Handbook

Instead of piling food waste into bins and, ultimately, landll,
food waste disposers can be used to grind food scraps
which is then sent via the sewerage system to a wastewater
treatment plant. Here appropriate facilities use a process
called ‘anaerobic digestion’, to convert waste to biogas.
Anaerobic digestion is a collection of processes by which
microorganisms break down biodegradable material such as
organic food waste in the absence of oxygen.
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The anaerobic
digestion process produces a biogas methane.
When cleaned, the methane fraction can be stored,
pressurised and used to generate on-site power and heat.
The power can be used on-site with surplus fed into the
electricity grid. Methane can also be upgraded to natural
gas-quality biomethane, and a by-product of the digestion
process is a nutrient-rich digestate which can be used as
fertiliser
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for areas such as golf courses, playing elds
and pasture lands.
What happens to food that is thrown away?
Food waste and renewable energy
In the face of a rapidly growing population, nding an
appropriate method of dealing with household waste
continues to be a matter of heightened importance. Food
waste accounts for more than 30% of the total rubbish
in household garbage bins therefore suitable treatment
options for this organic component could help alleviate a
global waste problem.
At a global level countries are keen to reduce their reliance
on fossil fuels and provide alternatives to wood fuel. At a
national level, residents, commerce and industries want to
reduce their dependency on unpredictable price uctuations
of fuels. From a waste management and environmental
impact perspective, state and local governments are
committed to the issue of climate change and proving
measures to avoid methane emissions from landlls.
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Therefore alternative methods of food disposal would
potentially impact signicantly. Food waste disposers while
serving a practical function in terms of household hygiene
and convenience have the potential to provide a number of
benets on a far broader scale.
Introduction
Australia is heavily dependent on landll as a means of
waste management. In fact, the majority of non-recycled
waste will end up in landll sites.
Estimates suggest each household produces close to 1.5
tonnes of waste each year. And nearly half (47% in 2009-
10) of all household waste is organic – namely food scraps.
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One concern is that waste generation has been growing
at a disproportionate rate. Between 1997 and 2012 – when
overall population growth was 22% – the volume of waste
production jumped by 145%.
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The problem here is that landlls are effectively an ‘out of sight,
out of mind’ solution. They potentially have a detrimental impact
on surrounding air, water and land quality. There are, however,
better ways of managing wastes, especially food waste.
A by-product of anaerobic organic waste decomposition is
a gas which consists of around 50% methane. Methane in
the atmosphere is a strong contributor to climate change,
being over 20 times more potent in this regard than carbon
dioxide.
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However, if captured and ‘cleaned’, it can be
harnessed as a valuable renewable energy source. Using
a food waste disposer can facilitate just that without the
social dis-amenity associated with landlling.
Waste generation, Population & GVA, 1997-2012
INDEX WASTE GENERATED POPULATION GVA
300
250
200
150
100
50
0
1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12
Source: Australian Bureau of Statistics Waste Generation, Population & GVA 1997-2012
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