Life Cycle Assessment modelling of stormwater treatment systems

A comparative life-cycle assessment and cost analysis of biofilters amended with sludge-based activated carbon and commercial activated carbon for stormwater treatment

Environmental and economic issues resulting from the unsustainable management of sewage sludge from wastewater have necessitated the development of eco-friendly sewage sludge disposal methods, whereas stormwater effluent contains tremendous amounts of pollutants. This study compares the feasibility and environmental impacts associated with incorporating biofilters with sludge-based activated carbon (SBAC) versus commercial activated carbon (CAC) for stormwater treatment. The results demonstrate that the construction and disposal life-cycle stages are the dominant contributors to several environmental impact categories, including resource scarcity, carcinogenic toxicity, terrestrial ecotoxicity, and ozone formation indicators. Across multiple impact categories, the incorporation of biofilters with SBAC can reduce the negative environmental impacts associated with biofilter construction and disposal by 40% over a 50-year analysis period. In contrast, the most significant improvement is on construction-dominant indicators, where the decreased need for biofilter reconstruction results in a higher reduction in environmental impacts. Economically, amending the biofilter with SBAC can increase profits by up to 66% due to extending its lifespan. This study shows that SBAC has similar performance as CAC for lowering the negative environmental impacts resulting from biofilter construction, while increasing the overall net profits of the system. However, converting sewage sludge to an effective sorbent (SBAC) and incorporating SBAC into a biofilter to capture pollutants from stormwater is an economically and environmentally sustainable solution available to practitioners to manage sewage sludge and stormwater effluent. This solution protects the environment in a cost efficient, sustainable manner.

Towards carbon neutrality: what has been done and what needs to be done for carbon emission reduction?

Carbon emissions embodied in anthropogenic activities represent the major cause of global warming. Countries, regions, and cities have implemented comprehensive, multi-level and multi-scale measures to reduce emissions and move towards carbon neutrality. The demand for carbon emission reduction (CER) is made more challenging by different geographical locations, country-owned natural resources, and economic development stages. The main objectives of this paper are to conduct a bibliometric analysis to map the frontiers and directions of CER and to explore the paths and development models of CER from the perspective of spatio-temporal, multi-scale, multi-sectoral, and multi-responsible subjects. This study reveals that carbon emission evaluation and prediction, correlation and causal relationship analysis, and CER-related policy simulation and optimization are the most critical hotspots. Additionally, we point out the shortcomings of and future developments for the three study dimensions above. The bibliometric analysis also highlights the fact that a cooperative global value chain as well as amendable policies and mechanisms for CER will help with climate change mitigation and adaptation through the use of advanced carbon capture and storage technologies. We review the technical measures for and policy responses to CER adopted by different countries and industries at the theoretical and practical levels and provide new recommendations. Our work provides important information for climate actions in different countries and sectors and for developing more effective CER strategies and policies.

The Life cycle Assessment Integrated with the Lexicographic Method for the Multi-Objective Optimization of Community-Based Rainwater Utilization

Community-based rainwater utilization (CB-RWU) has the advantage of easy maintenance and multiple benefits. However, its promotion proves to be a complicated task due to difficulties in quantifying and evaluating external benefits. This study integrated the life cycle assessment (LCA) with a multi-objective optimization model to optimize the relationship among all stages of CB-RWU, considering the trade-offs among the benefit-cost ratio, water-saving efficiency and environmental impact. The LCA results identified abiotic depletion potential for fossil fuels (ADPF) as the key impact indicators throughout the life cycle of CB-RWU. The optimal solution from the lexicographic method was 0.3098, 28.47% and 24.68 MJ for the benefit-cost ratio, water-saving efficiency and ADPF, respectively. Compared with the traditional optimization method, the lexicographic method improved the three object functions by 26%, 43% and 14%, respectively. The uncertainty of the environmental impact was the highest (C_V = 0.633) with variations in the floor area ratio, total runoff coefficient and reservoir volume. Changes in the total runoff coefficient were the main source of the uncertainty, which suggested that more attention should be paid to the area ratio of each underlying surface. In addition, economic support from the government is urgently required for the further promotion and development of CB-RWU.

Coupling with high-resolution remote sensing data to evaluate urban non-point source pollution in Tongzhou, China

Urban non-point source (NPS) pollution has gradually become one of the important factors affecting the urban water environment. The quantitative evaluation of urban NPS pollution is the priority to identify key control area of urban NPS pollution. Current model applied in China is mainly focused on small-scale area, large-scale spatial continuous simulation is lacking. In this study A spatial continuous evaluation method coupled with high-resolution remote sensing data has been established and the method was applied to Tongzhou, China. With the spatial distribution of land-use type and built-up area which were been obtained by remote sensing technology, the accumulative and wash-off load of urban NPS nitrogen and phosphorus were estimated for the prominent problems of nitrogen and phosphorus nutrient pollution in the rivers in the study area. The main sources of urban NPS Nitrogen and phosphorus pollution are roof and road rainfall runoff respectively. Compared to other urban NPS pollution models, the method developed in this study can quickly realize spatial visualization assessment of urban NPS pollution and provide a means to estimate urban NPS loads in entire city or urban agglomeration, it is applicable for common urban NPS pollutants and also has advantages in areas without data.

Life Cycle Environmental Impact of Underground Plastic Recharge Chambers in Stormwater Management

Life cycle assessment is used to systematically evaluate the environmental impact of underground plastic recharge chambers (RCs) used for stormwater management. Using cradle-to-gate life cycle assessment and a functional unit of 1 m3 stormwater capacity, different RC structure types, manufacturing processes and materials are considered. The inventory is based on various commercially available RCs, including injection-molded or extruded polypropylene and polyvinylchloride polymers and typical installation materials and methods. A new dataset is developed to estimate the manufacture and use of recycled polypropylene granulate. TRACI 2.1 is used to investigate the midpoint life cycle impact assessment metrics, acidification, eutrophication, global warming, and fossil fuel resources. Results indicate that plastic represents as much as 99% of the total cradle-to-gate impact, driven largely by the polymer processing method. Injection molding has on average a 50% higher impact per kg of material than extrusion. Processing and transport of backfill material to the project site is approximately 20% of the total cradle-to-gate impact. The transport distance is highly significant: long transport distances can cause the transportation impact to exceed the plastic impact.

Lifecycle sustainability assessment for the comparison of traditional and sustainable drainage systems

Urban drainage is a topic of increasing interest due to its key role for managing water-related disasters, which are being exacerbated by the effects of Climate Change and urbanization. Since traditional drainage systems struggle to deal with the combined action of these phenomena, Sustainable Drainage Systems (SuDS) are gaining attention as an alternative to help manage these high-water management demands. In this context, this research aimed at conducting a lifecycle sustainability assessment for comparing the economic, environmental and social performance of both drainage systems. The three dimensions of sustainable development were addressed with the support of the concepts of Net Present Value (NPV), Life Cycle Assessment (LCA) and a combination of the Leopold matrix and a semi structured interview, respectively. The results of applying this approach to the case study of the Rancho Bellavista housing development (Querétaro, Mexico) showed that SuDS outperformed traditional drainage systems in environmental and social terms; however, their high maintenance costs and shorter life expectancy hindered its economic feasibility. As such, future urban plans should focus on complementary designs whereby the strengths of both drainage alternatives are combined to boost their contributions to achieving sustainable development.

From landfills to landscapes-Nature-based solutions for water management taking into account legacy contamination

Nature-based solutions (NBS) can be used in combination with the reopening of piped rivers to support area development. In certain cases, piped rivers can run through disused landfills. This presents a complicating factor because landfills provide the possibility for river water to be contaminated by waste. In Skien municipality, close to Oslo, Norway, NBS are being considered as part of a potential reopening of the Kjørbekk stream. A 4-km stretch of the stream is contained in an aging pipe infrastructure that is buried under two disused landfills. The pipe infrastructure does not have the physical capacity to cope with an increase in precipitation brought about by current climate change, and in certain areas, the pipe has started to leak. This means that surface water runoff that cannot be accommodated by the pipe, as well as water that leaks from the pipe, can become contaminated by the waste in the disused landfill. Furthermore, the water can be transported with the stream course to the final recipient, taking the contamination with it. Reopening the stream and providing new water pathways can alleviate these problems, but it must be carried out so that contamination is not allowed to spread. This case study reveals how certain NBS that focus on reducing the amount of water in contact with pollutants, reducing the amount of particle spreading, remediating contaminated water, and remediating contaminated soil could be implemented at the site and function as a catalyst for an incremental city development. Integr Environ Assess Manag 2022;18:99-107. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Optimal Design of Combined Sewer Overflows Interception Facilities Based on the NSGA-III Algorithm

The interception facility is an important and frequently used measure for combined sewer overflow (CSO) control in city-scale drainage systems. The location and capacity of these facilities affects the pollution control efficiency and construction cost. Optimal design of these facilities is always an active research area in environmental engineering, and among candidate optimization methods, the simulation-optimization method is the most attractive method. However, time-consuming simulations of complex drainage system models (e.g., SWMM) make the simulation-optimization approach impractical. This paper proposes a new simulation-optimization method with new features of multithreading individual evaluation and fast data exchange by recoding SWMM with object-oriented programming. These new features extremely accelerate the optimization process. The non-dominated sorting genetic algorithm-III (NSGA-III) is selected as the optimization framework for better performance in dealing with multi-objective optimization. The proposed method is used in the optimal design of a terminal CSO interception facility in Wuhan, China. Compared with empirically designed schemes, the optimized schemes can achieve better pollution control efficiency with less construction cost. Additionally, the time consumption of the optimization process is compressed from days to hours, making the proposed method practical.

A Review of Urban Green and Blue Infrastructure from the Perspective of Food-Energy-Water Nexus

Small scale urban green-blue infrastructure (indicated as GBI hereafter) comprises huge underexploited areas for urban development and planning. This review article aims to highlight the relevance and knowledge gaps regarding GBI from the perspective of the food–energy–water (FEW) nexus, these being key resources for the survival of human communities. In particular, this review was focused on publications on urban ecosystem services (positive effects) and dis-services (negative effects) associated with different GBI typologies. The review proved that GBI can contribute environmentally, socially, and economically to FEW security and urban sustainability. Yet, such positive effects must be considered against ecosystem dis-services tradeoffs, including urban food production, commonly connected with heavy water and energy consumption, specifically under dry climate conditions, and sometimes related to an excessive use of manure, pesticides, or fertilizers. These conditions could pose either a risk to water quality and local insect survival or serve enhanced mosquito breeding because of irrigation. Up to now, the review evidenced that few nexus modeling techniques have been discussed in terms of their benefits, drawbacks, and applications. Guidance is provided on the choice of an adequate modeling approach. Water, energy, and food are intrinsically associated physically. However, depending on their management, their tradeoffs are often increased. There is a need to minimize these tradeoffs and to build up synergies between food, energy, and water using a holistic approach. This is why the FEW nexus approach offers good insights to address the relation between three important individual resource components of sustainability.

Assessment of green infrastructure performance through an urban resilience lens

Green infrastructure (GI) is widely recognized for reducing risk of flooding, improving water quality, and harvesting stormwater for potential future use. GI can be an important part of a strategy used in urban planning to enhance sustainable development and urban resilience. However, existing literature lacks a comprehensive assessment framework to evaluate GI performance in terms of promoting ecosystem functions and services for social-ecological system resilience. We propose a robust indicator set consisting of quantitative and qualitative measurements for a scenario-based planning support system to assess the capacity of urban resilience. Green Infrastructure in Urban Resilience Planning Support System (GIUR-PSS) supports decision-making for GI planning through scenario comparisons with the urban resilience capacity index. To demonstrate GIUR-PSS, we developed five scenarios for the Congress Run sub-watershed (Mill Creek watershed, Ohio, USA) to test common types of GI (rain barrels, rain gardens, detention basins, porous pavement, and open space). Results show the open space scenario achieves the overall highest performance (GI Urban Resilience Index = 4.27/5). To implement the open space scenario in our urban demonstration site, suitable vacant lots could be converted to greenspace (e.g., forest, detention basins, and low-impact recreation areas). GIUR-PSS is easy to replicate, customize, and apply to cities of different sizes to assess environmental, economic, and social benefits provided by different types of GI installations.

Performance evaluation of time-sharing utilization of multi-function sponge space to reduce waterlogging in a highly urbanizing area

Urban waterlogging is a dilemma faced by many highly urbanizing areas. To solve the contradiction between the space requirement for waterlogging control and the scarcity of urban space, time-sharing utilization of the multi-function sponge space (MFSS) is promoted in some urbanizing areas. The MFSS is designed to have certain social or economic functions during dry or light rain events and detains stormwater on heavy rain events. However, there is lack of understanding on how to achieve the maximum benefit of multi-function. In this study, three time-sharing utilization modes are proposed to use MFSS to detain runoff: when the rain event begins (Mode A), when cumulative rainfall is greater than a specific threshold (Mode B), or when rainfall intensity is higher than a specific threshold (Mode C). A methodological framework based on the Storm Water Management Model (SWMM) is proposed to evaluate the waterlogging reduction performance of the three modes under different rainfall conditions and thresholds for enabling MFSS in an urbanizing catchment in Shenzhen, China. The performance is measured by comparing the total volume of overflow from manholes of the drainage system with and without MFSS during a storm event. The results indicate that: (1) Under Mode A, the performance is more effective under a light storm event with an early peak; (2) Under Mode B, as the cumulative rainfall threshold for enabling MFSS increases, the overflow first decreases and then increases. Different threshold values have to be set for different types of rainfall events to achieve the best performance; (3) Under Mode C, as the rainfall intensity threshold for enabling MFSS increases, the overflow also first decreases and then rapidly increases at a high threshold value. The mode has an identical range of optimal thresholds under different types of rainfall events. Furthermore, Mode C has higher efficiency in overflow reduction than the other two modes, no matter whether under design storms or historical storms. Therefore, Mode C is recommended as an efficient and stable utilization mode for MFSS.

A spatial life cycle cost assessment of stormwater management systems

Although widely implemented, the research and understanding of the economic impacts and benefits of green infrastructure (GI) systems remain limited. Currently, few studies have investigated the economics of GI systems from a spatial perspective and typically opportunity costs related to land and property tax were ignored. This study aims at bridging these gaps by investigating both the equivalent annual costs (EAC) and cost effectiveness of seven GI systems and compare them against local wastewater treatment facilities in five different US cities. To do this, we utilized capital and maintenance cost data obtained from GI systems that are currently installed at the University of New Hampshire. The costing data were then extrapolated across five different cities considering reported local material, land, tax, and labor rates. A system dynamics model was utilized to calculate the total stormwater reduction as well as the amounts of nitrogen and phosphorous removed by each GI system over its life cycle under a certain city setting. Based upon these outcomes, the cost effectiveness (CE) in terms of stormwater reduction, nitrogen treatment, and phosphorous treatment of the GI systems was calculated. Land and tax costs were found to be a significant component of the EAC for GI systems with larger footprints in cities with higher property values, accounting for up to 78% in some cities. The rankings of the GI systems differ significantly when different types of cost effectiveness are under consideration. The tree filter performs the best when the CE is calculated based on stormwater reductions, while the subsurface gravel wetland performs the best considering nitrogen treatment, and either the subsurface gravel wetland or the sand filter performs the best considering phosphorous treatment. Our study suggests recommendations of GI systems need to be made based on local needs and issues to achieve the most cost-effective solution.

Cost-benefit analysis of low-impact development at hectare scale for urban stormwater source control in response to anticipated climatic change

Investigation of the cost-effectiveness of low-impact development (LID) practices at the hectare scale in response to impacts of possible climate change was conducted using representative concentration pathways (RCPs). An LID project in Guangzhou has been selected to illustrate changes in the hydrologic performance for alternative source control strategies for a variety of future climate models and scenarios. Frequent storms of shorter duration in RCP 8.5 cause more dramatic fluctuation of hydrologic performance. Hydrologic performance of LID practices on reducing runoff volume and peak flow in test catchment are different in climate scenarios. Based on the constraints of life cycle costs and environmental impacts of LID alternatives, comprehensive strategies were found effective in managing surface runoff at the source to adapt to the influence of climate change. The methodology described herein could be useful in considering LID practices for critical source management with limited budgets and considering environmental impacts under long-term climate change.

Life cycle modeling for environmental management: a review of trends and linkages

With the dynamics in current industry-environment interaction, it has become essential to diagnose the impacts that one is leaving on the environment. The requirement of assessment has brought many changes in the analysis techniques and research methodologies. Life cycle assessment (LCA) is one such validated technique as a scientific tool in the diagnosis of environmental impacts with accuracy. Over the past few years, LCA has attracted more attention with different approaches and applications. But, there is a lack of efforts to review the LCA applications for environmental management. The aim of this study is to evaluate the trends and to address the evolution of linkages in the field of LCA modeling and environmental management. The review employs the PRISMA statement for systematic literature review amalgamated with a visualization technique using VoSviewer. The meta-analysis addressing the findings from the academic articles published until the end of May 2019 using the Scopus online database was considered. The study reveals a total of 23 eligible papers regarding LCA modeling and environmental management. Analysis of these articles and keyword visualization network depicts that most of the studies on LCA modeling application were based on waste management-related decision-making and construction sector focusing primarily on environmental impacts, environmental performance evaluations, and scenario modeling for decision support. This study not only contributes in summarizing the LCA research trends of the methods in the application areas but also attempts to identify the potential scope and research directions. LCA thus has proven to be an excellent evaluative tool for future analysis.

A dynamic life cycle assessment of green infrastructures

As stormwater and its associated nutrients continue to impair our nation's waterways, green infrastructures (GIs) are increasingly applied in urban and suburban communities as a means to control combined sewer system overflows and stormwater related pollutants. Although GIs have been widely studied for their life cycle impacts and benefits, most of these studies adopt a static approach which prevents that information from being scaled or transferred to different spatial and temporal settings. To overcome this limitation, this research utilizes a dynamic life cycle assessment (LCA) approach to evaluate seven different GIs by integrating a traditional LCA with a system dynamics model which simulates the daily loadings and treatments of nutrients by the GIs across a 30-year life span. A base model was first developed, calibrated, and validated for seven GIs that are currently installed on the campus of the University of New Hampshire. The base model was then expanded to assess different scenarios in terms of geographic locations, land uses, GI design sizes, and climate changes. Our results show these aforementioned factors have significant influences on GIs' life cycle performances, with life cycle nitrogen reductions varying -100.90 to 512.09kgNeq. and life cycle phosphorous reductions varying from -23.77 to 63.43kg P eq. Furthermore, nutrient loading thresholds exist for certain GIs to offset nutrient emissions from their construction and maintenance activities. Accordingly, an optimal GI design size can be estimated for a given spatial and temporal setting. Such thresholds and optimal sizes are important to be identified to inform the decision-making and future planning of GIs.

Cradle-to-grave life cycle assessment (LCA) of low-impact-development (LID) technologies in southern Ontario

A comparative cradle-to-grave life cycle assessment (LCA) of a low-impact-development (LID) parking lot test-site is performed to quantify the environmental costs of the manufacturing, construction, transportation, operation, maintenance and decommissioning of three bioretention cells and three permeable pavement systems (PPS) located in Mississauga, Ontario, as well as a hypothetical stormwater management pond. The LIDs' influent and effluent water quality and volume data is used to quantify the environmental benefits offered by the LIDs. Ecoinvent v3 LCA database is utilized to create an inventory of the materials and energy used during the life cycle of the LIDs. Using TRACI 2.1 impact assessment method, an LCA is conducted to simulate impacts on ten midpoint categories using a functional unit of "1 m² of impervious area treated". It has been found that manufacturing of raw materials has the largest impact (∼50%) on ozone depletion, global warming, smog potential, acidification, carcinogenic emissions, respiratory effects and fossil fuel depletion. The LIDs offer a significant avoidance of eutrophication potential, non-carcinogenic emissions and ecotoxicity, which are all mostly associated with the water quality benefits offered by the LIDs. The bioretention impacts are ∼90% lower than the PPS' on a "per 1 m² of impervious area treated" basis due to its larger impervious area treatment relative to its size compared to the PPS. The benefits offered by bioretention are significantly higher on "per 1 m² LID area" basis (∼12x), but comparable on "per 1 m² impervious area treated" basis. The impacts normalized by per-capita emissions in Canada in the year 2005 show that the negative impacts of the LIDs are insignificant compared to the benefits they provide. A comparison of the LIDs to a traditional pipe-and-pond infrastructure of an equivalent treatment capacity reveals that the cradle-to-grave impacts of LIDs are ∼20% lower compared to the detention pond's, and the benefits accrued by the LIDs are ∼300% higher compared to the detention pond, making a strong case for the selection of LIDs over traditional stormwater management practices.

Prediction of Life Cycle Carbon Emissions of Sponge City Projects: A Case Study in Shanghai, China

In recent years, China has been vigorously carrying out the planning and implementation of Sponge City. Since the implementation of Sponge City projects involves substantial materials and energy consumption, it is significant to account corresponding carbon emissions and sinks. The existed studies about carbon emission of stormwater management measures, however, are not able to take the whole life cycle and different facilities into consideration. Therefore, this study develops a comprehensive accounting model based on Intergovernmental Panel on Climate Change (IPCC) guidelines and life cycle assessment (LCA) method to predict carbon emissions and carbon sinks of Sponge City projects more comprehensively and accurately. The model is applied to an actual residential community in Shanghai as a case study. Results show that the total indirect carbon emission is estimated to be 774,277 kg CO2 eq during a 30-year lifespan, among which carbon emissions from operation and maintenance phases are 2570 kg CO2 eq/year and 7309 kg CO2 eq/year, respectively, both directly proportional to the service life of the facilities. Three kinds of achievable carbon sinks are carbon sequestration in green space (5450 kg CO2 eq/year), carbon sink from rainwater utilization (15,379 kg CO2 eq/year) and carbon sink from runoff pollutant removal (19,552 kg CO2 eq/year). Carbon neutrality is expected to be reached after approximately 19 years. The established carbon emission accounting model can contribute to better planning and construction of Sponge City in China and enhance further energy conservation and carbon emission reduction.

Are stormwater pollution impacts significant in life cycle assessment? A new methodology for quantifying embedded urban stormwater impacts

Current life cycle assessment (LCA) models do not explicitly incorporate the impacts from urban stormwater pollution. To address this issue, a framework to estimate the impacts from urban stormwater pollution over the lifetime of a system has been developed, laying the groundwork for subsequent improvements in life cycle databases and LCA modelling. The proposed framework incorporates urban stormwater event mean concentration (EMC) data into existing LCA impact categories to account for the environmental impacts associated with urban land occupation across the whole life cycle of a system. It consists of five steps: (1) compilation of inventory of urban stormwater pollutants; (2) collection of precipitation data; (3) classification and characterisation within existing midpoint impact categories; (4) collation of inventory data for impermeable urban land occupation; and (5) impact assessment. The framework is generic and can be applied to any system using any LCA impact method. Its application is demonstrated by two illustrative case studies: electricity generation and production of construction materials. The results show that pollutants in urban stormwater have an influence on human toxicity, freshwater and marine ecotoxicity, marine eutrophication, freshwater eutrophication and terrestrial ecotoxicity. Among these, urban stormwater pollution has the highest relative contribution to the eutrophication potentials. The results also suggest that stormwater pollution from urban areas can have a substantial effect on the life cycle impacts of some systems (construction materials), while for some systems the effect is small (e.g. electricity generation). However, it is not possible to determine a priori which systems are affected so that the impacts from stormwater pollution should be considered routinely in future LCA studies. The paper also proposes ways to incorporate stormwater pollution burdens into the life cycle databases.

Evaluation of Life Cycle Assessment (LCA) for Roadway Drainage Systems

Roadway drainage design has traditionally focused on cost-effectively managing water quantity; however, runoff carries pollutants, posing risks to the local environment and public health. Additionally, construction and maintenance incur costs and contribute to global environmental impacts. While life cycle assessment (LCA) can potentially capture local and global environmental impacts of roadway drainage and other stormwater systems, LCA methodology must be evaluated because stormwater systems differ from wastewater and drinking water systems to which LCA is more frequently applied. To this end, this research developed a comprehensive model linking roadway drainage design parameters to LCA and life cycle costing (LCC) under uncertainty. This framework was applied to 10 highway drainage projects to evaluate LCA methodological choices by characterizing environmental and economic impacts of drainage projects and individual components (basin, bioswale, culvert, grass swale, storm sewer, and pipe underdrain). The relative impacts of drainage components varied based on functional unit choice. LCA inventory cutoff criteria evaluation showed the potential for cost-based criteria, which performed better than mass-based criteria. Finally, the local aquatic benefits of grass swales and bioswales offset global environmental impacts for four impact categories, highlighting the need to explicitly consider local impacts (i.e., direct emissions) when evaluating drainage technologies.