Comparison of Plastic Packaging Waste Management Options: Feedstock Recycling versus Energy Recovery in Germany

Plastics recycling, especially as prescribed by the German Ordinance on Packaging Waste (Verpackungsverordnung), is a conspicuous example of closing material loops on a large scale. In Germany, an industry‐financed system (Duales System Deutschland) was established in 1991 to collect and recycle packaging waste from households. To cope with mixed plastics, various “feedstock‐recycling” processes were developed. We discuss the environmental benefits and the cost‐benefit ratio of the system relative to municipal solid waste (MSW) incineration, based on previously published life‐cycle assessment (LCA) studies. Included is a first‐time investigation of energy recovery in all German incinerators, the optimization opportunities, the impact on energy production and substitution processes, an estimation of the costs, and a cost‐benefit assessment. In an LCA, the total environmental impact of MSW incineration is mainly determined by the energy recovery ratio, which was found on average to reach 39% in current German incineration plants. Due to low revenues from additional energy generation, it is not cost‐effective to optimize the plants energetically. Energy from plastic incineration substitutes for a specific mixture of electric base‐load power, district heating, and process steam generation. Any additional energy from waste incineration will replace, in the long term, mainly natural gas, rather than coal. Incineration of plastic is compared with feedstock recycling methods in different scenarios. In all scenarios, the incineration of plastic leads to an increase of CO2 emissions compared to landfill, whereas feedstock recycling reduces CO2 emissions and saves energy resources. The costs of waste incineration are assumed to decrease by about 30% in the medium term. Today, the calculated costs of CO2 reduction in feedstock recycling are very high, but are ex‐pected to decline in the near future. Relative to incineration, the costs for conserving energy via feedstock recycling are 50% higher, but this gap will close in the near future if automatic sorting and processing are implemented in Germany.     

The Environmental Importance of Energy Use in Chemical Production

In many cases, policy makers and laymen perceive harmful emissions from chemical plants as the most important source of environmental impacts in chemical production. As a result, regulations and environmental efforts have tended to focus on this area. Concerns about energy use and greenhouse gas emissions, however, are increasing in all industrial sectors. Using a life cycle assessment (LCA) approach, we analyzed the full environmental impacts of producing 99 chemical products in Western Europe from cradle to factory gate. We applied several life cycle impact assessment (LCIA) methods to cover various impact areas. Our analysis shows that for both organic and inorganic chemical production in industrial countries, energy‐related impacts often represent more than half and sometimes up to 80% of the total impacts, according to a range of LCIA methods. Resource use for material feedstock is also important, whereas direct emissions from chemical plants may make up only 5% to 10% of the total environmental impacts. Additionally, the energy‐related impacts of organic chemical production increase with the complexity of the chemicals. The results of this study offer important information for policy makers and sustainability experts in the chemical industry striving to reduce environmental impacts. We identify more sustainable energy production and use as an important option for improvements in the environmental profile of chemical production in industrial countries, especially for the production of advanced organic and fine chemicals.     

Carbon Nanofiber Production

Holistic understanding of nanotechnology using systems analysis tools is essential for evaluating claims about the potential benefits of this emerging technology. This article presents one of the first assessments of the life cycle energy requirements and environmental impact of carbon nanofibers (CNFs) synthesis. Life cycle inventory data are compiled with data reported in the open literature. The results of the study indicate relatively higher life cycle energy requirements and higher environmental impact of CNFs as compared to traditional materials, like primary aluminum, steel, and polypropylene, on an equal mass basis. Life cycle energy requirements for CNFs from a range of feedstock materials are found to be 13 to 50 times that of primary aluminum on an equal mass basis. Similar trends are observed from the results of process life cycle assessment (LCA), as conveyed by different midpoint and endpoint damage indicators. Savings in life cycle energy consumption and, hence, reductions in environmental burden are envisaged if higher process yields of these fibers can be achieved in continuous operations. Since the comparison of CNFs is performed on an equal mass basis with traditional materials, these results cannot be generalized for CNF‐based nanoproducts. Quantity of use of these engineered nanomaterials and resulting benefits will decide their energy and environmental impact. Nevertheless, the life cycle inventory and the results of the study can be used for evaluating the environmental performance of specific CNF‐based nanoproducts.     

Environmental Life Cycle Assessment of a Swedish Dissolving Pulp Mill Integrated Biorefinery

The pulp industry plays an important role in the structure of the European economy and society. The production of pulp has been traditionally considered an important source of pollution due to the use of large amounts of chemicals, fuels, and water and its intensive energy consumption. Currently, this situation is changing due to the potential use of biomass to produce value‐added products, which minimizes environmental impacts and increases sustainability. This article uses life cycle assessment (LCA) to identify and quantify the environmental impacts associated with a Swedish softwood‐based biorefinery where total chlorine‐free (TCF) dissolving cellulose is produced together with ethanol and lignosulfonates. The system was defined according to a cradle‐to‐gate perspective—that is to say, from forest activities to the output of the biorefinery mill. According to the results, forest activities associated with the production of soft roundwood play a minor role in all the environmental impact categories under study. In contrast, the production of chemicals consumed in the cooking and bleaching stages, the sludge treatment generated in the wastewater treatment plant, and the on‐site energy production system were identified as the elements that negatively contribute the most to all impact categories. The production of steam from biorefinery wastes, biogas, and methanol in external boilers reduces the environmental impact in all categories. Specific actions associated with the reuse of wastes and improved gas treatment systems would improve the environmental profile of this production activity.     

Wax production from renewable feedstock using biocatalysts instead of fossil feedstock and conventional methods

Background, aim, and scope

Using renewable feedstock and introducing biocatalysts in the chemical industry have been suggested as the key strategies to reduce the environmental impact of chemicals. The Swedish interdisciplinary research program “Speciality Chemicals from Renewable Resources—Greenchem” is aiming to develop these strategies. One target group of chemicals for Greenchem are wax esters which can be used in wood coatings to replace paraffin wax made from fossil crude oil. The aim of this study was to conduct a life cycle assessment of wax esters based on rapeseed oil produced by biocatalysts (enzymes). The scope was to compare the environmental performance of wax esters with paraffin wax produced by conventional methods.

Materials and methods

The study has a cradle-to-gate perspective and the functional unit is “1-kg wax product ready to use in a wood coating product.” Extensive data collection and calculations have been performed for the wax esters, whereas existing life cycle inventory data have been used for the paraffin wax.

Results

The energy input into the wax ester production is about one third of the energy input in paraffin wax production. However, the wax ester has a higher contribution to the global warming potential (GWP) due to high emissions of nitrous oxide from rapeseed cultivation. Referring to a cradle-to-grave perspective, including waste incineration, the contribution to the GWP will, however, be 3.5 times higher from paraffin wax. Wax ester makes a higher contribution to the acidification and eutrophication potential, due to emissions from soil from rapeseed cultivation, but five times lower contribution to the photochemical ozone creation potential. From a land-use perspective and a global warming point of view, it is more efficient to produce paraffin wax and grow high-yielding, short-rotation coppice (Salix) to replace fuel oil than it is to grow rapeseed for wax ester production.

Discussion

Overall, this study shows the importance of studying the environmental performance of a product not only from a gate-to-gate perspective but, instead, considering the environmental performance from cradle-to-gate. The biocatalytic production of the wax ester consumes less energy than the conventional chemical method, but the raw material step, cultivation of rapeseed contributes much to both acidification and eutrophication. When the waste treatment step is included, the contribution to GWP, however, for paraffin wax will be 3.5 times higher than for the wax ester.

Conclusions

From a gate-to-gate perspective, replacing conventional chemical processes by biocatalysts using enzymes leads to energy savings and reduces emissions. However, from a cradle-to-gate perspective, the use of renewable feedstock, such as rapeseed oil, may counteract some of these benefits. Concerning the GWP benefit from using renewable feedstock instead of fossil feedstock, the final waste treatment step must be included, thereby applying a cradle-to-grave perspective.

Recommendations and perspectives

The introduction of biocatalysts as a key strategy in reducing the environmental impact from the chemical industry is supported by the results in this study. On the other hand, it is not obvious that the key strategy of using renewable feedstock in chemical production per se leads to benefits concerning all environmental impact categories. Thus, much more attention needs to be paid to the choice of potential renewable feedstock options, the minimization of energy inputs, and the biological emissions from the soil in the cultivation of feedstock crops, improved gas cleaning in nitrogen fertilizer production plants, and the alternative use of the arable land, in optimizing the overall environmental benefits of an increased use of renewable feedstock in the chemical industry.     

Assessing the Environmental Impact of Water Consumption by Energy Crops Grown in Spain

The environmental impact of the water consumption of four typical crop rotations grown in Spain, including energy crops, was analyzed and compared against Spanish agricultural and natural reference situations. The life cycle assessment (LCA) methodology was used for the assessment of the potential environmental impact of blue water (withdrawal from water bodies) and green water (uptake of soil moisture) consumption. The latter has so far been disregarded in LCA. To account for green water, two approaches have been applied: the first accounts for the difference in green water demand of the crops and a reference situation. The second is a green water scarcity index, which measures the fraction of the soil‐water plant consumption to the available green water. Our results show that, if the aim is to minimize the environmental impacts of water consumption, the energy crop rotations assessed in this study were most suitable in basins in the northeast of Spain. In contrast, the energy crops grown in basins in the southeast of Spain were associated with the greatest environmental impacts. Further research into the integration of quantitative green water assessment in LCA is crucial in studies of systems with a high dependence on green water resources.     

Environmental Impact Assessment of Wood Use in Japan through 2050 Using Material Flow Analysis and Life Cycle Assessment

In this study, we used material flow analysis and life cycle assessment to quantify the environmental impacts and impact reductions related to wood consumption in Japan from 1970 to 2013. We then conducted future projections of the impacts and reductions until 2050 based on multiple future scenarios of domestic forestry, wood, and energy use. An impact assessment method involving characterization, damage assessment, and integration with a monetary unit was used, and the results were expressed in Japanese yen (JPY). We found that environmental impacts from paper consumption, such as climate change and urban air pollution, were significant and accounted for 56% to 83% of the total environmental impacts between 1970 and 2013. Therefore, reductions of greenhouse gas, nitrogen oxide, and sulfur oxide emissions from paper production would be an effective measure to reduce the overall environmental impacts. An increase in wood use for building construction, civil engineering, furniture materials, and energy production could lead to reductions of environmental impacts (via carbon storage, material substitution, and fuel substitution) amounting to 357 billion JPY in 2050, which is equivalent to 168% of the 2013 levels. Particularly, substitution of nonwooden materials, such as cement, concrete, and steel, with wood products in building construction could significantly contribute to impact reductions. Although an increase of wood consumption could reduce environmental impacts, such as climate change, resource consumption, and urban air pollution, increased wood consumption would also be associated with land‐use impacts. Therefore, minimizing land transformations from forest to barren land will be important.     

Revealing the Environmental Advantages of Industrial Symbiosis in Wood‐Based Bioeconomy Networks: An Assessment From a Life Cycle Perspective

The German government has recently initiated funding schemes that incentivize strategies for wood‐based bioeconomy regions. Regional wood and chemical industries have been encouraged to act symbiotically, that is, share pilot plant facilities, couple processes where feasible, and cascade woody feedstock throughout their process networks. However, during the planning stages of these bioeconomy regions, options need to be assessed for sustainably integrating processes and energy integration between the various industries that produce bio‐based polymers and engineered wood products. The aim of this paper is to identify the environmental sustainability of industrial symbiosis for producing high‐value‐added, bio‐based products in the wood‐based bioeconomy region of Central Germany. An analysis was conducted of three possible future scenarios with varying degrees of symbiosis in the bioeconomy network. A life cycle assessment (LCA) approach was used to compare these three scenarios to a traditional fossil‐based production system. Eleven environmental impact categories were considered. The results show that, in most cases, the bioeconomy network outperformed the fossil‐based production system, mitigating environmental impacts by 25% to 130%.     

Construction Materials from Stainless Steel Slags: Technical Aspects,Environmental Benefits,and Economic Opportunities

State‐of‐the‐art technologies that implement theindustrial ecology concept only make it to the market if environmental gains and economic benefits are significant. Therefore, the article investigates, in an interdisciplinary way, two innovative technologies that valorize stainless steel (SS) slags as block masonry (bricks): carbonation and thermo‐alkali‐activation. The technical, environmental, and economic features of three SS bricks—solid bricks, perforated bricks, and lightweight aerated blocks—are compared to commercially available construction materials. Although the produced bricks meet industrial standards, technical challenges, such as optimization of alkali addition and use of metal molds, should be dealt with before upscaling to industrial production. A cradle‐to‐gate life cycle assessment that aggregates the results of the various impact categories shows that the environmental impact of solid and perforated SS bricks is lower than the impact of conventional clay‐baked bricks owing to the avoidance of additives for slag stabilization and energy consumption for sintering clay. The impact of aerated SS bricks was found to be similar to the commercially available aerated blocks. More specifically, the carbon dioxide uptake from carbonation reduces the overall environmental impact, whereas use of alkalis increases the impact. A strengths weaknesses opportunity threats analysis highlights the economic advantages of SS bricks originating from lower energy requirements, reduced dependence on primary resources, and improved metal recovery from slag. However, in order to apply the innovative technologies at industrial scale, challenges related to processing conditions, feedstock variability, and potential competition from existing brick suppliers have to be overcome.     

Comparative life-cycle assessments for biomass-to-ethanol production from different regional feedstocks

This study compares life-cycle (cradle-to-gate) energy consumption and environmental impacts for producing ethanol via fermentation-based processes starting with two lignocellulosic feedstocks: virgin timber resources or recycled newsprint from an urban area. The life-cycle assessment in this study employed a novel combination of computer-aided tools. These tools include fermentation process simulation coupled with an impact assessment software tool for the manufacturing process life-cycle stage impacts. The process simulation file was provided by the National Renewable Energy Laboratory (NREL) and was modified slightly to accommodate these different feedstocks. For the premanufacturing process life-cycle stage impacts, such as the fuels and process chemicals used, transportation, and some preparatory steps (wood chipping, etc.), a life-cycle inventory database (the Boustead Model) coupled with an impact assessment software tool were used (the Environmental Fate and Risk Assessment Tool). The Newsprint process has a slightly lower overall composite environmental index (created from eight impact categories) compared to the Timber process. However, the Timber process consumes less electricity, produces fewer emissions in total, and has less of a human health impact. The amount of life-cycle fossil energy required to produce ethanol is 14% of the energy content of the product, making the overall efficiency 86%. Process improvement strategies were evaluated for both feedstock processes, including recycle of reactor vent air and heat integration. Heat integration has the greatest potential to reduce fossil-derived energy consumption, to an extent that fossil-derived energy over the life cycle is actually saved per unit of ethanol produced. These energy efficiency values are superior to those observed in conventional fossil-based transportation fuels.     

An integrated environment and cost assessment method based on LCA and LCC for mechanical product manufacturing

Purpose

The purpose of this study is to provide an integrated method to identify the resource consumption, environmental emission, and economic cost for mechanical product manufacturing from economic and ecological dimensions and ultimately to provide theoretical and data support of energy conservation and emission reduction for mechanical product manufacturing.

Methods

The applied research methods include environmental life cycle assessment (LCA) and life cycle cost (LCC). In life cycle environmental assessment, the inventory data are referred from Chinese Life Cycle Database and midpoint approach and EDIP2003 and CML2001 models of life cycle impact assessment (LCIA) are selected. In life cycle cost assessment, three cost categories are considered. The proposed environment and cost assessment method is based on the theory of social willingness to pay for potential environmental impacts. With the WD615 Steyr engine as a case, life cycle environment and cost are analyzed and evaluated.

Results and discussion

The case study indicates that, in different life cycle phases, the trend of cost result is generally similar to the environmental impacts; the largest proportion of cost and environmental impact happened in the two phases of “material production” and “component manufacturing” and the smallest proportion in “material transport” and “product assembly.” The environmental impact category of Chinese resource depletion potential (CRDP) accounted for the largest proportion, followed by global warming potential (GWP) and photochemical ozone creation potential (POCP), whereas the impacts of eutrophication potential (EP) and acidification potential (AP) are the smallest. The life cycle “conventional cost” accounted for almost all the highest percentage in each phase (except “material transport” phase), which is more than 80% of the total cost. The “environmental cost” and “possible cost” in each phase are relatively close, and the proportion of which is far below the “conventional cost.”

Conclusions

The proposed method enhanced the conventional LCA. The case results indicate that, in a life cycle framework, the environment and cost analysis results could support each other, and focusing on the environment and cost analysis for mechanical product manufacturing will contribute to a more comprehensive eco-efficiency assessment. Further research on the life cycle can be extended to phases of “early design,” “product use,” and “final disposal.” Other LCIA models and endpoint indicators are advocated for this environmental assessment. Environmental cost can also be further investigated, and the relevant social willingness to pay for more environmental emissions is advocated to be increased.

     

Environmental hotspots of lactic acid production systems

Using selected bio‐based feedstocks as alternative to fossil resources for producing biochemicals and derived materials is increasingly considered an important goal of a viable bioeconomy worldwide. However, to ensure that using bio‐based feedstocks is aligned with the global sustainability agenda, impacts along the entire life cycle of biochemical production systems need to be evaluated. This will help to identify those processes and technologies, which should be targeted for optimizing overall environmental sustainability performance. To address this need, we quantify environmental impacts of biochemical production using distinct bio‐based feedstocks, and discuss the potential for reducing impact hotspots via process optimization. Lactic acid (LA) was used as an example biochemical derived from corn, corn stover, and macroalgae (Laminaria sp.) as feedstocks of different technological maturity. We used environmental life cycle assessment (LCA), a standardized methodology, considering the full life cycle of the analyzed biochemical production systems and a broad range of environmental impact indicators. Across production systems, feedstock production and biorefinery processes dominate life cycle impact profiles, with choice in energy mix and biomass processing as main influencing aspects. Results show that uncertainty decreases with increasing technological maturity. When using Laminaria sp. (least mature among selected feedstocks), impacts are mainly driven by energy utilities (up to 86%) due to biomass drying. This suggests to focus on optimizing or avoiding this process for significantly increasing environmental sustainability of Laminaria sp.‐based LA production. Our results demonstrate that applying LCA is useful for identifying environmental impact hotspots at an earlier stage of technological development across biochemical production systems. With that, our approach contributes to improving the environmental sustainability of future biochemical production as part of moving toward a viable bioeconomy worldwide.     

Environmental Assessment of Single‐Walled Carbon Nanotube Processes

The environmental assessment of nanomanufacturing during the initial process design phase should lead to the development of competitive, safe, and environmentally responsible engineering and commercialization. Given the potential benefits and concerns regarding the use of single‐walled carbon nanotubes (SWNTs), three SWNT production processes have been investigated to assess their associated environmental impacts. These processes include arc ablation (arc), chemical vapor deposition (CVD), and high‐pressure carbon monoxide (HiPco). Without consideration of the currently unknown impacts of SWNT dispersion or other health impacts, life cycle assessment (LCA) methodology is used to analyze the environmental impact and provide a baseline for the environmental footprint of each manufacturing process. Although the technical attributes of the product resulting from each process may not be fully comparable, this study presents comparisons that show that the life cycle impacts are dominated by energy, specifically the electricity used in production. Under base case yield conditions, HiPco shows the lowest environmental impact, while the arc process has the lowest impact under best case yield conditions.     

Hierarchical Activity Model for Risk‐Based Decision Making

For the practical implementation of the assessment of environmental impact, actual procedures and data requirements should be clarified so that industrial decision makers understand them. Researchers should consider local risks related to processes and environmental impact throughout the life cycle of products simultaneously to supervise these adverse effects appropriately. Life cycle assessment (LCA) is a useful tool for quantifying the potential impact associated with a product life cycle. Risk assessment (RA) is a widely used tool for identifying chemical risks in a specific situation. In this study, we integrate LCA and RA for risk‐based decision making by devising a hierarchical activity model using the type‐zero method of integrated definition language (IDEF0). The IDEF0 activity modeling language has been applied to connect activities with information flows. Process generation, evaluation, and decision making are logically defined and visualized in the activity model with the required information. The activities, information flows, and their acquisitions are revealed, with a focus on which data should be collected by on‐site engineers. A case study is conducted on designing a metal cleaning process reducing chemical risks due to the use of a cleansing agent. LCA and RA are executed and applied effectively on the basis of integrated objective settings and interpretation. The proposed activity model can be used as a foundation to incorporate such assessments into actual business models.     

Life Cycle of Titanium Dioxide Nanoparticle Production

Life cycle impact of emissions, energy requirements, and exergetic losses are calculated for a novel process for producing titanium dioxide nanoparticles from an ilmenite feedstock. The Altairnano hydrochloride process analyzed is tailored for the production of nanoscale particles, unlike established commercial processes. The life cycle energy requirements for the production of these particles is compared with that of traditional building materials on a per unit mass basis. The environmental impact assessment and energy analysis results both emphasize the use of nonrenewable fossil fuels in the upstream life cycle. Exergy analysis shows fuel losses to be secondary to material losses, particularly in the mining of ilmenite ore. These analyses are based on the same inventory data. The main contributions of this work are to provide life cycle inventory of a nanomanufacturing process and reveal potential insights from exergy analysis that are not available from other methods.     

Life Cycle Assessment of Offshore Wind Farm Siting: Effects of Locational Factors,Lake Depth,and Distance from Shore

According to previous studies, the life cycle energy intensity of an offshore wind farm (OWF) varies between 0.03 and 0.13 megawatt‐hours (MWh) of primary energy for each MWh of electricity generated. The variation in these life cycle energy intensity studies, after normalizing for capacity factor and life span, is significantly affected by OWF location because of geographical properties, namely, wind speed and water depth. To improve OWF siting, this study investigates how an OWF's distance from shore and geographical location impacts its environmental benefit. A process‐based life cycle assessment is conducted to compare 20 OWF siting scenarios in Michigan's Great Lakes for their cumulative fossil energy demand, global warming potential, and acidification potential. Each scenario (four lake locations at five offshore distances) has unique foundation, transmission, installation, and operational requirements based on site characteristics. The results demonstrate that the cumulative environmental burden from an OWF is most significantly affected by (1) water depth, (2) distance from shore, and (3) distance to power grid, in descending order of importance, if all other site‐relevant variables are held constant. The results also show that when OWFs are sited further offshore, the benefit of increased wind energy generation does not necessarily outweigh the increase in negative environmental impacts. This suggests that siting OWF nearer to shore may result in a better life cycle environmental performance. Finally, we demonstrate how much an OWF's environmental burdens can be reduced if the OWF system is either recycled, transported a shorter distance, or manufactured in a region with a high degree of renewable energy on the grid.     

Construction Matters: Comparing Environmental Impacts of Building Modular and Conventional Homes in the United States

Modular construction practices are used in many countries as an alternative to conventional on‐site construction for residential homes. While modular home construction has certain advantages in terms of material and time efficiency, it requires a different infrastructure than conventional home construction, and the overall environmental trade‐offs between the two methods have been unclear. This study uses life cycle assessment to quantify the environmental impacts of constructing a typical residential home using the two methods, based on data from several modular construction companies and conventional homebuilders. The study includes impacts from material production and transport, off‐site and on‐site energy use, worker transport, and waste management. For all categories considered, the average impacts of building the home are less for modular construction than for conventional construction, although these averages obscure significant variation among the individual projects and companies.     

Implementing a Dynamic Life Cycle Assessment Methodology with a Case Study on Domestic Hot Water Production

This work contributes to the development of a dynamic life cycle assessment (DLCA) methodology by providing a methodological framework to link a dynamic system modeling method with a time‐dependent impact assessment method. This three‐step methodology starts by modeling systems where flows are described by temporal distributions. Then, a temporally differentiated life cycle inventory (TDLCI) is calculated to present the environmental exchanges through time. Finally, time‐dependent characterization factors are applied to the TDLCI to evaluate climate‐change impacts through time. The implementation of this new framework is illustrated by comparing systems producing domestic hot water (DHW) over an 80‐year period. Electricity is used to heat water in the first system, whereas the second system uses a combination of solar energy and gas to heat an equivalent amount of DHW at the same temperature. This comparison shows that using a different temporal precision (i.e., monthly vs. annual) to describe process flows can reverse conclusions regarding which case has the best environmental performance. Results also show that considering the timing of greenhouse gas (GHG) emissions reduces the absolute values of carbon footprint in the short‐term when compared with results from the static life cycle assessment. This pragmatic framework for the implementation of time in DLCA studies is proposed to help in the development of the methodology. It is not yet a fully operational scheme, and efforts are still required before DLCA can become state of practice.     

Steel‐versus‐Concrete Debate Revisited: Global Warming Potential and Embodied Energy Analyses based on Attributional and Consequential Life Cycle Perspectives

In the study of sustainable building materials, the comparison of the life cycle environmental performance of steel and reinforced concrete has been a popular and important topic. Based in Singapore, this is one of the first studies in the literature that applies both attributional and consequential life cycle approaches to compare the global warming potential and embodied energies of these two materials, which are widely used for the structural parts of buildings. It was found that 1 kilogram (kg) of steel can be replaced by 1 or 4.25 kg of reinforced concrete. Two consequential scenarios for each of three combinations of primary and secondary steel were assessed. It was found that reinforced concrete produces less carbon dioxide emissions and incurs less embodied energy in most of these cases, but when different sustainable primary steel‐making technologies were incorporated, these results may be reversed. We applied consequential life cycle assessment and scenario analysis to describe how changes in the demand for structural steel and reinforced concrete in Singapore's building industry give rise to different environmental impacts. Specifically, the consequential life cycle approach revealed that, over the short term, the impact of substituting steel with reinforced concrete depends on the difference in impacts resulting from the transportation of these two materials within Singapore. Based on these lessons, integrated technology policies to improve the overall sustainability of using steel for construction were proposed.