Four demonstrators have been fined a total of £850 after laying siege to Grangemouth docks in a protest against plans by the port’s owners to build four large biomass power stations in east Scotland.

Hannah Downie, 22, Almuth Ernsting, 42 and Kimberley Ellis, 24, were each fined £200. Alistair Coutts, 52, was fined £250. Three others had their not guilty pleas accepted by the prosecution.

The four admitted blocking access to the port on May 16 by "obstructing the lawful passage" of other people and failing to stop when required by police officers.

After the hearing the demonstrators said they "had no choice" but to break the law.

They claimed they brought the entire port to a standstill for six hours in protest at "plans which would involve burning vast quantities of wood".

Forth Energy, a company mainly owned by Forth Ports, plans to build one of the power stations at the docks in Grangemouth. The others are scheduled for the ports of Leith, Rosyth and Dundee.

The stations would burn biomass, mainly in the form of imported wood and in quantities equivalent to two-thirds of the UK's entire annual wood production. The protesters claim local sourcing of the wood would be impossible.

The demonstrators blockaded the port from 7.45am on May 16.

At one entrance they used a 20ft high tripod made of scaffolding poles to which three protestors attached themselves. The other entrance was made impassable by five protestors who locked themselves together using "arm tubes".

Meanwhile 12 supporters held banners and handed out leaflets to drivers and port workers explaining the reason for the protest.

Police used cutting equipment and a scaffolding construction to remove the protestors.

After her court appearance, Ellis said: "The government seems to be taking no notice of the problems these power stations would create; the destruction of forests and other ecosystems, climate change impacts and the displacement of communities and indigenous peoples.

"Locally it will lead to health problems associated with air pollution. On top of it all, the disposing of warm waste water will kill fish and other sea and river life by causing unnatural temperature changes."

Coutts added: "There are so many ways that these plans are bad that I saw no alternative but to get involved. Creating such a vast new demand for wood can never be sustainable despite the energy being classed as renewable."