Agave's biofuel potential

Could the agave plant hold the key to sustainable biofuel production in Australia?

A team of researchers at the University of Sydney, University of Exeter and University of Adelaide has discovered that the agave plant — traditionally used to make tequila — could be established in semi-arid regions as an environmentally friendly solution to Australia’s transport-fuel shortage.

The efficient, low-water process could also help produce ethanol for hand sanitiser, which is currently in high demand due to the COVID-19 pandemic.

Publishing findings in the Journal of Cleaner Production, University of Sydney agronomist Associate Professor Daniel Tan, along with international and Australian colleagues, has analysed the potential to produce bioethanol (biofuel) from the agave plant, a high-sugar succulent widely grown in Mexico to make the alcoholic drink tequila.

The plant is being grown as a biofuel source on the Atherton Tablelands in Far North Queensland by MSF Sugar. Associate Professor Tan, from the Sydney Institute of Agriculture, said the plant promised some significant advantages over existing sources of bioethanol such as sugarcane and corn.

“Agave is an environmentally friendly crop that we can grow to produce ethanol-based fuels and healthcare products,” Associate Professor Tan said.

“It can grow in semi-arid areas without irrigation, and it does not compete with food crops or put demands on limited water and fertiliser supplies. Agave is heat- and drought-tolerant and can survive Australia’s hot summers.”

Associate Professor Tan assembled the research team and led its economic analysis.

Lead author Dr Xiaoyu Yan from the University of Exeter, who led the life cycle assessment, said, “Our analysis highlights the possibilities for bioethanol production from agave grown in semi-arid Australia, causing minimum pressure on food production and water resources.

“The results suggest that bioethanol derived from agave is superior to that from corn and sugarcane in terms of water consumption and quality, greenhouse gas emissions, as well as ethanol output.”

The study used chemical analysis of agave from a pilot agave farm in Kalamia Estate, Queensland (near Ayr) undertaken by Dr Kendall Corbin for her University of Adelaide PhD, supervised by Professor Rachel Burton.

“It is fabulous that the results of my chemical analysis can be used in both an economic and environmental footprint study and have real-world applications,” Dr Corbin said.

Associate Professor Tan commented, “The economic analysis suggests that a first generation of bioethanol production from agave is currently not commercially viable without government support, given the recent collapse in the world oil price. However, this may change with the emerging demand for new ethanol-based healthcare products, such as hand sanitisers.

“This is the first comprehensive life cycle assessment and economic analysis of bioethanol produced from a five-year agave field experiment in North Queensland. Our analysis shows a bioethanol yield of 7414 litres a hectare each year is achievable with five-year-old agave plants.”

The study found that sugarcane yields 9900 litres per hectare each year. However, agave outperforms sugarcane on a range of measures, including freshwater eutrophication, marine ecotoxicity and — crucially — water consumption.

Agave uses 69% less water than sugarcane and 46% less water than corn for the same yield. For US corn ethanol, the yield was lower than agave, at 3800 litres per hectare a year.

“This shows agave is an economic and environmental winner for biofuel production in the years to come,” Associate Professor Tan said.

Image caption: Associate Professor Daniel Tan from the University of Sydney with agave plants.