Abstract
Sustained demand for natural resources, resulting in increasing material prices, has prompted an increased focus on reclaiming materials from waste. As a result, for many items virtually 100% of materials that once comprised industrial waste, such as metals, paper, plastics, various chemicals, and food production residues, are now recovered before they even enter the waste stream. When it comes to most municipal solid waste (MSW), however, the situation is much different as more than 80% of the world’s MSW is still landfilled or incinerated (in some cases with energy recovery). So why is this? For a waste material to be suitable for recovery, certain requirements must be fulfilled. A fundamental prerequisite for recovery of a given material from waste is that the necessary chemical, physical and/or biological processes for recovery are commercially available, proven in practice, and cost-effective. Just as importantly, the products of a recycling operation must consistently meet or exceed raw material quality standards as specified by the buyer/user of secondary materials. Furthermore, the sale price for materials diverted or recovered from the MSW stream must be economically competitive with virgin materials prices so that the recycling process is economically sustainable. This means essentially that the secondary materials should be available to manufacturers in sufficient quantities to make their recovery economically viable and that the cost of preparation, storage, and shipment is sufficiently low to compete with price of virgin materials.
When it comes to MSW, processes for recovery of the majority of materials (paper, plastic, glass, metal and biodegradable waste, such as food waste) are relatively simple, well developed, economically competitive, and applicable in practice. Furthermore the global, annual quantity of MSW (in 2012) equals more than 2.5 billion tonnes; thus, material quantity is not the problem. The key problem is that of consistency of secondary material quality.
To achieve sufficient material quality the effective separation of the waste at the source of generation is required. It is very difficult if not impossible to separate ‘pure’ materials from a mixed MSW stream in order to obtain quality raw materials that can be substituted for virgin materials. Achieving sufficient secondary material qualities typically requires that an effective source-separation system is in place and that the waste producers (a city’s citizens) are able and willing to use it properly and consistently.
Implementation and operation of municipal source-separation programmes face several hurdles. First, such systems are more costly to own and operate, often requiring substantial investment in bins, collection vehicles, and processing/storage yard, and the labour and fuel to make it all work. Another hurdle is lower cost and in-place traditional waste management systems. For instance, in many regions municipalities have already made significant investments in new waste-to-energy incinerator capacity and are thus reluctant to reduce reliance on their proven and in-place infrastructure in favour of source separation and materials recovery. In North Europe for example, waste-to-energy incineration systems already supply secondary materials and also provide significant heat and electric power to the regional district heating and power grids that would need to be replaced with energy from other sources.
Many source-separation programmes have failed because of insufficient and/or un-sustained citizen participation. Even if source separation is implemented, materials recovery may still be unsuccessful because the waste generators do not separate their wastes adequately for many reasons, not the least of which are inconvenience, lack of storage space in the home, and resistance to change. Such issues are especially important in multi-family dwellings. Systems where multiple materials are deposited in the same container, collected, and subsequently sorted mechanically can alleviate the problem to some degree; however, here the challenge is the efficiency of the subsequent mechanical separation. It is apparent that no source-separation system can be perfected enough to capture all MSW generated by a city’s population.
Another problem that sometimes occurs is that the waste producers do not understand why they have to separate their waste materials. They are therefore often not willing to participate in a source-separation programme. This behaviour is often connected to cultural background or traditions.
The challenges associated with source-separation costs and competition with existing waste management systems can probably be mitigated by implementing adequate waste management policies and providing the required resources, for implementing them for instance via legislation and public financing. Thus, meeting these challenges is more a question of economics and politics rather than technology. In contrast, challenges associated with the behaviour of waste regenerators (willingness to participate and understanding the importance of material recovery) have proved to be much harder to overcome.
To this day citizen participation remains the major impediment to a successful MSW source-separation programme. As there have been multiple successful examples of source-separation programmes, it is likely that planners can draw on the experience of those in Europe, North America, and elsewhere who have built a successful materials recovery programme. Researchers are encouraged to continue documenting the success stories by collecting and analysing pertinent data and publishing the results in journals including Waste Management & Research.
