INGENIEUR
The economics of recycling varies. In developed
countries, recycling has been ‘rediscovered’ since
the 1980s, as an alternative ‘sink’ to alternative
treatment and disposal methods. This has been
driven by policies such as landfill tax aimed at
diverting waste from landfill, at least in part to
mitigate greenhouse gas emissions.
Recycling, along with waste prevention and
the environmentally sound management of waste,
has substantial potential for reducing a country’s
overall greenhouse gas emissions by perhaps 1520%.
In developing countries, recycling is generally
performed by the ‘informal sector’, and therefore
a purely private sector activity, undertaken only
if the prices received for the separated materials
cover all of the direct costs of the recycler and
yield some profit. For some materials, and at times
in the cycle, when prices of other materials are
relatively high, certain components in the waste
stream become more sought after, leading to
competition.
All of this is much easier with clean material
cycles. So separating dry recyclables from wet
organics at source is a central component of many
initiatives to improve the working conditions and
the livelihood of informal sector recyclers and to
integrate them within the mainstream waste and
resources sector.
The applicability of recycling demands that it
make economic, social and environmental sense. It
must be carried out in a sound manner, protecting
both human health and the environment. Such
considerations are key when judging the relative
position of recycling in the waste hierarchy –
for example, exporting ships for ship-breaking
on the beaches of an ill-equipped developing
country is not equivalent to sound recycling in a
modern, permitted and inspected shipyard; and
the long-term sustainability of emerging country
markets as a destination for plastics and other
recycled materials from high-income countries
depends on the success of national Government
efforts to eliminate the low-tech, uncontrolled
and unregulated recycling facilities which still
operate alongside modern environmentally sound
facilities.
The role of design is crucial to the move from a
linear, TAKE - MAKE - USE - WASTE, economy to a
more sustainable circular economy.
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26
VOL
– DECEMBER 2015
VOL64
55OCTOBER
JUNE 2013
ENERGY RECOVERY FROM WASTE
What is the optimum level of recycling in a solid
waste management system? This will depend
on how the balance is drawn between the
often-conflicting drivers of policy, economics,
environmental impact and sometimes resource
scarcity. One ‘rule of thumb’ is to maximize
sustainable recycling, and to recover energy
from any residual waste. Again, there is no clear
‘dividing line’. From an environmental point of
view, the use of a specific life-cycle assessment
to consider the particular local circumstances is
recommended.
Biomass is one of the major renewable energy
sources available as an alternative to fossil fuels.
So for many types of waste of natural origin (socalled ‘biogenic waste’), including agricultural crop
residues, forestry waste and wood waste from
industry, energy recovery from either thermal
processing or from anaerobic digestion has clear
benefits, although seasonal variations in supply
may be an issue – again, life-cycle assessment
should be used to compare recycling the nutrients
and organic matter with energy recovery in any
specific case.
The relative merits of recycling and energy
recovery for mixed waste, including commercial
and industrial waste and municipal solid waste,
are perhaps less clear cut. The calorific content
of residual waste remain