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Biogas-A viable energy source

This has prompted stakeholders in the energy sector to look for alternative energy sources like the shelved methane gas project in Lupane, solar energy, mini-hydro plants and biogas.

 

Professor Christopher Chetsanga, the president of Zimbabwe Academy of Sciences and the chairman of ZESA said the methane gas from different sources has to be tapped as fossil fuels are soon to deplete while biogas, which is green energy, can be the solution for the country’s power shortages.

 

The use of biogas also known as mash gas, landfill gas or digester gas, depending on the site it has been produced, can be part of the answer to the country’s perennial energy challenges.

 

Urban areas have been seriously affected by energy challenges and yet these areas have the potential of producing large amounts of biogas as they have the feedstock for biogas plants in the form of sewage.

 

Biogas is produced by anaerobic digestion or fermentation of organic matter such as manure, sewage sludge, municipal waste, or bio-degradable waste at temperatures between 3’ and 70’c.

 

With the big sewage treatment plants in the country, especially in large cities like Harare, the production of biogas becomes a more viable project, which the city council and the private sector can invest in.

 

Engineers working with the city council established biogas plants at Firle and Crowborough Sewer Works several years ago.

 

Firle Sewer Works in the capital has the capacity of producing about 97000 cubic meters of biogas in three hours.

 

Experts from BOC gasses said methane in biogas has more heat producing capacity than coal, which is usually used in thermal power stations; hence the city councils can generate electricity using the gas.

 

However the biogas plant equipment in Harare is now in a state of disrepair.

 

Mr Leslie Gwindi, the spokesperson for the City of Harare said they had thrown a tender for the refurbishment of the sewer works, which are currently not working efficiently.

 

He said there is need for financing the biogas project as the city council is faced with financial challenges to resuscitate the project.

 

Biogas production and use is not new in the in the country.

 

According to a 1986 journal published by the then Department of Energy and Water Resources, the government assisted towards the construction of more than a hundred biogas plants in rural areas and tertiary institutions in the 1980s.

 

Currently the Ministry of Energy and Power Development has revived the projects and over 400 plants have been constructed at homestead level in Hwedza, Sanyati, Chirumanzu, Gutu and Chipinge.

 

According to the Ministry’s spokesperson the beneficiaries provide labour and finance towards setting up the biogas plants while the Ministry provides the technical expertise.

 

In countries like Thailand, Rayong Municipality produces organic fertilizer from biogas plant wastes while the gas is used to generate at least 5000 mwh of electricity per year at its sewer plant.

 

Another typical example of a large-scale biogas plant is of Vestal Farm in Kenansville, North Carolina, in America, which rears pigs.

 

The farm produces biogas from pig manure, which is used to generate electricity.

 

At the project biogas is compressed and used to operate a 30kw micro turbine.

 

The energy produced results in reduction of annual electricity bills for the farm.

 

The expert at BOC gas said the biogas could be piped to the end users or put in canister, though it needs to be liquefied first before packaging.

 

He said the best and cost effective way is to pipe the gas straight to the end users like the Mozambique to SASOL pipe in South Africa.

 

Industries and domestic users can also tape the gas thereby generating revenue for the city council.

The expert said packaging the gas is an expensive venture, which requires the establishment of an air separation plant, which liquefies the gas using liquid nitrogen before it is filled in gas bottles and canisters.

 

Professor Chetsanga encouraged the private sector to participate fully in energy production for the development of the country.

 

“The human resources and the raw materials are available, and urban centers have to utilize their effluent in energy production rather than dumping it and causing an environmental threat

 

“This will also reduce the strain on the over burdened local power utility company”, he said.

 

According to the ministry of Energy and power development, funding and maintance of the plants is the major stumbling block in rural areas.

 

The ministry is urging the corporate sector and donors to venture into these projects to assist in power generation for the rural population in order to stop the rampant deforestation caused by the use of firewood.

 

The spokesperson said it costs about US$600 to US$1000 to set up a viable household biogas plant.

 

The cost includes raw materials and labour.

 

Given the current situation of incessant power cuts, there is great need for use of alternative renewable energy sources.

 

According to Professor Chetsanga this will widen the industrial base and create employment for the youths.

 

 

Local authorities can generate revenue by proper waste management whilst rural areas can retain their forests.

 

Even dumpsites dotted around several cities and towns can produce biogas if proper machinery is used to tape the gas.

 

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