Solid waste is a global concern.
Municipal solid waste is currently greater in developed countries than in developing countries,
with numbers in the latter expected to rise as development increases in these.
In the USA, the Pollution Prevention Act of 1990 states that pollution should be
prevented or reduced at the source. If this is unavoidable, it should be recycled in an
environmentally safe manner. Only as a last resort should waste be disposed of.
Similarly, in South Africa, NEMA: Waste Management Act of 2008
regulates that reasonable measures should be made to prevent pollution, including solid waste.
NEMA also specifies that the person that causes or has caused significant pollution
is responsible to prevent the pollution from occurring, continuing, or recurring. Waste
charges will be levied against the polluter, and as such, the “polluter-pays” principle holds.
Solid waste can be classified into two categories: residential and non-residential wastes.
Additionally, it can be divided into municipal solid waste, comprising garbage and food
as well as waste from waste water treatment, hazardous waste (petroleum sludge and mining
waste) and others waste (construction, autobodies and industrial wastes).
To dispose of solid waste, two common methods are used: landfilling and incineration. While
many landfills are approaching capacity, incineration alleviates this issue, but can
pose the risk of air pollution. A better solution is zero waste, where all materials are recycled.
To avoid solid waste, an integrated waste management plan is needed.
This includes “Cleaner Technology” which uses less packaging, uses more durable products and
allows for on-site composting. “Resource Recovery” involves collecting, processing
and using recycled materials in products. Waste can also be compacted to reduce landfill space.
A common approach to integrated solid waste management is that we wish to reduce,
reuse, recycle, recover, and only as a final option would we dispose of any wastes.
More recently the idea of a circular economy has taken over as the preferred way of thinking.
However, solid waste disposal is always going to exist. Since landfill sites should ideally
be far away from residential areas, to transfer the material to these sites,
solid waste transfer sites may exist. Here, smaller trucks collect the waste and deliver it to
a transfer station for larger trucks to travel the longer-distance to the final waste disposal site.
Landfill sites can be expensive and are the main drivers for recycling.
They also result in short-term effects such as odours, pests and litter,
as well as long-term effects such as water pollution and other issues. As mentioned before,
landfilling should be used as a last resort. Why is landfilling expensive?
Because it is not simply a hole in the ground. Designing a landfill requires detailed planings
and various considerations. These include multiple layers of lining at the bottom of the landfill,
water and leachate collection, methane gas collection, as well as considerations
for covering the landfill once it is full. In a landfill, solid waste undergoes four
processes of breakdown. Anaerobic decomposition, an acid phase, unsteady state methanogenesis and
steady-state methanogenesis. Complete breakdown of solid waste can take years to complete.
One alternative to landfilling is composting. This is the anaerobic digestion of organic
materials under controlled conditions. While this reduces the volume needed for landfilling,
and provides a useful product, it is only suitable for organic materials.
Another alternative is waste to energy combustion.
Refuse derived fuel allows for energy to be recovered after combusting certain wastes.
Low pressure steam can be used for heating water or to drive turbines for power generation.
Despite concerns regarding air pollution, this is a potential solution to a landfilling problem.
Wastes could also undergo gasification or pyrolysis to produce energy.