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JULY 2006


Use of alternative-fuels in cement kilns debated

The use of alternative fuels in cement kilns continues to spark debate among industry, civil society and nongovernmental organizations.

Cement production is characterized by an extremely high-temperature combustion process, most commonly using fuels such as coal, natural gas and other nonrenewable resources.

In the drive towards sustainability, cement manufacturers have recognized their responsibility to manage the environmental impact associated with the manufacture of their product and, as part of this commitment, the industry is pursuing an ongoing strategy of reducing nonrenewable fuel use through the adoption of alternative fuels, also referred to as waste-derived fuels.

The use of alternative fuels in cement kilns is widespread and various countries, including the UK, the Netherlands, Germany, Sweden and the United States have cement companies that use alternative fuels. Natal Portland Cement (NPC) operations manager Laurence Stevens comments, “The cement industry has clearly embarked on a trend toward applying the principles of the so-called industrial ecology, based on using by-products of other industries as raw materials and fuel.

“This trend was inspired by the self-containment of most natural ecosystems that normally produce waste.” However, the term ‘alternative fuel’ is the cause of some contention.

According to Groundwork director Bobby Peek, the debate surrounding alternative fuel use is “being fudged by cement companies”.

“Cement companies are proposing to burn hazardous waste. But by attempting to create a debate that hazardous waste is an alternative fuel, this could, in turn, result in hazardous waste being reclassified as a fuel which could potentially lead to the importation of hazardous waste into South Africa, a practice that is forbidden by the Basel Convention and Bamako Convention,” elaborates Peek.

The technical and environmental review published by the European Cement Association refers to alternative fuel materials as those that are rich in energy and can be used to replace coal or gas, provided they do not contain harmful substances.

Holcim South Africa alternative fuels manager, Johan Schoonraad argues that a common misconception about alternative fuel use is that all alternative fuel, in the categories earmarked, are suitable; instead, alternative fuels are based on very specific waste streams.

“We have strict rules about what materials can and cannot be used. In addition, we have a ‘no-go’ list, which is strictly adhered to, that prohibits the use of untreated medical waste, radioactive waste, explosives, high-cyanide wastes, asbestos-containing wastes, bio-hazardous wastes, electronic wastes and unsorted municipal garbage, among others.”

Holcim South Africa cement operations director, Dr. Stephan Olivier continues, “We are not becoming waste collectors. The material required for our operations must be of the correct volume and chemical composition.”

To assist in the sourcing and collection of these specific waste streams, Holcim has formed a joint-venture company with Enviroserve, to oversee this operation.

In addition, the company is in talks with other waste producers and petrochemicals companies. However, Earthlife Africa director Richard Worthington believes that the use of waste as alternative fuel serves to entrench the current unsustainable waste-management and waste-generation practices, as he explains that, in many cases, waste could be designed out of industrial systems.

Worthington believes that the use of waste material in cement kilns is, at best, a dressed-up form of disposal, despite industry arguments that cement producers are reusing waste and are part of the waste hierarchy (minimize, reduce, reuse and recycle).

In the case of Holcim, Worthington comments that many of the materials considered by the company as alternative fuels are waste streams that it should just not be generating.

“In some cases, there are products we need to replace, particularly a number of petrochemical products.” These materials include tires, rubber, paper, sludge, plastics, solvents and industrial tars.

“Kilns are very expensive and cannot be put at risk. As a result, we, at Holcim, are incredibly careful about what we place in the kilns.

“In addition to large volumes we also need materials of which the chemistry will remain constant,” says Schoonraad. Schoonrad explains Holcim’s policy: “Only if a material does not lend itself to recycling, do we consider using it.”

Tires are a classic example. “The rubber industry is able to recycle about 40% of used tires at the most; the remaining 60% are probably subjected to incineration or assigned to landfill sites adding to the burgeoning issue of waste disposal globally,” indicates Schoonraad.

Peek, however, disagrees. “There are various acceptable ways of dealing with waste tires globally that do not result in incineration – one of which is using tires to mix with tar for road surfaces.” Consequently, the use of cement kilns, in terms of community waste-management options as effective alternatives for the disposal of selected waste materials when compared to conventional disposal techniques, are championed by cement manufacturers.

Stevens also emphasizes the use of kilns to assist society in safely disposing of waste, after approval by the waste-management hierarchy.

“This service will reduce the size of landfills; create a new waste market, new companies and job opportunities.

“In less developed countries or regions, it has the added bonus of creating waste management infrastructure and promoting economic and social progress,” says Stevens.

Peek, however, insists that burning hazardous waste is not a suitable way to deal with such material.

“Also, the burning of chlorinated waste may lead to the formation of dioxins and other persistent chemicals which are proven carcinogens,” says Peek. Schoonraad concedes that a poorly-run combustion process does have the potential to release some dioxins but is quick to point out that cement kilns have rigidly-controlled operational conditions to ensure quality of cement.

Schoonraad points out the stringency of Holcim’s national and international standards, which include the installation of monitoring equipment, annual testing, free flow of information and a strict internal focus on emission control.

Cement kilns are permitted and regulated by government as cement-manufacturing facilities and, as such, they do not have to meet the same stringent standards of performance and emissions limits as “hazardous-waste incinerators to safeguard human health”.

However, Stevens notes that “the nature of the requirements for cement-kiln design to enable production of clinker, results in a thermal processing device which far exceeds the legislated requirements for incinerators”.

According to Peek and Worthington, the benefits of using alternative fuels in cement kilns are mostly to do with cost cutting and efficiency. “The benefits to cement companies are that they make profit because of the high fuel costs involved in making cement.

Regardless, both NPC and Holcim believe the application of alternative fuels is in line with responsible practices and sustainable development.

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