Plans have been put forward for a new green waste processing plant in Herefordshire that would generate a versatile and valuable product.

Berkshire-based Onnu has applied for planning permission (number 241551) to build a “green hub” near Leominster which would turn felled trees and branches into “biochar” while also generating energy.

It would be housed in a 1,000-square-metre pitched-roof building on the site of a former waste transfer station off the B4361 near the Cadbury’s factory at Marlbrook, where planning permission has already been granted for industrial units.


The company says the facility would benefit the local tree care industry by providing a way to “upcycle” what for them would be a waste product amounting to 25,000 tonnes a year, with volumes swollen by the many ash trees in the county being felled as a response to ash dieback.

These would undergo pyrolysis, a “carbon-positive” process of heating organic material in the absence of oxygen, breaking it down into gases and a carbon-rich biochar.

The gases would then be burned to produce some of the energy to sustain the pyrolysis process, to dry the feedstock, and to generate electricity.

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This would then power two adjacent shipping container-type data centres, which would be rented to companies needing extra computing capacity for AI tasks, “in particular the pharmaceutical industry”, according to the application.

The biochar meanwhile has many uses across farming, horticulture, manufacturing and construction, in what Onnu’s application calls “a rapidly evolving and potentially profitable market”.

Able to retain nutrients and water when added to soil, biochar provides a greener alternative to plant fertiliser, or it can increase methane yields in anaerobic digestion systems, while also locking up atmospheric carbon, potentially for hundreds of years.


There would also be a separate biochar “bunker” and also an office block at the site.

The scheme would generate around five lorry deliveries of feedstock per day, and a further daily lorry trip to take the biochar away, Onnu says.

Comments on its proposal can be made until August 1.