What type of energy should I generate?

When it comes to generating your own electricity, there are numerous possibilities. What should you choose? Two experts say the emphasis should be on affordability and practicality.

Because of southern Africa’s climate, photovoltaic electricity generation (solar power) is almost always the first type of alternative energy which people consider. Wind power and the generation of electricity from the burning of biogas or solid material, such as timber, are however, other options farmers should consider.

Mr Adrian Bowles, director of the energy consultancy, The Tree Wise Men Limited, says different kinds of farming enterprises offer different types of materials for the generating of bio-energy.

“Traditionally it has been sugar cane, poultry, pig and forestry farming enterprises that have generated this type of energy because these farms have sufficient waste material for generating electricity. Poultry farms, for example, produce large quantities of manure that can be processed and utilised,” he says.

The amount of electricity generated depends on how effectively the material can be converted into heat.


Energy can be generated on a large scale in this way, as is evident by the recent agreement between BMW South Africa and Bio2Watt.

Bio2Watt processes about 40 000 tons of cow dung annually from Beefcor’s feedlots near Bronkhorstspruit for its biogas plant and a further 20 000 tons of mixed organic waste.

“Pig farmers can use the same technology, but they should be careful of antibiotics and trace elements. The slurry which is produced by the digester may not be used as compost.”

A PVC-sheet catches biogas on a dairy slurry dam, to be burned in an engine that will drive a generator.


Crop farmers can also generate energy from their waste products instead of getting rid of them. Unlike a slurry-type biogas plant at a poultry or pig farm, a crop, sugar cane or timber farmer can rather consider a plant that burns the waste material directly in order to generate energy.

The regulations which control the planting of exotic trees for energy purposes could, however, cause a bit of a headache for those considering the timber option.

“In addition, fast-growing exotic trees use a lot of water and the authorities are concerned that they compete with food crops for water. They also ask whether the timber used to generate electricity will be for personal use or for a commercial purpose,” says Adrian.

“Farmers should also remember that biomass can change. Where it has a moisture content of 50% today, it might be 45% tomorrow,” he says. The technology they use should therefore take this into account.

The initial process – from the planning to the generating of the first electricity – is very expensive. The smaller the plant, the more expensive the technology. It is therefore advisable for farmers to set up a plant together through a co-op system, says Adrian.


One problem that farmers could encounter is that they may generate too much electricity and it can’t be stored. Mr Steve Lennon, managing director of the companies, SolaJoule and Shanduvan, says farmers must first optimise their own electricity usage and capacity and determine their demand before deciding how much electricity to generate electricity. This will already present a saving.

Each farm’s electricity needs are different, depending on how many pumps are powered, the heating and cooling and whether processing and packaging is done on the farm. If a surplus is generated, they must decide what to do with it. It can be returned to the grid or stored in batteries.

It is a very good idea to store excess electricity that you generate, but batteries are the most expensive electricity components. Luckily, they are getting cheaper.


Steve advises farmers to be on the lookout for affordable electricity storage options. He expects the cost of batteries to drop by about 60% to 70% over the next five years.

“If one takes into account that a battery can last for 10 years and that a 10-year plan for battery power can be considered, then these options are even more feasible. It therefore makes more sense to add more storage capacity to the existing grid.”


Instead of a large photovoltaic system, solar power can also be used on a small scale outside the grid. Although solar pumps can be expensive initially, their lifespan is quite long, and with the electricity saved, they can pay for themselves within a relatively short time.

“It may be advisable to call in a knowledgeable electrician to help review the entire pump system and to determine whether each pump really needs to be connected to the central grid. It may in the long run be cheaper to replace existing pumps with solar powered pumps,” says Steve.

A fairly big solar installation in South Africa.

ENQUIRIES: Mr Adrian Bowles, email:

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