In urban Africa, informal street food trade is often accompanied by processing activities, including slaughtering, brewing, grilling or cooking. Food and drinks are often prepared on open fires using wood as a fuel. When wood is used as a fuel, it generally emits smoke containing various pollutants.
Previous studies showed that limited capital, lack of education and expression are the main barriers to the implementation of new technologies in the informal sector. It has been argued that the use of cleaner technologies, especially those relevant for the energetic aspect of informal production, would provide affordable net benefits to society in terms of public health, climate change mitigation and food security, but without showing how this could be done in a specific case.
This thesis investigated whether a cleaner production approach would be beneficial: economically and for health and safety to road side vendors in an informal context. The study aimed to provide insights as to whether government could show presence in such settings not only as (unwelcome) regulator, but in a supportive way by introducing cleaner and more efficient means of production, mainly clean- burning technologies in the informal food and drinks preparation.
The specific objectives of this thesis were to:
➢ Compare the resource usage and pollution loads associated with traditional vs. cleaner methods of informal roadside food and drink preparation;
➢ Establish whether the cost-savings deriving from increased resource efficiency of cleaner methods would be sufficient motivation for producers to adopt these;
➢ Observe and document other constraints to the adoption of cleaner methods of production by attempting to demonstrate resource efficiency gains and emission reductions possible under real conditions of informal food and drinks production.
Two cleaner technologies were considered: efficient wood stoves, which are known to have sizeable benefits in terms of reduced fuel wood usage and smoke emissions (though investigated to date mainly in the context of household energy usage), and anaerobic digestion, which can potentially serve simultaneously as receptacle and treatment for organic wastes, and produce biogas to serve fuel needs.
This study combined qualitative and quantitative field observations in a case study setting with experimental work to study the biogas production potential of slaughtering waste. The case study location, Nyanga township in Cape Town, served as a representation of the many urban African settings in which roadside catering occurs.
Nyanga township has both formal and informal housing. Its population including many unskilled and unemployed people also makes it a good place for informal activities.
One common informal economic activity in Nyanga is the production of cooked meals and drinks. This is done on street corners alongside the road around the transport interchange, where many people pass by and vendors provide various services. The cooked meals include roasted lamb, pork and beef. Live chickens are slaughtered and plucked, and also sold whole for home preparation. An African beer known as umqombothi is locally prepared in two processes, with each process involving approximately two hours of cooking using a 230 L drum.
In the field work, it was investigated how much wood was used in open fires compared to efficient wood stoves, specifically for the activity of chicken plucking and umqombothi mashing. The respective fuel costs were calculated and the air quality in the street-side work place were measured in term of levels of particulate matter less than 10 micron (PM10).
It was observed in the field that in most cases sheep and chicken slaughter waste was dumped alongside the road. This dumping was due to the lack of slaughtering facilities in the area. Many other reports have stated that the lack of adequate infrastructure in informal settlements is the cause of inappropriate waste dumping.
The qualitative observations confirmed that the meat and other cooked meals were prepared using inefficient methods linked not only to the waste of resources but also to waste of money and exposure to polluted air from burning wood.
Air quality measurements showed smoke levels near open fires to be about 8 times higher than when using an efficient wood stove. PM10 levels of 4 900 ±1 500 μg/m3 were measured near chicken pluckers using open fires for their hot water, while when using a stove the PM10 averaged 590 ± 130 μg/m3. Smoke levels near biogas stoves were measured at 310 ±140 μg/m3.
The stoves used in this study reduced the quantity of wood used for plucked chicken production by a factor of 6. This reflected a reduction in energy otherwise wasted around the pot in the inefficient traditional cooking method. Stove use reduced the solid waste as well as the smoke accordingly. If a stove lasted 3 years, the vendors would save an estimated R33 700 on fuelwood in case they used harvested wood, and if wood waste is used, the fuelwood savings over three years would be R6 300.
It was estimated that 100 kg of slaughtering waste dumped every day could generate enough biogas for 7 vendors to be provided with enough thermal energy for their catering trades. Based on the experimental work conducted, it was calculated that a digester of a size of 76 m3 would be needed for this amount of slaughtering waste.
The main conclusions of the thesis are:
• Cleaner technologies, in the form of efficient wood stoves and biogas reactors and stoves, showed significant saving potential in the informal roadside food and drink production processes investigated in Nyanga, Cape Town.
The wood stoves investigated in this study were suitable for chicken plucking (which use 25 L pots) but not for the mashing stage of umqombothi preparation (which is done in 230 L drums).
The use of these stoves resulted in a 6-fold reduction in wood burned, as well as an 8-fold reduction in particulate air pollution in the work place. These stoves also offered a very fast
payback time (of the order of a few weeks) and significant fuel wood cost savings to caterers.
Biogas stoves were the cleanest of the three methods compared and should be affordable to caterers if a reasonably priced gas supply were available, but the biogas reactor installation
represents an infrastructure investment that could not be paid for by the caterers.
A biogas intervention would ensure the reduction of slaughter waste, which is often
indiscriminately dumped and thus a significant health hazard. The main recommendations of the study are:
Since wood stoves would offer fast payback times for fuel wood using traders, the local economic development section of local government should aim to stimulate and develop local business to provide such stoves to caterers.
While the slaughter waste can be used as a substrate for biogas generation, for it to become available to the vendors, local government should invest in this as a form of urban infrastructure.
Slaughtering facilities should be built for the vendors where the waste can be kept together and may be used by the municipalities or other bodies.
Similar studies in other developing countries are also encouraged, so as to develop the specific insights on the affordability of achieving benefits to society in terms of public health, climate change mitigation and food security worldwide.
Enough time should be allocated for research that combines social interactions in the field with scientific measurements.