South African dairy goes green with manure power
GROBLERSDAL, South Africa – Thandeka Mabuza’s small-scale dairy farm, on the banks of the Olifants River, gives off hardly any of the earthy smell you might expect from a thriving dairy operation.
But the lack of manure odour is hardly the only benefit from the farm’s pioneering biogas dairy. By using vats to digest cow dung and then harvesting and burning the methane, Mabuza now produces electricity for her house and barns.
“This project is a triple win situation,” said the former agricultural extension officer with the South African department of agriculture and land affairs. “I can confirm that through turning manure into energy, I have reduced my electricity bill by a quarter. And I am preventing deforestation by reducing destructive harvesting of fuel wood,” a major source of power for many small farming operations.
The 12-hectare farm in South Africa’s Limpopo province, about 150 kilometres (94 miles) northeast of Pretoria, has a 16 dairy cows, whose manure is fed into three anaerobic digesters. The resulting gas is then burned to produce electricity, Mabuza said.
The fermentation process benefits the farm both by offering a way to dispose of manure and by producing electricity, she said.
Mabuza invested more than $6,700 in the project in 2007, after attending a biogas conference in Nairobi. She became interested in biogas after learning in her government job that livestock contribute more to global warming than vehicles.
“With new research suggesting that methane emission by livestock is higher than previously estimated, I said to myself, ‘I will go into dairy production with environmentally friendly production knowledge in my mind and it is going to define my business,’” she said.
“Livestock has been my love and I engaged technical people who assisted me in designing diets for my cows to eat better, stay more energetic and secrete smaller amounts of the offensive gas,” she said.
COWS A MAJOR SOURCE OF METHANE
Dairy farming plays an important role in driving climate change, as cows emit large quantities of methane, one of the most powerful greenhouse gases.
According to a 2006 U.N. Food and Agriculture Organization report , the entire livestock commodity chain, from land use and feed production to livestock waste and product processing, contributes about 18 percent of total greenhouse gas emissions.
On Mabuza’s farm, the bio-slurry from the digesters, after the methane is captured, is used as an organic fertiliser to produce food crops such as tomatoes, vegetables and maize that she sells in the nearby town of Groblersdal.
At the farm, cow dung from specially adapted cattle sheds is mixed with water and channeled into fermentation pits.
The resulting gas produced as a by-product of this fermentation is collected in a simple storage tank and piped directly into the farmer’s home and her milking parlour to provide energy for cooking, laundry and lighting.
“Burning biogas is much cleaner than burning woody biomass. Apart from being smokeless, it emits only carbon dioxide and water to the atmosphere during combustion whereas a wood fire generates a much greater level of global warming and pollution,” she said.
“This technology improves hygienic conditions, especially for women and children, by eliminating indoor air pollution and by stimulating better management of animal dung since livestock stables are cleaned and the dung fed into the digester on a daily basis,” she said.
“We have to bring a balance between feeding the nation and protecting the environment as farmers,” Mabuza added. “I feel the dairy sector should be pro-active and not wait for legislation to be put in place when it comes to climate change.”
After using Mabuza’s project as a yardstick, the Limpopo provincial government has started to roll out biogas technology to nearby villages. So far more than 300 villages in the district use biogas.
“People’s living conditions and the environment have improved, forests are protected and the labour force has more time for agricultural production. A large amount of straw, which was previously burned, is now put into biogas tanks to ferment. This further reduces air pollution from smoke and helps produce high-quality organic fertilizer,” she said.
The organic sludge left over from the manure and straw fermentation process is also increasing crop yields in the area, said Zola Majavu, a local villager.
As well, biogas units reduce the risk of manure contaminating rivers and landfills and lower the demand for wood and charcoal, which are implicated in both climate change and respiratory illnesses.