At a fuel plant near Hull, 20 tonnes of wheat are being poured from a lorry into storage, ready to be turned into ethanol – a type of alcohol that, when blended with petrol, reduces emissions.

But this week’s delivery, grown in the fields of Lincolnshire, is the last one on order for Vivergo Fuels.

The owners of the UK’s largest bioethanol plant, at Saltend, say its future is in doubt following a government decision to end a 19% tariff on US imports of the fuel as part of the recent UK-US trade deal.

Last month, Vivergo, which is owned by Associated British Foods (ABF), began consulting staff about shutting down the plant due to the uncertainty.

Managers are calling for financial help from ministers. Without it, they say production at the site – which employs more than 160 people – may halt before 13 September.

They estimate about 4,500 jobs in the supply chain will be affected, including the farmers who grow the wheat and the truck drivers who transport it.

The government says it is in formal discussions with the company and wants to find “a way forward that protects supply chains, jobs and livelihoods”.

Stacey Monkman, who has worked at Vivergo for three years in the commercial and logistics departments, says it has been difficult to keep up morale.

“We’re motivated because we’ve still got our jobs to do, but it’s very unsettling.

“Being in limbo and waiting, not knowing which way it’s going to go, it’s hard,” she says.

“We’ve all got families, we’ve all got bills to pay… a lot rides on it for us.”

Production manager Nick Smalley began as an apprentice and now manages about 65 people at the refinery.

“It’s really frustrating that these decisions are being made and we have no influence over them,” he says.

“I care deeply about the team that I have here, I want a bright future for all of those people. We really need quick action now, it’s getting to crisis point.”

Production at Saltend had already been cut due to low bioethanol prices, with ABF initially raising the prospect of closure in April. The trade deal followed in May.

It is not only Vivergo employees who are affected. The plant buys more than a million tonnes of British wheat each year from more than 4,000 farms and says it has purchased from 12,000 individual farms over the past decade.

Farmer Matt Pickering, of Pickering and Sons, near Gainsborough, Lincolnshire, sold the last load of wheat to Vivergo.

“We struggle with the quality of our land type, so we tend to go for out-and-out bulk volume shed fillers,” he says.

“Vivergo has been a fantastic home for us to sell feed wheat into.”

Meanwhile, Aghaul Limited, which transported the final wheat load to the plant, is among transport companies feeling the blow.

Managing director Mike Green believes the potential loss of the contract will have a significant “knock-on effect” for his haulage business.

“The government needs to have a look at this because it doesn’t just affect me, there’s a humongous amount of people that it’s going to affect.”

Ben Hackett, the managing director of Vivergo, describes the plant as a “key foundation on the whole green economy”.

Removing the tariff on US imports destroyed the market, he argues.

“The customers have gone overnight. That’s given us a real crisis. We cannot afford to operate this facility as a loss,” he adds.

Mr Hackett wrote to growers earlier this year explaining that the plant will only be able to honour existing contractual obligations for wheat purchases while the uncertainty continues.

He has urged the government to support bioethanol production by creating a clear framework in order to boost demand, in addition to providing financial help during the transition.

“We are weeks at most away from Associated British Foods having to make a decision on the viability of the business,” he says.

“This site could very well close unless the government takes action.”

A government spokesperson said the bioethanol industry had been facing “significant challenges” for some time and ministers were working with Vivergo on a plan to protect jobs and the supply chain.

Engagement with the companies continued “at pace” and external consultants had been brought in to help.

“We recognise this is a concerning time for workers and their families which is why we entered into formal discussions with the company on potential financial support last month,” the spokesperson said.

“We will continue to take proactive steps to address the long-standing challenges the company faces and remain committed to working closely with them throughout this period to present a plan for a way forward that protects supply chains, jobs and livelihoods.”