The study, published in Frontiers in Environmental Science, examined a 1.8-hectare park restored with concrete and steel, artificial planting and extensive hard shoreline protection, and a 1.5-hectare park restored with ecological bricks, recycled wood-plastic composites, native vegetation, permeable paving, rainwater harvesting and a rain garden. The conventional site contained 70% hard revetment, 80% impervious paving, ornamental trees and lawn, while the ecological site used ecological-brick revetment, permeable paths, a multilayer community of trees, shrubs and herbaceous plants, and rainwater collection. Both parks occupy transitional zones between urban development and tidal flats in a subtropical monsoon climate, where salinization, erosion, storm surges, flash flooding and degraded hydrological connectivity are important constraints. The researchers used one hectare of parkland as a common functional unit, with operation and maintenance modeled over 10 years and a 50-year service life assumed for hard infrastructure.

Rather than operating as three unrelated assessments, the methods shared a life-cycle inventory covering raw-material extraction and production, transportation, construction, operation and maintenance, demolition and disposal, as well as vegetation and soil carbon sequestration. Carbon-footprint accounting was treated as the climate-change category within life-cycle assessment, using activity data and emission factors for carbon dioxide, methane and nitrous oxide. Emergy analysis converted natural and human-made inputs—including solar radiation, rainwater, wind, soil loss, diesel, electricity, steel, cement and seedlings—into solar emjoules, a common measure of the natural work embodied in those inputs. This combination allowed the researchers to compare both emissions and resource dependence while retaining the distinct accounting logic of each method.

Construction was the largest source of emissions in both parks, although its share was substantially lower in the ecological case. The conventional scheme emitted 275.0 tonnes of carbon dioxide equivalent during construction, 68.0 tonnes during 10 years of maintenance, and an estimated 12.0 tonnes during demolition, while vegetation and soil sequestration offset 107.6 tonnes. The ecological scheme produced 58.0 tonnes during construction, 24.0 tonnes during maintenance and 4.0 tonnes during demolition, with 84.0 tonnes sequestered. Its construction emissions were only 21% of those from the conventional scheme. In the conventional park, material production accounted for 74% of construction-stage emissions, with concrete and steel as the main sources. Annual operation and maintenance emissions fell from 6.8 tonnes in the conventional park to 2.4 tonnes in the ecological park, a 65% reduction; lawn-mowing electricity and irrigation water were the leading operational sources in the conventional site, whereas rainwater collection and organic fertilizer accounted for more of the ecological site’s operational footprint.

The carbon-payback calculation expresses how long vegetation uptake would take to offset construction emissions. Based on an average measured sequestration rate during the first six years, the conventional project required approximately 65 years, while the ecological project required about 10 years. The difference reflected both lower construction emissions and greater annual sequestration in the multilayer native planting, whose observed average was 5.6 tonnes of carbon dioxide equivalent per year, compared with 4.2 tonnes in the conventional park. The authors cautioned that carbon uptake does not rise linearly: replacing the linear assumption with a saturation curve extended the estimates to about 72 years and 12 years, respectively, without changing their relative ranking. The absolute payback periods therefore remain sensitive to the assumed trajectory of vegetation growth.

Emergy accounting told a parallel story, while showing how the two parks depended differently on purchased and renewable resources. The conventional case required 2.41 × 10^17 solar emjoules, of which 71% came from non-renewable purchased inputs, principally cement, steel and diesel; renewable natural resources contributed 16%, and non-renewable natural resources 13%. In the ecological case, total input fell to 6.83 × 10^16 solar emjoules. Its renewable share rose to 38%, its purchased-input share fell to 47%, and its non-renewable natural-resource share was 15%. The emergy investment ratio, which measures reliance on purchased and non-renewable inputs, declined from 4.85 to 1.55, while the environmental loading ratio fell from 4.18 to 1.23. The emergy self-sufficiency ratio increased from 0.29 to 0.53. These results indicate lower dependence on externally supplied resources and a larger contribution from free natural inputs, particularly rainwater captured for use in the park.

The researchers developed two indicators to synthesize the results. A carbon–emergy trade-off coefficient was calculated after normalizing the ecological case’s carbon emissions and emergy input against the conventional baseline. The emission ratio was 0.21 and the emergy ratio was 0.28, producing a coefficient of 0.75. This means the ecological scheme reduced emissions about 1.33 times as much, in proportional terms, as it reduced emergy input. Despite the indicator’s name, the two dimensions did not conflict in this comparison because both improved. The coefficient instead measured asymmetry between the rates of improvement, a distinction that neither carbon accounting nor emergy analysis could provide alone. A comprehensive performance index, with equal weights of 0.5 assigned to carbon and emergy, gave the conventional case a baseline score of 1.00 and the ecological case 2.74. The ecological score rose to 2.93 when carbon received a weight of 0.7 and fell to 2.48 when emergy received a weight of 0.7, but its ranking never changed.

Several design and management differences appeared to reinforce one another. The ecological park reduced concrete consumption from about 560 tonnes to 85 tonnes and balanced earthworks, lowering soil excavation and transport by roughly 70%. Diesel use fell from 12.8 tonnes to 3.2 tonnes, while annual mowing electricity declined from 1,200 to 260 kilowatt-hours as herbaceous coverage replaced part of the lawn. Rainwater harvesting reduced irrigation demand from 3,200 to 800 cubic metres per year, and organic fertilizer use lowered estimated fertilizer-production emissions from 0.9 to 0.2 tonnes per year. The native tree–shrub–herb community also achieved higher measured annual carbon sequestration than the conventional tree–lawn structure. However, this was a comparison of complete restoration schemes rather than a controlled experiment isolating the contribution of vegetation. The observed advantage arose from the combined strategy and cannot be assigned independently to any one feature.

Sensitivity analysis broadly supported the comparison. The researchers varied carbon-emission factors, emergy conversion rates, carbon-sequestration rates and maintenance frequency by 20%, then examined additional extreme parameter combinations. Changing the carbon-emission factor altered net life-cycle emissions by 14.2% for the conventional case and 12.8% for the ecological case, while changes in emergy conversion rates produced respective ranges of 15.6% and 11.4%. Lowering sequestration rates by 20% extended carbon payback from 65 to 82 years in the conventional case and from 10 to 13 years in the ecological case; raising them shortened the periods to 54 and 8 years. The most influential variables were the concrete emission factor, tree sequestration rate and diesel emergy conversion rate, but the ecological case retained its advantage across the tested variations.

The evidence remains limited by the study’s two-case design, short observation period and reliance on literature values for some material factors, emergy conversion rates and initial soil-carbon conditions. The one-hectare functional unit is suited to these similarly sized parks but may not represent parks with different scales or recreational services, and the carbon and emergy calculations share part of the same inventory, so their weighted combination should be understood as multicriterion aggregation rather than the merging of statistically independent variables. The authors also note that carbon payback does not capture biodiversity gains, long-term sequestration after stabilization, cost or service differences. Nevertheless, within the stated life-cycle boundary, the study shows that redesigning materials, construction, vegetation and maintenance together can yield large simultaneous carbon and emergy gains, while the combined framework makes the pace and balance of those gains visible rather than reducing the decision to a single environmental indicator.

Subject of Research: Life-cycle environmental performance of two coastal park ecological restoration schemes

Article Title: An integrated LCA‐emergy‐carbon framework for environmental performance assessment of coastal park ecological restoration

Article References: Lei, J., Zhang, J., Wang, H., Asutosh, A. T., & Song, G. (2026). An integrated LCA‐emergy‐carbon framework for environmental performance assessment of coastal park ecological restoration. Frontiers in Environmental Science, 14, Article 1887338. https://doi.org/10.3389/fenvs.2026.1887338

Image Credits: AI Generated

DOI: 10.3389/fenvs.2026.1887338

Keywords: coastal parks, ecological restoration, life-cycle assessment, emergy analysis, carbon footprint, carbon sequestration, low-carbon design, resource efficiency, environmental performance, integrated, emergy, carbon