1. Introduction

Greenhouse gas (GHG) emissions caused by human activities have led to an increase in natural disasters that endanger biodiversity and future generations (IPCC 2021). The food system has been recognized as one of the greatest global environmental and health challenges as it is responsible for a third of global anthropogenic greenhouse gas emissions (Takacs and Borrion 2020). The restaurant industry and food sector in general have a big role, being responsible for 30% of the world’s total energy consumption and around 22% of total GHG emissions (Norton 2023). A restaurant business needs to be aware of its carbon footprint generated both directly on-site and indirectly throughout the restaurant supply chain.

Various emission sources are associated not only with the restaurant operations but also throughout a restaurant’s supply chain. Most GHG emission discussions are linked to food ingredients preparation, and cooking, including water use. The associated environmental impacts have been mainly focused on farming practices, geographic proximity, and the seasonality of food items. In addition, the transport of food ingredients from the farm to the restaurant is of concern. The amount of food scraps and waste generated is connected to food preparation techniques. Food waste is another issue of high interest as that can be linked to methane emissions in landfills. The heating, ventilation, and air conditioning system of the restaurant buildings was highlighted as a key issue. However, there are several aspects of restaurant operations that contribute to its consumption of energy, such as refrigerators.

One of the most energy-intensive businesses in the service industries is restaurants, as energy is required to prepare, handle, cook, store, and deliver food (Nonaka et al. 2015). By applying the IPCC’s Tier 1 approach, Özgen et al. (2021) reported that 1919.818 tCO₂e were emitted from restaurants in Turkey during a 5-yr period, with the use of liquefied petroleum gas being the major contributor to GHG emissions. Cerutti et al. (2016) investigated the carbon footprint of the catering industry and discovered that 61%–70% of GHGs were emitted during the production phase, 6%–11% during the provisioning phase, and 24%–28% during the urban distribution phase. A similar conclusion was reached by McLellan et al. (2015), who demonstrated that the production stage of food inputs (from agriculture to processing) had the greatest carbon footprint impact, followed by transportation. According to Messier (2016), the main contributors to GHG emissions from restaurants were upstream emissions, accounting for 78% of the emissions, followed by on-site operations (21%) and downstream activities (1%). The processing of food ingredients and the electricity generated for space cooling and ventilation constituted the main source of upstream emissions. However, the primary source of GHG emissions from on-site operations was stationary combustion. Similarly, Falciano stated that the production of all ingredients was responsible for 74% of the carbon footprint, while energy consumption corresponded to 5% of the carbon footprint (Falciano et al. 2022).

Manteghi et al. (2021) reported that carbon footprint reduction is very popular in modern restaurants, including customer awareness, to assure sustainability across the whole food supply chain from manufacturing to delivery. In addition, several studies have confirmed that the GHG emissions in a restaurant came from raw material acquisition, transportation, and waste management. For example, Baloglu et al. (2020) conducted a study of the important GHG emissions from casual restaurants in Las Vegas to investigate the green practices applied and found that water efficiency and waste management and recycling were the largest sources of GHG emissions, accounting for 53.2% and 48.30%, respectively. Similarly, Li et al. (2022) found out that more than 60% of GHG emissions from the food supply chain in Japan came from the food production stage and 38% from the wholesale and retail stages. Poore and Nemecek (2018) demonstrated that high GHG emission levels from food supply chains came from raw materials in the production stage (beef and pork meat). Globally, 17% of all food is transported across borders, regularly involving long distances (Poore and Nemecek 2018). Regarding transportation in the food supply chain, Tubiello et al. (2021) reported that over the period 1990–2018, world total GHG emissions from domestic food transport increased globally 80%, amounting to 511 MtCO₂e yr⁻¹, with GHG emissions from food waste disposal, including solid food waste, industrial wastewater, and incineration, reaching 996 MtCO₂e yr⁻¹. In addition, Pulkkinen et al. (2016) suggested that labeling logo of Climate Choice and Better Climate Choice on low-carbon meals for communicating information on carbon footprints to consumers helped to decrease the total carbon footprint in restaurants in Finland by 25% for an average meal.

Internationally standardized measurement of GHG emissions is essential for global reporting of GHG emissions. A joint initiative of the World Resources Institute and the World Business Council for Sustainable Development convened a multistakeholder partnership of businesses, nongovernmental organizations, and governments to create the GHG Protocol as an international standard for companies and organizations to measure and manage their GHG emissions and reporting emissions. The GHG Protocol Corporate Accounting and Reporting Standard provides a step-by-step guide for companies to use in quantifying and reporting their GHG emissions, categorizing GHGs into scopes 1, 2, and 3 based on GHG emission sources. The standard covers the accounting and reporting of seven greenhouse gases covered by the Kyoto Protocol—carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Through the use of standardized approaches and principles, industry, NGOs, and governments can prepare a GHG inventory that represents a true and fair account of their emissions and derive GHG reduction strategies. However, there is no specific guidance on GHG accounting and reporting for the food service sector, including restaurants.

Despite the widespread application of GHG accounting or life cycle assessment (LCA) for the food service sector, there are still no published studies on the assessment of GHG emissions covering all of scopes 1, 2, and 3. In the past, it was mandatory to include scopes 1 and 2 when assessing the GHG emissions for organizations. Recently, it has also been made mandatory to include scope 3 but only for the significant sources. Scope 3 GHG emissions for food and drinks business are substantial and so should not be overlooked when formulating reduction strategies. Operational guidelines are needed for GHG measurement and management of both direct and indirect emissions along the whole supply chain to identify which GHG emissions sources should be included in scope 3. The main purpose of the current study was to fill this knowledge gap by identifying which scope 3 activities that should be taken into account for reporting and reducing GHG emissions in the food and service industry. Restaurants specializing in northeastern Thai cuisine are very popular, as are Japanese restaurants, which are continually increasing in Thailand. Consequently, it is of interest to compare these two types of most popular restaurants regarding their GHG emissions.

2. Methodology

The GHG emissions were assessed using the methodology described in the national guidelines for carbon footprint of organizations, which were developed in accordance with ISO 14064-1, “Greenhouse gases—Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals” (Thailand Greenhouse Gas Management Organization 2022). Following the GHG protocol, as well as the national guideline on reporting GHG emissions, the GHG emission sources of restaurants can be classified into three scope levels. Scope 1 GHG emissions are linked with the use of liquefied petroleum gas (LPG), alcohol fuel, and refrigerants for food storage, preparation, and service activities, whereas scope 2 is mainly associated with the electricity use and methane emission from septic tanks. Scope 3 includes all other indirect emissions that occur in an organization’s value chain. At least 16 categories of scope 3 emissions should be considered, although not every category will be relevant to all organizations (Greenhouse Gas Protocol 2013).

The reporting boundaries for the selected Thai and Japanese restaurants were associated with the operationally control activities of these restaurants. The GHG sources were identified along the whole supply chains and all associated activities of these restaurants. Identified GHG emission sources were allocated to the relevant scope category, where scope 1 covers direct emissions from owned or controlled sources and scope 2 covers indirect emissions from the generation of purchased electricity, steam, heating, and cooling consumed by the reporting company. According to the identified GHG emission sources covering scopes 1 and 2, GHG inventory data were collected based on annual activity in 2021. The activity data on LPG and solid alcohol for food preparation, refrigerant leakage, and methane emission from septic tank were collected from the financial system and maintenance reports. The GHG emission source in scope 2 was mainly from the use of purchased electricity; hence, the inventory data of electricity use were based on the bills over the 12 months in 2021.

Scope 3 GHG emission sources associated with the studied restaurants were identified and then assessed for their level of importance using the developed criteria for such evaluation. The practical criteria for the food industry were specified: the magnitude of important indirect GHG emissions, reduction potential to minimize GHG emissions, and risks or opportunities for business operation. All GHG emissions according to the guidelines were identified and crosschecked with another study (Takacs and Borrion 2020).

The identified GHG emissions from the scope 3 sources were evaluated for their importance level using a scoring matrix analysis (Table 1). To assess the importance level, the selected criteria considered the magnitude (quantity level of GHG emissions), reduction potential (resulting from applied measures), and the risks/opportunities for the business operation. Each criterion could be ranked using a numerical scale in the range 1–5, where 1 = low GHG emissions, low GHG reduction potential, and low risk or low opportunity for the business operation; 3 = medium GHG emissions, medium GHG reduction potential, and medium risk or low opportunity for the business operation; and 5 = high GHG emissions, high GHG reduction potential, and high risk or low opportunity for the business operation. Furthermore, GHG emissions less than 5% (compared to the total GHG emissions from scopes 1 and 2) were considered low magnitude, where the GHG emissions varied in the range 5%–40%, they were considered as medium magnitude, whereas those greater than 40% were considered as high magnitude. This was consistent with the approach suggested in the science-based target setting manual (Greenhouse Gas Protocol 2013). A total score in the range 7–15 was considered important, whereas a total score in the range 3–6 was considered unimportant. Table 1 shows the importance assessment results for both types of restaurants based on the scoring matrix analysis. It can be seen that the important GHG sources for both restaurants were mainly 1) purchased goods and services, 2) upstream transportation and distribution, and 3) waste generated in operations.

Table 1.

Assessment of significant levels of scope 3 GHG emission sources from life cycle activities of restaurants studied.

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Then, the identified important sources (raw material acquisition, transportation of raw materials, and waste management and disposal) were included in the evaluation of GHG emissions according to the national guidelines. Notably, there were no GHG emission sources in categories 13–16. The activity data in each item were collected mainly through the internal accounting systems and documentation, such as electricity bills, bills for purchased raw materials and their loading, bills for water use, bills for food delivery, and from the waste management form. The fuel consumption was calculated from the fuel consumption rate of each type of vehicle and the traveling distance according to the place of loading and delivery.

3. Results

The total GHG emission results from scopes 1 to 3 (including only the important GHG sources for scope 3) showed that the Japanese restaurant emitted 310.78 tCO₂e yr⁻¹, whereas the Thai restaurant emitted 190.84 tCO₂e yr⁻¹ (Figs. 1 and 2). The scope 1 GHG emissions were rather similar for the Thai and Japanese restaurants being 12.45 and 11.01 tCO₂e yr⁻¹, respectively. For scope 2, the Japanese restaurant emitted 61.06 tCO₂e yr⁻¹, whereas the Thai restaurant emitted 22.06 tCO₂e yr⁻¹. For the scope 3 emissions, the Japanese restaurant (237.27 tCO₂e yr⁻¹) emitted much more than the Thai restaurant (157.77 tCO₂e yr⁻¹). The almost 3 times higher level of emissions by the Japanese restaurant was because of its higher energy use resulting from the larger service area. However, the carbon intensity on a per area basis was higher for the Thai restaurant than the Japanese restaurant.

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GHG emissions from scopes 1 to 3 of the Japanese restaurant.

Citation: Weather, Climate, and Society 16, 3; 10.1175/WCAS-D-23-0095.1

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GHG emissions from scopes 1 to 3 of the Thai restaurant.

Citation: Weather, Climate, and Society 16, 3; 10.1175/WCAS-D-23-0095.1

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Compared to the total GHG emissions from scopes 1 and 2, the scope 3 emissions from both restaurants were significant with contributions of 78% and 82% from the Japanese and Thai restaurant, respectively. For the Japanese restaurant, the scope 3 GHG emissions were largely from raw material acquisition (176.25 tCO₂e yr⁻¹), transportation of raw materials (57.93 tCO₂e yr⁻¹), waste management (15.30 tCO₂e yr⁻¹), and water consumption (3.01 tCO₂e yr⁻¹) which was approximately 344% of the total GHG emissions from scopes 1 and 2. This was also the case for the Thai restaurant with the scope 3 GHG emissions being associated mainly with raw material acquisition (111.02 tCO₂e yr⁻¹), transportation of raw materials (18.65 tCO₂e yr⁻¹), waste management (20.73 tCO₂e yr⁻¹), and water consumption (1.37 tCO₂e yr⁻¹).

From this study, the hotspots generating important GHG emissions, especially from scope 3 activities, that require special attention regarding GHG management measures were purchased food products, upstream transportation, distribution, and waste management. It was suggested that the restaurants should focus on purchasing local food ingredients (such as Japanese rice from Thai farmers and Thai beef), including raw materials from nearby locations, as well as simulating transport routes to minimize the distance of transport, which reduce GHG emissions by about 14%.

4. Discussion

The results from this study were very similar to another study of six restaurants in the United States with different service styles (catering, quick service, and full service) in the Chicago, Illinois, metropolitan area and the Washington, D.C., metropolitan area. The results indicated that food procurement or raw material acquisition was the leading source of environmental impact for climate change, being about 53% of total GHG emissions (Baldwin et al. 2011). The same hotspots had been identified by another study (Takacs and Borrion 2020), where food production, transportation and distribution of products and ingredients, food storage and preparation, food serving and consumption, and waste disposal appeared to be important sources of scope 3 GHG emissions in the food service sector. This was supported by another dining restaurant study that reported differences in the GHG emissions attached to food transportation from local locations compared to nonlocal locations were because the local locations contributed to reduced GHG emissions from fuel combustion for transport (Striebig et al. 2019). It was also suggested to use food products within the region instead of imported food products, which could potentially reduce average GHG emissions by 60%–90% (Vicente-Vicente and Piorr 2021). Using locally sourced foods and reducing the amount of animal-based protein on menus were additional suggestions to encourage GHG reduction and a more sustainably focused food service industry (Hatjiathanassiadou et al. 2019).

Separation of food wastes from recyclable packaging wastes for further uses could help to reduce GHG emissions by around 13%. This GHG management measure was suggested in other studies. For example, Jang et al. (2020) reported that recycling single-use plastic wastes (such as packaging from food delivery and PET bottles) could reduce GHG emissions from the incineration of plastic waste by an estimated 13%. Arunan and Crawford (2021) found that using packaging for online food delivery services in Australia with 50% recycled raw materials could potentially reduce GHG emissions by 9% and reduce energy use in the production of plastic by 62%.

In addition, changing menus from a high carbon footprint to a low-carbon footprint could be a practical, sustainable choice. Restaurants should flag low-carbon footprint meals on their menus to engage their customers to contribute to GHG reductions. This was similar to the study by Brunner et al. (2018), which reported that the consumers in a Swedish university restaurant chose the meals made with vegetables, fish, and chicken due to the lower associated GHG emissions of these items. Likewise, Kolbe (2020) found that vegan dishes could reduce GHG emissions by 65% and 10% compared to meat and ovo-lacto-vegetarian recipes, respectively.

To improve the restaurant industry in the goal toward zero emissions and being carbon neutral, proposed strategies for GHG emission reduction could be enhanced via the following actions. Referring to the purchased goods and services, sustainable procurement policy should be taken place; low-carbon footprint ingredients should be primarily selected, and they should be locally produced to support sustainable agriculture as well as to reduce GHG emissions from long distance transportation. Limiting the home delivery services (i.e., single-use plastic) and incorporating reusable containers for food packaging would provide a unique opportunity to engage customers in sustainable practices to reduce packaging wastes and their associated GHG emissions. In terms of waste management, designing menus with overlapping ingredients could potentially prevent food waste. Another potential approach is to offer smaller portion sizes at a lower price so that customers could finish it all and are less likely to leave behind uneaten food. In addition, predicting the orders based on the historical trends during a given period could be helpful. Identifying local organizations like charities, food banks, or homeless shelters that can accept food donations could be a good option for food waste management. More importantly, setting targets to reduce food loss and waste could raise awareness and tracking food waste inventory data would call for direct attention from staff to help to decrease food loss and waste. Along with a composting program, it would stimulate the progress toward zero waste to landfill. Low-carbon food choices or zero food waste dishes must be communicated to customers to stimulate their selection of lower carbon dishes as a more sustainable choice; this would attract particularly Gen Z customers who are climate conscious and would like to contribute to GHG reduction. However, this study was restricted to case studies involving northeastern Thai cuisine and Japanese–Thai fusion in Thailand. Notably, different restaurants have their own characteristics in serving diverse dishes requiring numerous raw materials and using different types of cooking methods.

5. Conclusions

This study demonstrated that the scope 3 GHG emissions for food and service industry are significant and should not be overlooked. GHG emissions sources along the whole supply chain, in addition to scopes 1–2, must be identified and quantified for better GHG measurement and management strategies. Scope 3 activities that should be taken into account for reporting and reducing GHG emissions from this study could be used as a guideline. Scope 3 emissions were generally the largest portion of a restaurant’s carbon footprint contributing around 80% of the total GHG emissions. The main hotspots for scope 3 emissions were 1) purchased goods and services, 2) upstream transportation and distribution, and 3) waste generated in operations. It is worth noting that specific GHG sources in scope 3 should be identified for each type of restaurant. Then, strategies to reduce GHG emissions could be used to shift the potential environmental impacts from one category to another, with other potential impacts besides GHGs being taken into consideration. In addition, the cost of GHG reduction should be calculated as a part of the decision-making process before selecting GHG reduction options. The key findings from this study should be useful in identifying the hotspots to apply improvement options for better and more sustainable restaurant outcomes.

Data availability statement.

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due their containing information that could compromise the privacy of research participants.