ABSTRACT
This study evaluates the carbon neutrality of eco-slope protection projects to understand their role in climate change mitigation. Utilizing life cycle assessment, it defines system boundaries and compiles inventories to calculate and analyze carbon emissions and assimilations of a wet-spraying vegetation concrete eco-slope protection project in China, simplifying previous methodologies and emphasizing the critical role of vegetation. Findings indicate lifecycle carbon emissions total 608.01 tCO2e, broken down by source as follows: material (54.69%), maintenance (40.11%), energy (3.27%), transport (1.32%), and workforce (0.6%). Slope protection plants are estimated to assimilate 2,676.30 tCO2. The project is estimated to reach carbon neutrality in its 4.59th year, with an anticipated net carbon sink contribution of 2,068.29 tons over its lifespan. These results underscore eco-slope protection projects’ significant carbon neutral capacity, highlighting their importance in combating climate change and fostering the civil engineering industry's green transformation.
HIGHLIGHTS
People are getting more serious about global warming. The Paris Climate Agreement of 2015 sets targets to limit global temperature rise.
A large number of traditional slope protection projects have generated a significant amount of GHG emissions, and eco-slope protection methods have attracted widespread attention.
Wet-spraying vegetation concrete eco-slope protection produces 608.01 tCO2e over its lifecycle.
Slope protection vegetations absorb 2,676.30 tCO2 over their lifecycle.
INTRODUCTION
Since 1979, China has seen unprecedented economic growth, leading to substantial development in water conservancy, urban infrastructure, and transportation networks. This rapid expansion has introduced environmental challenges, notably a surge in exposed slopes that bear significant geological hazard risks, threatening ecological stability and human safety (Koca & Kıncal 2004; Stokes et al. 2014; Hu et al. 2021).
Traditional methods of slope protection have often relied on soil erosion prevention and slope stability. However, these techniques may potentially impair vital ecological functions. For example, hard revetments can disrupt the ecological interplay between water bodies and soils (Oda et al. 1991; Nordstrom 2014; Wu et al. 2017). Moreover, the materials traditionally used in these projects, particularly cement and steel, contribute considerably to global carbon emissions, accounting for approximately 11% of the total emissions (Habert et al. 2020; Benhelal et al. 2021; Zhang et al. 2022a). The extensive use of materials such as cement and steel in slope stabilization projects has been linked to soil compaction and increased salinity, adversely affecting the viability of local flora and fauna as well as the overall microbial health of the soil (Bilen et al. 2019; Ismail et al. 2023). As such, the environmental integrity of many river revetments and road protection structures has been severely compromised due to traditional slope protection methods, which not only disrupt ecological connectivity but also significantly contribute to climate change by releasing substantial amounts of greenhouse gases (GHGs). The environmental repercussions of these practices have prompted a re-evaluation of conventional approaches, with a growing recognition that they may not align with contemporary sustainable development goals.
As global challenges such as climate change and ecological degradation intensify, there is a growing collective consciousness about environmental stewardship. The Paris Climate Agreement of 2015 exemplifies this shift, setting ambitious targets to limit the global average temperature rise to well below 2.0 °C above pre-industrial levels, with aspirations to keep the increase to no more than 1.5 °C (IPCC 2013, 2014; Hoegh-Guldberg et al. 2019). In pursuit of these goals, nations worldwide are advancing research into green technologies to address the multifaceted aspects of the climate crisis (Feulner 2017; Dinerstein et al. 2019; Shim et al. 2019). In the field of civil engineering, ecological slope protection technology has emerged as an innovative solution that aligns with these global sustainability efforts. This approach marries ecological principles with engineering techniques to create interventions that are both structurally sound and environmentally integrated. Appreciated for its ability to facilitate ecological restoration while meeting engineering needs, ecological slope protection has seen widespread adoption across various countries (Mitsch & Jørgensen 2003; Liu et al. 2007).
Prevalent ecological slope stabilization methods, such as artificial plant protection, spray-seeding, and the use of structural skeletons for slopes, prioritize the use of materials and structures that are less damaging to the environment (Yao et al. 2024). By harnessing the natural strength and water management capabilities of plant roots, stems, and leaves, these natural processes enhance soil shear strength, curtail surface runoff, and mitigate soil erosion, effectively contributing to slope stabilization (Gray & Sotir 1996; Muzylo et al. 2009; Eab et al. 2015). The integration of vegetation in these projects not only provides structural benefits but also reduces reliance on materials with high-carbon footprints, such as cement and steel. This synergy fosters biodiversity and ecosystem recovery on slopes, expanding green spaces considerably (Medl et al. 2017). As a result, eco-slope protection not only minimizes environmental impact and carbon emissions in comparison to traditional methods but also capitalizes on the carbon dioxide absorption and oxygen production capabilities of plants throughout their life cycle (Zhang et al. 2014). Such attributes underscore the environmental importance of eco-slope projects and their potential contribution to achieving carbon neutrality.
However, scholarly inquiries into ecological slope protection have predominantly concentrated on the materials used for slope stability, the physical stability of the slopes themselves, and the biomechanical properties of root systems. Research into the quantification of carbon emissions specific to ecological slope protection projects remains relatively underdeveloped. Particularly, there is a scarcity of studies that quantify the carbon sequestration capabilities of the vegetative components utilized in slope protection. The current methodologies for calculating carbon emissions, which largely rely on life cycle assessment (LCA) theory, lack the granularity needed for the precise evaluation of eco-slope projects. Consequently, these methods fall short in their capacity to rigorously assess the carbon neutrality potential that these projects may offer.
Therefore, the present study aims to develop an enhanced carbon emission calculation framework for eco-slope protection projects, drawing on refined LCA methodologies while incorporating the carbon uptake capabilities of vegetation. The framework is designed to facilitate a deeper understanding of the various sources of carbon emissions and the sequestration potential inherent in the plant species used in these projects. Such insights are crucial for enabling decision-makers to strategically select and tailor engineering solutions from the outset of eco-slope projects. The ultimate goal is to reduce the carbon footprint of such initiatives and augment their capacity to function as net carbon sinks over their lifecycle, thereby advancing environmental protection and supporting the sustainable evolution of civil engineering practices. Given the prevalent existence of riverbank protection projects (Li et al. 2013), the study will analyze an actual ecological river revetment project.
METHODS
Study area
The Huama Lake Connecting Channel Slope Protection Project is situated in Ezhou City, Hubei Province, China, near the southern bank of the Yangtze River's middle section. The lake covers an area of 20.07 km² and stretches over 2.2 km in length, with the channel's bottom width being 40 m. The elevation varies significantly along the slope, with a height difference ranging from 5 to 67 m from the channel's bottom to the top of the slope interception ditch. The slope inclines vary widely, from gentle slopes of 15° to steep slopes of 80°. The geographical features of the slope include predominantly rocky areas, interspersed with regions where rocky and soil slopes merge.
Schematic diagram of wet-spraying vegetation concrete eco-slope protection.
Spraying process of wet-spraying vegetation concrete eco-slope protection.
Life cycle assessment
This study utilizes the LCA method to scrutinize the environmental impacts of the Huama Lake eco-slope protection's second phase. LCA, a comprehensive approach endorsed for its efficacy in environmental impact evaluation (Buyle et al. 2013), systematically quantifies the inputs and outputs throughout a product's lifecycle. This includes the procurement of raw materials, manufacturing processes, usage, and end-of-life disposal. Adhering to ISO 14040 standards, the LCA methodology consists of defining the study's goal and scope, inventory analysis, impact assessment, and results interpretation (ISO 2006; Ecoinvent 2016).
Goal and scope
Life cycle inventory
Data collection content of life cycle inventory for eco-slope protection. Note: ‘(–)’ represents the carbon offset item in the life cycle inventory for eco-slope protection.
Data collection content of life cycle inventory for eco-slope protection. Note: ‘(–)’ represents the carbon offset item in the life cycle inventory for eco-slope protection.
Life cycle impact assessment and interpretation
The diversity of output factors identified during inventory analysis suggests diverse potential environmental impacts. To assess the severity of these impacts, a specific assessment methodology is applied during the life cycle impact assessment and interpretation stage. This crucial phase highlights areas for improvement within the product system and helps prioritize such enhancements. It involves characterizing and evaluating the environmental performance of the system or its unit processes, providing essential insights and guidance for decision-makers (Curran 2013).
CALCULATION METHOD
Calculation methods of carbon emissions
These equations provide a comprehensive framework for quantifying the total carbon emissions from the eco-slope protection project over its whole life cycle. By applying these formulas, emissions from all life cycle stages – material production, transportation, workforce involvement, energy usage, and vegetation maintenance – are systematically consolidated, enabling a precise calculation of the project's comprehensive carbon footprint.
Calculation methods of vegetation carbon assimilations
RESULTS AND DISCUSSION
Calculation results of carbon emissions
The carbon emissions from primary materials used in eco-slope protection are quantified in this research. The results are detailed in Table 1. The consumption of these materials has been determined through engineering data, and the associated carbon EFs are derived from the Chinese Standard for Building Carbon Emission Calculation (GB/T 51366-2019), the China Products Carbon Footprint Factors Database (CPCD 2023), and relevant literature studies (Chen et al. 2016; Shi et al. 2020; Zhang et al. 2022b).
Carbon emissions from material
Category . | Unit . | Amount . | Emission factor . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Cement | Ton | 168.00 | 735.00 kgCO2e/t | 123.48 |
Admixtures | Ton | 192.00 | 181.00 kgCO2e/t | 34.75 |
Organic matter | Ton | 34.60 | 27.00 kgCO2e/t | 0.93 |
Compound fertilizer | Ton | 5.28 | 2,470.00 kgCO2e/t | 13.04 |
Galvanized steel wire mesh | Ton | 53.26 | 1,230.00 kgCO2e/t | 65.51 |
Anchor bar | Ton | 32.64 | 2,600.00 kgCO2e/t | 84.87 |
Dry mixed mortar | m3 | 21.20 | 234.00 kgCO2e/m3 | 9.92 |
Total carbon emissions (EM) | 332.51 tCO2e |
Category . | Unit . | Amount . | Emission factor . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Cement | Ton | 168.00 | 735.00 kgCO2e/t | 123.48 |
Admixtures | Ton | 192.00 | 181.00 kgCO2e/t | 34.75 |
Organic matter | Ton | 34.60 | 27.00 kgCO2e/t | 0.93 |
Compound fertilizer | Ton | 5.28 | 2,470.00 kgCO2e/t | 13.04 |
Galvanized steel wire mesh | Ton | 53.26 | 1,230.00 kgCO2e/t | 65.51 |
Anchor bar | Ton | 32.64 | 2,600.00 kgCO2e/t | 84.87 |
Dry mixed mortar | m3 | 21.20 | 234.00 kgCO2e/m3 | 9.92 |
Total carbon emissions (EM) | 332.51 tCO2e |
The results derived from computing carbon emissions pertinent to the transportation stage in eco-slope protection are enumerated in Table 2. The data regarding the weight and distance of transportation goods covered are gleaned from construction logs, while the respective carbon EFs are sourced from the Chinese Standard for Building Carbon Emission Calculation (GB/T 51366-2019).
Carbon emissions from transport
Category . | Weight (ton) . | Distance (km) . | Emission factor (kgCO2e/t·km) . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Cement | 168.00 | 50.00 | 0.129 | 1.08 |
Admixtures | 192.00 | 150.00 | 0.129 | 3.72 |
Organic matter | 34.60 | 150.00 | 0.129 | 0.67 |
Compound fertilizer | 5.28 | 150.00 | 0.179 | 0.14 |
Galvanized steel wire mesh | 53.26 | 200.00 | 0.129 | 1.37 |
Anchor bar | 32.64 | 200.00 | 0.129 | 0.84 |
Dry mixed mortar | 33.92 | 50.00 | 0.129 | 0.22 |
Total carbon emissions (ET) | 8.04 tCO2e |
Category . | Weight (ton) . | Distance (km) . | Emission factor (kgCO2e/t·km) . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Cement | 168.00 | 50.00 | 0.129 | 1.08 |
Admixtures | 192.00 | 150.00 | 0.129 | 3.72 |
Organic matter | 34.60 | 150.00 | 0.129 | 0.67 |
Compound fertilizer | 5.28 | 150.00 | 0.179 | 0.14 |
Galvanized steel wire mesh | 53.26 | 200.00 | 0.129 | 1.37 |
Anchor bar | 32.64 | 200.00 | 0.129 | 0.84 |
Dry mixed mortar | 33.92 | 50.00 | 0.129 | 0.22 |
Total carbon emissions (ET) | 8.04 tCO2e |
The carbon emissions from workforce associated with eco-slope protection are outlined in Table 3. The necessary working days for each main process have been drawn from the construction quotas (Han & Yang 2012). According to CEIC (2020) statistics, the per capita energy consumption for China in 2020 was documented at 0.456 metric tons of standard coal. This value is subsequently transformed by utilizing the emission of 2.460 tCO2e per metric ton of standard coal (IPCC 2006). Assuming the period of one year to be 365 days with each working day entailing 8 h. Finally, the workforce carbon emission factor is determined to be 1.024 kg CO2e/days.
Carbon emissions from workforce
Main procedure . | Work days (days) . | Emission factor (kgCO2e/day) . | Carbon emission (kgCO2e) . |
---|---|---|---|
Slope surface finishing | 150.00 | 1.024 | 153.67 |
Drainage construction | 188.00 | 192.59 | |
Anchor installation | 2,250.00 | 2,304.99 | |
Fixed wire mesh | 678.00 | 694.57 | |
Eco-concrete base materials production | 300.00 | 307.33 | |
Eco-concrete base materials spraying | 18.00 | 18.44 | |
Total carbon emissions (EL) | 3.67 tCO2e |
Main procedure . | Work days (days) . | Emission factor (kgCO2e/day) . | Carbon emission (kgCO2e) . |
---|---|---|---|
Slope surface finishing | 150.00 | 1.024 | 153.67 |
Drainage construction | 188.00 | 192.59 | |
Anchor installation | 2,250.00 | 2,304.99 | |
Fixed wire mesh | 678.00 | 694.57 | |
Eco-concrete base materials production | 300.00 | 307.33 | |
Eco-concrete base materials spraying | 18.00 | 18.44 | |
Total carbon emissions (EL) | 3.67 tCO2e |
The carbon emissions arising from energy consumption in the eco-slope protection project are presented in Table 4. This includes energy usage by various construction machinery, which is calculated from the number of operating days and energy consumption per operating day. The latter is calculated based on the machinery's rated power. The carbon emission factor for diesel, used in powering machinery, is calculated by multiplying the fuel's heat value carbon emission factor (72.59 tCO2e/TJ) with its average lower heating value (0.042652 TJ/t), following the guidelines of IPCC (2006) and GB/T 2589-2020 standards. The carbon emission factor for electricity is derived from existing literature (Kong et al. 2017).
Carbon emissions from energy
Category . | Type . | Consumption . | Emission factor . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Forced mixer | Electricity | 5,192.00 kWh | 1.014 kgCO2e/kwh | 5.26 |
Vibrating sieving machine | Electricity | 806.40 kWh | 1.014 kgCO2e/kwh | 0.82 |
DTH drilling | Electricity | 832.00 kWh | 1.014 kgCO2e/kwh | 0.84 |
Pneumatic handheld drill | Electricity | 6,133.60 kWh | 1.014 kgCO2e/kwh | 6.22 |
Loader | Diesel | 910.63 kg | 3.096 kgCO2e/kg | 2.82 |
Wet-spraying machine | Diesel | 437.42 kg | 3.096 kgCO2e/kg | 1.35 |
Boat for spraying | Diesel | 832.00 kg | 3.096 kgCO2e/kg | 2.58 |
Total carbon emissions (EP) | 19.89 tCO2e |
Category . | Type . | Consumption . | Emission factor . | Carbon emission (tCO2e) . |
---|---|---|---|---|
Forced mixer | Electricity | 5,192.00 kWh | 1.014 kgCO2e/kwh | 5.26 |
Vibrating sieving machine | Electricity | 806.40 kWh | 1.014 kgCO2e/kwh | 0.82 |
DTH drilling | Electricity | 832.00 kWh | 1.014 kgCO2e/kwh | 0.84 |
Pneumatic handheld drill | Electricity | 6,133.60 kWh | 1.014 kgCO2e/kwh | 6.22 |
Loader | Diesel | 910.63 kg | 3.096 kgCO2e/kg | 2.82 |
Wet-spraying machine | Diesel | 437.42 kg | 3.096 kgCO2e/kg | 1.35 |
Boat for spraying | Diesel | 832.00 kg | 3.096 kgCO2e/kg | 2.58 |
Total carbon emissions (EP) | 19.89 tCO2e |
The carbon emissions from vegetation maintenance in eco-slope protection are delineated in Table 5. This assessment is founded on detailed field investigations, through which the quantities of various plant types used in the eco-slope protection are determined. Moreover, maintenance-related carbon EFs for each plant species were obtained from referenced literature sources (Luo et al. 2023).
Carbon emissions from maintenance
Category . | Unit . | Amount . | Emission factor (kgCO2e/unit·a) . | Annual carbon emission (tCO2e/a) . |
---|---|---|---|---|
Tree | Single tree | 526.00 | 1.00 | 0.53 |
Shrub | Single tree | 4,230.00 | 0.71 | 3.00 |
Herbaceous plant | m2 | 10,941.33 | 0.42 | 4.60 |
Total annual carbon emissions (EY) | 8.13 tCO2e/a | |||
Life cycle carbon emissions | 243.90 tCO2e |
Category . | Unit . | Amount . | Emission factor (kgCO2e/unit·a) . | Annual carbon emission (tCO2e/a) . |
---|---|---|---|---|
Tree | Single tree | 526.00 | 1.00 | 0.53 |
Shrub | Single tree | 4,230.00 | 0.71 | 3.00 |
Herbaceous plant | m2 | 10,941.33 | 0.42 | 4.60 |
Total annual carbon emissions (EY) | 8.13 tCO2e/a | |||
Life cycle carbon emissions | 243.90 tCO2e |
Sensitivity analysis of carbon EFs
Sensitivity analysis quantitatively assesses how input variables' changes impact output variables in a model. This method alters input factors within a defined range and recalculates outcomes to pinpoint which inputs notably affect the project's total life cycle carbon emissions. Identifying these critical elements enables the formulation of targeted reduction strategies, potentially minimizing their contributions to carbon emissions.
Considering the results from the previous sections, this study selects the carbon EFs of cement, anchor bar, galvanized steel wire mesh, and the maintenance of herbaceous plants and shrubs for sensitivity analysis. The analysis involves adjusting the values of these factors by increments of −20, −15, −10, −5, 5, 10, 15 and 20%, respectively, to observe shifts in the eco-slope protection's overall life cycle carbon emissions.
Sensitivity analysis of carbon emission factors for five key factors.
Calculation results of vegetation carbon assimilations
The vegetation species used in eco-slope protection are divided into two categories: woody plants (encompassing trees and shrubs) and herbaceous plants. The calculation results for the annual carbon assimilations of these species are detailed in Tables 6 and 7. This study undertook detailed field investigations to accurately determine the variety and quantity of woody plants, as well as the biomass per unit area and the extent of areas planted with herbaceous species. The annual carbon assimilation capacity of these plants was established through an examination of relevant scholarly works (Wang & Mu 2014; Guo 2017; Long et al. 2022).
Carbon assimilations from woody plants
Latin name . | Category . | Amount . | Carbon assimilation capacity (kgCO2e/unit·a) . | Annual carbon assimilations (tCO2/a) . |
---|---|---|---|---|
Robinia pseudoacacia | Tree | 168.00 | 59.58 | 10.01 |
Broussonetia papyrifera | Tree | 242.00 | 49.57 | 12.00 |
Rhus chinensis | Tree | 116.00 | 49.57 | 5.75 |
Indigofera amblyantha | Shrub | 2,445.00 | 8.35 | 20.42 |
Amorpha fruticosa | Shrub | 1,436.00 | 21.10 | 30.30 |
Senna tora | Shrub | 349.00 | 8.35 | 2.92 |
Total annual carbon assimilations (AW) | 81.40 tCO2/a | |||
Life cycle carbon assimilations | 2,442.00 tCO2 |
Latin name . | Category . | Amount . | Carbon assimilation capacity (kgCO2e/unit·a) . | Annual carbon assimilations (tCO2/a) . |
---|---|---|---|---|
Robinia pseudoacacia | Tree | 168.00 | 59.58 | 10.01 |
Broussonetia papyrifera | Tree | 242.00 | 49.57 | 12.00 |
Rhus chinensis | Tree | 116.00 | 49.57 | 5.75 |
Indigofera amblyantha | Shrub | 2,445.00 | 8.35 | 20.42 |
Amorpha fruticosa | Shrub | 1,436.00 | 21.10 | 30.30 |
Senna tora | Shrub | 349.00 | 8.35 | 2.92 |
Total annual carbon assimilations (AW) | 81.40 tCO2/a | |||
Life cycle carbon assimilations | 2,442.00 tCO2 |
Carbon assimilations from herbaceous plants
Latin name/category . | Biomass (kg/m2) . | Planting area (m2) . | Annual carbon assimilation (tCO2/a) . |
---|---|---|---|
Cynodon dactylon | 0.246 | 1,869.33 | 0.84 |
Medicago sativa | 0.334 | 3,580.00 | 2.19 |
Local wildflower combination | 0.475 | 5,492.00 | 4.78 |
Total annual carbon assimilations (AH) | 7.81 tCO2/a | ||
Life cycle carbon assimilations | 234.30 tCO2 |
Latin name/category . | Biomass (kg/m2) . | Planting area (m2) . | Annual carbon assimilation (tCO2/a) . |
---|---|---|---|
Cynodon dactylon | 0.246 | 1,869.33 | 0.84 |
Medicago sativa | 0.334 | 3,580.00 | 2.19 |
Local wildflower combination | 0.475 | 5,492.00 | 4.78 |
Total annual carbon assimilations (AH) | 7.81 tCO2/a | ||
Life cycle carbon assimilations | 234.30 tCO2 |
It should be highlighted that the average values of 49.57 and 8.35 kgCO2e/unit·a are used in this study to make up for the lack of research on the carbon assimilation capacities of some trees and shrub species, respectively.
Proportion of life cycle carbon assimilations of different vegetation types.
Carbon neutral capacity of eco-slope protection
Carbon neutral time and life cycle net carbon sinks of eco-slope protection.
DISCUSSION
The findings indicate that in the realm of wet-spraying vegetation concrete technology, while cement is still a primary component, its use has been reduced by about 30% compared to conventional shotcrete methods, significantly lowering the carbon emissions associated with materials (Xu et al. 2004; Han et al. 2008). Nonetheless, the imperative to curtail the use of materials with high embodied carbon – such as anchor bars and galvanized steel wire meshes – persists. The integration of sustainable materials, particularly bio-composites, and use low-carbon cement or cement produced with carbon-reduction technologies have emerged as a promising avenue for further reducing carbon emissions (Cao et al. 2017; Ryłko-Polak et al. 2022). By substituting conventional high-carbon materials with these greener alternatives, the technology's carbon footprint could be substantially lessened.
The study uncovers that while vegetation plays a vital role in carbon assimilation, the potential benefits may be offset by the carbon emissions associated with maintenance activities. Specifically, the lifecycle maintenance carbon emissions of herbaceous plants contribute to 58.90% of their total carbon assimilations. This significant proportion markedly undermines their net contribution to carbon sequestration. It underscores the necessity of implementing scientifically backed and efficient maintenance practices to lower these emissions effectively. For instance, transitioning from conventional labor-intensive maintenance methods to advanced smart irrigation systems can lead to a considerable reduction in maintenance-related carbon emissions (Zou et al. 2023).
Additionally, this analysis uncovers the critical influence of plant selection and configuration on the carbon neutrality of eco-slope protection initiatives. Shrubs, characterized by their compact spatial requirements and moderate carbon absorption capabilities, emerge as significant contributors to carbon sequestration when employed at high densities. Conversely, trees, despite their strong individual carbon absorption rates, are limited in their density by their larger size, resulting in comparatively modest total carbon sequestration. Herbaceous plants, covering more extensive areas, exhibit minimal carbon sequestration but are vital for the initial stabilization of eco-slope protections. Hence, optimizing the proportion of shrubs, alongside ensuring structural integrity at project inception, can markedly enhance a project's capacity for carbon neutrality. Furthermore, plants exhibit enhanced carbon sequestration under optimal environmental conditions (Yang et al. 2023). It is thus prudent to prioritize native plant species that are well-adapted to local conditions and possess high-carbon sequestration capacities. While prioritizing local plant species for their adaptability and reduced transportation-related emissions is paramount, incorporating exotic species with demonstrably higher carbon sequestration capacities may be considered when native species' carbon absorption proves significantly lower. This approach ensures the ecological compatibility and effectiveness of carbon sequestration efforts within the eco-slope protection strategy.
The findings of this study are consistent with prior research (Yu et al. 2021), which examined the life cycle carbon footprint of an ecological revetment case study and determined that materials were the largest source of carbon emissions. Their analysis also underscored the advantages of eco-slope protection over traditional methods, particularly in terms of diminished environmental impacts and lower costs. Extending beyond these findings, our study elaborates on the significant impact of maintenance practices on the carbon emission profile of eco-slope protection initiatives and articulates the critical contribution of plant carbon absorption to these projects. This nuanced understanding underscores the capacity of eco-slope protection efforts to significantly contribute to ecological restoration and mitigate the effects of climate change, offering a comprehensive view of their environmental benefits.
In the context of current global efforts toward carbon neutrality, evaluating the carbon neutral capacity of eco-slope protection projects is crucial. These evaluations provide decision-makers with the insights needed to identify key project components, enhancing ecological restoration outcomes and carbon sequestration effectiveness under the constraints of limited land and resources. Moreover, the ability to convert net carbon sinks into tradable carbon credits opens up economic opportunities in the carbon market (Oke et al. 2024), underscoring the value of assessing the carbon neutrality of eco-slope protection endeavors. This approach not only supports the goals of carbon neutrality but also offers economic benefits, encouraging the development of environmentally friendly projects with substantial carbon offset capabilities. As a result, it accelerates both ecological restoration and the achievement of carbon neutrality objectives, fostering a virtuous cycle within the industry.
The study faces three main limitations. Firstly, data on eco-slope protection projects are limited and challenging to compile due to the variety of materials, equipment, and plant species each project requires, alongside the technical variances across different geographies which result in discrepancies in carbon EFs. Despite efforts to gather and analyze the available data, these challenges have limited the scope and depth of the analysis. Second, the dynamic and complex nature of plant evolution in eco-slope protection projects complicates the assessment of their net carbon sink. This study is conducted based on an ideal state of fixed vegetation configuration, yet the diverse growth rates, life cycles, and adaptability of plant species to environmental changes can alter the vegetation composition over time, impacting carbon absorption performance. Finally, there is less data on the carbon sequestration capacity of various vegetation types. Some of the lack of data on plants can only be replaced by the average value of that type of plant, which may lead to a bias between the results of carbon uptake by plants and the reality.
CONCLUSIONS
This research thoroughly assesses the carbon neutrality of the Eco-slope Protection Project's second phase at Huama Lake, Ezhou City, Hubei Province, China, with a focus on optimizing the calculation of carbon emissions across five sources: materials, transport, workforce, energy, and maintenance. Anticipated to reach carbon balance by the 4.59th year, the project is projected to contribute a net carbon sink of approximately 2068.29 tons over its lifespan. A significant insight from this study is the critical role of vegetation – particularly the strategic use of local shrub species with high-carbon absorption capacities – in enhancing the carbon neutral capacity of eco-slope protection without undermining slope stability.
Furthermore, this investigation highlights the potential for reducing carbon emissions through the use of sustainable materials and the implementation of effective maintenance strategies, underscoring the broader applicability to eco-slope protection projects. These findings advocate for policy and practice shifts toward more environmentally sustainable approaches within civil engineering, suggesting that such projects can serve as a viable model for achieving carbon neutrality. The study underscores the necessity of integrating ecological considerations into infrastructure development, offering a blueprint for future projects to contribute meaningfully to climate change mitigation and the green transformation of the industry.
This study underscores eco-slope protection projects as critical in combating climate change and promoting sustainable development within civil engineering. It provides actionable insights for stakeholders on selecting plant species, utilizing environmentally friendly materials, and implementing efficient maintenance practices. This aids in formulating more environmentally friendly and efficient strategies during the project's inception, thereby optimizing environmental performance and contributing new insights and robust empirical evidence toward achieving global carbon neutrality objectives. While this investigation stops short of delving into carbon trading specifics, it acknowledges the promising impact that the net carbon sink from eco-slope projects could have on the carbon market, highlighting a fertile ground for future research. In the future, the application of advanced technologies, such as artificial intelligence and blockchain, can be used as a means to surmount existing hurdles in data collection and analysis, promising to elevate the accuracy of life cycle assessments for eco-slope protection projects. Moreover, collaborating closely with ecologists to secure up-to-date data on plant species will enrich research into the dynamic evolution of vegetation, enhancing predictions on long-term carbon sequestration capabilities, and reducing biases in assessment results. Such interdisciplinary efforts will solidify a more scientific foundation for evaluating the carbon neutrality of eco-slope protection endeavors.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.