**2.2 The development of LCA**

minimization of the artificial disturbance [15]. Therefore, reducing the environmental impact caused by maintenance tasks will contribute to the sustainable

**1.4 The literature review of environmental impact in urban green space**

mental impacts of green space maintenance. The University of Florida, in the "Florida-Friendly Landscaping Guidelines," proposed that the maintenance team should sign a contract with the green space owners and enact a detailed working plan before maintenance operations. The working plan should estimate the types of maintenance tasks and detail workload. This is important to improve working efficiency, save maintenance materials, and reduce environmental impacts [16]. The "Sustainable Sites Initiative" (proposed by the US Lady Bird Johnson Wildflower Center and US Botanic Garden) point out that during the complete life cycle of the urban landscape (design, construction, operation, maintenance, and disposal), the maintenance procedure occupied around 10–20% of the total environmental impact [17]. Some research point out reducing the maintenance workload can decrease the environmental impact and improve the ecological benefits of the green space. Zhao and Liu pointed out that the city managers should reduce the area of grassland and plant more native woodland to improve the adaptability and tolerance of urban green space. Extensive use of wildflowers and meadows can also benefit to the urban wildlife and reduce the maintenance requirement [18]. Guo in the renewable and recyclable landscape research indicated that the self-maintenance green space is able to maximize the utilization of energy and materials and reduce environmental pollution in the use process [19]. Min put forward that the conservation green space is to improve the utilization rate of maintenance resources and energy use and obtain the maximum ecological, environmental, and social benefits [20]. Shu-Hua pointed out that symbiotic cyclic urban landscape architecture should adopt the design of low environmental impact, including the selection of recyclable, lowconsumption, and high-durable building materials, and pay attention to reduce the

Few urban environment assessment systems are mentioned about the environ-

development of urban green space.

*Sustainability in Urban Planning and Design*

maintenance material input in the later period [21].

**2. Life cycle assessment of the environmental impact**

urban green space [23].

**2.1 Introducing of LCA**

**222**

The quantitative study on the environmental impact of urban green space maintenance is limited. After finishing 3 years of urban green space maintenance carbon emission data collection for the three major cities, Seoul, Chuncheon, and Gangneung, Hyun found that the annual increase of urban green space carbon emissions is between 10 and 20%. The average carbon (CO2-eq) emissions are 264.9, 37.0, and 67.9 t/ha/y<sup>1</sup> in Seoul, Chuncheon, and Gangneung, respectively. The annual carbon storage in the three urban green spaces (the amount of CO2-eq) is about 50% of the respective carbon emissions [22]. Lynch et al. believe that pruning, fertilization, pest control, and other works in green space maintenance can cause heavy carbon discharge. The design phase can directly influence the maintenance workload, such as the time investment, energy, and water consumption in

Life cycle assessment (LCA) is a comprehensive tool for evaluating the environmental impact of products or behaviors. This method can comprehensively analyze

**maintenance**

LCA was initially applied primarily to research on resource consumption and environmental impacts of product packaging. In the early 1980s, due to the global energy crisis, environmental problems mainly focused on fossil energy consumption and combustion pollutant emissions, and the life cycle assessment method also entered the stage of academic discussion. At the same time, with the global solid waste problem that emerged from the late 1970s to the mid-1980s, the life cycle method has gradually become a resource analysis tool and has entered the field of scholars. Research at that stage mainly focuses on the assessment method construction, with limited case studies. The earlier LCA research was concentrated in the United States and encouraged by the government [27].

After entering the 1990s, LCA entered a stage of rapid development. In 1990, for the first time, the International Society of Environmental Toxicology and Chemistry (SETAC) hosted an international seminar on LCA. The concept of "life cycle assessment" was first presented at the conference. In the following years, the SETAC hosted and held several academic seminars and conducted extensive research on the theory and methods of life cycle evaluation [28]. Although the current life cycle assessment methodology still has many issues worth studying, the SETAC and the International Standards Organization (ISO) have been actively promoting the international standardization of LCA. The ISO 14040 standard (Environmental Management—Principles and Framework for Life Cycle Assessment) was promulgated on 1997, and the corresponding series of standards ISO 14041 (list analysis), ISO 14042 (impact evaluation), and ISO 14043 (interpretation of impact statements) are also in the following [24]. The standard system has a great improvement to the standardization steps of the LCA concept and the technical framework.

Construction of the LCI database is a vital factor in the development of LCA. LCI database includes the total environmental impact data on every life cycle stage of the upstream product. The LCI database construction starts from the early 1990s.

**Figure 3.** *The framework of LCA [24].*

Currently the word mainstream database includes "ecoinvent" in Europe and "Chinese life cycle database" (CLCD) in China [26].
