Cement
Portland and masonry cement are hydraulic cements that can set and harden under water. Cement is made by controlled high-temperature burning in a horizontally-mounted, rotating refractory-lined cylindrical steel vessel called a rotary kiln of a measured blend of calcareous rock (usually limestone) and, as needed, lesser quantities of siliceous, aluminous and ferrous materials.
Portland cement can be sold directly to concrete manufacturers or other customers, converted at the cement (or concrete) plant into blended portland cement product of similar properties by adding other cementitious or pozzolanic extenders (siliceous materials requiring added lime to become cementitious), or can be mixed with plasticizing materials such as ground limestone or lime to make masonry-type cements used in mortar.
Environmental Impact on Air Quality
Air pollutants associated with cement manufacturing may be characterized as follows: (please note: some of the pollutants may not be present at significant mass rates or measurable concentration levels at some Canadian facilities)
Criteria Air Contaminants (CAC):
- Particulate Matter (total PM or TPM, PM10, and PM2.5)
- Nitrogen Oxides (NOx)
- Sulphur Oxides (SOx)
- Carbon Monoxide (CO)
- Volatile Organic Compounds (VOC) - e.g. Benzene, Toluene, Ethylenebenzene, Xylene.
- Ammonia (NH3)
- Carbon Dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O)
Other Substances:
- Acidic Compounds - e.g. Hydrogen Chloride (HCl), Hydrogen Fluoride (HF), Sulphuric Acid (H2SO4)
- Heavy Metals - e.g. Arsenic (As), Cadmium (Cd), Chromium (Cr), Lead (Pb), Mercury (Hg), and Nickel (Ni)
- Organic Compounds - e.g. Polychlorinated Dibenzo-p-dioxins (PCDD), Polychlorinated Dibenzofurans (PCDF), Polychlorinated Biphenyls (PCBs), Hexachlorobenzene (HCB), Polycyclic Aromatic Hydrocarbons (PAHs)
Annual mass emissions of the main air pollutants are shown in the following table.
| Province | TPM kt | PM10 kt | PM2.5 kt | NOx kt | SOx kt | VOC kt | CO kt | CO2 mt |
| Quebec | 0.8 | 0.7 | 0.4 | 9.5 | 6.1 | 0.0 | 1.4 | - |
| Ontario | 4.6 | 3.6 | 1.7 | 23.3 | 26.4 | 0.1 | 10.5 | - |
| Saskatchewan | na | na | na | na | na | na | na | - |
| Alberta | na | na | na | na | na | na | na | - |
| British Columbia | 1.1 | 0.7 | 0.3 | 0.3 | 4.0 | 0.1 | 1.2 | - |
| Total | 13.7 | 7.2 | 3.2 | 40.9 | 41.8 | 0.3 | 14.4 | 10.3 |
| All Industrial Sectors | 572.7 | 259.9 | 140.7 | 654.4 | 1,536.5 | 987.6 | 1,358.0 | 117 |
| Percent of Total Industrial Emissions | 2.4 | 2.8 | 2.3 | 6.4 | 2.7 | 0 | 1.1 | 8.8 |
Source: Environment Canada National Emissions Inventory-2000
Canadian Context
Canadian producers operated 16 portland cement manufacturing facilities in five provinces in 2001-2003. Fifteen produce grey cement and one produces white cement, which is used in concrete for architectural applications. White cement is made from raw materials low in iron and manganese and takes more energy to produce than grey cement.
The total world production of portland cement was 1,652 million tonnes in 2001. Canadian production accounted for less than one percent (about 13.6 million tonnes cement) and United States production accounted for approximately five percent (91 million tonnes cement).
Canadian Cement Manufacturing Sites (2001-2003)
Emissions Management Practices and Regulations
In 1974, Environment Canada promulgated National Emission Guidelines that prescribed limits for particulate emissions from the cement manufacturing industry.
Voluntary, non-regulatory emission limits are contained in two National Guidelines of the Canadian Council of Ministers of the Environment (CCME) as follows:
- National Emission Guideline for Cement Kilns (NOx Guideline- published in 1998): This guideline sets a NOx limit of 2.3 kg/t clinker (monthly average) for large new cement plants of capacity greater than 1,500 tonnes per day built after January 1, 1998.
- National Guidelines for the Use of Hazardous and Non-hazardous Wastes as Supplementary Fuels (Hazardous Waste Guidelines - published in 1996): These Guidelines contain emission limits for total particulate matter, metals, hydrogen chloride, and PCDD/PCDF.
All provincial jurisdictions have operating permit programs. The form of emission limits varies among jurisdictions and while all address PM (limits vary from 25 to 120 mg/Nm3), not all of them have provisions for NOx, SOx and other pollutants. One facility has a NOx mass rate limit and one has a SOx mass rate limit prescribed. Several jurisdictions namely, Alberta, Ontario and Quebec also have either general regulations that apply broadly to industrial sectors or specific regulations that apply to cement manufacturing.
In addition to regulatory programs, a number of policy and program initiatives are underway in several of the provinces in which cement plants operate. The provinces of Ontario, Alberta and British Columbia are at various stages of implementing air management strategies that identify industries' share in emission reduction programs to meet ambient air quality goals as well as to reduce the regional transboundary transport of air pollutants to the United States. In 2002-2003, the Province of Quebec was in the process of developing new standards for industry sectors as part of a broader regulatory program update.
Take Action
Supplementary cementing materials, either used to replace cement in blended cements or used in concrete mixes, offer significant potential to conserve raw materials and fossil fuels thereby avoiding pollution generated in the cement manufacturing process.
The application of best available techniques including process design, process control optimization, high efficiency dust collectors, primary NOx control measures, and post-combustion control technologies have the potential to reduce future emissions and offset the general trend to increasing emissions as clinker/cement production increases.
Continuous improvement across all sources of pollution is a critical component of effective environmental management.
There are many opportunities to take action and reduce pollution.
