Forging a path to low-carbon lime

Lime and calcium products are essential building blocks to the modern world, used to purify drinking water, preserve foods, control pollution, improve crop yields, stabilize soil, pave roads and support the production of steel, cement, glass and many other industrial processes. While lime is essential to society, it also has a sizable carbon footprint. Approximately 30 percent of the scope 1 greenhouse-gas emissions generated during lime production are related to fuel combustion, while the remaining 70 percent are created by the unavoidable chemical reactions during calcination. Changing regulations impacting lime Lime operations are subject to both federal and state requirements for air emissions, water use and disclosures. At the national level, operations listed as major sources of air pollutants are subject to Environmental Protection Agency (EPA) maximum available control technology (MACT) standards. Tighter MACT standards for the lime industry are slated to go live in 2027 — however, the current administration is reviewing these regulations. In light of potential changes to federal emissions standards, some states are pursuing legislation regarding mandatory disclosures. Despite a shifting regulatory landscape, capital projects to reduce the carbon footprint of lime production can have a long-time horizon. For example, investing in fuel flexibility may entail five or more years to construct natural-gas pipelines or renewable energy sources. Carbon capture and sequestration technologies may take as long as a decade to adopt when they become feasible. As a result, lime producers must plan administration-agnostic approaches to support long-term sustainability needs five, 10 or 15 years from now. The National Lime Association has published “A Roadmap to Carbon Neutrality for the U.S. Lime Industry,” discussing the industry’s plan to become carbon neutral by 2050 and aligning the industry around a shared approach to reducing lime’s carbon footprint. By reducing carbon emissions and improving sustainability, lime producers can meet evolving regulations, provide business continuity, manage climate-related risks and help customers reduce their scope 3 emissions to meet their own sustainability goals. Confronting the challenges of sustainable lime production While low-carbon or zero-carbon lime is attainable, the road is long and has many challenges. It will require not only lime producers’ own commitment, but also supportive infrastructure, technologies and partnerships. Upgrading the energy efficiency of aging equipment — such as kilns and burners — requires significant capital expenditures and supportive infrastructure. However, only around a third of current carbon emissions from lime production can be mitigated through energy considerations. Addressing the unavoidable emissions of calcination will require advanced innovation in the field of carbon-capture technology. These investments also impact downstream sustainability, such as customer scope 3 emissions and risks associated with climate, labor and consumer product safety. Evaluating supplier sustainability has become a routine part of lime procurement for many companies. Deploying sustainable practices and technology Responsible lime companies are adopting sustainability tactics such as wastewater recycling, modernizing equipment, transitioning to cleaner energy sources and optimizing lime usage to reduce waste.Lime manufacturers mostly use fossil fuels in lime kilns, which release carbon dioxide (CO2) into the atmosphere, as well as water from city supplies and water tables for processes. Increasingly, manufacturers are looking to reduce dependence on solid fuel, enhance energy resilience and recycle water drawn from public sources. Proven methods that reduce lime’s carbon emissions include upgrading kilns, investing in natural-gas capabilities and incorporating renewable energy. Lime producers are also evaluating the feasibility of emerging technologies so they will be available when needed. Evolving kiln technology. Most new lime kilns constructed today are cleaner-burning vertical kilns, which are more sustainable than coal-fired rotary kilns, their predecessors. There are also options to incorporate renewable energy and blends, such as biomass with natural gas. Renewable energy. Lime manufacturers are exploring alternative fuels, such as hydrogen, to understand how they impact kilns, the final product and the cost of production. For example, MLC has partnered with Centrica to generate hydrogen power at their UK operation, replacing a portion of natural gas used to fuel the kilns. The proposed project has been shortlisted for the UK Hydrogen Allocation Round 2 funding. Alternative fuels can also include renewable resources such as wood chips, organic waste or even spent railway ties. Some manufacturers have already successfully implemented solutions, such as MLC’s anaerobic digestor plants in the UK, which break down organic waste to produce renewable, low-carbon electricity equivalent to 99 percent of the lime operation’s average monthly consumption. Water recycling. Stormwater can be captured and used for the manufacturing of some nonfood-grade lime products, as well as for dust suppression on site roadways. MLC uses wastewater to irrigate the hayfields the company leases to local farmers at its Ste. Genevieve, MO site. The lease agreements also require leaseholders to farm the land sustainably. Supply-chain optimization. Improving logistics efficiency can reduce the environmental impact of the lime supply chain. Distribution terminals shorten distances to customers. Transloading improves flexibility, enabling companies to minimize trucking emissions by using barge or rail for part of the journey. While these solutions are effective to address energy-related emissions, they do not address the carbon emissions that come from the lime itself when heated in kilns. One of the primary methods to address calcination emissions is through carbon-capture technology. There are carbon capture and storage (CCS) technologies that are deployable today. However, they are expensive, energy-intensive, require chemicals and risk potential CO2 leakage, creating more carbon waste streams. Technological innovation is necessary to make CCS feasible for the lime industry.It is important to note that despite the unavoidable calcination emissions from production, lime products reabsorb CO2 from the atmosphere over time. Up to 29 percent of CO2 emitted during production is reabsorbed in many major lime applications. This partially offsets production emissions and may be used in calculations for total carbon impact. Supporting sustainability in customer markets Through innovation and collaboration, lime companies can contribute directly to their customers’ sustainability. For example, lime optimized for low impurities, consistent particle sizes and reactivity can reduce volume requirements, and thus reduce the environmental footprint of transport, storage and labor. Lime manufacturers can also provide equipment and application expertise to optimize the efficiency and performance of lime processes. This promotes sustainability in many mature markets where lime plays a pivotal role — such as steel, agriculture, energy utilities and municipal water. It is also increasingly used in growing markets with demand for sustainable offerings. According to a 2022 McKinsey study titled “Accelerating toward net zero: The green business building opportunity,” the addressable market size for zero-carbon technologies and other net-zero offerings could reach $12 trillion by 2030, with the most significant opportunities in transport, buildings, power and water. Lime is used in many of these applications, including lithium hydroxide conversion for electrification, soil stabilization, and fiberglass for wind farms, carbon-absorbing building materials and flue-gas treatment in energy-from-waste plants. In addition to supporting sustainable markets, the lime industry is working to establish best practices to meet the need for measuring and sharing sustainability data. For example, a National Lime Association working group, composed of representatives from member companies and independent experts, is developing guidelines for lime product lifecycle assessments (LCAs) to create a consistent basis for environmental product declarations (EPDs). For fair carbon accounting, companies should employ a cradle-to-grave lens for the product’s entire lifecycle. Accountability through transparency Responsible lime manufacturers are partnering with third-party organizations to measure, track and report sustainability data. By tracking emissions, energy use and waste reduction with a data-driven approach, lime manufacturers strengthen accountability by clearly demonstrating tangible progress toward environmental goals. Leveraging globally recognized common frameworks for reporting sustainability data — such as SASB, GRI and TFCD — makes it easier to compare and understand performance across the industry. These frameworks highlight achievements, identify pain points and enable lime producers to improve strategies using accurate data while also fostering more credibility with customers who want to reduce scope 3 emissions. Procurement and ratings platforms like Sedex and EcoVadis can also help companies assess and share their sustainability performance. Committing to a sustainable future for lime Through strategic investment, innovation, transparency and partnership, lime manufacturers can forge a path to net-zero lime while providing reliable supply of this essential mineral to critical sectors. But the industry needs a future-focused mindset and a long-term commitment to realizing that goal.Simply meeting the minimum requirements of today — whether they are from regulators, customers or investors — is not a viable strategy for long-term success. To move the lime industry forward, manufacturers need to set ambitious but achievable goals and demonstrate continual progress.The journey to more sustainable lime manufacturing is not easy, and it is not fast. Meaningful, lasting progress takes time, continuous investment and deep commitment. Lime manufacturers that work toward that goal with a spirit of transparency, cooperation and accountability can help bring the lime industry into a new era of sustainable production, protecting the planet’s future and ensuring the industry’s long-term success.

Forging a path to low-carbon lime

Authored by: Fiona Woody

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