e})=[\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}(\mathrm{k}\mathrm{m})\mathrm{a}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}(\mathrm{k}\mathrm{m}/\mathrm{L})]\times \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{n}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}(\mathrm{C}{\mathrm{O}}_2/\mathrm{L})$(2)

Where, distance is the total distance commuted by the car in one trip measured in kilometres (km), Average consumption is the average kilometres the car can travel using 1 Liter of fuel, and fuel carbon emission of 1 Liter of fuel, as shown in Table 6.

Table 6. Commuting carbon footprint calculations.

Average Kilometers (km/L)	Fuel Type	fuel carbon emission (CO2/L)	Total distance (Km)	kg CO2e	MT CO2e
	Diesel	2.64
	Gasoline	2.392
	LPG	1.665
	Low-calorific CNG	2.252
	High-calorific CNG	2.666

The main formula used to calculate electric cars’ carbon emission:

(3) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}=\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}(\mathrm{k}\mathrm{m})\times \mathrm{a}\mathrm{l}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{n}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}$(3)

Where, distance is the total distance commuted by the car in one trip measured in kilometres (km) and the fuel factory is deducted from UNFCC Greenhouse Gas Emissions Calculator, as shown in Table 7.

Table 7. Electric cars’ carbon footprint calculations.

Fuel Type	Fuel Factor	Total distance	kg CO2e	MT CO2e
Battery electric car	0.05
Hybrid	0.12
Plug-in hybrid electric	0.1

3.2.2. Water use

The main formula is used to calculate water carbon emission:

(4) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}=\mathrm{W}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}({\mathrm{m}}^3)\times \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}$(4)

Where, Water consumption is the total amount of water supplied to the building per 1 year and can be measured through water metres, as shown in Table 8.

Table 8. Water carbon footprint calculations.

Water supply: water derived through the main supply network
Type	Unit	Factor	Amount	kg CO2e	MT CO2e
Water supply	M^3	0.1490
Water treatment: Water returned into the sewage system through the main drains
Type	Unit	Factor	Amount	kg CO2e	MT CO2e
Water supply	M^3	0.2720

3.2.3. Energy efficiency

The main formula is used to calculate electricity carbon emission:

(5) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}=\mathrm{E}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{c}\mathrm{i}\mathrm{t}\mathrm{y}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}(\mathrm{k}\mathrm{W}\mathrm{h})\times \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}$(5)

Where, Electricity consumption is the total amount of electricity used per 1 year, and the national grid average emission factor for the Arab Republic of Egypt is 0.533 MT CO₂e/MWh based on Institute for Global Environmental Strategies, IGES, database and the latest registered wind farm CDM project, as shown in Table 9.

Table 9. Electricity carbon footprint calculations.

Electricity grid: Electricity used by an organisation at sites owned
Type	Unit	Factor	Amount	kg CO2e	MT CO2e
Electricity	kWh	0.53330

3.2.4. Refrigerants

The main formula is used to calculate refrigerants emission:

(6) $\mathrm{G}\mathrm{H}\mathrm{G}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}=\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{q}\mathrm{u}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{y}\mathrm{o}\mathrm{f}\mathrm{r}\mathrm{e}\mathrm{f}\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{t}(\mathrm{k}\mathrm{g})\times \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}$(6)

Where, the total amount of refrigerants from air leakage of air conditioning and refrigeration units are measured in kilograms, and the emission factor is deducted from UNFCC Greenhouse Gas Emissions Calculator, as shown in Table 9.

3.3. Phase three: mitigation strategies to reduce carbon footprint

Phase three includes the final step, mitigation strategies that could be adopted in the building operational phase to reduce carbon footprint, as shown in Tables 10–14. The mitigation strategies are based on proposals and studies made by various professionals and researchers from around the globe in the field of building energy efficiency. A study discussed the strategies for zero-carbon eco-cities. The strategies include using renewable energy sources and water-efficient appliances Dabaieh et al. (2019). Another study was conducted to improve the existing technologies in the operational phase, such as HVAC systems and lighting Ohene et al. (2022). Also, Building cooling effects on climate change need mitigation strategies addressed in this study, where passive cooling strategies were the leading solution. Strategies such as natural ventilation and thermal insulation. Khourchid et al. (2022). Other studies were concerned with the integration of building and transportation energy use. The mitigation strategy methodology was based on energy-efficient vehicle and transportation demand management (TDM) strategies. TDM’s purpose is to reduce the demand for individual vehicle travel and replace it with other means of transportation, such as public transportation. Karan et al. (2016).

Table 10. Refrigerants carbon footprint calculations.

Refrigerant and others: From leakage of air-conditioning and refrigeration units
Emission	Unit	Factor	Amount	Kg CO2e	MT CO2e
HFC-134a= R134a	kg	1430
HCFC-22/R22 = chlorodifluoromethane	kg	1810
R410A	kg	2088

Table 11. Commuting carbon footprint reduction.

Total Amount of MT CO2e
Mitigation Strategies
1- Switch vehicles to a greener alternative, such as hybrid or electric vehicles
2- Schedule all the buses to have their full capacity to avoid buses with empty seats
3- Introduce a transportation application that encourages the idea of carpooling
4- provide drivers with training to show them the benefits of fuel-efficient journeys
5- Encourage employees by using public transportation

Table 12. Water carbon footprint reduction.

Total Amount of MT CO2e
Mitigation Strategies
1- Set up a water action plan with employees
2- Consider installing a greywater system for reusing water in flushing toilets and watering plants.
3- Install low-flow fixtures, such as dual flush toilets.
4- Always check for toilet leaks. Put a dye into the tank to appear in the bowl in case of leaking.
5- plant greenery that requires less water.
6- Keep swimming pools covered when not in use to avoid evaporation.
7- arrange seminars to raise awareness about water reduction
8- Save and reuse rainwater for watering gardens.

Table 13. Electricity carbon footprint reduction.

Total Amount of MT CO2e
Mitigation Strategies
1- Install motion and occupancy sensors in the rooms and corridors to automatically turn off the lights when it is not occupied.
2- Install energy-efficient light units.
3- Use renewable energy sources by using solar panels, especially on roofs and vast spaces.
4- Use a power strip to reduce plug loads.
5- Make sure appliances are energy efficient.
6- For landscape lighting, instal solar-powered devices.
7- Establish a set of bylaws requiring the students and staff to turn off unused equipment.
8- Create a reward system for the most minor electricity consumption departments.

Table 14. Refrigerants carbon footprint reduction.

Total Amount of MT CO2e
Mitigation Strategies
1- Maintain the air conditioning systems.
2- Always check for leakage from existing appliances.
3- Use a refrigerant gas with lower environmental impact: Use a refrigerant gas with zero ozone depletion potential (ODP) and low global warming potential (GWP).
4- Ensure correct end-of-life treatment of refrigerant gases.
5- Use refrigeration or air conditioning systems less often.
6- Ensure that AC/Heating systems are only operated in occupied rooms.

A. Commuting

B. Water use and conservation

C. Energy efficiency

D. Air conditioning/ventilation/heating

4. Case study 01: Nile university

This case study is conducted on an educational institute to observe the proposed framework’s usage and how it can estimate the carbon footprint of medium-scale buildings.

4.1. Gathering data

4.1.1. About the Nile university

Sustainability in higher education institutes is increasing, but its main focus is academic research. Nile University (NU) went beyond these initiatives. The university is releasing its very first carbon footprint report to have a futuristic insight into carbon emission reduction in its institutions aligning with the national strategy against climate change. NU is the first non-governmental and non-profit research university in Egypt. It is located in Juhayna Square on 26 July Corridor, Sheikh Zayed, Giza, with a built space of almost 54,000 m2. Regarding NU faculty, staff and student population, Academic Year (AY) 2020–2021, NU consisted of 3,100 students and 471 staff members.

4.1.2. Scope of the inventory

The operational boundary that the GHG emission would be estimated would be the buildings: classroom building (B1), service and administrative building (B2) and the MicroFactory building (B4), as shown in Figure 2 and Figure 3.

Figure 2. The whole framework diagram.

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A flowchart discussing the exact steps of following our framework.

Figure 3. Comparison between our framework and an existing similar framework.

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A flowchart discussing the steps of following two different frameworks.

• Classroom Building – B1: The building is divided into four floors, each has an area of 5,000 m₂. The main areas are laboratories, classrooms, lecture halls and administrative offices. A cafeteria of a 10 m₂ area is excluded from NU’s operational boundaries.

• Service and administrative building – B2: The building is divided into four floors, each having an area of 7,000 m₂ and a roof of 3,500 m₂. It consists of 2 main areas; the service sector is electricity distribution rooms, water tanks, and generators. The administrative sector includes administrative offices and a gymnasium.

• The Microfactory building – B4: This building consists of 1 floor with a total area of 2,500 m₂. The main areas are moulds, plastic, and sheet metal factories.

4.2. Calculations

The operational stage counts as the primary contributor to carbon emission in the life cycle assessment. The process accounts for 85.4% of the total emission. Peng and Wu (2015). Thus, we were directed to study Nile University in its Operational stage and the GHGs emitted between 1 September 2020 until 30 August 2021. The main GHGs used in calculating are Carbon Dioxide (CO₂), Methane (CH4), Nitrous Oxide (N2O), and Hydrofluorocarbons (HFCs). Each emission is reported in metric tons CO₂ equivalent emissions (MT CO_2e).

The data gathered was through several site visits and interviews with the stakeholder at Nile University as shown in Figure 4 and Table 15 with the proposed framework explained earlier. The objective was to identify the university’s carbon-intensive activities with a greater potential for reducing GHG emissions, and this differs from one organisation to another, which shows the importance of the first step of our questionnaire. Upon surveys and stakeholders’ demand, the results are classified into Scope 1, direct emissions from sources owned or controlled by the Nile University, and Scope 2, indirect emissions from energy sources not owned or controlled by the Nile University.

• Scope 1 direct emissions are subdivided into the following main categories:

Figure 4. The operational boundary of Nile University.

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The master plan of Nile University, where the study buildings are highlighted in yellow.

Table 15. Summary of activity data Collected.

Scope	Emission source	Activity Data	Quantity	Unit
Scope 1	Stationary Combustion	Diesel Fuel Consumption	1,500	Litres
	Mobile combustion	Motor Gasoline Consumption	3,774.51	Litres
		Diesel Fuel Consumption	14,248.06	Litres
	Fugitive emissions	Refrigerants (R- 22) charge	54.4	Kg
		Laboratories	179	gm CO2
Scope 2	Electricity	Electricity Consumption	4,107	MWh

Stationary combustion sources: These emissions are due to the combustion of fuel.

Mobile Sources: These emissions are due to vehicles owned by/controlled by the university

Fugitive emissions: These emissions are due to leaks and other releases of gases.

• Scope 2 indirect emissions from energy sources such as electricity.

4.2.1. Scope 1 direct emissions

The direct emission sources are breakdown in Table 16.

Table 16. Breakdown of Scope 1 direct emission sources.

Emission Source Type	Emission Source in the Nile University	MT CO2e/Year
Stationary Combustion Sources	Generators	4.07
	Total	4.07
Mobile Sources	Owned buses	39.06
	Owned cars	8.82
	Total	47.88
Fugitive Emissions	A/C and refrigerants	9.57
	Laboratories	0.0002
	Total	9.57
Scope 1 – Direct Emissions Total		61.53

4.2.2. Scope 2 indirect emissions

The direct emission sources are breakdown in Table 17.

Table 17. Breakdown of Scope 2 indirect emission sources.

Emission Source Type	Emission Source in the Nile University	MT CO2e/Year
Electricity	-	2,188.02
Scope 2 – Indirect Emissions Total		2,1888.02

4.3. Mitigation strategies for Nile university

• Improve the carbon footprint calculation:

Provide details on every quantity used and explore the physical and chemical properties of fuels used to learn about the exact carbon footprint of these.

• Energy Efficiency:

• Installing motion and occupancy sensors in the rooms and corridors to automatically turn off the lights when it is not occupied.

• Installing energy-efficient light units.

• Establish a set of bylaws that requires the students and the staff to turn off any unused equipment.

• Create a reward system for departments with the most minor electricity consumption.

• Use renewable energy sources by using solar panels, especially on the roofs and vast spaces around campus.

• Initiate awareness campaigns to highlight the importance of reducing energy consumption and how this affects carbon reduction.

• Quality air:

• Use non-chlorofluorocarbon (CFC) compliant refrigerants instead of refrigerant R22.

• Ensure doors and windows are closed when HVAC systems are used.

• Commuting:

• Introduce a transportation application that encourages the idea of carpooling

• Schedule all the buses to have their full capacity to avoid buses with empty seats, leading to high fuel consumption.

5. Discussion

The results are classified into Scope 1 direct and Scope 2 indirect emissions. The overall GHG emission is 2,250 MT CO₂e; Scope 1 accounts for 61.53 MT CO_2e, representing 2.74%, and Scope 2 is 2,188.02 MT CO₂e representing 97.26% of the total GHG emissions.

Scope 1 is direct emissions from sources owned or controlled by the Nile University, such as stationary combustion sources, mobile sources, and fugitive emissions. The stationary combustion sources at Nile University are two generators only used as a backup in case of a power outage. During the reporting period, the total diesel consumed was 1500 litres. The site-specific carbon content of the fuel was unavailable, so the GHG emissions from Stationary Combustion sources were estimated based on the fuel consumed and fuel type. Mobile sources are vehicles either owned or controlled by Nile University. Similar to stationary combustion, the fuel consumption approach for mobile sources is based on the volume of fuel combusted, vehicle categorisation and the net calorific value (NCV) since the carbon content of the fuel is not available. Vehicles owned or controlled by the Nile University were assumed to have no control technology emission applied, so they were assumed to be ‘Uncontrolled’ mode category. The total emissions from mobile sources are 47.88 MT CO2e/year representing 77.82% of the Scope 1 Direct Emissions and 2.13% of the total GHG emissions. The most emitting source is the buses owned by the university, which consumed the maximum amount of fuel, diesel, during the reporting period − 14248 L. The fugitive emissions from conditioning and refrigerant charge are 9.57 MT CO2 e/year. This contributes to 15.56% of the Scope 1 emissions. The equipment uses a variety of refrigerant gases: and these are R22 and R134A, which were all calculated. As for the fugitive emissions from laboratories, Nile University has numerous laboratories that allow the students to perform a variety of experiments during the reported year. These experiments resulted in relatively negligible greenhouse gas emissions. During the reported year of 2021, only one GHG was released from laboratory experiments, with a minimal quantity.

Scope 2 is indirect emissions from energy sources not owned or controlled by Nile University. The Nile University receives its electricity supply from the national grid of electricity. Electricity is the primary energy source for the buildings at Nile University in the reporting period. The total net electricity consumption was 4,107 MWh. The national grid average emission factor for the Arab Republic of Egypt is 0.533 MT CO₂e/MWh based on Institute for Global Environmental Strategies, IGES, database and the latest registered wind farm CDM project. Scope 2 emissions are estimated as 2,188.02 MT CO₂ e/year, representing 97.26% of the total GHG emissions of Nile University for the base year 2021.

Scope 1 and scope 2 are calculated in order to measure GHG emissions key performance indicators and benchmark Nile University GHG emissions. However, during the calculations, some data related to the NCV of all fuels consumed and the operating emission rates of the air conditioning equipment were assumed. To address the data gap, continuous data collection should be made by Nile University. The data gap is the ratio between the number of parameters assumed over the total required parameters during the calculation process. Table 19 below identifies the data gap value for each emission activity data. So, for example, in the first entry of stationary fuel combustion, the parameters/data required to estimate the relevant GHG emissions were eight; four of the eight parameters were assumed. Hence, the data gap of stationary fuel combustion emission was 50%. The table also states the respective recommendations in case of a data gap. Finally, the overall data gap was aggregated, which was the ratio between the overall assumed data within the table and the overall data required.

Based on Table 19, the data gap of the GHG Inventory is calculated to be 21.65%; in other words, 78.35% of the data required were site-specific, while the remainder 21.65% were assumed based on guidance and default values IPCC.

Our goal was to measure GHG emissions key performance indicators. They are essential to track performance over the years as they are quantifiable metrics that reflect the university’s environmental performance in the context of achieving its broader goals and objectives, as shown in Table 18. The results of emissions intensity are used for benchmarking. Therefore, NU must use environmental KPIs to capture the link between environmental and financial performance adequately.

Table 18. Data gaps and recommendations.

Emission Source	Data Requirement	Applied Assumptions	Data Gap	Recommendation
Stationary fuel combustion (generators)	Fuel type Fuel quantity Fuel NCV Fuel density	DensityFuel NCV Fuel NCV	50%	Provide fuel density and NCV
Mobile fuel combustion – owned buses	Vehicle type Fuel type Fuel quantity Fuel NCV Fuel density	DensityFuel NCV Fuel NCV	40%	Provide fuel density and NCV
A/Cs and refrigerants	The type of equipment charged Number of equipment charges Type of refrigerant Quantity of refrigerant Operating emission rate	Operating emission rate	20%	Provide operating emission rate
Electricity consumption	Total electricity consumption Excluded electricity consumption	None	0%	None

Table 19. GHG emission intensity of NU.

Employees’ Share of Total GHG Emissions

As of 2021, Nile University employed 471 employees. Accordingly, each employee’s share of the total GHG emissions is 4.78 MT CO2e/employee/year.

Students’ Share of Total GHG Emissions

As of 2021, Nile University had 3,100 students. Accordingly, each student’s share of the total GHG emissions is 0.726 MT CO2e/student/year.

Building Space Share of Total GHG Emissions

With the three buildings (B1, B2 and B4) and hence, a total area of 54,000 m2, the share of the total GHG emissions per area is .042 MT CO2e/m2

This step was followed by benchmarking the Nile University GHG emissions, where Benchmarks are standards, or guidelines, for key performance metrics and indicators as shown in Table 20. They represent the average of key performance indicators. Rankings of selected institutions of higher education by greenhouse gas emissions per total enrolment are shown in Table 19.

There are many potential areas of focus that Nile University should consider after calculating its carbon emission. First, implementing the mitigation techniques proposed by the framework suitable to emission already calculated. In order to ensure the efficiency of applying the techniques, constant monitoring and progress tracking should be followed. This can be done by a regular check and measuring within an estimated time gap and comparing it to the previous data. After measuring GHG emissions key performance indicators and concluding the share of each employee and student from the total GHG, The Nile University should encourage them to participate in the university’s decision to be sustainable. This can be done by awareness-raising campaigns and incentives offered to stakeholders engaging in these practices.

Finally, benchmarking against other institutes can lead to collaboration with them or with other organisations to share the best practices used and resources needed. This way Nile University can help create a more sustainable present and future.

6. Conclusion

The construction industry is one of the most significant contributors to greenhouse gas emissions. Furthermore, to reduce these emissions, monitoring the building through its life cycle is crucial. The International Organisation for Standardization (ISO) proposed a framework called the life-cycle assessment (LCA) to study the environmental impact during a building’s life cycle. The main classification of the building life cycle consists of 4 stages: production, construction, operation/use, and end-of-life.

Although the four stages significantly contribute to carbon emission, studies showed that the operational phase is considered the highest. The constant consumption of energy used for heating, cooling, and ventilation is responsible for the main portion of the building’s emissions. This challenge.

Table 20. Benchmarking of NU GHG emissions against selected institutions of higher education.

University	Reporting Year	Emissions per Student (MT CO2e/student/yr)	Emissions per Unit Area (MT CO2e/m^2/yr)
Nile University (NU)	(2020–2021)	0.726	0.042
American University in Cairo (AUC)	(2019–2020)	3.8	0.122
American University in Sharjah (AUS)	(2018–2019)	11.35	0.045

This challenge was addressed by proposing a framework to calculate and reduce carbon emissions in the operational phase of a building. A calculation methodology for the carbon footprint was developed, and a framework was made in a define accurate steps to help stakeholders understand and take an action to reduce the carbon footprint worldwide. The primary methodology was bridging the gap between the organisation’s daily consumption and carbon emissions. This was achieved by Identifying the organisation’s carbon-intensive activities with tremendous potential for reducing GHG emissions, collecting data that can be transcribed into quantities, quantifying the energy consumption and greenhouse gas emissions, and proposing mitigation strategies to start the action.

The framework was applied in a case study, the Nile University operational phase. There was a different classification based on the need of the entity. Nevertheless, within the 3 phases proposed, the data were gathered, calculated, and strategies were provided. It was proven that the strength of the framework is in its flexibility. Further enhancement and widening are required to include more types of buildings and calculate more pollutant sources of carbon emissions.

Reducing greenhouse gas emissions in the construction industry, especially in the operational phase of the building, is mandatory to overcome the challenges of climate change. While our proposed framework is a valuable tool for stakeholders and organisations to calculate, monitor, and mitigate carbon emissions of buildings, certain limitations should be addressed in future work to have a larger scale. One of these limitations is the focus on the operational phase of the building, while the other phases also contribute to carbon emissions. Future work could expand the scope to largen the scale of work.

Moreover, while our proposed framework worked on the ease of collecting data and narrowing the time consumed, future work could explore using artificial intelligence and machine learning to automate these data from the first day of operation of a building. Finally, our framework might have given the space for stakeholders to be part of the process. However, economic aspects of sustainability, such as the financial availability of the proposed practices, should be more considered to provide a more comprehensive assessment of the building’s sustainability in a way that will guarantee to apply it.

Disclosure statement

There are no relevant competing interests.

Data availability statement

Data available on request.

Additional information

Funding

This work was supported by the Science and Technology Development Fund [43204].

Notes on contributors

Hagar Hammad

Hagar Hammad In 2021 she earned her BSC in Architecture Engineering at Ainshams University, Egypt. She won first place in EERI-SDC Competition in 2021;

Yasmin Elhakim

Yasmin Elhakim She was a PhD student at the American University in Cairo. She is involved in multiple research topics related to advancements in the construction industry. She won the Mohamed Bin Abdulkarim A. Allehedan Award in 2020 for demonstrating excellence in sciences and engineering studies from the American University in Cairo;

Yara Hossam

Yara HossamIndustrial engineer and Research Assistant, Smart Engineering Systems Research Center, Nile University, Cairo, Egypt;

Mohamed Mahmoud

Mohamed Mahmoud Thirty-one years of in-depth successful experience in Engineering firms, Project Management and General management experience in many consultant engineering offices and contracting companies. I finished my BSc. in Civil Engineering, Cairo University, Egypt, in 1991, then earned my master’s and PhD. in Architectural Engineering at Cairo University, Cairo, Egypt;

Tawfik Ismail

Tawfik Ismail He manages several types of research in implementing optical transceivers for FSO and PON. Dr Tawfik is currently the CoPI of an Optical Access Network – FPGA-based research project funded by NTRA (National Telecom Regularity Authority) in collaboration with the University of Toronto, Canada.;

Irene S. Fahim

Irene S. Fahim Associate Professor, Industrial and Service Engineering and Management department, Nile University Cairo, Egypt. She is the Director of the Smart Engineering systems research centre at Nile University. She won the state encouragement award for women 2020, the Hazem Ezzat Research Excellence Award 2021 and the Loreal UNESCO for Women in Science 2021 Egypt young talents program. She received a grant for Egypt Higher Education Climate change partnerships Grants in collaboration with Nottingham University and the British Council.