Breeding sorghum in South Africa could be breakthrough for biofuels

A breakthrough by the African Centre for Crop Improvement in the breeding of sorghum could have far-reaching implications for the biofuel and bioplastic industries in South Africa.

For the last decade, ACCI director Professor Mark Laing has been working on developing sorghum and sugar beet varieties, as part of an integrated package to provide crop material (feedstock) for these two industries. His interest in the project started about 15 years ago when the price of oil rose to $150 a barrel.

“A large plastics company couldn’t get enough ethylene to make the quantities of polythene on order, so they wanted to start their own sugar-to-polythene plant and approached me about suitable sugar crops for the interior of South Africa,” he says.

With funding from Technology Innovation Agency (TIA), which is based in South Africa’s Department of Science and Technology (DST), Laing has been working on how to produce year-round feedstock on an industrial scale, by rotating sorghum and sugar beet.

Three primary sugar crops are used in the production of biofuel: sugar cane, sorghum and sugar beet. Laing says sweet sorghum, which is naturally high in sugar, is drought tolerant and yields 100 tonnes per hectare at 13-18% sugar in six months, compared to sugarcane, which can only be grown in frost-free areas, takes one to two years to reach maturity and yields approximately 75 tonnes per hectare at 9-14% sugar in South Africa.

Sugar beet is difficult from an agronomic perspective because it is a northern hemisphere crop, but the ACCI is developing varieties that can be grown in South Africa in winter. It has a sugar content of up to 24% and yields 50-75 tonnes per hectare in six months.

Importantly, it is a winter crop and can be rotated with sorghum, which grows in summer, thereby providing year-round feedstock.

Shortage of feedstock

“The world of bioplastics and biofuels is going to happen but in Africa at the moment it can’t take off because it doesn’t have crops to feed it,” says Laing, explaining his motivation for pursuing this project.

“Once we’ve got the hybrids and agronomy available it means that people can start up factories producing bioplastics and biofuels. That’s been my vision and sorghum and sugar beet are the best crops to do it. We can get 31 tonnes of sugar per hectare per annum if we plant these two crops for six months each.”

The project has taken ten years to reach this point because sorghum is challenging to grow. “It’s difficult to pollinate because it self-pollinates, but we’ve cracked that,” he says, explaining that ACCI PhD graduate Dr Precious Mangena has successfully developed sweet sorghum hybrids using a chemical called E4FO, a male gametocide that ensures cross-pollination.

“It sterilizes the pollen but doesn’t affect the ovaries. The plants you spray become females and the neighbours pollinate them. So you force the plant to become an outcrossing crop,” says Laing. “This accelerates our breeding programme and it allows us to produce hybrids.”

Laing said this breakthrough could be a global first for the ACCI. “Other scientists have done it for breeding and experimental purposes, but we are perhaps the first to be using it as the basis for hybrid seed production of sorghum.

Funding

Laing says DST is excited by the project because it is looking for ways to drive the green economy. “If this value chain works it is literally bio-based manufacturing, and it’s creating jobs. This is exactly what DST means by a green economy.”

Dr Xolisa Melamane, TIA’s Agriculture portfolio manager, says the project is attractive because it involves the use of novel technologies such as the rotation of sweet sorghum with sugar-beet, and the crops under development will possess advantages such as adaptation to drought, pests and diseases.

“The project owns the intellectual property, which is one of the fundamental factors TIA looks at when funding projects,” says Melamane, adding that the project also ticks other boxes such as redressing inequality, creating jobs and addressing environmental pollution.

“Another aspect examined is the commercialisation potential of the technology after development. In this project hybrid seed of the two crops will be licensed to seed companies, and already SeedCo has expressed interest in assisting with the development and marketing of hybrid seed of these crops,” she says.

Industry partner

To make the plan come to life the ACCI has been working with eThala Biofuels, a company that is trying to secure funding to establish a factory to produce biofuels.

“They’ve got land and production agreements organised with commercial and small-scale farmers, and they have plans to build a biofuels factory, but they don’t have the right crops to grow and process,” says Laing. “They want to produce ethanol to start with and I’ve convinced them to also think about producing bio-plastics such as polyethylene from sugar.

Laing says although this plastic would not be biodegradable, it would be carbon neutral. “The advantage of this plastic would be that it is sustainable and not subject to the oil price. Plus it would not be contributing carbon to the atmosphere. The crop takes carbon out of the air and if it goes into a landfill the carbon is sequestered.”

“Ironically, a plastic bag can sometimes be environmentally friendly even when it’s in a landfill because it’s more carbon that’s been taken out of the atmosphere.”