Sweet sorghum: huge potential for food and energy

The spotlight is on sweet sorghum as a new Australian research study shows the crop’s huge potential as a single source of energy, food and animal feed.

While the crop has previously received global interest, little research has been conducted under Australian growing conditions or using Australian processing facilities - until now.

Conducted by the Queensland University of Technology in collaboration with industry partner AgriFuels, the study examined sweet sorghum’s agronomy, ability to be processed using existing processing infrastructure, carbon footprint, use in human and animal food products, and its possible use to produce biofuels.

Sweet sorghum is a fast-growing plant that produces a stalk with a concentration of fermentable sugars similar to that of sugarcane. It produces a large panicle of edible grain similar to that of grain sorghum. Unlike many other crops used for renewable energy production, sweet sorghum can simultaneously produce food and feed co-products.

Associate Professor Ian O’Hara, the project’s lead researcher, says sweet sorghum has a wide potential cropping area, including tropical and sub-tropical Queensland, the Northern Territory and temperate regions of New South Wales, Victoria and Western Australia.

“Our research showed that several varieties of sweet sorghum grew very quickly in field trials, reaching maturity in only 16–20 weeks, with fermentable sugar concentrations similar to those of sugarcane under optimal conditions,” Associate Professor O’Hara said.

“Our research indicates there are significant short-term opportunities for the co-location of sweet sorghum and sugarcane production to increase feedstock availability for bio-ethanol production. In fact, we found that adding sweet sorghum juice to sugarcane juice resulted in higher ethanol yields than fermenting sugarcane juice alone.”

As part of the study, the research team also produced a range of sweet sorghum food and feed products including sweet sorghum flour, syrup, sweet sorghum-based breakfast cereal, fish and animal feed pellets and human dietary fibre products.

“When we analysed the nutritional quality and economics of these products, it was shown that there are significant opportunities for manufacturing food and feed products from sweet sorghum in Australia. These products include livestock feed from sweet sorghum grain, syrup or molasses feed supplements, stock feed from sweet sorghum bagasse, and the production of mixed animal and fish feed products incorporating all three residues,” Associate Professor O’Hara said.

A carbon footprint analysis of six biorefinery process options for the conversion of sweet sorghum to fuel and animal feed products under Australian conditions was also carried out and the results were positive, Associate Professor O’Hara said.

“Sweet sorghum is one crop that has significant potential to contribute to the development of Australia’s bioeconomy. Further research and commercialisation activities will be required to help develop sweet sorghum potential for commercial cultivation and processing at a large scale in Australia,” Associate Professor O’Hara said.

The research project was funded by the Rural Industries Research and Development Corporation (RIRDC) and AgriFuels.

The complete research report, ‘Sweet sorghum - opportunities for a new renewable fuel and food industry in Australia’, is available here.