Meeting industrial decarbonization goals: a case study of and roadmap to a net-zero emissions cement industry in California

Recent decarbonization policies are expected to significantly impact high greenhouse gas (GHG) emitting industries, as they will be forced to find ways to operate with a lower environmental footprint. Due to the energy required for the kilns and the unavoidable chemical-derived emissions during manufacturing, in addition to its high global consumption levels, the cement industry is anticipated to be among the early industries affected. California State Bill (SB 596) is one of the first rigorous legislative measures that sets GHG emissions from cement production to net-zero by 2045. As such, a case study on California cement production is evaluated here. While several groups have developed cement technology roadmaps with GHG mitigation strategies, these roadmaps do not consider concomitant environmental impacts, such as those that can influence local populations, thus limiting potential implementation from a policy perspective. Here, we examine several GHG emissions mitigation strategies for cement production and show the greatest reduction from an individual measure is from implementing carbon capture storage for cement kiln flue gas (87%), use of alternative clinkers (78%), or use of alkali-activated materials (88%). Yet even if GHG emissions are reduced, use of high-polluting energy sources could increase risks to human health impacts. Further, the efficacy of these decarbonization measures is lowered if multiple measures are implemented simultaneously. Finally, we examine the potential to meet net-zero emissions, focusing on California production due to recent legislation, and find a pathway to 96% GHG emissions reduction. Notably, these reductions do not reach goals to hit zero emissions, suggesting direct air capture mechanisms will need to be implemented.


Introduction
The notable environmental impacts from concrete and cement production pose a challenge to meeting the goal posed by the Intergovernmental Panel on Climate Change (IPCC) to reach net-zero carbon dioxide (CO 2 ) emissions by mid-century [1].Concrete is a critical component of infrastructure and has supported development as early as the Egyptian and Roman empires [2].Although technology has improved to expand the performance and applications of concrete, the main materials required to create concrete have remained consistent for decades: Portland cement (a hydraulic powder, referred to herein as cement), water, and aggregates.As global development increases, so do the projections for future concrete demands [3].Emerging economies in regions like Southeast Asia, Central Asia and sub-Saharan Africa are projected to rely heavily on concrete for infrastructure development [4].Today, concrete production is responsible for nearly 9% of annual global anthropogenic CO 2 emissions [5].Cement production alone accounts for ∼7% of these global CO 2 emissions [6], making it the largest target of greenhouse gas (GHG) mitigation strategies for concrete and other cement-based materials (herein referred to jointly as concrete).The considerable emissions from cement production are driven by three factors: (1) the substantial amount of cement produced annually (∼4 billion metric tons per year globally [7]).(2) the chemical decarbonation of cement's primary raw material, limestone (CaCO 3 to CaO); this reaction releases CO 2 and accounts for approximately 60% of total CO 2 emissions from cement production.(3) the thermal energy demand for cement kilns; these kilns reach ∼1450 o C to form reactive compounds in an intermediary product called 'clinker' , which is interground with mineral additives to form cement. GHG emissions tied to this thermal energy account for about 35% of total CO 2 emissions (the remaining ∼5% of emissions are predominantly attributed to electricity demand).
The need to drive down emissions of GHGs has brought considerable attention to cement manufacturing.Impressively, California recently passed Senate Bill 596 (SB 596) that set the goal of net-zero GHG emissions from cement production by 2045, a first in United States (US) state legislation [8].California is not only the second largest producer of cement in the US (with more than 10 million metric tons produced each year [9]), but also it releases among the lowest GHG emissions per kg of cement produced compared to other US states.Thus, it is uniquely poised to be a leading case study for meeting industrial decarbonization goals.However, for this goal to be achieved decarbonization measure must be extended beyond California; it will require swift and aggressive actions by policy makers, government regulators, and industry.Without collective and immediate action, unprecedented natural disasters resulting from climate change, such as extreme flooding [10] and prolonged fire seasons [11], will continue at an accelerating rate.To support these efforts, several academic [5,12], non-governmental [6,13], and industry groups [14][15][16] have developed technology roadmaps to meet both global and regional climate goals.These reports highlight key technologies for GHG emissions mitigation within cement production that are intended to be rapidly deployed to meet these climate targets.
These GHG emissions roadmaps to net-zero for cement, however, estimate GHG emissions quantifications without presenting the influence on other environmental impact categories and only one (Cao and Masanet [17]) uses open data modeling methods.In doing so, such work limits the ability of future customizable analyses to be specific to region or cement plant and prevents monitoring of consequences to other environmental impacts beyond GHG emissions (e.g.particulate matter with diameter less than 2.5 µm (PM 2.5 ) and volatile organic compounds (VOCs)).The latter issue is particularly pertinent to limiting unintended local consequences of implementing measures to curb global GHG emissions, which while benefiting climate goals, could cause disproportionate burdens to local populations [18].Without mitigation efforts, GHG emissions from cement production are expected to increase with the rising global cement demand [17,19].To ensure mid-century climate goals are not compromised, a clear pathway for decarbonization is necessary.
In this work, we provide a summary of key, frequently discussed GHG mitigation technology strategies and consider their efficacy at contributing to net-zero GHG emissions goals.We base our analysis on the production of cement in California, as this is the first region to have passed legislation requiring this shift for the industry.Noting that measures are frequently considered in isolation, we then examine how the efficacy of measures changes as a function of using multiple mitigation strategies in sequence.Further, we use these measures to quantify the ability to meet net-zero emissions and the effects of these measures on other environmental impacts that could influence local populations (and as a result, policies).Finally, we discuss potential qualitative cost impacts associated with each strategy.

Methods
To quantify the reduction of GHG emissions from mitigation strategies and to initiate exploration of co-benefits or unintended consequences of netzero pathways to other environmental impacts, we conduct a series of environmental impact assessments based on life cycle assessment methodologies.Noting pressing legislation in California, we conduct measurements using current cement production in California as our baseline.We use environmental inventories and impact assessment models from OpenConcrete (see supplementary materials for model details), an open data environmental quantification tool [20], which reports GHG emissions (modeled using 100a global warming potentials for CO 2 -eq from the IPCC [21]) as well as 10 other environmental impacts.Here we examine emissions of nitrogen oxide (NO X ), sulfur oxide (SO X ), particulate matter (PM) with diameter less than 10 µm (PM 10 ), PM 2.5 , VOCs, carbon monoxide (CO), and lead (Pb), as well as water consumption and energy demand.This assessment focuses on cradle-to-gate, just before cement is sent for concrete production (see figure S1).
Here, noting that the majority of GHG emissions from concrete are driven by cement production and California's legislation targets the cement industry, we focus on the efficacy of technologies within the cement sector.The type of cement plant (e.g.new build or retrofit) is not considered in this study.The basis of comparison is the production of 1 kg of cement or 1 kg of a cement alternative.The baseline to which these strategies are compared uses the US Environmental Protection Agency's (US EPA's) Power Profiler for California in 2020 to determine electricity grid [22] and the California Air Resources Board Greenhouse Gas Mandatory Reporting Program for 2017 to determine cement kiln fuel mixture [23].We examine six mitigation methods that are highlighted by the International Energy Agency (IEA) [19], the Global Cement and Concrete Association (GCCA) [16], and the Portland Cement Association (PCA) [14] as key methods to reduce GHG emissions from cement production in California:

Energy efficiency and 'clean' electricity grid use.
Increased energy efficiency provides emissions reductions by lowering the energy demand, and thus emissions from energy resources.For the purposes of this work, we consider this strategy to also include switching the electricity mix used throughout cement production to less carbonintensive energy solutions (e.g.renewable energy such as wind power).In California, all plants have already adopted the use of efficient dry kilns with preheaters and precalciners [12,13].In this work, this mitigation strategy switches the electricity mix used in California (from the US EPA [22]) to one with 100% wind power (modeled as zero GHG-emitting electricity sources, based on emissions factors in OpenConcrete [20]).2. Fuel switching in kilns.In California, the GHG emissions from the fuel required for thermal energy in cement kilns represents about 35% of total GHG emissions from cement production [13].Thermal energy fuel switching happens at the clinker production level by replacing the fuel used in cement kilns from high emitting resources (e.g.coal) to less carbon intensive fuels (e.g.natural gas, biomass).Natural gas as a kiln fuel generates less GHG emissions to produce 1 kg of cement than coal (environmental impacts of fuel types are based on values in OpenConcrete [20]), while biomass and certain waste fuels are frequently considered to have neutral (net-zero) GHG emissions [19].However, it must be noted that the carbon accounting of such energy resources as netzero is not consistently accurate.In some cases, biomass and certain waste fuels cannot entirely replace conventional fuels if they cannot provide a high enough temperature in the kiln [24] or if local policies preclude use of particular energy resources.A switch to natural gas is already happening in the US, while the switch to biomass for kiln fuel is currently happening in Europe [12,13].
On the global stage, cement companies in Europe and China are currently exploring electrification of cement kiln [25,26], presenting an opportunity for California to adopt.It should be noted that novel fuel alternative technologies such as concentrated solar [27] and hydrogen fuels [28] have also been discussed to reduce thermal demand in cement kilns; however, due to a lack of technical maturity these strategies are not included in this study.

Clinker reduction through use of mineral
additives.High amounts of CO 2 emissions occur during clinker production due to chemicalderived emissions from the decarbonation of limestone in kilns in addition to emissions from the fuel combustion required to heat the kilns.Consequently, decreasing the clinker demand of cement can reduce its associated GHG emissions.Supplementary cementitious materials (SCMs) as partial substitutes to cement are a common method to lower the amount of clinker in cement or to lower the amount of high-clinker content cement in concrete; it must be noted, it is most common in the US (and in California) to include SCMs at the concrete batching stage.
Here, we consider common SCMs such as fly ash, ground granulated blast furnace slag (GBFS), natural pozzolans (including calcined clays), and limestone among these mineral additives (environmental impact data for all SCMs are from OpenConcrete [20]).Depending on the mineral additive used, the levels of clinker replacement commonly ranges from 15%-50% (with even higher replacement levels possible) while still meeting performance requirements [29][30][31][32][33][34] (table S1 shows clinker replacement levels considered here).While currently less common in California, clinker reduction can also occur at the cement production stage (see figure S1) as is commonly the case of binary blended cements, such as with Portland-Limestone cements (PLC) and ternary blended cements, such as calcined clay limestone cements (LC 3 ).These blended cements can have clinker-replacement levels from 15% to 45% while still meeting performance requirements [35,36] [38].Table S2 in the supplementary materials summarizes the AAMs considered from our earlier work [39,40] and from the literature [41].Environmental impact data for solid precursors are modeled from OpenConcrete, while ecoinvent v2.2 is utilized for alkaline activators.

Carbon Capture, Utilization, and Storage (CCUS).
CCUS can be incorporated at the cement and/or concrete production stages.Within this value chain, post-combustion carbon capture and storage (CCS) of cement (which captures the flue gas generated from fuel combustion and limestone decarbonation) is the most widely researched technology, but it can also be used in carbon capture and utilization (CCU) at the concrete level batching [42].Some studies have reported that the injection of CO 2 at concrete batching can reduce the quantity of cement needed in concrete when paired with proper mixture design, thus reducing the GHG emissions associated with cement production [42,43], while others have reported an increase in GHG emissions in some cases [44].We note that in California, some cement plants are attempting to collaborate with emerging companies to incorporate CCU systems at the cement plant level [45].Current barriers to CCS implementation in California, and in the whole US, include the lack of pathways for pipeline installation and the time-consuming permitting required for permanent CO 2 storage (e.g.injection into geological reserves).In this work, post-combustion CCS is modeled with MonoEthanolAmine (MEA) scrubbing to chemically separate CO 2 from the flue gasses collected, based on models from The International Energy Agency (IEA) [46].Environmental impact inventory data for MEA production is taken from ecoinvent 2.2 [47].A combined heat and power (CHP) plant powered by natural gas is modeled to provide steam for MEA regeneration, as well as meet the remaining electricity requirements of the cement plant.The energy demands for the CHP are modeled based on Ravikumar et al [44].The amount of CO 2 captured (∼90% of total postcombustion cement production CO 2 emissions) is modeled based on reports from the IEA [46].
Lastly, the calculated GHG emission reductions are used to generate a technology roadmap for years 2025, 2035 and 2045.The timeline of deployment for each mitigation technology is based on their technology readiness levels (TRLs) pulled from reports for each of the considered technologies [48][49][50].The TRL scale follows the National Aeronautics and Space Administration (NASA) [51] classifications, commonly used in the US.The solutions range from ready for immediate deployment (e.g.increased use of SCMs) to requiring further technology validation (e.g.some alternative-clinker cements).

Efficacy of emissions-reducing strategies
A summary of the effects of the GHG emissions mitigation strategies considered in this work are presented in table 1.Here, the efficacy of each strategy is considered relative to the baseline of current California Portland cement production (0.846 kg GHG per kg cement).We note that cement kiln efficiency improvements could not be considered as a strategy because California already uses energy-efficient kilns.However, switching the electricity mix used throughout the production of cement and concrete was examined and only provides a 4% GHG emissions reduction.In California, about 74% of a cement kiln's fuel mixture is from coal and petroleum coke, and 9% is from natural gas [23].By using a fuel source with lower GHG emissions per MJ fuel and with appropriate properties to satisfy required processing conditions (e.g.natural gas) [52], fuel switching leads to a 15% decrease in GHG emissions for producing cement.If this were entirely natural landfill gas, a greater reduction in GHG emissions is possible due to its even lower carbon intensity [53].Due to the lower calorific value of most organic materials, the biomass fuel switching scenario modeled here utilizes 80% biomass and 20% natural gas, and results in an 8% reduction in GHG emissions.We note that if all thermal energy resources could be met through electrifying the cement kiln and a renewable energy grid was used, the greatest reduction in GHG emissions, 38%, could be achieved.
At the concrete batching stage, a 50% reduction in clinker with GBFS replacement leads to a 33% reduction in GHG emissions per kg of cement produced.Whereas at the cement production stage, a lower level of reduction in clinker with interground limestone (here modeled as 15% weight of cement to reflect blended PLC) leads to a 14% reduction in GHG emissions per kg of cement produced.LC 3 is a ternary blended cement (e.g. a mixture with Portland clinker and two other mineral binders) which reduces the clinker content in cement by 45% (here modeled as 15% from interground limestone and 30% from calcined clay) and leads to a 40% reduction in GHG emissions.
The C$AB cement modeled here reduces the thermal energy demand required in the kiln by 36% and has lower limestone decarbonation emissions, which leads to a 42% reduction in GHG emissions.In the case of the magnesium oxide cement (MOMS), the thermal energy demand reduces by 56% and has no limestone decarbonation emissions, which alone yields a 78% reduction in GHG emissions.If solidified via carbonation, the periclase magnesium oxide (MgO) in this cement also uptakes 0.524 kg CO 2 per kg of cement product, which brings the total reduction in GHG emissions for MOMS to 140% (a net uptake of CO 2 if proper CO 2 sources and processing are used).The elimination of thermal demand and limestone decarbonation emissions established by AAMs, allows for over 80% reductions in GHG emissions for mixtures with only one alkaline solution and the same solid precursors (GBFS and natural pozzolans).However, when the mixture utilizes different solid precursors (calcined clay and limestone), the efficacy of this strategy reduces to 63%.An 18% increase in GHG emissions compared to conventional cement is seen when an AAM uses the same solid precursors (GBFS and natural pozzolans) but with higher proportions of two alkaline solutions (sodium hydroxide and sodium silicate).Due to the high versatility in AAM mixture combinations, a large range of environmental impacts are possible as seen here.
Post-combustion CCS at the cement plant results in an 87% reduction in GHG emissions based on our model.This strategy produces conventional cement while capturing the flue gas from fuel combustion and limestone decarbonation.It is important to note, the energy required to capture the CO 2 emissions increases energy demand by 98% compared to conventional cement production.The rationale for differences between percent reduction in GHG emissions and percent efficiency of the CCS system is detailed in the supplementary materials.

Influence on combined mitigation efficacies
When examining each mitigation strategy in isolation, the reduction in GHG intensity for some technologies appear significant (e.g.88% reduction for AAMs).If two strategies are implemented together (e.g.88% reduction for AAMs and 87% reduction for CCS), it may initially appear that the total reduction of these two strategies can achieve over a 100% reduction in GHG emissions or net-negative (in the case of AAMs and CCS, 175%).However, reductions are not additive because once a mitigation strategy is implemented, the magnitude of reduction from the following implemented strategies decrease.So, if all cement plants have already implemented CCS technologies, the new GHG-intensity becomes 0.112 kg GHG emissions per kg of cement (see table 1) and then implementing the most effective AAM mixture will only actualize an additional 1% reduction in emissions (see figure 1).Similarly, if the electricity grid used for all cement plants is already fully renewable, adding kiln fuel-switching to natural gas will only yield a 17% decrease in GHG emissions per kg of cement instead of what might be an anticipated 20% reduction by adding both individual efficacies from table 1. Figure 1 shows the changes in efficacy of combined strategies.The change in emissions reduction of each mitigation strategy is based on the time in which other strategies are deployed.To keep it simple, we assume only one technology type is first implemented.However, all technology types are considered as secondly implemented.For the first implemented technologies, the electricity switch is modeled as 100% wind power; the fuel switch is 100% natural gas; the SCM is modeled as fly ash; the clinkered alternative cement is modeled as magnesium oxide cement; the AAM mixtures includes Na 2 SO 4, GBFS and natural pozzolans; the CCS is post-combustion at cement plants.The color shading represents the difference in efficacy between the two methodologies.Because their effectiveness changes as mitigation strategies are implemented, it is critical to look at these strategies in combination with each other when addressing climate goals.Savings gained from technologies we implement later down the line (after some mitigation measures have been put in use) will not be as effective as they are modeled today.

Co-benefits and unintended consequences of GHG emission mitigation strategies
In addition to GHG emissions, cement production also drives environmental burdens of NO X , SO X , PM, VOC, Pb and CO emissions as well as water consumption and energy demand.Air pollutants are linked to human health impacts, quality of life and mortality rates [54].Particularly, NO X , SO X and VOC emissions are precursors to PM emissions, which are linked to a wide range of diseases.These local burdens will affect populations neighboring cement plants, but they will not have the same global burdens as climate change.It is critical to explore the effects of mitigation mechanisms on varying environmental impacts concurrently to ensure technologies mitigate human health impacts in addition to GHG emissions.As such, figure 2 displays the influence of the GHG emissions mitigation strategies to nine additional environmental impact categories.
For most GHG emissions mitigation methods considered in this work, other environmental impacts follow similar reduction trends (i.e.there are cobenefits).However, there are a few key outliers.AAM mixture RS1 shows increases to all additional impact categories considered (i.e.there are unintended consequences), except for water consumption.For the CCS modeled in this work all impact categories, except for PM 2.5 , PM 10 and SO X emissions, are increased due to the production and regeneration of the chemical (MEA) used to separate CO 2 .The instances with increases to environmental impacts for RS1 are attributed to its high proportion of alkali solutions, and we note AAMs can be engineered with desirable performance and lower quantities of activator.In figure 2, water consumption is reduced for all strategies considered, with the exception of CCS.SO X emissions are reduced for all strategies, except for AAM mixture RS1.Pb emissions and energy demand are reduced for all categories except for AAM mixture RS1 and for CCS.NO X emissions are reduced in all strategies except for CCS, due to the increase in thermal demand modeled, and for two cases of AAMs, due to the high proportion of alkali solutions.In the cases of alternative cements and AAM mixture RS1, both PM 10 and PM 2.5 emissions (herein referred to jointly as PM) are increased.The alternative cements modeled all have a higher amount of raw material than our baseline cement, and thus a higher amount of PM emissions associated with raw material extraction.For all remaining cases, the PM emissions are also reduced.VOC emissions are reduced in all strategies except for AAMs and CCS, both due to the increases in chemical solutions.Particularly high increases to VOC emissions for all AAM cases result from the addition of alkali-activator solutions (e.g.NaOH), which have high VOC emissions during production.Based on emissions factors used in this work, natural gas has a higher CO emissions-intensity compared to coal or petroleum coke fuel (the majority of fuel used in California cement kilns), and therefore switching to fully natural gas emits slightly higher CO.Although increasing biomass fuels in cement plants can promote a circular economy by incorporating residue natural resources, emissions factors used herein indicate potential for higher NO X , VOC, CO emissions as well as water consumption.This shift is due to the increased emissions from upstream agricultural impacts from farming the primary plant.Addressing these trade-offs when selecting climate-beneficial solutions provides a more comprehensive understanding of potential unintended consequences as well as co-benefits, allowing local governing agencies to provide targeted regulatory protections (for strategies with unintended consequences) and incentives (to accelerate use of strategies with co-benefits).

Decarbonization roadmap
The roadmap in figure 3 introduces mitigation strategies based on the expected technical maturity at Although a 96% reduction is a significant improvement in GHG emissions, this means for California to meet net-zero emissions, technologies beyond cement production will need to be utilized.Recent studies have found direct air capture (DAC) to achieve net-negative CO 2 emissions [58,59] (e.g.DAC technologies emits less CO 2 than is captured and stored).Technologies like DAC will play a crucial role in assisting the cement sector in achieving net-zero emissions.

Cost considerations
While not the focus of this work, cost is an important consideration when evaluating emerging cement technologies as it impacts their feasibility, timeline, accessibility, and potential for widespread adoption.Table 3 qualitatively shows influences on costs for the GHG emissions mitigation strategies assessed

Mitigation strategy
Influences on cost

Electricity switching
Renewable energy prices have seen declines in recent years.It is projected to be a cost competitive option for fossil fuels, as the cost to build new renewable energy plants (e.g.solar farms and onshore wind) is lower than coal plants [60].

Fuel switching
The U.S. Department of Energy estimates a $60/ton CO2 cost increase for switching from coal to natural gas in 2040 [61].Pilot projects have shown production costs doubling for cement with use of electrification [62].

Supplementary cementitious materials (SCM)
SCMs can provide cost savings on thermal demand/fuel due to the reduced clinker demand.
SCMs that are by-products from industrial processes (e.g.fly ash, GBFS) are limited to the production of their primary products.Increase in demand, with limited supply can influence the cost of these mineral additives.SCMs can impact the cement/clinker supply chain.Purchase of these alternate materials may be more expensive but can also be partially offset by reduction in cement clinker costs.
Clinkered alternative cements Some alternative cements (e.g.reactive belite Portland cement) can result in energy cost savings due to lower thermal demands while others (e.g.BYF) can increase costs due to increases to raw material demands [63].

Alkali-activated materials (AAM)
AAMs would disrupt the cement market, as it is an entirely new material to conventional cement.
Depending on the type of raw materials selected for these mixtures, some studies found AAMs to be cost competitive to Portland cement, [64] while other studies found increases in cost by 40% [65].
Carbon capture storage (CCS) Current estimates have shown CCS installations to be two times the cost of installing a new cement plant [12].Although this can impact the material cost of CCS cement, preliminary studies have shown that end-users may not experience much change in cost (∼1%) [66].
in this work.It will be critical for California, and other regions, to provide regulatory protection and financial support (e.g.incentives) when costs may act as a barrier to implementation by the cement industry.

Conclusion
As mid-century approaches, action towards meeting climate targets needs to happen quickly and collectively.There have been recent policy and industry efforts to lower GHG emissions from cement and concrete production; however, there remain limitations in utility of transparent, customizable models to draw robust comparisons among concrete mixtures to mitigate environmental burdens.Regionspecific technology roadmaps developed with open data tools will assist government and industry to work together in achieving these goals.Monitoring of environmental impacts beyond GHG emissions can inform efforts to advance climate change mitigation, while providing a broader perspective on environmental burdens that should be considered based on the needs of the local populations.Particularly, when considering mitigation strategies with high GHG emissions reduction potential, such as CCS, it is critical to quantify potential shifts in other environmental burdens and provide regulatory protections when necessary.Reduction potentials in currently available technologies show high GHG emission reduction potentials in California's cement industry, but they also highlight the need to include technologies outside the industry to reach net-zero emissions by mid-century (i.e. through the advancement of methods such as DAC).It is important to note that technologies along the value-chain and beyond the life-cycle scope of cement production (e.g.improving material efficiency in concrete; recycling concrete to promote a circular economy) must also be utilized concurrently to support swift decarbonization action.Only when all stakeholders work together to consider how mechanisms can be scaffolded will these regional and global climate goals be achieved.

Figure 1 .
Figure 1.Changes in efficacy in mitigating GHG emissions if technologies are (a) implemented in sequence and (b) as strategy reductions added together.The color shading represents the difference in (a) and (b), or the difference in methodology used to calculate the combined strategy efficacy.(CAC-clinkered alternative cements; CCS-carbon capture storage; NP-natural pozzolans).

Figure 2 .Figure 3 .
Figure 2. Increases and decreases to nine alternative impact categories for decarbonization strategies considered.Shades of blue indicate a co-benefit in alternate impact category (i.e.reductions in environmental impact), while shades of red indicate a consequence to an alternate impact category (i.e.increases in environmental impact).(WC-water consumptions; ED-energy demand.)

Table 1 .
Strategies with percent reductions in greenhouse gas emissions (GHG) for each strategy if implemented alone.

Table 2 .
Technology readiness levels (TRLs) for each mitigation strategy and estimated years of implementation.

Table 3 .
Influences to cost for cement mitigation strategies compared to conventional cement.