Domestic biogas technology is a clean, renewable form of energy that is accessible to lowincome
households through anaerobic digestion of readily available organic waste. The
objective of this desktop study was to determine the amount of biogas required for substitution
of conventional domestic fuels (fuelwood, paraffin and coal), to quantify the health benefits
from reduced indoor air pollution due to such a substitution and to evaluate the availability of
feedstock for adoption of domestic biogas technology in South Africa.
The energy demand by low?income South African households for cooking with fuelwood was
calculated to be 27 MJ/day and the total energy demand to be 68 MJ/day. Approximately 80%
of the total energy is used for cooking, water heating and space heating and approximately 20%
is used for lighting. To meet the energy demand for cooking (27 MJ/day) with fuelwood with a
thermal efficiency of 13%, it was calculated that 2 500 L/day/household of biogas is required
which is in line with studies conducted in India and China. In order to meet the total energy
demand of 68 MJ/day by low?income South African households, it was calculated that biogas of
approximately 6 250 L/day/household is required of which 5 000 L/day/household is used for
cooking, water heating and space heating and also 1 250 L/day/household for lighting. A
photovoltaic (PV) solar home system is recommended for lighting in rural households instead of
using the inefficient biogas lamps which often pose a safety risk to the household members.
Complete substitution of fuelwood used for cooking with 2 500 L of biogas per day results in
cost savings of R904 per household per annum which is 4.3% savings of the average household
income and translates to a gross national annual cost savings of approximately R 1.5 billion.
Complete substitution of fuelwood as a source of energy results in cost savings of R1 808 per
household per annum which is 8.6% of the household income and translates to a gross national
annual cost savings of R4 ? 5 billion.
In terms of burden of disease and mortalities, it was determined that fuelwood use in South
African households results in 702 790 and 22 365 attributable disability?adjusted life years
(DALYs) lost and mortalities respectively. It was also determined that 50% of the attributable
DALYs lost and mortalities from solid fuel use can be avoided by substitution of fuelwood used
for cooking with 2 500 L of biogas per day per household whereas complete substitution of
fuelwood with biogas can result in the avoidance of approximately 85.4% of total DALYs lost
and mortalities from solid fuel use.
It terms of feedstock availability, it was determined that there is potential for domestic biogas
technology utilising cattle and pigs waste as feedstock. Due to access to sufficient cattle dung, it
was determined that approximately 613 662 households can potentially benefit from 2 500
L/day capacity biogas digester installations fed with cattle dung. Approximately 131 392
households can potentially benefit from 5 000 or 6 250 L/day capacity biogas digester
installations fed with cattle dung. The number of households that have access to sufficient pigs
waste to benefit from installations of 2 500 or 5 000 or 6 250 L/day capacity biogas digesters
fed with pig waste are 12 089. Due to the number of chickens required and the average number
of chickens kept by South African households, it can be deduced that it is not feasible to
operate a biogas digester fed solely with chicken waste. It was also determined that South
African households do not generate sufficient human excreta and food waste to feed a biogas
digester of a sufficiently large size. It is therefore recommended that community digesters in
peri?urban areas/informal settlements be co?fed with 1:1 mixture of sewage and food waste. It
is also recommended that the households interchangeably utilize the biogas from the
community digester for cooking purposes.
Non?sewered households with access to on?site water supply generate sufficient greywater for
feeding a domestic biogas digester. This is therefore recommended over drinking water. Nonsewered
households with access to off?site water supply generate insufficient greywater for
feeding biogas digesters of 5 000 L/day and 6 250 L/day capacity. It is therefore recommended
that in non?sewered households with access to off?site water supply greywater be augmented
with harvested storm water or water from nearby rivers, dams and streams.
Since the present work is a desktop study, it is recommended that a pilot scale study be
launched to confirm the findings of this study regarding the quantity of biogas required to
substitute conventional domestic fuels as well as the feasibility of domestic biogas technology
in low?income South African households or at community level.