By Pamenus Tuso
Bulawayo dumping site
The mere mention of the name ‘Ngozi Mine’ for most residents in Zimbabwe’s second largest city of Bulawayo evokes images of heaps of horrible fly-infested smelling garbage.
But to environmentalists, Ngozi Mine is a common reference to the Bulawayo City Council’s rubbish dumpingsite and a potential source of energy which if exploited fully can be the panacea not only to the city’s electricity shortages, but to the country’s as well.
Zimbabwe is relying on uneconomical and unsustainable power imports from neighbouring countries.
An assortment of rubbish dumped at the “mine”, located on the outskirts of the city which has become a haven of waste harvesters, could easily solve the city’s energy crunch for good if the powers that be are willing and committed.
For example, in Sweden more than 99 percent of household waste is recycled in one way or another, turning it into gas, heat or any other raw materials.
As in Sweden, many countries particularly those in the developed world are already harnessing methane gas from landfills and converting it to useful energy. This is opposed to allowing it to escape into the atmosphere where it becomes greenhouse gas harmful to the ozone layer.
Renewable energy expert and principal energy development officer in the Ministry of Energy and Power Development, Blessing Jonga, said there is huge potential for municipalities to utilise bio-degradable waste to produce energy.
Jonga said local authorities in Zimbabwe can sustainably generate energy through water treatment at sewage treatment plants or vegetable markets and landfills.
“Big cities and towns have sewerage treatment plants that treat sewer from residential and industrial areas. Most of this waste is organic. At sewage treatment plants in cities like Harare and Bulawayo, there are digesters which help in treating organic waste through decomposition of these organic materials by methane producing bacteria.
“Biogas, which is a gas composed mainly of methane, carbon dioxide and hydrogen sulphide and traces of other gasses is produced in these digesters during fermentation,” explained Jonga in an interview.
Through this process, Jonga said biogas for domestic use such as cooking and lighting can be harnessed through pipes. He, however, stressed methane gas must be contained because of its adverse effects towards global warming if allowed to escape into the atmosphere.
Biogas can also be used to generate electricity using biogas generators which are called combined heat and power systems.
Small towns and growth points can also install digesters and use their sewerage stabilisation ponds to produce biogas that can be used for power generation.
The expert also concurred with environmentalists that municipalities were failing to utilise their dumpsites to generate power for the benefit of residents.
“There is a potential to convert all dump sites in cities and towns to proper landfills in order to produce methane for power generation.
“ This process requires waste separation first. Inorganic materials should go for recycling whilst the organic waste goes to well lined landfills so as to avoid environmental hazards such as fires and water pollution,” said Jonga.
Bulawayo City Council is one of the municipalities in the country which has embraced the concept of renewable energy.
Nesisa Mpofu, Bulawayo council‘s senior public relations officer, said:
“Bulawayo city council has allowed for funding under the Bulawayo Water and Sewerage Services Improvement Project (BWSSIP), for feasibility studies to be carried out to determine the scope of the bio-gas generation and the resultant areas of usage, be it electricity generation or industrial and domestic heating.
“It is only after the feasibility studies have been concluded that a concrete decision shall be taken to either invest in the technology or not.”
Mpofu said the council is also engaging strategic partners on the importance of investing in the sector.
Currently, biogas generated at the city’s sewerage treatment plants is released into the atmosphere as there is no infrastructure in place to harness the gas for sustainable use.
The City of Harare has also made significant inroads in generating electricity through bio-gas from vegetable waste. Currently the council is constructing an 800 cubic metres biogas digester system at Mbare Musika near Matapi Flats.
The digester will be fed by vegetable waste from the market place, sewer from the flats as well as organic food waste from surrounding restaurants and houses. The biogas produced will be used to generate electricity.
Besides harnessing energy and bio-slurry (organic fertiliser), city council officials say this project will save the local authority costs in transporting organic waste to Pomona dumping site.