A business incentive scheme dubbed "RHI on steroids" by environmental campaigners could lead to payments of more than a billion pounds to UK investors over the next 20 years.
And the possibility has now been raised that up to seven huge agricultural companies could be milking the subsidies, over-claiming by as much as £38m for the installation and running of anaerobic digestion plants.
According to Friends of the Earth, payments which are made following the granting of a renewables obligation certificate (ROC) to a facility are four times higher in Northern Ireland than the rest of the UK.
An FOI request by the environmental group confirmed 179 anaerobic digestion units have planning permission in Northern Ireland, with 69 currently in operation.
They convert slurry into methane gas, creating energy which is fed back into the main electricity grid.
Based on information available on gas and electricity regulator Ofgem's website, campaigners estimate each unit will be entitled to around £900,000 per year in ROC payments with around £1.24bn set to be paid out on the 69 currently running over two decades.
Investigative website SourceMaterial this week named several companies they believe are making multiple claims for a single facility under different company names.
Director of Friends Of The Earth Northern Ireland, James Orr, said: "This is looking very serious. It's RHI on steroids and there must be an enquiry."
An increase in large factory pig farms is part of the government's Going For Growth strategy and Mr Orr said the environmental, social and financial impact across the country makes it a "much bigger scandal".
"This growth of already profitable farms is being further bolstered by these massive financial incentives for anaerobic digesters," he said.
There has been a long-running campaign against a plant operating in Newtownabbey and another against plans for a similar scheme in Limavady.
Energy watchdog Ofgem said: "We take allegations of this nature very seriously. Any allegation of fraud is referred to our counter-fraud team.
"In addition to assessing projects against the scheme's eligibility requirements, Ofgem runs an auditing programme of current or prospective scheme participants. Audits are undertaken by independent assessors who can make site visits any time after an application for accreditation has been received.
"In the event of any potential non-compliance, error or fraud being identified through the audit programme, new information or other regular checks, Ofgem investigates thoroughly and, where appropriate, can withdraw accreditation and revoke or withhold certificates awarded. If there is evidence of fraud we also contact the police."
The Department of Agriculture, Environment and Rural Affairs has not yet responded.