Waste utilization in building

Most joumals that deal with technological and developmental topics focus each issue on a special theme, and one of the themes that appears fairly often is "Waste" - in one form or other. It may deal with common household or municipal waste, agro-forestry or industrial waste, and may refer to the safe disposal of hazardous components, reprocessing of materials for other uses, partial or complete recycling, or to the environmental, social and political aspects. It is a very wide field, so only a few aspects can be dealt with each time.

This issue of BASIN-NEWS is mainly concerned with "Waste Utilization in Building", whereby some of the articles deal with "Waste" in a broader context (such as "Yemen's Environmental Problems " in the WA S SECTION, and "Municipal Solid Waste Management in Developing Countries" in the RAS SECTION). Nevertheless, they all have to do with human settlements in developing countries, and altogether help to acquire a multifaceted view of an extremely complex subject and one of the most burning issues of today - waste management.

Waste utilization is nothing new in developing countries. The article by Guido Ast explains how traditional recycling systems functioned in Yemen's cities and villages, and this is true for most other countries. Waste disposal started to become a problem, the moment the so-called "underdeveloped" countries decided to become "developing" countries, which in other words meant adopting western technologies and lifestyles, not knowing that they were also importing western problems. Of course, a number of other causes, such as uncontrolled population growth and urbanization, and the resulting social decline of the majority of the population, economic disasters, political disorder and several other factors, have all contributed to the present situation. But this issue of BASIN-NEWS was not conceived to investigate the causes - the main intention was to present possible solutions.

Waste Utilization or Recycling?

In this context, it seems necessary to explain the difference between "waste utilization" (which the articles in this issue deal with) and "recycling of waste". The wastes in the first case can be defined as by-products (of agricultural, forestry, industrial or even household processes), which do not essentially have anything to do with building, but which, with special processing and treatment, or in conjunction with other materials, can economically substitute (or even improve the quality of) conventional building materials, or help to economize in their production (eg "Using Waste Material as an Alternative Fuel for Firing Bricks in Zimbabwe").

Recycling of waste, on the other hand, means the reuse of a material or component for exactly the same purpose, for which it had been used previously. A classical example is the traditional pueblo house of the Hopi and Zuni Indians of Southwestern United States. The walls were made of adobe (mud) blocks, and the roofs were supported by thick cedar beams. Since timber is scarce in that region, the beams were not cut to the required lengths, but allowed to project through the face of the exterior walls. Thus they were used over again for hundreds of years, and the old mud walls were crushed, mixed with water and made into new adobe blocks for the new houses.

Demolition waste from conventional buildings today may continue to serve as building materials, but usually in a different way. Broken concrete may be used as aggregate in new concrete. Brick waste can be finely ground and used as a pozzolanic binder. It can also be crushed to a maximum size of 20 mm and used as coarse aggregate in concrete construction, which is especially important in countries, like Bangladesh, in which natural aggregate is scarce. However, when using waste material as aggregate, fresh cement is needed to make new concrete, while clay and fuel are needed to produce new bricks. Therefore, this is waste utilization - not recycling, as it is often called.

Recycling - in its true sense - is also possible in building construction today, but would need very careful consideration in the design stage. If components, such as windows, doors, lintels, beams, columns, slabs, pipes and so on, are designed and installed in a way that facilitates dismantling without destroying them, their reuse is possible. But also during the manufacturing process and during installation at the building site, excess material, clippings, etc should be avoided or reused within an internal recycling system to avoid producing waste.

Since recycling reduces the amount of new materials and components needed, it is the most desirable form of waste utilization from an environmental and economic point of view, but it will probably never be achievable for the entire building. Nevertheless, any form of waste utilization is worth consideration, in view of the evident advantages:

* Conservation of scarce and expensive resources, utilization of locally available materials and reduction of material and transportation costs.

* Reduction of environmental degradation of large areas, that would otherwise be destroyed by excessive quarrying, or disfigured by the establishment of additional manufacturing plants or waste dumps.

* Reduction of pollution by the use of materials that are difficult to dispose of, and avoidance of excessive production of new materials in polluting industrial processes.

* Considerable saving of energy, which would be required to produce new materials.

Limitations and Remedies

While all this makes good sense in theory - and the ideas are by no means new - there are several problems that make it difficult to introduce wastes as potential building materials:

* Although the total amount of available waste is large, it may be produced in numerous decentralized units, making collection extremely difficult.

* Handling of wastes can be dangerous, eg inhaling of fine particles; blisters, bums and illness from toxic substances; severe cuts from broken glass and metal scrap.

* Once a by-product becomes a useful building material, higher prices are often charged, so that the benefit of using cheap materials is quickly lost.

* Not all building materials based on wastes provide the same strength and durability as the materials they were designed to substitute (but if the price is low, this drawback can be accepted).

* The concept of using wastes and the fear of future problems that may arise due to inferior qualities of materials makes builders reluctant to use them.

* However, with a series of well-implemented measures, such as the following, most of the problems can be overcome:

* Producers of useful by-products need to be well instructed on appropriate methods of handling and storage of the material in order to facilitate collection.

* Careful supervision and strict observance of safety precautions (eg use of gloves, goggles, protective clothing) in handling waste is of vital importance to reduce injuries and health problems.

* Especially in the case of lesser known but promising waste utilization, considerable efforts are needed to demonstrate the technology and its advantages. Prototype structures (preferably important public buildings) that are constantly used can convince most doubters.

* The use of wastes for building offers a wide field of research and should be given priority - even in the more affluent countries - as there is a great need in all countries to save resources, energy and costs, and at the same time provide more affordable and appropriate shelter for the homeless.

Unfortunately, progress in the field of recycling or waste utilization is still rather slow at present. The practical implementation of these concepts is still in the developing stage in the industrialized countries, and more so in the developing world. This has a great deal to do with the general awareness of the problem.

How large is the proportion of the world's population that is really worried about depleting resources and environmental pollution and destruction? In most countries they are very small minorities. And wherever one can observe some form of activity aimed at saving scarce resources and protecting the environment, it is either

* traditional practice,
* a vital economic requirement, or
* enforced by legislation (with severe consequences for non observance).

Those who appear to act in this way on idealistic grounds, without any of the above reasons, in reality know that the economic and social benefits will ultimately be on their side, particularly in terms of resources saved, a healthy environment and greater chances of achieving peace and happiness, as there would be enough resources to share with others.

However, there is no use emotionalizing this issue and appealing to the peoples' conscience. The only way to achieve a breakthrough is by convincing them of the practical benefits that would result from waste utilization and recycling. And in that respect, there is much to be done.

Forthcoming Tasks

The articles in this issue of BASIN-NEWS present a number of possible uses of wastes in the fields of wall building, cements and binders, roofing and earth construction. If many of these were to become normal practice, wherever the resources exist, we would be entering a new era in building technology. But that is still a long way off.

A great deal of research and development is needed to arrive at really practical solutions that involve all commercial disciplines, not only those of the building industry. If the same amount of money and effort were put into such research, as has been put into various other high tech industries, such as automobiles, computers, aviation, space and arms technologies, to name only some of the most obvious ones, a number of today's environmental problems would be solved, and the immense housing backlog would gradually diminish.

It is, therefore, up to the decision makers in governments and industries to provide the financial and technical means for increased research and development in the field of waste utilization and recycling. And it is up to the scientists, engineers, designers and other experts involved to exert all their creative energy to Find new and unconventional solutions.

Ideas could be taken up again, such as the one that was developed by a beer manufacturer in the 1960s, whereby the bottles were shaped like bricks, which were also used as such to build a prototype house. This idea could be carried further, such that all kinds of packaging (glass, metal, paper, synthetic materials) arc designed to be used in one way or other as a building material, after its original function has been fulfilled. The concept of using discarded car tyres for wall construction (as described in the EAS SECTION) is unconventional, but certainly an idea worth following up in places where old tyres normally end up on garbage dumps.

In Singapore, for instance, the problem of disposal of dewatered sewage sludge led to experiments in the production of bricks made of dried sludge or sludge ash, with astonishingly good test results compared to those of common burnt bricks. Admittedly, the idea of using sewage sludge may initially be unacceptable for many people, but with an intelligent marketing strategy, this problem can surely be overcome. In any case, the advantage of making a valuable resource out of a problem waste cannot be overrated.

More sophisticated technologies using heavy machinery which would not normally be considered appropriate technologies - should not be ruled out when it comes to reprocessing demolition waste, as there are indeed appropriate uses for them. In some industrialized countries, such technologies have been developed to separate and reprocess (usually crush and sieve) the waste, which - depending on the type of material - is successfully being used in road construction, or as concrete aggregate, or for the production of insulating material, light weight blocks and tiles, to name just a few uses. Such so-called "recycling plants" are also available as mobile units, which could be especially useful for the reconstruction of demolished buildings after natural disasters (earthquakes, hurricanes, etc), wars and other destructive events.

Improving the quality and durability of materials is also a form of waste management, as less waste results within a given period of time.

However, all these efforts to avoid or utilize waste materials in building cannot be implemented on a large scale, if the corresponding building codes, standards and specifications are not available. Architects, engineers, building technicians, decision makers in building authorities, suppliers of building materials and equipment, all have to be fully aware of the waste utilization and recycling options, their applications, advantages and limitations. Furthermore, such technologies must be integrated into the curricula of educational programmes and practical training courses on building technologies.

This shows that we still have a long way to go before waste utilization becomes a part of standard building practice. It may take another 50 or even 100 years -who knows? But in order to make sure that it does not take longer, we must intensify our efforts in achieving this goal - TODAY. And, until it is reached, there will be many more special issues on "Waste".

Kiran Mukerji Starnberg, Germany
He is an architect and consultant to the Wall Building Advisory Service since the establishment of BASIN.