Revised plans for an anaerobic digestion (AD) plant in Herefordshire have been granted permission by the Environment Agency (EA).

Landowner Nicholas Layton plans to build the unit at Whitwick Manor, near Ledbury. If approved, it would convert poultry manure and other agricultural waste into natural gas.

Although Mr Layton said the digester would not damage the River Wye ecosystem, environmental groups have raised serious concerns that it could harm an already fragile habitat.

A decision on its application for planning permission is expected to be made by Herefordshire Council in December, after first submitting proposals for the unit, near Yarkhill, two years ago.

If given the green light, the DA would import 116,000 tons of poultry manure and apple pulp from area farms each year, generating enough natural gas to power about 6,000 homes, the application states.

The project would also produce a nutrient-rich residue that could be sold as fertilizer.

But the project has attracted hundreds of objections from the public, raising concerns about pollution, landscape impact and traffic.

In January, an analysis by county council officers concluded there would be “an adverse effect on the integrity” of the protected River Wye catchment.

The status of the Wye was last year downgraded to “unfavorable – decreasing” by Natural England after fewer species, such as Atlantic salmon, were recorded.

Poultry waste contains phosphorus which can contribute to excessive algae growth in rivers.

In October, Mr Layton’s agent, Bourne Valley Associates, told the county council’s planning team that a modified scheme would result in a net decrease in phosphorus pollution.

The construction consultancy said no phosphate fertilizer produced by the digester would be resold within the River Wye catchment.

An EA spokesperson confirmed a permit had been issued, with a number of “pre-operational” conditions.

“This ensures that the proposed operations will not cause harm to the environment. We understand that the site will also be subject to planning permission,” they said.

However, environmental groups have called on the agency to explain why it issued the permit, given the poor condition of the Wye and its tributary, the Lugg.

“The granting of the permit is premature and appears to flout our democratic process for determining these applications, with due scrutiny and appropriate local expertise,” said Andrew McRobb, director of CPRE Herefordshire.

Tom Tibbits, chairman of Friends of the River Wye, warned there was a very real risk of a “catastrophic pollution event” in a sensitive part of the River Lugg catchment.