Biowaste to Biogas

Significance of waste digestion in developing countries
As a rule, roughly 10 kg of kitchen and market
waste are needed to produce 1 – 1.5 m 3 of biogas.
This amount of biogas contains approximately 6
kWh of energy which substitutes 0.5 l of diesel fuel.
After roughly 25 years of step-by-step improvements
and practical experience, biogas technology is still attracting
interest as a contribution to renewable energy
production, thereby creating independence from fossil
fuels. In China, an estimated total of 40 million domestic
systems were installed by 2011. India is home to
approximately 4 million domestic biogas systems, and
Vietnam had installed more than 100,000 systems by
2010. Further Asian countries to be highlighted are
Cambodia, Laos, Indonesia, and Nepal (225,000 by
2011). In Africa, where anaerobic digestion is less
prevalent due to climatic reasons, countries like Kenya
and Uganda (approximately 7,500 by 2017) are
amongst the frontrunners regarding domestic biogas installations,
while in the Republic of South Africa a significant
number of mid- and large-scale biogas plants
exist. In Latin America, apart from small biogas plants
for rural households, numerous agricultural waste projects
have been implemented, and in the urban environment
biogas is being extracted from several landfills
(landfill gas).
As mentioned, anaerobic digestion of organic household
waste in centralised high-technology plants has
become a standard in industrialised countries. On the
other hand, most regions of developing countries still
lack appropriate low-technology options. As a result,
anaerobic digestion as a waste treatment option for
urban settings, predominantly processing kitchen or
market waste, still plays a negligible role. There is little
knowledge and information available or accessible
on technical and operational feasibility, challenges and
opportunities.
In developing countries, the largest share of the MSW
consists of organics, and a relatively small amount of
glass, metals, paper and plastics. However, income
level, economic growth, lifestyle, and location strongly
influence MSW composition. Also, the composition of
municipal biowaste can change during the year given
seasonal variations and habits.
Organic waste recovery and recycling is still fairly limited
in developing countries and emerging economies.
Next to direct animal feeding, mulching of gardens, and
composting – or burning – the most common practice
for disposal of organic waste is dumping into unsanitary
landfills or open dumpsites, mixed with other waste
streams. However, the recycling of organic waste would
significantly reduce the amount of waste that needs
handling and thus reduces costs at the disposal facilities.
Less organic waste at the disposal site prolongs its
life span, and also reduces the environmental impact of
the disposal site, as the organics are largely responsible
for the polluting leachate, CH 4
and odour problems.
The implementation of anaerobic digestion or composting
as one step in a city-wide solid waste management
programme reduces the flow of biodegradable materials
to landfills. Nevertheless, its feasibility depends on the
market demand for the end products (gas, digestate or
compost), as well as the technical and organisational
set-up of the individual facilities. Enabling clear legislation,
policy and municipal strategies in terms of
organic waste management are further important prerequisites
for successful initiatives.
The characteristics of the waste materials used for biogas
production are highly dependent on the collection
system, and one of the fundamental issues is whether
the collected waste is contaminated by inorganic ma-
Compacting mixed
waste on a landfill
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