Global carbon removal goals are important yet daunting. One estimate suggests that “By 2050, the world must remove ten gigatons of CO2 per year.” That’s more than the current annual emissions of the United States. Excess carbon dioxide not only warms the atmosphere, it also increases ocean acidity. Atmospheric events grow more extreme, and marine ecosystems suffer.

Recently, McKinsey released a comprehensive report assessing the viability of net-zero carbon emissions goals. Its consultants take a deep dive into what it will take to achieve key carbon targets by the year 2050. Specifically, McKinsey “estimates the changes in demand, capital spending, costs, and jobs, to 2050.” It does this for economic sectors responsible for 85% of global emissions.

McKinsey’s analysis provides a framework for understanding where the planet’s atmosphere is and where it needs to be.

Emissions of Seven Global Systems

One of the report’s conclusions is clear. It is necessary to accelerate decarbonization efforts to meet 2050 targets. McKinsey estimates that the current shortfall in investment is $3.2 trillion. This seems like a massive number, but not when compared to what is produced each year. The International Monetary Fund says Global GDP (nominal) was $94.93 trillion in 2021 alone.

At the same time, leaders do not have the luxury of thinking only about carbon emissions. The atmosphere is already more dynamic. The need for more resilient structures is here and now. As always, concrete is well-equipped to answer the call.

Greenhouse Gas Emission by Sector

The McKinsey report looks at seven key sectors of the global economy. It breaks down the greenhouse gas (GHG) emissions of each.

• Power (electricity and heat generation) – 30% CO2, 3% N2O

• Industry (production of steel, cement and chemical production. Oil, gas, and coal extraction and refining. ) 30% CO2, 33% of methane, 8% N2O

• Mobility (road, aviation, rail, maritime, and all other transportation) 19% CO2, 2% N2O

• Buildings (heating and cooking) 6% CO2

• Agriculture (farm energy use, agricultural emissions, fishing) 1% CO2, 38% methane, 79% N2O

• Forestry (including land cover change) 14% CO2, 5% methane, 5% N2O

• Waste (solid waste disposal/treatment, incineration, and wastewater treatment) 23% methane, 3% N2O.

Note that three sectors, Power, Industry and Mobility, account for almost 80% of the world’s carbon dioxide emissions. Together, Industry and Agriculture are responsible for more than 70% of methane emissions. Agriculture alone accounts for almost 80% of nitrous oxide emissions.

Note that the Forestry sector provides a natural sink for carbon dioxide. Expanding forests increases the rate of carbon absorption. Unfortunately, every year, deforestation and infestation eliminate billions of board feet worth of trees from the equation.

Focus on Industry in General, Concrete Specifically

Based on 2019 data, the “Industry” category generates 30% of CO2 emissions. In turn, concrete accounts for roughly one-fourth of that total.

Decarbonizing cement and concrete production is an essential part of the net-zero quest in the Industry sector. For cement and concrete to succeed, a multi-pronged assault on emissions is essential.

Here are some contributors to the quest.

Substituting finely ground limestone

The production and use of Portland limestone cement continues to expand. Milled limestone replaces 10-15% of the Portland cement ordinarily used. Adoption is expanding, For example, in September 2021, LafargeHolcim announced it would convert its Midlothian, TX, plant to 100% Portland Limestone Cement (PLC). Its OneCem product contains up to 15% finely ground limestone.

Stronger concrete reduces the volume

Researchers continue to find ways to strengthen concrete. This makes it possible to use less concrete to meet structural requirements. This reduces a project’s carbon footprint in the process. Researchers are using everything from graphene to fibers to improve concrete performance.

Fossil fuels and calcination

Clinker production contributes more to the industry’s carbon footprint than any other process. Every year, the global cement industry uses about 350 million tons of fossil fuels (coal-equivalent).

Calcination is a high-temperature process converting raw materials (limestone, clay, shale) into clinker. Kiln exhaust gasses typically preheat the material before it goes into the kiln. This reduces fossil fuel use to a degree.

Fortunately, clinker production is well-suited to the use of alternative fuels (AF). Researchers are experimenting with a wide variety of feedstock. Biomass, waste oil, used tires and wastewater sludge are all possibilities. An optimized mix of non-recycled plastics and paper is another alternative.

Green hydrogen is an ideal AF since it is a zero-emission fuel. In the interim, blue hydrogen derived from natural gas and coal gasification can be a bridge technology. Blue hydrogen reduces carbon emissions by 80% or more.

Making better use of the heat energy already on site is another option. Waste heat recovery systems (WHRS) could generate up to one-third of a cement plant’s power needs. For example, hot gasses from the clinker cooler or pre-heater can generate steam.

Creative, longer-term solutions

Going forward, it is important for decision-makers to watch for disruptive technologies. That is, innovations that could dramatically accelerate the quest for carbon neutrality.

Hydrogen

Alternative energy sources must progress from novelty to mainstream usage. Hydrogen-powered trucks, buses and even passenger vehicles are now a reality. What if hydrogen-powered cement kilns were as well? What if onsite hydrogen production became a reality at cement plants?

One hopeful sign is that the hydrogen infrastructure is quickly evolving. The largest green hydrogen plant in the world is now under development near Montreal. Project leaders want it to go online in late 2023. A 88 Mw electrolysis installation will be able to produce 11,100 metric tons of hydrogen per year. The plant’s proximity to hydroelectric power is key to its reduced carbon footprint.

There’s a synergy to the development of a new energy source. Technological breakthroughs attract more attention, and this develops the market. As a renewable energy source, it is reasonable to assert that hydrogen is here to stay.

Concentrated solar power (CSP)

It is also possible that concentrated solar power (CSP) could power industrial processes. Clinker and steel production are two key examples. A computerized mirror array focuses heat energy with greater precision than ever. Heliogen has demonstrated the ability to achieve temperatures high enough for clinker production.

About PACA

The Pennsylvania Aggregates and Concrete Association (PACA) disseminates news about innovation and sustainability in the industry. If you have questions about your next project, please contact our team.