Life cycle assessment on the substitution of dung combustion by biogas systems in Ehtiopia
- Publication Type
- Contribution to conference
- Authors
- Lansche, J; Schock, S; Müller, J
- Year of publication
- 2011
- Conference name
- Tropentag 2011
- Conference location
- Bonn
- Conference date
- October 5 - 7, 2011
The utilization of dried dung cakes as a fuel for household cooking stoves is very common in
rural areas of Ethiopia. The greenhouse gases thereby emitted contribute to the global warming
potential (GWP) and endanger the human health of the local people. In industrialized countries,
biogas production by anaerobic digestion is assessed as an efficient way to reduce greenhouse
gas emissions from dung management and to preserve nutrients for plant production. The
objective of this study was to assess the environmental impacts of biogas systems used for the
provision of household energy in rural areas of Ethiopia. Two scenarios for the provision of
thermal household energy were taken into consideration. The first one describes the situation at
present, where cattle dung is dried and used in household cooking stoves (dung combustion
system). The second scenario was the usage of the fresh dung as a substrate for anaerobic
digestion to produce biogas and combustion in a biogas stove (biogas system). The method of
Life Cycle Assessment was used according to the ISO 14040 and 14044 standards. A model was
built with the GaBi-software and a credit approach was used to deal with additional functions of
the system. The life cycle inventory was mainly based on literature values e.g. for emissions of
dung cake combustion, methane losses of the biogas plants and methane conversion factors.
Impact assessment was done using the CML 2001 method in the version of 2007 for the impact
categories GWP, acidification potential, eutrophication potential and human toxicity potential
(HTP). The production of biogas leads to several environmental advantages compared to the
dung combustion system. The results indicate that the GWP can be reduced about 1.36 kg CO2
equivalents/MJ heat delivered to pot. The fertilizer value is increased due to a higher nitrogen
content of the biogas plants effluent compared with the ash of dung combustion. Furthermore,
emergence of cooking smoke in households is reduced considerably which results in a saving of
32 g DCB equivalents/MJ heat delivered to pot concerning HTP.