MANY university students waking up with a parched mouth and a thumping headache would attest to the likeness between tequila and rocket fuel.
It turns out they may not have been far off the mark, with researchers from three universities conducting a successful trial manufacturing biofuel from the agave plant, which is used in Mexico to make tequila.
Topically at present, there is also scope for it to be used to make hand sanitiser, which has been a hard to source item in the wake of the COVID-19 outbreak.
Excitingly agave could be grown over large tracts of Australia's semi-arid tropics currently unable to sustain crop.
Associate professor Daniel Tan, of the University of Sydney, who worked on the project together with teams from the British University of Exeter and the University of Adelaide, said the researchers had conducted trials at Rockhampton and Ayr in Queensland while MSF Sugar has a commercial agave farm on the Atherton Tablelands.
However, Prof Tan said that the crop would be equally suited to parts of Western Australia's dry tropics.
"It likes sandy soils and a summer dominant rainfall pattern as that is when it is growing, so it is not as well suited in winter-dominant rainfall Mediterranean zones to the south, but it is well adapted to northern Australia," Prof Tan said.
"We've actually found it can do better in northern Australia than in its native Mexico due to occasionally getting extra rainfall as a result of tropical storms.
"It can tolerate the wet weather which you can see in the Australian tropics following a cyclone just so long as it does not have wet feet for too long."
In terms of yields, Prof Tan said agave can achieve slightly lower yields as other potential sources of biofuel, such as sugarcane, but its water and nutrient usage was much lower.
"You will get a higher yield out of sugarcane but it needs a lot more water and nutrient for that crop."
He said agave yields over a five year period were reasonable compared to sugarcane.
"You can get the equivalent of 9900 litres of bioethanol a hectare a year with sugarcane, with agave that is around 7400 litres a hectare a year."
Prof Tan said, however, there were markedly different harvesting patterns.
Sugarcane is harvested annually, but he said the best results for the perennial agave came when it was harvested after five years.
"We did trials harvesting it once at three years or at five years and the longer period from planting to harvesting was best in terms of total yield."
Prof Tan said when used for making spirits like tequila in Mexico, only the stem, or pina, of the plant was used, but said the leaves could be used for biofuel.
"The waxy leaves are bitter which mean they are not very palatable but this is not an issue when making ethanol and they help boost the yield."
Similar to sugarcane, the agave has stems and leaves high in sugar (mostly inulin).
It is processed simply by steaming to aid sugar extraction and then fermenting, a different method than converting starches into sugars as is required when using cereals for ethanol.
Following the steaming it is then chopped up and fermented before being distilled.
The waste product can be used as biochar for energy creation.
In terms of harvesting, Prof Tan said a modified sugarcane harvester can be used.
The research found agave used 69 per cent less water than sugarcane and 46pc less water than corn for the same yield.