Carbon Footprint Study of Korean Green Tea Industry Using the Methods of the Life Cycle Assessment and Calculating Carbon Absorption in Agricultural Land

Noh-Hyun Lim ^1,*, Yongjin Lee ¹, Jieon Lee ², Jongsek Kim ³

1. Dev. of Certification Business, Institute of Global Sustainability Certification, Seoul, 03371, Republic of Korea

2. Dep. of Materials Chemistry and Engineering, Konkuk University, Seoul, 05029, Republic of Korea

3. Dep. of Environmental Engineering, University of Seoul, Seoul, 02504, Republic of Korea

* Correspondence: Noh-Hyun Lim

Academic Editor: Paul Dargusch

Special Issue: Case Studies of Carbon Management in Practice

Received: September 02, 2022 | Accepted: November 21, 2022 | Published: December 02, 2022

Adv Environ Eng Res 2022, Volume 3, Issue 4, doi:10.21926/aeer.2204047

Recommended citation: Lim NH, Lee Y, Lee J, Kim J. Carbon Footprint Study of Korean Green Tea Industry Using the Methods of the Life Cycle Assessment and Calculating Carbon Absorption in Agricultural Land. Adv Environ Eng Res 2022;3(4):13; doi:10.21926/aeer.2204047.

© 2022 by the authors. This is an open access article distributed under the conditions of the Creative Commons by Attribution License, which permits unrestricted use, distribution, and reproduction in any medium or format, provided the original work is correctly cited.

1. Introduction

The international community has recognized the need for joint efforts due to global warming and climate change, adopting the Paris Agreement in 2015 to launch a new climate system. After the Paris Agreement, carbon neutrality, matching emissions and absorption, has emerged as a global agenda to limit the rise in global average temperature from below 2°C to below 1.5°C by 2050. Accordingly, 127 countries, including many in Europe, the United States, China, and Japan, have declared that they have become or are in the process of becoming carbon neutral.

Korea has also declared carbon neutrality by submitting its “2050 Long-Term Low-Carbon Development Strategy” and “2030 National Greenhouse Gas Reduction Target” to the United Nations in December 2020. Although the agricultural sector is directly or indirectly affected by climate change with events such as crop death, flooding, sea ice, and loss of agricultural land, it also has the potential to reduce greenhouse gas (GHG) emissions.

Since 2018, Korea’s livestock emissions have been approximately 11.2 million tons of CO2 eq. and 1.4 million tons of CO2 eq. of GHG emissions must be reduced to achieve carbon neutrality. In particular, the importance of carbon neutrality is very high due to the high carbon absorption potential of forest biomass. Regarding agricultural production in Korea, the Agricultural Promotion Administration conducted a carbon footprint study on major crops such as rice, barley, potato, sweet potato, and bean in 2010, and has not conducted carbon footprint studies of other agricultural products since then [1,2,3,4,5].

However, Korea does not yet have a formal methodology for evaluating the carbon uptake potential of biomass. In addition, research on calculating carbon emissions throughout the product life cycle for a specific industry has been slow in Korea.

In the global beverage market, green tea is the second most consumed beverage after water, and the biomass of tea trees has considerable potential to absorb carbon during cultivation. Accordingly, life cycle assessment studies of tea are being conducted in major tea-producing countries such as China, Taiwan, India, and Sri Lanka (as shown in Table 1). However, the cultivation environment, cultivation method, and tea manufacturing method of green tea produced in Korea have some differences from other countries. Furthermore, there are differences in the system boundary and the scenario part of the use stage.

Table 1 Study case of life cycle assessment related to tea.

In this study, the environmental impact of green tea was quantified by performing a life cycle assessment of green tea produced in Korea that met the cultivation environment, cultivation method, and tea manufacturing method as well as the system boundary and the scenario part of the use stage in Korea. The carbon absorption amount of green tea biomass was calculated using the IPCC’s gain-loss method, and the net GHG emission from green tea plantations was calculated [13,14]. This study is the first study on carbon absorption in the green tea industry in Korea and aims to determine the carbon neutrality potential of green tea.

2. Methodology

In this study, the GHG emissions in the life cycle of green tea were calculated using the EPD guideline[15] from the Korea Ministry of Environment and the guideline[16] for Low Carbon Agricultural and Livestock Goods Certification of the Ministry of Agriculture, Food and Rural Affairs in Korea following the ISO 14040 and 14044 guidelines[17,18]. In addition, the carbon uptake of green tea biomass was calculated using the IPCC’s gain-loss method.

2.1 Goal and Scope of the Study

The target product of this study is green tea, which is used as an ingredient in food and food manufacturing, and the amount of green tea and water consumed when drinking a cup of green tea varies according to consumers’ tastes and types of tea. Therefore, a cup of tea containing 2 g of tea leaves and 200 mL of water was set as a functional unit of the tea-drinking method recommended by the Korean Tea Culture Association (as shown in Table 2).

Table 2 Product specification.

The system boundary included in this study are shown in Figure 1, including the green tea cultivation stage of growing tea leaves, the primary processing stage of steaming and drying the tea leaves to prevent oxidation, the production stage of packaging materials to distribute the dried green tea, the transportation stage of transporting the packaging material to the secondary processing area, the secondary processing and packaging stages of tea roasting and packaging, and the distribution stage of providing finished products to consumers. It also includes the use stage of green tea consumed by consumers and the disposal stage of discarding the brewed tea leaves and packaging materials after consumption by the consumer.

Figure 1 System boundary for green tea.

2.2 Data Collection and Calculation

Data collection by System boundary for green tea collected the average data of Korea in 2019, and if other data could not be collected, the international average data of LCI DB developed by ecoinvent was collected (as shown in Table 3).

Table 3 Data collection.

2.2.1 Pre-manufacturing

Cultivation Stage. Agricultural materials and energy consumption were collected using field data from green tea farms in Korea, “agricultural and livestock income data” and statistics from the Rural Development Administration. It also included the planting process of green tea seedlings, cultivation management such as fertilization, control, pruning, branch priming, and agricultural work such as tea leaf extraction.

The content of active ingredients in the crop protection agent used in the green tea cultivation stage refers to the “Common Guidelines for the Calculation of Greenhouse Gas Emissions from Agricultural Products” of the Agricultural Technology Commercialization Foundation. In addition, the IPCC 2006 Guidelines [19] and Methods were applied for nitrous oxide emissions from fertilizer use. In addition, the emission coefficients of each fuel in the Korea Environment Corporation’s “Guidelines for Calculating Local GHG Emissions” [20] were applied for the air pollutant emissions from gasoline and diesel combustion. For the landfill/incineration/recycling waste generated from the use of other agricultural materials (light-shielding film, drip hose), the Agricultural Technology Commercialization Foundation’s “Common Guidelines for Calculating Agricultural Product GHG Emissions” were applied. Lastly, since other agricultural materials are used for a long period, the annual usage was calculated by dividing by the lifespan.

Packaging Production Stage. The consumption of raw and subsidiary materials and the fuel used in the production stage of packaging material were collected, and air pollutants caused by liquefied petroleum gas combustion were calculated according to the guidelines of the Korea environmental industry & technology institute.

2.2.2 Manufacturing Stage

The manufacturing stage first included the processing of the tea leaves produced during the pre-manufacturing stage, secondary processing, product inspection, and packing and shipping of the final product.

First Processing. The consumption of electricity, liquefied natural gas (LNG), and kerosene was collected in the primary processing step of steaming and drying tea leaves to prevent oxidation. Air pollutants generated by combustion were calculated according to the guidelines of the Korea Environment Corporation [21,22].

Secondary Processing and Packaging. In the secondary processing step of roasting and packaging tea leaves, by-products other than green tea products are produced, which have economic value. Accordingly, the consumption of electricity and LNG, which were commonly used for products and by-products, were allocated by reflecting the economic value and production ratio. In addition, the packaging step for the produced product was also included.

Transportation. Transportation was calculated based on the distance from each region [23], including land transportation by truck and sea transportation to Jeju Island, based on the region where the delivered raw and subsidiary materials are input into the manufacturing process.

2.2.3 Distribution Stage

Distribution was calculated based on regional distance (EPD, 2019), including land transportation by truck and sea transportation to Jeju Island, and the region where the delivered product is sold to consumers.

2.2.4 Use Stage

According to the tea-drinking recommendation of the Korea Tea Culture Association, the amount of tea leaves used to drink a cup of tea was 2 g, and the amount of water was 200 mL. Assuming water was used as the energy source, from the standard temperature of 20°C to a boiling temperature of 100°C. In addition, electricity and city gas (LNG) were used as energy sources for boiling water at 46% and 54%, respectively. This conclusion was based on the assumption of electricity consumption and applied the 46% penetration rate of an electric port from the “2019 Home Appliance Supply Status Survey”.

-Electricity required to boil 1 kg of water (kWh) = specific heat capacity of water (4.187 kJ/kg K) × temperature (80 K)/conversion factor (3600 kWh/kJ)/electric pot thermal efficiency (85%) = 0.109 kWh

-The amount of LNG required to boil 1 kg of water (L) = specific heat capacity of water (4.187 kJ/kg K) × temperature (80 K)/heat capacity of LNG (42.7 kJ/L)/thermal efficiency of gas range (50%) = 16 L

2.2.5 Disposal Stage

The disposal stage was calculated by considering the items to be recycled, incinerated, or landfilled by material and applying the disposal scenario and data from the Ministry of Environment’s EPD certification guidelines [24,25].

2.3 Carbon Uptake Calculation

Methods for estimating the carbon absorption in agricultural land are divided into three types according to the application of emission factors and activity data.

Tier 1 is the method that applies the basic formula and basic coefficients provided by the IPCC. Tier 2 is the method that develops and applies country-specific coefficients. Tier 3 is a method to develop and apply country-specific coefficients with more detailed and clear data than Tier 2.

Currently, Korea has not developed a country-specific coefficient, so the Tier 1 method, IPCC's “Gain-loss method,” was applied to calculate the changes in carbon stock (absorption) of green tea biomass.

* Annual change in carbon stocks in biomass (Gain-loss method): ∆CLB = ∆CG – ∆CL

∆CLB: annual change in carbon stocks in biomass for each land subcategory, considering the total area (ton C/yr)

∆CG: annual increase in carbon stocks due to biomass growth for each land subcategory, considering the total area (ton C/yr)

∆CL: annual decrease in carbon stocks due to biomass loss for each land subcategory, considering the total area (ton C/yr)

(LB: living biomass, G: growth, L: loss)

-     2006 IPCC GL, Chapter 2, Equation 2.7

The gain-loss method assumes that all carbon in the removed perennial woody biomass is released in the year it is removed and that the carbon accumulation period is the same as the mature tree cycle. In this study, the green tea planted area and reduced area in Korea were collected through the "Special Crop Production Performance" published by the Ministry of Agriculture, Food and Rural Affairs (as shown in Table 4).

Table 4 Planting area of green tea in Korea from 2010 to 2019 (unit: hectare).

2.4 Net GHG Emissions Estimation

The net GHG emission of green tea was calculated considering the GHG emission of 1 kg of green tea calculated through the life cycle assessment method and the change in carbon dioxide accumulation in the green tea growing area calculated through the gain-loss method.

Net GHG Emissions = (GHG Emissions in the Product’s Lifecycle − Changes in Carbon Dioxide Accumulation)/yield of green tea

3. Results and Discussion

3.1 Life Cycle Impact Assessment (LCIA)

The LCIA quantifies the magnitude of the environmental impact on the entire process of a product or system. In this study, the GHG emissions of the entire process were calculated by applying the Ministry of Environment’s EPD certification guideline and the Korean Ministry of Agriculture, Food and Rural Affairs’ Low Carbon Agricultural and Livestock Goods Certification guideline. Considerable influence categories included global warming (GWP), resource depletion (ADP), acidification (AP), eutrophication (EP), ozone layer depletion (ODP), and photochemical oxide production (POCP).

As shown in Table 5, the GWP for a cup of green tea is 0.0318 kg CO₂-eq., which is mainly caused by the production of fuel and packaging materials consumed when brewing green tea.

Table 5 Characterization results by cmpact Category.

By analyzing the environmental impact on each cup of green tea at each stage of its life cycle, we observed that the use stage, the packaging material production stage, and the primary processing stage have larger impacts in the GWP and ADP impact categories. In addition, the packaging material production stage was identified as the major issue in the AP, EP, and PODP impact categories, and green tea cultivation was identified as the major issue in the ODP impact category (as shown in Table 6).

Table 6 Contribution analysis by impact category.

3.2 Calculation of Changes in Carbon Stocks

To calculate the change in carbon stock using IPCC’s gain-loss method, the change in the cultivated area was examined using the “Special Crop Production Performance” published by the Ministry of Agriculture, Food and Rural Affairs. For calculating the basic coefficients of carbon stock and carbon loss, we applied a temperate climate region (as shown in Table 7).

Table 7 Basic coefficients of aboveground perennial woody biomass.

However, it is difficult to apply the 30-year gain-loss method of IPCC as the mature age of green tea is 8 years in the “Measures for Stability of Green Tea Supply and Demand and Competitiveness Enhancement” of the Korea Rural Economic Research Institute. Therefore, we compared the biomass carbon loss by considering 30 years of temperate climate region of IPCC's gain-loss method and 8 years of the mature tree age of Korean green tea (as shown in Table 8).

Table 8 Basic coefficients of green tea biomass in Korea (estimated value).

The gain-loss method is a simple formula that subtracts the decrease from the increase in carbon stock, and the increase in biomass occurs due to the growth of green tea and the planting of driftwood seedlings in the existing green tea plantation. The increase in carbon accumulation was calculated by multiplying the green tea planting area by the carbon accumulation factor of 2.1 tons C/ha yr. The removal of tea trees resulted in a decrease in biomass. The reduction in carbon stock was calculated by multiplying the area reduced compared to the previous year by a carbon loss factor of 63 (or 16.8) tons C/ha. The results were presented in Table 9 and Table 10.

Table 9 Calculation results of green tea cultivation area and reduced area (unit: hectare).

Table 10 Calculation result of carbon stock change (unit: ton C).

The above results were converted to CO₂ standards (the atomic weight of carbon is 12 and the atomic weight of carbon dioxide is 44) and the amount of carbon accumulation change was converted to 1 kg of green tea by reflecting the annual green tea production (as shown in Table 11).

Table 11 Changes in CO₂ accumulation per 1 kg of green tea (unit: kg CO₂).

3.3 Net GHG Emissions Estimation

As shown in Table 12, the variation in net GHG emissions on an 8-year basis is smaller than on a 30-year basis. In addition, it was confirmed that carbon uptake from farmland varies greatly depending on the area of farmland cultivated, ranging from as high as 59% to as low as 3% compared to the GHG emission during the entire production process.

Table 12 Net GHG emissions per kg of green tea (unit: kg CO₂-eq).

4. Conclusions

In this study, the GHG emission was calculated using the life cycle assessment method for green tea, and the change in biomass carbon stock was calculated by the IPCC's gain-loss method to quantify the net GHG emission of green tea in Korea.

(1) According to the Ministry of Environment’s EPD certification guidelines, the calculated GHG emissions for 2 g green tea was 0.0318 kg/CO₂, which was converted to 15.9 kg CO₂/kg for 1 kg green tea.

(2) The change in biomass carbon stock calculated according to the IPCC’s gain-loss method was compared with the 30-year mature tree age of the gain-loss method and the 8-year mature tree age of green tea. 30 years, which is the mature tree age of the gain-loss method, had a large deviation. Therefore, we suggested that it would be better to apply it based on the 8-year mature tree age of green tea.

(3) The net GHG emission of green tea in Korea varies greatly from as high as 59% to as low as 3% in the carbon absorption of biomass due to farm maintenance, which significantly affects the net GHG emission result.

Considering the results of this study, the role of green tea producers is most important in achieving carbon neutrality in green tea. Producers should maximize carbon absorption at the planting stage by reserving farmland, simplify packaging materials in the design of green tea products, and seek to develop products that can use cold water instead of hot water to brew green tea.

In this study, the IPCC’s gain-loss method used to estimate carbon stock changes is a method that is applied to all perennial woody crops except tea trees. Therefore, if future studies are conducted on the absorption estimation method specific to tea trees, and absorption and loss coefficients specific to Korean tea trees are developed, we believe that net GHG emissions can be calculated with a high degree of accuracy.

Author Contributions

N.-H.L.(Ph.D) conducted the experiments and wrote the manuscript. Y.L. (Ph.D. student), J.L. (Master) and J.K. (Ph.D. student) wrote and revised the manuscript. All authors have read and agreed to the published version of the manuscript.

Competing Interests

The authors have declared that no competing interests exist.