1.2 Waste Management
Waste generations vary from one country to another, but many previous studies indicated that as gross domestic product (GDP) per capita increases, per capita municipal solid waste (MSW) generation and other types of wastes also increases. So, waste management is a must for conservation of natural resources as well as for protecting the environment in order to approach sustainable development.
The selection of a combination of techniques, technologies and management programs to achieve waste management objectives is called integrated waste management (IWM). The hierarchy of actions to implement IWM is reduction, reuse, recycle, treatment and final disposal (Tchobanoglous et al., 1993). Different sources use different terms and categories to describe the waste management hierarchy. The USEPA 1989 publication âThe Solid Waste Dilemma: An Agenda for Actionâ states that their hierarchy for waste management is source reduction, recycling, waste combustion and landfilling. Others would list source prevention, source reductions and reuse as two categories, while most of the literature combines them under source reduction. The New Jersey Department of Environmental Protection includes recycling, on-site composting and reusing at the source under source reduction. However, reviewing diverse literatures reveals that the traditional waste management hierarchy is dominantly reducing, reusing, recycling, recovery, treatment, and disposing. Incineration might be included within treatment because it is thermal treatment, or within recovery as waste-to-energy recovery, or can be discussed as an independent item as will be discussed in this chapter.
Reducing: Reduced material volume at the source can be enforced through extended producers and consumers polices (e.g. less unnecessary packaging for products). Indeed, changing the consumerâs practices is part of the source reduction concept. Reducing the raw material at the source will conserve the natural resources for other uses. Fortunately, statistics show that these trends are declining in developed countries. For example, the total source reduction in the USA, which includes prevention and reuse, increased from less than one million tons in 1992 to more than 50 million tons in 1999 (USEPA, 1999).
Reusing: Reuse means to continue using the product in its original or in a modified form. Reuse of materials involves extended use of a product (retrading auto tires) or use of a product for other purposes (tin cans for holding nails, glass bottles for holding water in refrigerators). Reusing the product does not return the material to the industry for remanufacturing or recycling. Reuse can be considered another aspect of source reduction which could be carried out not only by consumers but also by producers. Chemicals used in the tanning industry could be reused by installing an on-site chromium recovery unit. Source reduction and reusing can be encouraged through numerous regulations and programs such as the Pay-As-You-Throw program developed by USEPA as well as other programs.
It is clear that source reduction does not only include reduction in the use of material, but includes as well the activities that increase product durability and reusability. Source reduction, which includes source prevention and reuse, is the best option in waste management because it preserves natural resources and reduces pollution, and waste landfilling or incineration. The less preferred option in waste management is recycling.
Recycling: What cannot be reduced at the source is pumped in the waste stream. The above discussion shows that reuse has much to do with cultural habits and this is also the case with recycling but recycling involves additional technical know-how and could involve some capital investment. Recycling is the process of converting these wastes to raw material that can be reused to manufacture new products.
Through regulations governments have a great role to play in promoting recycling. Such regulations are even emerging in developing countries. For example, the Republic of Korea explicitly prescribes the Extended Producer Recycling system under the Resources Conservation and Recycling Promotion Law, amended in 2003 (IGES, 2005). In India and the Philippines, laws on the management of MSW have been enacted recently and the importance of material cycles is clearly mentioned in the laws (IGES, 2005).
Recovery: Recovery of materials or energy can take numerous forms. It is clear that material recovery is a limited activity worldwide and is mainly concerned with the recovery of energy from burning wastes. For example, the Oregon Department of Environmental Quality in the USA states that âconstruction and demolition wastes makes up the majority of the wastes being processed at MSW Recovery Facilities, followed by âdryâ commercial and industrial loads; virtually no recovery from residential garbage route trucks occursâ (ODEQ, 1997).
Recovery differs from recycling in that waste is collected as mixed refuse, and then various processing steps remove the materials. Separating oil from waste water effluent by a gravity oil separator (GOS) in the oil and soap industry is material recovery from waste. This material is then sold to another type of soap industry or returned to the industrial process within the same factory. The difference between recycling and recovery, the two primary methods of returning waste materials to industry for manufacturing and subsequent use, is that the latter requires a process to remove the material from the waste while the former does not require any processes for separation, sorting can be done manually.