Analysis of the factors affecting carbon emissions and absorption on a university campus – focusing on Pusan National University in Korea

ABSTRACT

Climate change has become a global issue. Universities, as major contributors to carbon emissions, have been asked to make efforts to reduce their carbon emissions. In this situation, carbon absorption by forests has been regarded as a means of mitigating carbon emissions. Therefore, this study examined the factors in carbon emissions, as well as the influence of carbon absorption on carbon reduction, through a data-centered analysis on the campus. An analysis of the Pusan National University campus, as an example, showed that the primary cause of carbon emissions is the use of electricity in buildings on the campus (63.8% of the total amount of emitted carbon), followed by indirect carbon emissions by movement of the campus’ members (21.5%). However only 0.66% of the amount emitted carbon is absorbed by forests. Therefore, effect of carbon reduction on the campus caused by carbon absorption is too small. Although the carbon absorption effect of the trees is inadequate, the value of trees still exists due to their environmental effects. Based on the results of this study, it is possible to reduce carbon emission by reducing electricity use and vehicle operation and provide a plan for using carbon absorption as a complementary measure.

KEYWORDS:

• green campus
• carbon absorption
• carbon emission

Introduction

Climate change, or global warming, is a big issue. All countries in the world have implemented policies for adaptation to climate change and its alleviation. On the other hand, although universities play a leading role in solving these problems, they consume large amounts of energy and emit large amounts of carbon [1]. According to a survey by the Korea Energy Management Corporation in 2006, 22 of 190 the Korean facilities that consume excessive amounts of energy belong to universities. The electricity used at universities accounts for approximately 13% of the electricity used in 190 research facilities [2]. Therefore, it is important for universities to make leading efforts to cope with climate change.

Carbon dioxide absorption by vegetation is considered an important response to climate change. As a result, considerable efforts have been made to improve carbon dioxide uptake by creating a green roof system and parking lot green systems on college campuses [2]. On the other hand, many problems are expected. These include making carbon-reducing plans and setting goals without thoroughly analyzing the actual carbon-reducing factors, such as energy consumption or carbon absorption rate, that come under the name of “green campus” in local universities. Therefore, this paper proposes effective methods to reduce the carbon level on campuses by performing an actual proof analysis of the carbon emission rate and absorption rate on university campuses, and understanding the critical factors of carbon reduction.

Research questions and previous research

Analysis of carbon emission factors

The primary aim of this study was to identify the factors affecting carbon emissions on university campuses. Understanding the factors affecting carbon emission on campuses is critical for improving the awareness of carbon emission rates and finding reducing methods. Therefore, the first research question of this study is as follows:

Research Question 1: What are the most critical factors affecting the carbon emission rate on university campuses? Among those factors, which one is most effective?

Because of the greater importance attached to universities’ role and responsibility for coping with climate change, considerable research related to green campuses has been conducted. Son and Nam young-suk [3], Lee [4] and Woo [5] examined the consumption of energy on campuses, and highlighted the importance of the green campus. They also addressed universities’ role and responsibility for carbon emission reduction. The Gyeonggi Research Institute [6], Association of Physical Plant Administrator (APPA) [7] and Eagan et al. [8] produced manuals for activities to put the green campus into action and provide guidelines for coping with climate change. Jung [9] provided a model that serves as a standard for greenhouse gas reductions by making plans for carbon emission reduction by category, considering the characteristics of emissions on campuses. Noh [10] and Cho et al. [11] used both a questionnaire-based survey and document-based research to derive important considerations in making plans for green campuses, providing objective and rational evidence for forming eco-friendly campuses.

Most studies have proposed methods for inventory composition to form green campuses, plans for forming green campuses and methods for evaluating the elements of the makeup of a green campus. They did not describe why the proposed methods and plans are necessary and important, and why they are valid. In other words, they failed to offer positive evidence of the influence of the proposed methods, plans and elements on carbon reduction on campuses. Consequently, this study conducted empirical analysis of the important factors that affect carbon reduction on campuses to make an analysis of their influence. This study is different from existing studies in that it proposes a plan based on evidence for carbon reduction.

Questions regarding the effects of carbon absorption of forests on campus

The second research question of this study was to determine the effects that green areas on campuses have on carbon absorption rates. As one of the measures for coping with climate change, carbon absorption by forests has been viewed as an important element of the plans for carbon emission reduction. The importance of carbon absorption attracted attention when the Kyoto Protocol at the UN COP3 in December 1997 was adopted, in which forest resources were recognized as a resource for carbon absorption [12]. Therefore, IPCC looks on the amount of reduced carbon of the Section of Land Use, Change in Land Use and Forests as the accomplishments of reduction for a climate change convention. Carbon absorption attracted attention as a global hot issue [13]. The Kyoto Protocol proposed plans for carbon reduction by increasing the rate of carbon absorption in a particular region to reduce carbon effectively and economically [12].

According to previous studies, understanding the carbon absorption rate of the greens on university campuses is expected to be an important factor for carbon neutrality. Therefore, a research question of this study is as follows:

Research Question 2: What effect does university campus green areas' carbon absorption rate have on carbon neutrality?

Hwang [14] and Lee and Park Chan [15] highlighted the importance of the role of vegetation and soil as an absorber of carbon, and proposed plans for making a plan for land use. Nowak and Crane [16], Cannell [17] and Cho [18] highlighted the importance of the role of urban afforestation in carbon reduction by calculating the amount of carbon absorbed by forests and woody plants in some cities in America, Britain and South Korea. Park [19] compared the results of research related to carbon absorption by green tracts of land in South Korea, USA and UK to show an annual amount of absorbed carbon and to derive the effect of carbon absorption.

In this manner, some research in South Korea has focused considerable attention on calculating the amount of carbon absorbed by green tracts of land and produced meaningful results showing that carbon absorption affects carbon reduction. Based on this research, this study examined the influence of carbon absorption on the amount of carbon emitted on campus and attempted to determine analytically whether carbon absorption can be an effective alternative to carbon emission reduction.

Research method

This study selected the Pusan National University campus as a sample for research, and relied on positive analysis to comprehend the impact of the important factors on carbon reduction. The campus is ranked eighth in the amount of energy consumed by universities in Korea [20], and it is ranked number one among Busan-based universities. On the other hand, the university has expressed its willingness to form a green campus by implementing the Project for Forming a Green-Energy Campus or a project for constructing green buildings.

The study examined the use of the IPCC guidelines to calculate the amount of carbon emitted on the sample campus by re-structuring the inventory categories. In addition, the amount of carbon absorbed by woody plants and forests on the campus was calculated to determine the influence of the important factors pertaining to carbon emission and absorption on carbon reduction.

Study area

The campus of Pusan National University, the spatial extent of this research, is located in the Busan Metropolitan City of Korea (Figure 1). The climate is temperate. The lowest daily temperature is below 0 °C on average from December to February, approximately 53 days, and the daily highest temperature is over 25 °C from July to September, 83 days, on average.

Figure 1. Location of Busan City.

Pusan National University attracts the most students among the national universities in Korea by the standard of the enrollment quota (for year 2011). The education workers of Pusan National University total 3246 people, and there are 489 staff, 21,613 undergraduate students and 8417 graduate students. The land size of the Busan campus of Pusan National University is 652,742 m² and the building area is 392,295 m² (Table 1).

Table 1. The current status of Pusan National University [21]).

	Classification	Current figures
Present number of education workers	Faculty	3426 people
	Staff	489 people
Present number of students	Undergraduate students	21,613 people
	Graduate students	8417 people
Present size of facilities	Land size	652,742 m^2
	Building area	392,295 m^2

Currently, the energy expense of the Busan campus of Pusan National University is composed of 88% of electricity and 12% gas. The 1-year electricity consumption of the Pusan campus of Pusan National University is counted as 43,604 Mwh, and gas consumption is counted as 1,485,000 m³ (Table 2).

Table 2. The current status of Pusan National University energy use [21].

Classification	Energy expense (KRW*)	Usage
Electricity	4,654,000 (88%)	43,604,000 Mwh
Gas	638,000 (12%)	1,485,000 m^3
Total	5,292,000	-

*1KRW = 1,191.50 (US$)

Method of calculating the amount of emitted carbon

The guidelines used most widely for carbon inventory calculation include the IPCC guidelines¹ developed for the national inventory calculation and World Resources Institute (WRI) / World Business Council for Sustainable Development (WBCSD) guidelines developed properly for an inventory calculation [6]. In South Korea, the Korea Environment Corporation and Korea Energy Management Corporation have studied the international guidelines to apply them suitably to domestic situations, such as domestic local governments and firms, to make good use of them [6]. On the other hand, South Korea does not have a concrete guideline to display the carbon inventory in a unit of campuses. Accordingly, this study revised the local government guidelines for calculating the quantity of greenhouse gas and clarified the definition of the sources of emission and the coefficient of emission according to the source of emission to mutually complement the methods of calculation.

The carbon inventories of Hanyang University and Hanshin University typically calculated by the Seoul National University and Gyeonggi Research Institute basically group the category of carbon inventory into the operation systems of Scope 1², Scope 2³ and Scope 3⁴ to select items for detailed examination. Regarding the Seoul National University inventory, Scope 1 selects stationary combustion as the amount of fuels used in buildings, and mobile combustion as the amount of fuels consumed by university-owned vehicles. Scope 2 forms an inventory of the amount of electricity purchased from outside, and the amount of waterworks used. Scope 3 includes waste, such as reclamation, incineration and waste water, to form its inventory. This scope also includes fugitive emissions. Scope 3 includes the amount of emitted carbon as mobile combustion to form one inventory category.

The research draws out the factors affecting carbon emission based on the emission quantity calculated by carbon inventory of the preceding cases produced before in rearranging the classification of the carbon inventory category. The resulting carbon inventory composition of this research is shown in Table 3.

Table 3. Makeup of the inventory of the amount of carbon emitted on the Pusan National University campus.

Large classification	Mid-classification	Small classification
Scope 1 (direct emission)	Stationary combustion (buildings)	Liquefied natural gas (LNG)
	Mobile combustion (movement inside the campus)	Road transportation
Scope 2 (indirect emission)	Stationary combustion (buildings)	Electricity
		Waterworks
Scope 3 (other kinds of indirect emission)	Mobile combustion (movement by car between home and campus)	Road transportation
	Waste	Solid waste
		Wasteworks

Table 3 lists the makeup of the carbon inventory in this study. The study used the greenhouse gases caused by the liquefied natural gas (LNG) fuels used in the buildings on the campus as the stationary combustion. The greenhouse gases emitted from vehicles running on the campus were used as the mobile combustion. The electricity and waterworks usage of buildings on campus are used as the fixed combustion of Scope 2. Scope 3, the emission sources indirectly emitted by the members of the target campus, is calculated with the emission quantity of greenhouse gases emitted from the vehicles and waste (solid waste and waste water) used with the purpose of commuting to work and school by the education workers and students of Pusan National University. Each carbon emission quantity formula is as follows, according to the calculation guide of the local government greenhouse gas emission quantities.

Scope 1 – LNG; Scope 2 – electricity

• Amount of emitted carbon = fuel consumption × emission factor

• - Amount of emitted carbon, GHG, fuel: amount of emitted GHG (greenhouse gases given by the type of fuels)

• - Fuel consumption: amount of consumed fuels (TJ)

• - Emission factor, GHG, fuel: including carbon-oxidation factor assumed to be 1 to emission factor (ton gas/TJ) CO₂ of GHG given by the type of fuels

Scope 1 – mobile combustion (movement inside the campus); Scope 3 – mobile combustion (movement by car between home and campus)

• - Emission: amount of CO₂ emission (kg)

• - VKT (vehicle kilometers of travel): total annual distance of drive (km)

• - EF: Emission factor (kg/km-number of vehicles)

• - CAR: Number of registered vehicles according to the type of vehicles (number of vehicles)

• - a: kind of vehicles (cars, buses, freight cars)

• - b: year of target

Scope 2 – water works

• Emission quantity = usage × emission factor

• - Emission quantity: indirect greenhouse gas emission quantity (t CO₂eq) caused by waterworks

• - Usage : waterworks usage

• - Emission factor: carbon-oxidation factor, assumed to be 1, is included for emission factor (ton gas/TJ) CO₂ of GHG given by the use of waterworks

Scope 3 – solid waste

• Emission quantity = throughput × emission factor

• - Emission quantity: indirect greenhouse gases emission quantity (t CO₂eq) caused by solid waste throughput

• - Throughput: solid waste throughput

• - Emission factor: carbon-oxidation factor, assumed to be 1, is included for emission factor (ton gas/TJ) CO2 of GHG given by handling solid wastes

Scope 3 – waste water

• Emission quantity = [(TOW − S) EF − R] GWP

• - Emission quantity: indirect greenhouse gases emission quantity (t CO₂eq) caused by waste water.

• - TOW: total organic material (ton BOD (biochemical oxygen demand)/yr) inside waste water

• - S: sludge generation rate (ton BOD/yr)

• - EF: emission factor (kg CH₄/kg BOD)

• - R: CH₄ recovery quantity

• - GWP: global warming potential

This study used the data on the amount of LNG and electricity use, waterworks use, solid waste, waste water in facilities and buildings on the campus as well as the current status of vehicle movement between home and campus and the number of registered vehicles of the General Affairs Department, and calculated the total amount of carbon emitted according to the standards in 2011.

Method for calculating the amount of absorbed carbon

A census of woody plants on the campus was taken from September 7 to October 7, 2011, to calculate the amount of absorbed carbon. Fifteen survey sites (districts of woody plants) on the campus were set as a method of survey. A 10 m × 10 m quadrate was installed in each site to provide diameter measurements of natural vegetation colonies and artificial forests;⁵ 12 survey sites were set and the enumeration districts were set randomly to provide diameter measurements. Table 4 lists the distribution of conifers and broad-leaf trees, and Table 5 shows the distribution of area of woody plants determined by the survey. Figure 2 shows the distribution of the forests.

Table 4. Current status of the distribution of conifers and broad-leaf trees on the Pusan National University campus.

Classification according to characteristics		Family	Species	Population
Needle-leaf tree	Evergreen needle-leaf tree	3	7	21,173
	Deciduous needle-leaf tree	1	1	22
Broad-leaf tree	Evergreen broad-leaf tree	5	6	81
	Deciduous broad-leaf tree	16	25	2410
Total		25	39	23,686

Table 5. Current status of the distribution of conifers and broad-leaf trees on the Pusan National University campus.

Total area of the campus	Natural vegetation colonies and artificial forests	Buildings, street trees, trees for landscape architecture
635,026 m^2	159,104 m^2	475,922 m^2

Figure 2. Sites (St.) of the survey of the current status of woody plants.

A range of methods for calculating the amount of absorbed carbon were evaluated. These methods can be divided into a method for using vegetation maps, a method for using the register of woody plants and a method for surveying sample blocks [14]. This study used the calculation method proposed by Lee [22] based on the methods of the register of woody plants and sample-black survey. Table 6 lists the formulae for the calculation. This is a suitable method for calculating the amount of carbon dioxide absorbed by woody plants using the diameter at breast height used in the survey of woody plants at Pusan National University, which is considered the best method for analyzing the data on the survey of woody plants and calculating the amount of absorbed carbon dioxide. Consequently, this study accepted a method for totalizing the calculations simultaneously, after calculating the amount of absorbed carbon dioxide according to the type of woody plants at the sites, as the method for calculating the amount of carbon absorption by woody plants.

Table 6. Equations for calculating the amount of CO₂ absorbed by woody plants and forests.

Items	Formulas of calculation by item
Amount of CO2 absorption by woody plants and forests (kg/week/year)	A = population of arbor broad-leaf trees × BT1 + population of arbor conifers × BT2 + population of shrub broad-leaf trees × BS1 + population of shrub conifers × BS1
	Here,
	BT1 (Amount of CO2 absorbed by arbor broad-leaves trees):
	Y = − 4.2136 + 1.9006DBHaver. − 0.0068DBHaver.^2
	BT1 (Amount of CO2 absorbed by arbor conifers):
	Y = − 2.7714 + 0.9714DBHaver. − 0.0225DBHaver.^2
	BS1 (Amount of CO2 absorbed by shrub broad-leaves trees):
	Y = 0.0333DAGaver.^1.5826
	BS1 (Amount of CO2 absorbed by shrub conifers):
	Y = 0.0568DAGaver.^1.3350

*DBHaver is the mean diameter at breast height (5∼40cm); DAGaver. is the mean diameter of the root, 15cm from the top part (1-4cm)

Data: Lee (2003), The Development of an Index for Sustainable Growth of Green Tracks of Land in Apartment Complexes, A PhD dissertation at Seoul National University

Analysis results

Calculation of the amount of emitted carbon

Scope 1: Stationary combustion – LNG sector

Although LNG is used as a fuel at Pusan National University, the amount of emitted carbon in the section of LNG in 2011 was estimated based on the data from 2007 to 2010 because there is no data on the amount of LNG use in 2011. The total area of the buildings in 2009 was used in terms of an original unit. The areas of the Construction Hall constructed in 2011, Hall of ‘Hyowon’ Industry-college Cooperation, the First Library and the Information and Computational Center were all multiplied to calculate the amount of carbon emitted. The amount of carbon emitted according to the year in the LNG sector at Pusan National University, as shown in Table 7, indicated an upward trend of LNG use in buildings because new buildings have been constructed.

Table 7. Results of an analysis of the amount of emitted carbon in the LNG* sector (buildings) by year at Pusan National University.

		Calculation of the amount of emitted carbon (t CO2eq)
Year	Amount of use (Nm^3)	CO2	CH4	N2O	Total
2007	1,474,744	3309.33	6.19	1.83	3317.35
2008	1,732,548	3887.84	7.28	2.15	3897.26
2009	1,667,132	3741.04	7.00	2.07	3750.11
2010	1,761,583	3952.99	7.40	2.18	3962.58
2011	1,912,684	4291.96	8.03	2.37	4302.37

*LNG: Liquefied natural gas.

Scope 1: Mobile combustion – road transportation (movement on the campus)

To calculate the amount of carbon emitted in the sector of movement on the campus, the program built in January 2011 at Pusan National University, in which the vehicles used for movement between home and campus were used, was applied to collect data on all vehicles used for movement between home and campus from January to October in the year. The total value acquired by adding the number of the vehicles from January to October 2011 to the monthly average number of vehicles in November and December was used to achieve the total number of those vehicles. The vehicles were considered middle-grade cars because of the difficulty in acquisition of data. The average distance of the movement of vehicles on the campus was derived from that of the vehicles registered in each college whose destination was clear. The mean distance of the registered vehicles was found to be 1.28 km. Table 8 lists the amount of carbon emitted in the sector of road transportation on campus.

Table 8. Results of an analysis of the amount of emitted carbon in the road transportation sector (movement on campus) in 2011 at Pusan National University.

	Calculation of the amount of emitted carbon (t CO2eq)
In-and-out vehicles (number)	CO2	CH4	N2O	Total
1,757,590	478.96	0.04	0.13	479.13

Scope 2: Stationary combustion – electricity (buildings) sector

As there was little data on the amount of electricity use at Pusan National University for 2011 [31], the data by year from 2007 to 2009 was used. As in the case of the LNG sector, which is based on the data for electricity use from 2007 to 2010, in terms of the original unit using the total areas of buildings in 2009, the areas of newly constructed buildings were multiplied to estimate the amount of emitted carbon in the electricity sector at Pusan National University in 2011. An upward trend in electricity consumption was observed because there has been an annual increase in new buildings, which has increased the carbon emissions. Table 9 lists the amount of emitted carbon each year.

Table 9. Results of an analysis of the amount of emitted carbon in the sector of electricity (buildings) by year at Pusan National University.

		Calculation of amount of emitted carbon (t CO2eq)
Year	Amount of use (Mwh)	CO2	CH4	N2O	Total
2007	35,590	16,560.03	4.04	29.79	16,593.85
2008	38,304.00	17,822.85	4.34	32.06	17,859.26
2009	38,422	17,877.76	4.36	32.16	17,914.27
2010	42,402	19,729.65	4.81	35.49	19,769.95
2011	45,908.58	21,421.48	5.22	38.53	21,465.23

Scope 2: Stationary combustion – waterworks sector

To calculate carbon emission quantity of the waterworks part in the school, the date of waterworks usage from year 2009 to 2011 were used. The waterworks usage for 2009 was 638,488 ton, 630,446 ton for 2010, and 584,209 ton for 2011, showing a gradually decreasing trend. The calculated result of carbon emission quantity of the waterworks part in the school is shown in Table 10.

Table 10. Results of an analysis of the amount of emitted carbon in the waterworks sector by year at Pusan National University.

Year	Amount of use (ton)	Calculation of amount of emitted carbon (t CO2eq)
2009	638,488	211.98
2010	630,446	209.31
2011	584,209	193.96

Scope 3: Mobile combustion – road transportation sector (movement by car between home and campus)

To calculate the amount of carbon emitted in the section of the campus members’ commute by car between home and campus, 3796 vehicles registered at the university as of 2011 were surveyed. The vehicles were estimated to be mid-grade because of the difficulty in related data acquisition. The distance of running between the members’ home and the campus was derived from a calculation of the total annual distance of running by the standards of the distance of running according to the kind of vehicles and fuel used. Table 11 lists the amount of carbon emitted in the sector of road transportation for movement between home and campus.

Table 11. Results of an analysis of the amount of emitted carbon in the road transportation sector (movement by car between home and campus) in 2011 at Pusan National University.

	Calculation of the amount of emitted carbon (t CO2eq)
Registered vehicles (number)	CO2	CH4	N2O	Total
3796	7163.93	0.67	2.02	7166.62

Scope 3: Waste – solid waste sector

Data from years 2009 to 2011 were used for solid waste emission quantity inside the campus. The solid waste emission quantity on the campus was 549.80 ton for 2011, 498.98 ton for 2009 and 500.03 ton for 2010, showing an increasing trend. Therefore, carbon emission quantity according to the above results is also in an increasing trend, and the calculated result of carbon emission quantity in the part of solid waste is shown in Table 12.

Table 12. Results of an analysis of the amount of emitted carbon in the solid waste sector by year at Pusan National University.

Year	Amount of use (ton)	Calculation of amount of emitted carbon (t CO2eq)
2009	498.98	19.90
2010	500.03	19.95
2011	549.80	21.94

Scope 3: Waste – waste water sector

To calculate indirect carbon emission quantity caused by waste inside the campus, the date of 2011 was used. The total inflow rate of annual waste inside the campus was 25,854 m³, the total organic materials in the waste water were 0.25 ton BOD, and the sludge generation rate was 0.12 ton BOD. Based on these results, the calculated result of carbon emission quantity in the part of waste water is shown in Table 13.

Table 13. Results of an analysis of the amount of emitted carbon in the waste water sector at Pusan National University.

Year	Waste water inflow rate (m^3)	Total organic material inside waste water (ton BOD*/yr)	Sludge generation rate (ton BOD/yr)	Calculation of amount of emitted carbon (t CO2eq)
2011	25,854	0.25	0.12	0.581

*BOD: Biochemical oxygen demand.

Result of the calculation of the amount of absorbed carbon

The total amount of carbon absorbed by woody plants and forests at Pusan National University was estimated to be 220.931 t CO₂/year (Table 14). A look at the amount of absorbed carbon according to site shows that the amount of absorbed carbon at Site 15 was ranked highest: 138.904 t CO₂/year. The estimated absorption at Site 14 and Site 2 was 21.096 t CO₂/year and 11.971 t CO₂/year, respectively. The hierarchy of the sites was proportional to the amount of woody plants and forests in each. This suggests that the amount of absorbed carbon increases with increasing woody plants and forests. The amount of carbon absorbed by street trees was estimated to be 5.540 t CO₂/year, which accounts for 2.5% of the total amount of absorbed carbon, which is an indication that street trees play a small role in carbon reduction.

Table 14. Amount of carbon absorbed by woody plants, by sites on the Pusan National University campus.

Site	Amount of absorbed carbon (t CO2/year)
St. 1	1.283
St. 2	0.236
St. 3	11.971
St. 4	0.160
St. 5	0.288
St. 6	2.265
St. 7	10.281
St. 8	5.927
St. 9	3.970
St. 10	4.660
St. 11	2.862
St. 12	0.516
St. 13	10.964
St. 14	21.096
St. 15	138.904
Street trees	5.548
Total	220.931

Analysis of the result of carbon inventory

As of 2011, the total amount of carbon emitted on the Pusan National University campus was calculated to be 33,629.83 t CO₂eq. The calculated amount of emitted carbon in terms of the original unit (m²) was 0.053 (t CO₂eq/m²), suggesting that the campus emits a larger amount of carbon per unit area than do the entire cities of Busan [0.034 (t CO₂eq/ m²)⁶] [23] and Geomjung-gu [0.013 (t CO₂eq/ m²)⁷] [24]. In other words, the campus emits a larger amount of carbon per unit area than the other local governments’ administrative districts do. Therefore, it is vital for the campus to make sustained efforts to reduce the amount of carbon emitted.

Influence of the major factors of carbon emission on the campus

Electricity use (buildings) accounts for 21,465.23 t CO₂eq (63.8%), showing that this sector is a major cause of carbon emission. The second cause of greater emission quantity was the carbon emission quantity that came from the commuting of university members, which covered 21.3% (7166.62 t CO₂eq) of the total. LNG emits 4302.37 t CO₂eq and accounts for 12.8% of the total amount of emitted carbon. Table 15 and Figure 3 show the ratios of the amount of carbon emitted by sector in a bar graph.

Table 15. Results of the calculation of the amount of emitted carbon by sector in 2011 at Pusan National University.

Sectors	Amount of emitted carbon (t CO2eq)
LNG (building)	4,302.37
Road transportation (movement on the campus)	479.13
Electricity (building)	21,465.23
Waterworks	193.96
Road transportation (movement by car between home and campus)	7,166.62
Solid waste	21.94
Waste water	0.581
Total	33,629.83

Figure 3. Ratios according to the emission factor.

Analysis of the effects of carbon absorption

The effect of carbon absorption that contributes to the reduction of carbon emission on campus was 0.66%, indicating that only 0.66% of the amount of carbon emitted on the campus is reduced. The result shows that the carbon absorption effect inside the campus is inadequate, and also shows that the difficulty exists to suggest an effective measure of carbon reduction inside the campus.

Table

Carbon neutral

• (Amount of absorbed carbon ÷ amount of emitted carbon) × 100%

= (220.931 t CO2eq ÷ 33,629,83 t CO2eq)

× 100% = 0.66%

Therefore, the logic of expanding trees, the carbon absorbers, to raise the carbon absorption volume is not persuasive. Although trees are inadequate in terms their carbon absorption effect, the value of tree still exists due to environmental effects such as recent mitigation of flood plain [25,26] and urban heat island effects [13,27], and the reduction of non-point pollutant sources [28,29], along with various other effects such as health and relaxation [30,31]. As mentioned previously, the most effective policy for carbon neutrality in university is to control the expansion of unnecessary buildings since the carbon emission quantity caused from the buildings is quite high. Moreover, minimizing new building construction as a rule and various energy-effective policies, such as applying new renewable energy to existing and new buildings, are required.

Conclusion and proposal

The results of the research questions are summarized as follows:

Research Question 1: What are the most critical factors affecting the carbon emission rate in university campuses? Among those factors, which is most effective?

After analyzing and considering the factors related to campus carbon emissions in Pusan National University, the major carbon emissions were caused by the buildings' electricity use (63.8%), followed by carbon emission from the commuting transportation used by the members of the university. The LNG used by buildings had the third highest effect, with transportation by movement within the campus having the least effect. The other causes analyzed had little influence. Therefore, application of alternative and new renewable energy for the electricity and LNG used in the buildings for reducing carbon emission quantity is required for the university, and voluntary participation of members using public transportation is needed to reduce vehicle usage.

Research Question 2: What effect does university campuses’ green carbon absorption rate have on carbon neutrality?

Carbon absorption by greens and trees on the campus appeared to have a slight effect in carbon reduction. The greens and trees only absorbed 0.66% of the carbon emitted by Pusan National University in 2011. Therefore, minimizing new building construction as a rule and various energy effective policies, such as applying new renewable energy to existing and new buildings, are required.

Based on these results, this study proposes some ideas for carbon reduction. First, it is necessary to take concrete action to make efficient use of the energy used in buildings, for example the adoption of new and renewal energy and standby power systems. As shown in the results of the research, because buildings consume considerable amounts of energy, to reduce carbon emissions it is important to take measures to use less energy or use it more efficiently. Second, a traffic policy and a program for increasing the recognition of efficient energy use by the campus members will be necessary to reduce the carbon emitted in the sector of their movement by car between home and campus. Efforts should be made to use these plans or develop methods to reduce car use and carbon emissions. Third, the strategy of minimizing new building construction for reducing carbon emission quantity is needed.

The Pusan National University has a significantly higher distribution rate of trees on-site compared to other institutions in Korea. Moreover, Korea recently has been expanding the importance of the reduction strategy of carbon emission quantity, and considering trees as the most important cause of carbon absorption. This research was started from the question of how many trees actually have carbon-neutral effects at some level, since universities in Korea recently have been emphasizing the importance of trees inside of the campus for expanding the carbon-absorption volume. However, the research showed that trees distributed inside of the university were analyzed as having an inadequate role to absorb carbon emissions in the quantity occurring in the university. Therefore, the policy of reducing carbon emission from buildings is more effective than the logic of expanding carbon absorbers for the policy of carbon neutrality in the university. This does not mean the importance of trees is low. Environmental effects such as urban heat island mitigation [13,27], flood plain mitigation [25,26], and reduction of non-point pollutant sources [28,29], and various effects provided to humans [30,31], are already proven effects of trees other than the carbon absorption effect. Therefore, this research has analyzed the inadequate effect of trees by looking at points of carbon neutrality, and further research is needed to prove the tree effect when combined with other virtues.

This study does not have sufficient data to apply those derived factors to all universities, because it used only one example for its empirical analysis. Different universities may have different topological features and different structures of buildings. Hence, different universities with their unique characteristics may have different factors in carbon emissions. Accordingly, this study needs to analyze a range of campus examples to draw a more universal conclusion. More study will be needed to provide a model that makes it possible to analyze the factors of carbon emission according to university characteristics, to reflect university-unique measures against carbon emissions. Furthermore, the analysis of scenarios regarding how much reduction is actually made in carbon emission volume, according to the new renewable energy policy of the university and the effect of the traffic policy suggested in this research, is proposed for future research.

Acknowledgements

This research was supported by the grant “A Study on Enhancing the Community Capacity for Hazard Mitigation in Climate Change” [MPSS-NH-2013-63] from the Natural Hazard Mitigation Research Group, Ministry of Public Safety and Security of Korea.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. The WRI/WBCSD guidelines provide a comprehensive system for the process and method of calculating the amount of greenhouse gases emitted using a standardized approach. Currently, they are credible so that most firms use them as a guideline for inventory calculations.

2. Scope 1 indicates the amount of greenhouse gases emitted by the direct source managed by the inventory-calculating organization, including greenhouse gases emitted by direct-combustion equipment, such as boilers; greenhouse gases emitted by combustion equipment, such as cars; greenhouse gases emitted in the process of goods manufacturing; and fugitive gases by the moving and loading of fossil fuels and by equipment leakage in the process of goods manufacturing.

3. Scope 2 indicates the amount of carbon emitted by the secondary energy used by the inventory-calculating organization. Although greenhouse gases from electricity production are not found in the area measured, power plants emit greenhouse gases, which are calculated as the amount of indirectly emitted carbon.

4. Scope 3 is the result of an inventory calculation by selective report category, and indicates the amount of emitted greenhouse gases that do not occur in facilities under the control of the organization concerned.

5. Diameter measurement, of the kind of trees, height of trees, and diameter at breast height (DBH) in the enumerated district concerned, refers to an inspection of the basic information on woody plants and forests in enumerated districts.

6. This is the calculated total amount of carbon emitted by Busan City in terms of an original unit, as of 2010, based on the final report on the Amount of Emitted Greenhouse Gases in 2007 by Busan Metropolitan City [29].

7. This is the calculated total amount of emitted carbon of Geumjeong-gu in terms of the original unit, as of 2011, provided by Kim Mi-rim et al. [24].