Modernizing cement manufacturing in China leads to substantial environmental gains

Buildings and construction account for roughly 40% of global final energy use and energy- and process-related greenhouse gas emissions, with cement as an essential input. China has been the largest producer and consumer of cement for decades, peaking around 2014, and has rapidly shifted its cement manufacturing technologies (CMTs) from shaft kilns and other rotary kilns to new suspension preheater (NSP) rotary kilns. Despite numerous studies on environmental burdens of cement, gaps remain: the national-to-provincial pathway of CMT transformation and its environmental implications have not been mapped; key non-climate impacts (e.g., fossil depletion, photochemical ozone formation) need comprehensive assessment; provincial heterogeneity and local soil/water impacts are underexplored; and the cumulative environmental achievements of China’s modernization efforts have not been quantified. This study addresses these gaps by reconstructing CMT evolution from 1996–2021, assessing life-cycle environmental impacts, mapping provincial burdens, performing scenario analysis to quantify gains from technology upgrades, and benchmarking CO2 and electricity intensities internationally.

Prior research has documented China’s cement dominance and associated emissions (e.g., CO2, NOx, heavy metals) and analyzed life-cycle impacts of cement production. However, earlier work often emphasized climate change while underrepresenting other important categories such as fossil depletion, photochemical ozone formation, terrestrial acidification, and ecotoxicity. Studies have noted provincial variations in industry structure but rarely quantified the provincial evolution of CMTs or localized environmental impacts. Policy efforts to close outdated capacity and promote cleaner production have been discussed, yet their aggregate environmental outcomes over time were not comprehensively evaluated. This study builds on and extends these literatures by integrating national and provincial CMT shares, conducting LCA across major kiln types, and quantifying the environmental gains attributable to modernization.

Industrial structure and CMT shares: The authors estimated provincial and national market shares of three major cement kiln technologies—shaft kilns, other rotary kilns (e.g., wet-process, dry hollow, vertical preheater), and NSP rotary kilns—from 1996 to 2021. Using reported NSP market shares for 2005–2009, they applied linear regression to infer NSP shares from 2001–2021. Shares of shaft kilns and other rotary kilns were derived using field investigations (2006, 2012) and equations relating designed capacities and observed NSP penetration. Pre-2000, when NSP accounted for <10% of production, only shaft and other rotary kilns were considered. National production by CMT was computed by multiplying total cement output by the corresponding CMT shares. Data sources include China Cement Almanac, Almanac of China Building Materials Industry, and the National Bureau of Statistics of China. Life-cycle assessment (LCA): The study conducted process-based LCA of 1 ton of ordinary Portland cement (functional unit), covering resource extraction, raw material preparation, clinker calcination, and cement grinding. Transport and packaging were excluded. Life-cycle inventories for the three kiln types were compiled from Chinese studies (Gong, Yu, Li). Modeling was performed in GaBi v10.5 using ReCiPe2016 v1.1 midpoint(H). Eight impact categories were assessed: climate change (kg CO2 eq), fossil depletion (kg oil eq), photochemical oxidant formation (kg NOx eq), terrestrial acidification (kg SOx eq), particulate matter formation (kg PM2.5 eq), human toxicity and terrestrial ecotoxicity (kg 1,4-DCB eq), and freshwater consumption (m3). Midpoint normalization used world 2010 factors to compare relative contributions across categories. Scenario analysis: Two scenarios were constructed to quantify environmental gains from CMT upgrading over 1996–2021. Actual Situation used observed CMT shares and production. Assumed Scenario held technology constant as if no NSP adoption occurred after 2000, fixing the shares of shaft and other rotary kilns at their 1996–2000 average levels. Annual and cumulative environmental impacts were computed by combining total production, CMT shares, and kiln-specific characterization factors, enabling estimation of percent reductions attributable to modernization. International benchmarking: For cross-country comparison, the study calculated average CO2 emissions per ton of cement by dividing total cement-related CO2 emissions by total cement production for each country and year (1990–2015), and compiled electricity use per ton of cement by country for 2018 from the IEA. This contextualized China’s performance relative to peers and linked observed intensities to technology mixes (e.g., NSP penetration, use of alternative fuels, waste heat recovery).

• Technology transition: NSP rotary kilns expanded rapidly after 2001, overtook other technologies in 2007, became dominant after 2010, and reached ~99% of China’s cement production by 2021. Cement output grew sharply from 2001, peaking at 2476 Mt in 2014 before gradually declining.
• Environmental impact profile: The most significant impact categories for cement manufacturing are fossil depletion (FD), climate change (CC), and photochemical ozone formation (POF). With CMT upgrading, the dominant impact shifted from FD to CC. Local soil/water-related burdens are mainly terrestrial acidification (TA) and terrestrial ecotoxicity (TE).
• Performance of NSP kilns: NSP rotary kilns markedly reduce environmental impacts compared to shaft and other rotary kilns due to higher production efficiency, better heat utilization (shorter kiln), and advanced burners (e.g., multi-duct pulverized coal, enabling lower NOx and alternative fuels). Approximately 50% less fossil fuel is consumed in NSP systems relative to older technologies.
• Provincial dynamics: Environmental burdens correlate with production scale and technology mix. Guangdong, an early adopter of NSP, exhibits stronger alleviation in particulate matter formation (PMF) despite production growth, whereas Sichuan shows less mitigation when upgrades lag.
• Environmental gains from modernization (1996–2021 cumulative, Actual vs Assumed Scenario without NSP): PMF −53%, TA −47%, TE −34%, POF −30%, CC −29%, human toxicity −25%. Resource savings include ~2270 billion tons of fossil fuel and ~28 billion tons of freshwater.
• International comparison: By 2015, China’s and India’s average CO2 intensities were below 400 kg CO2 per ton of cement, while Vietnam exceeded 500 kg/t, reflecting its continued reliance on shaft kilns (<30% rotary kilns). In 2018, electricity use per ton of cement was >130 kWh/t in Canada and the U.S. (linked to increased alternative fuel use), versus ~80 kWh/t in China and India, where NSP share exceeded 95%. China’s widespread excess heat recovery (~90% of clinker capacity equipped) and India’s efficient grinding systems contributed to lower electricity intensities.

The modernization of China’s cement manufacturing technologies yielded substantial environmental benefits across multiple impact categories, confirming that transitioning from shaft and other rotary kilns to NSP systems effectively reduces energy and emissions. Regional analysis underscores that impacts concentrate in major production provinces and depend on local technology mixes, important for targeting mitigation where resource extraction and pollutant releases (e.g., heavy metals to soil/water) are most acute. Policy and technology pathways include further deployment of innovative pollution-reduction measures (renewable energy, carbon capture and storage), fuel and raw material substitutions aligning with modern concrete technologies, and utilization of green building material certifications (e.g., EPDs) to steer markets toward low-carbon products. Globally, where outdated kilns dominate (e.g., Vietnam), prioritizing CMT upgrading and stricter emission standards, consolidating capacity, and phasing out obsolete plants can substantially cut impacts. In markets already dominated by NSP, coordinated management of key pollutants (CO2, SO2, NOx), broader adoption of excess heat recovery, switching to low-carbon, low-moisture fuels, improving auxiliary equipment efficiency, and advanced grinding (high-pressure rolls, vertical roller mills) can further reduce burdens; however, additional measures (e.g., low-NOx combustion, staged combustion, SCR) are needed to address photochemical oxidant formation.

China’s cement industry underwent a major cleaner production transition from shaft and other rotary kilns to NSP rotary kilns, reaching ~99% NSP market share by 2021. This shift, uneven across regions with slower progress in some western and northern provinces, significantly reduced environmental impacts across multiple categories. The dominant environmental burden shifted from fossil depletion to climate change as technology advanced, with NSP kilns consistently outperforming older technologies. By 2021, cumulative reductions relative to a no-upgrade scenario were substantial (PMF −53%, TA −47%, TE −34%, POF −30%, CC −29%, HT −25%), alongside large savings in fossil fuels and freshwater. International benchmarking shows China’s lower CO2 and electricity intensities compared to many developed countries, attributable to advanced technologies such as NSP and excess heat recovery. Future work should emphasize pollutant co-control, further energy efficiency improvements, low-carbon fuels, CCS, and policy instruments (e.g., EPDs) to drive continued decarbonization and environmental performance both in China and globally.

Key limitations include: (1) limited data on provincial CMT market shares necessitated the use of linear regression to estimate trends from 1996–2021; (2) lack of province-specific life-cycle inventories led to application of a national LCI, which may obscure regional differences; and (3) variations in cement product categories (e.g., 32.5, 42.5, 52.5) across regions imply differing manufacturing requirements and environmental impacts not fully captured here. Further engagement with local associations and enterprises is needed to refine CMT shares, develop provincial LCIs, and characterize regional product mixes and their burdens.