The proponent of a contentious wind farm on a Tasmanian island has been asked to come up with a plan to compensate for the loss of hundreds of hectares of Tasmanian devil habitat.
Renewables company ACEN Australia is seeking to build a wind farm with up to 122 turbines on Robbins Island, off the state's north-west coast.
The proposal has already been given the go-ahead by Tasmania's Environment Protection Authority and has also received the green light from the local council.
But the project still needs approval from the federal Environment Department, which has requested ACEN provide "an offset strategy and offset management plan to compensate for the loss of up to 366.2 hectares of Tasmanian devil habitat".
The department's Head of Environment Approvals Division Bruce Edwards told a Senate estimates hearing they had not received adequate information from the proponent "in relation to the impacts of the devils or how they might offset those".
"We're asking how offsets would work and what a strategy would look like," he said.
"The proponent actually needs to explain to us why something would be manageable and acceptable under national environmental law.
"Then we will asses whether that claim stacks up."
The department notes "suitable offsets must deliver an overall conservation outcome that improves or maintains the viability of the protected matter as compared to what is likely to have occurred under the status quo, that is if neither the action nor the offset had taken place".
This is the latest hurdle for the 900-megawatt wind farm, which was given approval by the state on the condition the turbines would be non-operational for five months of the year to protect critically endangered orange-bellied parrots.
ACEN said the "confusing" operating condition would effectively kill the project, and an appeal against it is currently playing out in the Tasmanian Civil and Administrative Tribunal.
Proponent not fazed by request
Tasmanian Greens Senator Peter Whish-Wilson, who raised questions about the project during senate estimates, said he believed the $1.6-billion project should be stopped.
"I think the proponent should abandon the project, it's not an appropriate place to put one of the biggest wind farms in the world," he said.
"To build a massive industrial wind farm in that area is only going to add pressure to the Tasmanian devils.
"I just don't know how they are going to find a solution and I think they are better to walk away from the project."
But chief operations officer for ACEN Australia David Pollington said the department's request was "just another step in the process" and was "not unusual".
He said the federal department used a "fairly complex mathematical calculation" to determine what offsets, if any, were needed.
"Over the next month or two, we will prepare information for all those variables to go into the offset calculator," he said.
"It would be fair to say that the Tasmanian assessment, along with our expert assessment, says there is no impact to devils."
Mr Pollington said a covenant may need to be put in place, meaning "an area is set aside for protection that would limit any impact to that area to enable it to be left for the devil's habitat".
"One approach is that you could find land elsewhere within Tasmania but it is also permissible to do that within the island," he said.
"There are areas where potentially a covenant could be applied which would limit any further developments and limit access which might have a detrimental effects on devils.
"It's a might and it's an assessment that the department needs to do in terms of the operation of their offset calculator."
While the department notes "current evidence indicates that the Robbins Island Tasmanian Devil population is free from devil facial tumour disease", Mr Pollington said it was not an isolated population.
"The genetic information that we got proved they weren't an isolated species and were interbreeding with other devil populations," he said.
A Tasmanian devil was recently found to have the disease on the Tasmanian mainland, not far from Robbins Island, in an area previously thought to be free of the disease.
