Proposals to boost support for tidal energy have been launched by the Scottish Government.

The consultation also includes plans to remove financial support for large-scale biomass electricity generators.

Energy Minister Fergus Ewing has launched a consultation on the Renewables Obligation (Scotland) (ROS) proposing increasing the number of renewable certificates, called ROCs, allocated to tidal energy generation from three to five per megawatt hour.

Electricity suppliers are required to provide an increasing share of power from renewable sources, and different numbers of ROCs are awarded for different types of renewable energy generation.

The consultation also proposes a cap on the size of biomass plant which would receive support.

Smaller, more efficient biomass projects would continue to receive support, but large-scale electricity-only stations, above a certain generating capacity, would no longer be eligible for support under the ROS.

Mr Ewing said: "Scotland's renewable resources are unparalleled. The changes proposed in this consultation will help make sure we continue to make the most of this valuable potential."

He also said that UK ambitions for large-scale, electricity-only woody biomass plants are an "inefficient use" of a finite resource.

He said: "We have serious concerns around the sustainability of supply. If proposed levels of imports are not matched with forecast demand or become more difficult to access, there is the danger that energy generators will find it easier to access their feedstocks from domestic wood-processing industries' well-established wood supply chains.

"By re-examining and proposing to reduce this subsidy we are sending a clear message about the best use of biomass and reducing the potential detrimental impacts on Scotland's timber industries and the thousands of rural jobs they support.

"We have a quarter of Europe's tidal stream, and the increase in support for this technology will encourage energy firms to capitalise on the enormous potential this presents."

WWF Scotland welcomed the consultation.

Dr Dan Barlow, head of policy at WWF Scotland, said: "Renewables have a vital role in supporting Scotland to become a low-carbon economy and ending our reliance on polluting coal, gas and nuclear power.

"Confirmation of renewables support levels is key to providing the investment certainty needed to realise the huge wind, wave and tidal opportunities on our doorstep, and make a 100% renewable energy future for Scotland a reality.

"With funding for tidal energy boosted and the retention of enhanced support for wave power, Scotland can maintain its position at the forefront of marine energy development.

"Proposals to cut support for large-scale biomass electricity stations is good news given concerns about the efficiency and sustainability of such plants."

He added: "Investment in renewables will not only help green our entire energy system but protect us from volatility of oil and gas prices, reduce bills for consumers over the long term and provide unrivalled economic opportunities for Scotland."