Waste

This article is about waste matter. For the computer program, see WASTE.

Waste is unwanted or undesired material left over after the completion of a process.

Waste can exist as a solid, liquid, or gas. When released as a liquid or gas, waste is referred to as emissions. Identifying waste is a subjective matter, and waste is only defined as such when perceived as such. Some see waste as a negative externality, but it can also be viewed as a potential resource as in industrial ecology.

Natural waste and Human waste

Waste produced in the wild is reintegrated through natural recycling processes, such as dry leaves in a forest decomposing into soil. Outside of the wild these wastes may become problematic, such as dry leaves in an urban environment. The highest volume of waste, outside of nature, comes from human industrial activity: mining waste, industrial waste, post-consumer waste, and so on. Most manufactured products are destined to become waste at some point in time, with a volume of waste production roughly similar to the volume of resource consumption. Lids is an example of Human Waste.

Sustainable use requires a system view of environment issues. Let's suppose a consumer has a choice between apples coming from his own country, and those imported by ship. Which apple would consume the most energy to acquire? It depends on the consumer: if he goes by bicycle to the shop, the homegrown apple requires less energy. However, if he goes to buy the apple by car, it might be that the energy requirement of the car from home to the shop be higher than the energy required to import the apple to the shop, not even counting CO₂ emissions.

Solid wastes and emission wastes

When one considers that every product ends up as waste, it might be a good idea to analyse matter entering the production cycle, rather than analysing wastes that are usually diluted as a result of the process. For example, a consumer buying products containing heavy metals in small quantities will probably not detect these heavy metals in the resulting waste. An analysis of products entering the production system, and a guarantee from the provider, might be a wiser approach to prevent the final pollution (example : a farmer receiving sewage sludge to landfill on some of his field for fertilizing; the sewage sludge analysis is more likely to reveal the pollution than the soil itself after a couple of years) (see also The Natural Step).

Solid wastes : to eliminate, to reuse, to avoid

Post-consumer waste is the waste produced by the end-user (the garbage one puts outside in the trash can). This is the waste people usually think of. But though the most visible, this is very small compare to the waste created in the process of mining and production.

The ecological rucksack of industrial production is the total amount of waste related to a good in the course of its life cycle. For some metals, such as gold, the rucksack can be of a volume of 500 000 times the volume of metal extracted. For each gram of gold produced, 500 kg of mining waste is produced, containing other heavy metals which may pollute the atmosphere in their powdered form. These manufacturing wastes are by far the greatest output of many industrial production systems. In the United States, 93% of natural resources extracted are never transformed in goods, 80% of goods sold are thrown away after only one use, 99% of resources in a good are "waste" within 6 weeks of sale. There are very large potential gains in eco-efficiency, increasing the ratio of production unit per unit of natural resource, and decreasing the ratio of waste generated as a by-product. But mining waste is often perceived as waste only in case of an ecological crisis or as undesirable emissions.

Industry is slowly moving toward better use of its wastes. Industrial ecology for example is a method which consists of using the waste of a factory (matter or heat) as resources for another factory. (See the industrial district of Kalundborg in Sweden). Most wastes issues are due to products rejected outside of the manufacturing process, or those for which industries do not feel responsible: disposable packaging, free goods for advertisement. Shifting from service leasing rather than goods selling might be a solution.