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Abstract
The cement industry is one of the largest producers of CO2 in the world. The widespread and common use of concrete as a building material has allowed for continued growth of the cement industry. Worldwide cement production is expected to almost double by 2050. This paper explains some of the basics of the global cement industry providing data on where cement is made today and in the future. The paper also provides an explanation of the sources of CO2 emissions in cement manufacture.

The paper explores the International Energy Agency’s (IEA) “cement technology roadmap” for CO2 emissions reductions in the cement industry. This roadmap was developed under the guidance of World Business Council for Sustainable Development and the Cement Sustainability Initiative. It calls for roughly a two-fold reduction in specific CO2 emissions per ton of cement produced. Each of the three traditional levers for the industry; energy efficiency, alternative fuels, and clinker substitution will be explained. The limits for each lever will be identified, thus identifying the gap that will exist after current known levers are exhausted.

As a main conclusion, we can say that given the magnitude of the challenge ahead, even with the sectorial approach promoted by the IEA, the cement industry will likely have to rely heavily on carbon capture and storage to meet the CO2 reduction targets. This would imply very high operating and capital costs for the industry and mandates further innovation. Lafarge’s AetherTM cement is one such example with a CO2 footprint reduced by up to 30%.

Introduction
In this article, unless otherwise mentioned, we use units from the International System.

The cement industry is one of the largest producers of CO2 in the world. According to IEA data [IEA(2010)], in 2007, the cement industry was responsible for 2.0Gt (billion tons) of CO2 emissions which represents a share of 26% of the industrial emissions of CO2 (7.6Gt) and a share of 7% of the total manmade CO2 emissions (29Gt). The cement manufacturing process requires large amounts of thermal and electrical energy. This energy requirement combined with the widespread use of concrete in global construction defines the magnitude of the challenge at hand.

Defining the terms
Cement or more precisely Ordinary Portland Cement (OPC) is a manufactured inorganic substance. Cement is the powdered binder that is used almost exclusively to produce concrete. Concrete is produced by adding cement to a mixture of sand, aggregate and water. Different chemical admixtures are often added to enhance specific properties of the concrete. Cement is the “true” binder that transforms the mixture into the artificial stone known as concrete. The cement provides cohesion and strength to the mix as well as low permeability and high durability.