Process-based Life Cycle Assessment Research Articles

An integrated life cycle assessment and energy simulation framework for residential building walling systems

Designing building wall systems is a multi-criteria problem characterised by a complex interplay of variables that drive long-term energy and environmental performance. Achieving holistic sustainability outcomes will require the application of life cycle thinking to the design and evaluation of building walling systems. However, the aspiration for minimising operational and embodied energy and mitigating the environmental impacts requires conflicting strategies. Therefore, this study proposes a comprehensive, integrated life cycle and energy simulation (ILES) methodology for analysing different walling systems of residential buildings in India and Australia. This method involves performing a process-based life cycle assessment to compute the environmental impacts of various walling materials, followed by energy modelling to evaluate the performance of these materials in the operational phase of buildings in combination with embodied energy analysis, which accounts for energy consumption during the material manufacturing phases. The results reveal that insulated cavity-clay masonry or concrete walls with extruded polystyrene are favourable Australian walling options, while metal cladding-based walling systems have significant environmental and energy burdens. For India, autoclave aerated block, fly ash bricks, and concrete block-based walling systems are recommended, while reinforced concrete and clay brick walls exhibit significant environmental and energy burdens. This study also advocates the consideration of supply chains in mitigating Scope 3 emissions from building walling systems in residential buildings.

Life cycle assessment of green–grey coastal flood protection infrastructure: a case study from New Orleans

The study compared the life cycle environmental impacts of three coastal flood management strategies: grey infrastructure (levee), green–grey infrastructure (levee and oyster reef), and a do-nothing scenario, considering the flood damage of a single flooding event in the absence of protection infrastructure. A case study was adopted from a New Orleans, Louisiana residential area to facilitate the comparison. Hazus software, design guidelines, reports, existing projects, and literature were utilized as foreground data for modelling materials. A process-based life cycle assessment was used to assess environmental impacts. The life cycle environmental impacts included global warming, ozone depletion, acidification, eutrophication, smog formation, resource depletion, ecotoxicity, and various human health effects. The ecoinvent database was used for the selected life cycle unit processes. The mean results show green–grey infrastructure as the most promising strategy across most impact categories, reducing 47% of the greenhouse gas (GHG) emissions compared to the do-nothing strategy. Compared to grey infrastructure, green–grey infrastructure mitigates 13%–15% of the environmental impacts while providing equivalent flood protection. A flooding event with a 100-year recurrence interval in the study area is estimated at 34 million kg of CO2 equivalent per kilometre of shoreline, while grey and green–grey infrastructure mitigating such flooding is estimated to be 21 and 18 million kg, respectively. This study reinforced that coastal flooding environmental impacts are primarily caused by rebuilding damaged houses, especially concrete and structural timber replacement, accounting for 90% of GHG emissions, with only 10% associated with flood debris waste treatment. The asphalt cover of the levee was identified as the primary contributor to environmental impacts in grey infrastructure, accounting for over 75% of GHG emissions during construction. We found that there is an important interplay between grey and green infrastructure and optimizing their designs can offer solutions to sustainable coastal flood protection.

Environmental and Climate Impacts of a Large-Scale Deployment of Green Hydrogen in Europe

Green hydrogen is expected to play a vital role in decarbonizing the energy system in Europe. However, large-scale deployment of green hydrogen has associated potential trade-offs in terms of climate and other environmental impacts. This study aims to shed light on a comprehensive sustainability assessment of this large-scale green hydrogen deployment based on the EMPIRE energy system modeling, compared with other decarbonization paths. Process-based Life Cycle Assessment (LCA) is applied and connected with the output of the energy system model, revealing 45% extra climate impact caused by the dedicated 50% extra renewable infrastructure to deliver green hydrogen for the demand in the sectors of industry and transport in Europe towards 2050. Whereas, the analysis shows that green hydrogen eventually wins on the climate impact within four designed scenarios (with green hydrogen, with blue hydrogen, without green hydrogen, and baseline), mainly compensated by its clean usage and renewable electricity supply. On the other hand, green hydrogen has a lower performance in other environmental impacts including human toxicity, ecotoxicity, mineral use, land use, and water depletion. Furthermore, a monetary valuation of Life Cycle Impact (LCI) is estimated to aggregate 13 categories of environmental impacts between different technologies. Results indicate that the total monetized LCI cost of green hydrogen production is relatively lower than that of blue hydrogen. In overview, a large-scale green hydrogen deployment potentially shifts the environmental pressure from climate and fossil resource use to human health, mineral resource use, and ecosystem damage due to its higher material consumption of the infrastructure.

Evaluating Carbon Emissions during Slurry Shield Tunneling for Sustainable Management Utilizing a Hybrid Life-Cycle Assessment Approach

The construction sector is one of the principal contributors to carbon dioxide emissions (CDEs) and has a vital role to play in responding to the issue of long-term environmental sustainability. This research proposes a process-based hybrid life-cycle assessment (LCA) method depending on a process-based LCA and an input–output LCA. The process-based hybrid LCA model provides a supplementary method to quickly estimate carbon emissions that are not considered in the system boundary due to the limitation of inventory data. The proposed hybrid method was applied to a carbon emissions assessment in a slurry shield tunnel. The results suggest that 93.88% of emissions are from materials. Of the materials contribution, 55.9% comes from steel and 34.55% arises from concrete. It has also been found that emissions during the tunneling stage are negatively correlated with the efficiency of tunnel construction. Recommendations for carbon emissions reductions in tunnel construction are provided for promoting sustainable transportation and management.

Process-based life cycle inventory framework for assessing the carbon footprint of products from complex production paths: Case of dual-phase automotive strip steel

The production paths of industrial products are usually complex, leading to difficulties and a large workload when conducting traditional process-based life cycle assessment (P-LCA). Existing studies on reducing LCA workload have focused mainly on simplifying the process or combining LCA with correlation methods. For complex production paths that cannot be simplified or changed, the methods have weak generality. To fill in these research gaps, a process-based life cycle inventory (P-LCI) framework for complex production paths is proposed. P-LCI contains accurate classification and definition methods for input, output and unit processes, and an interconnection model for calculating process coefficients according to the complexity of the linkages among processes is proposed. Based on the proposed framework, a case study of the dual-phase automotive strip steel (DP) production process is performed. The results show that the production of 1 kg of DP steel consumes 0.679 kg of molten steel from a basic oxygen furnace plant and 0.557 kg from the another. Coke plants produce the largest carbon footprint (CF) per unit of coke, which is 0.889–1.231 kgCO2e/kg-coke. For the cradle-to-gate lifecycle of DP steels, the BFP has the largest CF at 0.614 kgCO2e/kg-DP, accounting for 26.32%. Through the proposed P-LCI framework, unit processes can be clearly defined, and the interconnection model can be used as the basis for environmental impact analysis. When the production path changes, the model can be flexibly adjusted, and the workload of repeated model construction can be reduced.

From quarry to carbon sink: process-based LCA modelling of lime-based construction materials for net-zero and carbon-negative transformation

Materials science, process engineering and environmental science were combined to demonstrate carbon negative scenarios over the life-cycle of a lime-based plaster.

Sustainability assessment of peri-urban organic horticulture — A case study in the United Kingdom

PurposeThere is a growing concern about the resilience and sustainability of horticultural production in the United Kingdom (UK) as a result of high energy costs and insufficient local labour, causing over-reliance on imports. In this study, we present an integrated environmental and economic assessment of organic peri-urban horticulture using primary data from a farm in Sheffield.MethodsThis study includes a farm-to-gate hybrid life cycle assessment (LCA) using the ReCIPE (H) approach for the functional unit of 1-kg tomatoes produced in an unheated polytunnel without supplementary lighting, and 1 kg of field-grown courgettes. All analyses were conducted in SimaPro software using environmental data from the ecoinvent database. Results were compared with those from a systematic literature review of similar studies.ResultsWe found that the production of organic tomatoes and courgettes resulted in a global warming potential (GWP) of 0.61 kg CO2-eq and 0.11 kg CO2-eq respectively using a process-based LCA approach. Using a hybrid LCA approach, however, yielded a GWP of 3.53 kg CO2-eq and 1.70 kg CO2-eq for the production of organic tomatoes and courgettes respectively. An additional scenario included farmgate-to-warehouse transportation for both domestic and imported produce from Spain, but found that the GWP of tomatoes in the case study was 1.87 times higher than those from Spain. Economic analysis showed that the marginal increase in the prices of tomatoes and courgettes from the case study farm was 4.6 and 5.15 times less than the market prices.ConclusionWe conclude that the studied production system is both economically and environmentally sustainable as compared to the existing scenario. Other potential benefits of peri-urban organic horticulture include employment, mental health, community cohesion, which remain to be explored in a future qualitative study. The present study is novel as it appears to be the first application of hybrid LCA to UK horticulture. The findings are highly topical given the recent horticultural supply constraints in the UK.

Life Cycle Assessment (LCA) of Solid Waste Management Systems in African Countries: A Systematic Review

Life cycle assessment (LCA) is a vital tool for evaluating the environmental burden of solid waste. This study investigated the outcomes of selected studies that applied the LCA methodology in assessing the environmental consequences of solid waste management (SWM) systems in Africa. Thirteen process-based LCA studies on SWM were reviewed, drawing from established criteria in databases such as SCOPUS, Elsevier, and Google Scholar. These studies were distributed across various African countries, with three conducted in Mauritius and Nigeria each, two in Zimbabwe and South Africa each, and one in Tanzania, Ghana, and Uganda, respectively. The evaluated parameters included aspects such as goal and scope, functional unit, system boundary, impact assessment categories, and sensitivity analysis. The findings revealed that majority of the studies employed similar waste management scenarios to determine the most environment-friendly, yet they differed considerably in some parameters. Climate change and global warming were the most assessed impact categories. Municipal solid waste (MSW) and plastic waste were the leading waste categories. MSW typically comprises paper, bottles, metal, plastics, glass, organics, and mixed waste proportions. The study also stated that the lack of reliable data on solid waste was a significant challenge faced by African countries in LCA studies. The paper’s findings highlighted that a significant number of the studies, particularly in Nigeria, did not incorporate sensitivity analysis into their assessments, a crucial component for result interpretation. Consequently, the study emphasizes the importance of conducting more LCA research studies in African countries to produce pertinent data on SWM.

Life cycle assessment perspective on waste resource utilization and sustainable development: A case of glyphosate production

The growing demand for pesticide manufacturing and increasing public awareness of sustainable development, have let to urgent requirements for a refined environmental management framework. It is imperative to conduct process-based life cycle assessments (LCAs) to promote clean and environment-friendly technologies. Herein, the cradle-to-gate LCA of glyphosate production was executed as an example to investigate crucial production factors (materials or energy) and multiple environmental impacts during the production processes. Results showed that methanol caused the highest environmental damage in terms of toxicity, with a normalized value of 85.7 × 10−8, followed by coal-fired electricity in 6.00 × 10−8. Furthermore, optimized schemes were proposed, including energy improvement (electricity generated by switching from coal-fired power to solar power) and wastewater targeted conversion. Regarding the normalization results before and after optimization, the latter showed more significant results with the normalized value decreasing by 21.10 × 10−8, while that of the former only decreased by 6.50 × 10−8. This study provides an integrated LCA framework for organophosphorus pesticides (OPs) from upstream control and offers an important supplement to managing the key pollution factors and control links of the OP industry. Moreover, it reveals the positive influence of optimized schemes in facilitating cleaner production technologies, thus ultimately promoting new methodologies for resource recycling.

Lifecycle Assessment of Two Urban Water Treatment Plants of Pakistan

Water treatment technologies are striving to retain their ecological and economic viability despite the rising demand, conventional infrastructure, financial constraints, fluctuating climatic patterns, and highly stringent regulations. This study evaluates the lifecycle environmental impact of urban water treatment systems within the two densely populated South Asian municipalities of Islamabad and Rawalpindi, Pakistan. The scope of this study includes a process-based Life Cycle Assessment (LCA) of the entire water treatment system, particularly the resources and materials consumed during the operation of the treatment plant. The individual and cumulative environmental impact was assessed based on the treatment system data and an in-depth lifecycle inventory analysis. Other than the direct emissions to the environment, the electricity used for service and distribution pumping, coagulant use for floc formation, chlorine gas used for disinfection, and caustic soda used for pH stabilization were the processes identified as the most significant sources of emissions to air and water. The water distribution consumed up to 98% of energy resources. The highest global warming impacts (from 0.3 to 0.6 kg CO2 eq./m3) were assessed as being from the coagulation and distribution processes due to extensive electricity consumption. Direct discharge of the wash and wastewater to the open environment contributed approximately 0.08% of kg-N and 0.002% of kg-P to the eutrophication potential. The outcome of this study resulted in a thorough lifecycle inventory development, including possible alternatives to enhance system sustainability. A definite gap was identified in intermittent sampling at the treatment systems. However, more stringent sampling including the emissions to air can provide a better sustainability score for each unit process.

Quantifying the greenhouse gas emissions of New Zealand households’ food purchases: An analysis by demographic variables

New Zealand has committed to a 50% reduction in greenhouse gas emissions (GHGEs) from 2005 levels by 2030. Dietary changes within New Zealand could simultaneously improve population health and contribute towards the nation's emissions reduction target, as globally, food production is estimated to account for between one quarter and one third of GHGEs. This research aimed to quantify the GHGEs associated with household purchases of major food groups in New Zealand and identify the demographic characteristics that are associated with per capita household dietary emissions. Household dietary emissions were estimated using the Nielsen Homescan(R) consumer panel — a large sample of households within New Zealand (N = 1775) who report purchasing data of take-home food and beverages. The sample is nationally representative in terms of broad geographical regions and selected key demographic characteristics. Carbon emission estimates were assigned to 1,908,485 total purchases in 2019 using a process-based life cycle assessment (LCA) dataset initially constructed in the United Kingdom (UK) and adapted for New Zealand. The emissions from purchases of major food groups were then estimated. Multiple linear regression was used to examine the relationships between household variables and per capita dietary emissions. Purchases of red and processed meat (35%) and dairy products (19%) were responsible for the greatest proportion of emissions using a 100-year time horizon. The age group of the primary household shopper as well as household size were predictors of per capita dietary emissions — households with primary shoppers >65 years had, on average, 33% (95% CI: 19%–49%) higher per capita dietary emissions, compared to households with primary shoppers ≤ 34 years; and every additional household member was associated with, on average, 11% (95% CI: 9%–13%) lower per capita dietary emissions. We have shown in this large representative sample of New Zealand households that purchases of just two food groups — red and processed meat, and dairy — were responsible for 54% of dietary greenhouse gas emissions in 2019. Larger households had lower per capita dietary greenhouse gas emissions, and older shoppers had relatively higher greenhouse gas emissions. Whilst similar associations have been reported elsewhere, more research is needed to confirm these latter findings. With enhanced understanding of the observed association between age of a household's primary shopper and per capita dietary emissions, interventions may be devised that encourage shoppers to purchase lower-emitting foods, particularly less meat and dairy.

Life cycle assessment of energy consumption and carbon emissions of a green maintenance material for asphalt pavement: Warm mix OUFC-5

The warm mix (WM) 4.75 mm nominal maximum aggregate size (NMAS) Open-Graded Ultra-thin Friction Course (WM OUFC-5) represents an innovative green preventive maintenance material boasting commendable road performance. Its potential to address carbon peak and neutrality goals objectives has garnered significant interest. This study aims to quantify the energy-saving and carbon reduction benefits of WM OUFC-5. Three commonly used preventive maintenance materials, including thin overlay (TO), synchronous surface dressing (SSD), and micro-surfacing (MS) in Hubei province, China, were selected as a control group. Employing the process-based life cycle assessment (PLCA), an evaluation framework and computational model was devised to gauge the energy and carbon footprints of each maintenance material. A comparative analysis was then conducted to identify the primary energy and emission contributors of WM OUFC-5 across different life-cycle phases. The results indicate that WM OUFC-5 is a highly sustainable material with low energy consumption and carbon emissions, with its energy consumption being merely 47.2% of TO and 50.7% of MS. And its carbon emissions are 64.3% lower than TO, 26.9% lower than MS, and 49.8% lower than SSD. Throughout the maintenance life cycle, the raw materials production and processing phase and the mixture production phase emerged as the predominant contributors to energy consumption and carbon emissions. The study also provided actionable recommendations to curtail energy and carbon footprints across all phases of the asphalt pavement maintenance life cycle. This study provides support for the low-carbon development of asphalt pavement maintenance in China.

Process-based life cycle assessment of waste clay for mineral carbonation and enhanced weathering: A case study for northeast England, UK

The potential of enhanced silicate rock weathering for long-term carbon dioxide sequestration is substantial, but it is dependent on the availability of suitable materials and proximity to appropriate field application locations. This paper evaluates the implementation of waste clay in the form of filter cake on agricultural land in northeast (NE) England for mineral carbonation (MC) and enhanced weathering (EW) over 26 years from 2024 to 2050. Process-based life cycle assessment (LCA) is used in this study to provide an effective evaluation of CO2 emissions. Our results show that the potential levels of CO2 sequestration of filter cake through MC and EW are 0.16t CO2eq/t and 0.29t CO2eq/t respectively. Considering the sequestration potential of 580,000 ha of agricultural land in the NE England, it is shown that the deployment of waste clay in the form of filter cake on that land could capture 0.77 to 1.62 Mt CO2eq with an application rate of 11.2 t/ha for MC and EW respectively, while the corresponding CO2 emissions throughout the application of the processes involved are calculated to be only 0.27 Mt CO2eq over 26 years. This study demonstrates the importance of waste clay valorisation on agricultural soil in NE England in reducing CO2 in the atmosphere and its role in the UK's ‘Net Zero’ ambition.

Analytic hierarchy process-based life cycle assessment of the renewable energy production by orchard residual biomass-fueled direct-fired power generation system

Orchard residues (OR), primarily consists of pruned fruit tree branches (PFTB), serve as a significant biomass source in China and many other countries. In this study, we established a comprehensive life cycle assessment (LCA) model for PFTB-based BDP (PFTB-BDP) using LCA and the analytic hierarchy process (AHP). The model was employed to evaluate the environmental impacts (EIs), abiotic depletion (AD), and comprehensive performance of PFTB-BDP. Our findings revealed that the comprehensive performance index (COPI) of PFTB-BDP ranged from 0.005 to 0.019 (person·year)/MWh. EIs exerted a more significant influence on comprehensive performance compared to AD, with the impact strength of EIs following the order of local > equal > regional > global. The maximum COPI value of PFTB-BDP amounted to 48.72% of the minimum COPI value of a coal-fired power generation (CP) system, demonstrating the superiority of PFTB-BDP over CP. The comprehensive performance of PFTB-BDP was most sensitive to total solid waste (SW) (−21.79%–17.89%) and the raw material consumption rate (−13.01%–11.58%). The outcomes of this study provide a crucial theoretical foundation and reference data for PFTB-BDP research.

Exploring alternative normalization approaches for life cycle assessment

PurposeThis work investigates the use of alternative approaches to normalization in life cycle assessment (LCA) and shows the relevance of the normalization step in the interpretation of the results of life cycle impact assessment (LCIA) by testing the use of five alternative normalization sets.MethodsFive normalization sets are applied and compared. The five sets are based on the following: (i) a production-based approach at global and (ii) at EU level; (iii) a consumption-based approach at EU level based on process-based LCA; (iv) a consumption-based approach at EU level based on environmental extended input/output; and (v) a planetary boundaries-based approach. The five normalization sets are applied to the environmental impacts of 144 products, and the resulting normalized impacts are aggregated into a single score by adopting two alternative weighting sets to investigate how the adoption of different normalization and weighting sets can affect the interpretation of LCIA results. The relative contribution of each impact category to the single score is derived and the ranking of impact categories is compared for each normalization and weighting option.Results and discussionThe relative contribution of the impact categories to the aggregated score of a product is significantly affected by the choice of the normalization set and to a lesser extent by the application of different weighting sets. The main benefits and limitations of each normalization approach presented are discussed together with their implications on the interpretation of the results deriving from the application of each set.ConclusionsThe dominating role of the normalization step on the interpretation of the results emphasizes the need to choose the most suitable normalization set according to the goal and scope of the study and to make sure that normalization references are based on comprehensive inventories of emissions and resources, well aligned with the impact assessment methods used in terms of coverage and classification, to avoid the risk of biased normalization. Future research needs for developing more robust and comprehensive normalization sets are identified.

Evaluating Carbon Footprint in the Life Cycle Design of Residential Concrete Structures in Jordan

The construction industry is a significant source of greenhouse gas emissions, and there is a growing global interest in reducing the environmental impact of carbon dioxide emissions associated with building construction and operation. Concrete, the most commonly used material in construction, is known to release a substantial amount of environmentally harmful waste throughout its life cycle, including production, construction, operation, and demolition. The worldwide production and consumption of concrete contribute to approximately 5% of all human-related CO2 emissions each year. To assess the carbon footprint of concrete manufacturing and its application in construction projects, a comprehensive approach called life cycle assessment (LCA) is necessary. This paper presents a new process-based LCA approach to analyze carbon emissions and evaluate the carbon footprint of concrete from raw material extraction to the end-of-life stage. To address carbon emissions throughout the life cycle of concrete structures in the Middle East, the study adopts a case study approach, focusing on selected concrete structures in Jordan. The findings from these case studies highlight that the operational phase of concrete structures is the primary contributor to carbon emissions. By thoroughly examining the carbon cycle within structures and their interactions with the surrounding ecosystem, significant reductions in CO2 emissions, environmental deterioration, and its consequences can be achieved. Doi: 10.28991/CEJ-2023-09-07-07 Full Text: PDF

#3286 ENVIRONMENTAL PERFORMANCE OF HEMODIALYSIS THROUGH LIFECYCLE ASSESSMENT (LCA): IN-CENTRE HEMODIALYSIS VS HOME-HEMODIALYSIS

Abstract Background and Aims Despite being energy and resource-intensive, hemodialysis (HD) is the most common therapy for end stage kidney disease. Considering the extensive amount of energy, water, and consumables involved, this modality is expected to have a significant environmental impact. Through a comparative lifecycle assessment (LCA), this study aims to analyze the environmental impacts of hemodialysis in British Columbia, Canada. Method A process-based life cycle assessment was performed for three hemodialysis modalities: i) in-centre HD (ICHD), ii) home HD with NxStage machine (HHD-Nx), and iii) home HD with Baxter AK-98 machine (HHD-B). The scope of study included patient and staff commute, supply transportation, dialysis services, patient training for home hemodialysis, and waste management. The functional unit considered is HD energy and material consumption for one patient per year. Based on the patient's record, two prescriptions including standard (three dialysis sessions per week for 4 hours daily) and extended (six HD sessions per week for 8 hours daily) were considered. LCAs were performed using ISO 14040, 14041 standards in which ReCiPe (world) midpoint method and a cut-off criterion of 0.5% was used to assess the environmental impacts of selected impact categories. Results For both prescriptions, ICHD had highest impact on all environmental impact categories (climate change, human toxicity, freshwater eutrophication, particulate matter formation, marine ecotoxicity and water depletion), except ozone depletion in which HHD-B had highest impact. The fewest impacts were associated with HHD-Nx. CO2 emissions observed for a standard HD prescription are 3590 kg carbon dioxide equivalents (CO2eq) per patient/year by ICHD, 1350 kg CO2eq/patient/year by HHD-B and 733 kg CO2eq/patient/year by HHD-Nx. For extended prescriptions, the highest impact observed is from HHD-B (2210 kg CO2eq/patient/year) followed by HHD-Nx (1110 kg CO2eq/patient/year). With respect to ICHD, HHD-Nx only accounts for 13% (standard) and 18% (extended) of total environmental impact. Patient and staff commute in ICHD (40% of total impact) and dialysis services in HHD (75% in HHD-B and 63% in HHD-Nx) are the highest contributors to the majority of environmental impacts. Conclusion Our study demonstrates the environmental impacts of various modes of HHD through LCA. HD modalities have substantial differences in their environmental impacts as compared to ICHD, both HHD systems have lower impact, with NxStage having less impact than Baxter. Our results also demonstrate that a shift from standard to extended prescriptions increases overall environmental impact by 5%. Combined with existing clinical and economic data, these results could assist policy and decision-makers to optimize the provision of kidney replacement therapies. Lower environmental impact of HHD may add to the patient and provider appeal of these therapies, and when clinical equipoise exists, NxStage may be preferred over Baxter in eligible patients.

Carbon Footprint Accounting and Influencing Factors Analysis for Forestry Enterprises in the Key State-Owned Forest Region of the Greater Khingan Range, Northeast China

This paper constructed a carbon footprint calculation model and analyzed the carbon footprint characteristics and impact mechanism of forestry enterprises in the Greater Khinggan Range, northeast China, based on the survey and statistical data during 2017–2021. The process-based life cycle assessment (LCA) was used to calculate the total carbon footprint and carbon footprint intensity; then, a panel data model combined with ridge regression was used to explore the impacts of different factors on the carbon footprint of the forestry enterprises. Results showed that the forestry enterprises’ total carbon footprint and carbon footprint intensity showed a general trend of increasing first and then decreasing from 2017 to 2021. The average annual carbon footprint of the forestry enterprises ranged from 2354 t CO2-eq to 24,354 t CO2-eq, and the average annual carbon footprint intensity ranged from 3.48 kg CO2-eq hm−2 to 31.76 kg CO2-eq hm−2. Fire area, the number of hired labor, and vehicle usage intensity are significant driving factors of the carbon footprint in forestry enterprises. The study results can provide references for policy formulation in relation to carbon footprint control in forest regions.

Understanding the greenhouse gas emissions from China’s wastewater treatment plants: Based on life cycle assessment coupled with statistical data

Wastewater treatment plants (WWTPs) are significant contributors to energy consumption and anthropogenic greenhouse gas (GHG) emissions. For achieving carbon reduction in the wastewater treatment industry, the direct and indirect GHG emissions generated by WWTPs need to be understood from a holistic perspective. This study estimated GHG emissions from WWTPs at the country scale by integrating process-based life cycle assessment and statistical data. On-site data were collected from 17 WWTPs of various regions in China. Uncertainty analysis based on Monte Carlo was also performed, so as to provide more reliable results. The results show that life cycle GHG emissions generated from the wastewater treatment process vary from 0.29 kg CO2 eq/m3 to 1.18 kg CO2 eq/m3 based on 17 sample WWTPs. The key factors contributing to overall GHG emissions are also identified as carbon dioxide (fossil) and methane (fossil) to air mainly generated from electricity generation, and methane (biogenic) and nitrous oxide (biogenic) to air mainly generated from wastewater treatment. National average GHG emissions was evaluated with the value of 0.88 kg CO2 eq/m3, with on-site GHG emissions and off-site electricity-based GHG emissions accounting for 32% and 34%, respectively. The total GHG emissions generated from wastewater treatment are 56.46 billion kg CO2 eq in 2020, with Guangdong province having the dominant contribution. Policy suggestions (e.g., further adjusting the electricity grid toward a low carbon structure, improving technology to promote treatment efficiency and energy recovery) were highly recommended so that national GHG emissions of WWTPs can be reduced. In order to achieve the synergy of pollutant removal and GHG emission reduction, policy-making on wastewater treatment should be tailored to specific local conditions.

Life cycle carbon emission assessment of large-span steel structures: A case study

Buildings take up a significant part of global carbon emissions and are a major contributor to the climate crisis. Large-span steel structures usually consume more materials, need more complex construction processes, and thus have a larger environmental impact. This study presents a comparative analysis of the life cycle carbon emissions of three typical large-span steel structures, i.e., a cable dome, a reticulated shell, and a suspendome, based on a design case. A tiered hybrid method using the process-based life cycle assessment for the processes with emission factors and using input–output-based life cycle assessment for the processes without emission factors is proposed to assess the life cycle carbon emissions. Comparisons on the carbon emissions of the three structures reveal that the cable dome is the best of the three, having the lowest steel consumption and the lowest carbon emissions. Although the component production phase appears to contribute most of the total emissions, the construction phase is also of considerable importance in alleviating the present emission pressure, especially for the cable dome and suspendome. Further analysis shows that carbon emissions of large-span steel structures are not simply linearly related to steel consumption and need to be considered as a separate design objective. This study provides a useful reference for life cycle carbon emission assessment and low-carbon design of large-span steel structures.