Gas field: Grass could soon be heating UK homes

Gas converted from grass could be used to heat up to 4,000 UK homes thanks to a new partnership between UK firm Ecotricity and Finnish shipping giant Wärtsilä at their planned new biofuels plant in Reading.

Powered by anaerobic digestion, the unmanned plant is set to be the first green gas mill in Britain when it opens in 2023 and forms a crucial backbone in both companies' plans to reduce carbon emissions.

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Grass is the primary feedstock for the machine, which is placed in a silo and held for two months where it will slowly break down, before being transferred into a digester, where it emits methane, which is then collected by the refinery. The resultant biogas is then sent directly to energy grids. 

At peak capacity, it could churn out anywhere from 500 to 6,000 normal cubic metres (Nm3/h) of gas per hour. Turnover time is anywhere from 8 to 11 months.

The heat generated by homes through the grass gas can also be recovered at a roughly 90% rate, according to the plant's website. Its "plugin and play" model also means tech can be easily moved.

“Replacing fossil fuels with grass gas could provide significant green energy benefits while allowing existing gas boilers installed in homes all around Britain to still be used, but in a much more sustainable way", said Chris Ives of Paul Winter Consulting Ltd, an engineer hired by Ecotricity to manage the project.

He said the biogas could prove effective in allowing UK homes to shift away from natural gas for power. 

Ecotricity plans to build dozens more green gas mills in the future. If successful, it could provide power to as many as 22 million homes in Britain.

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The process to convert the grass into gas was discovered by the UK firm, but Wärtsilä will be supplying the tech for the plant itself.

The idea that grass can be turned into energy was first unveiled a few weeks ago. Ecotricity claims this technique could be used to power "all UK homes" if it could be scaled up effectively.

Overall, the initial plant will cost around £11 million (€12.7 million) to build, but Ecotricity founder Dale Vince has stated it will not interrupt local livestock or agricultural supply chains.

He expects the plant to be operational "by this time next year", adding that the tech that turns the grass into renewable gas is "a very exciting discovery".

"This is our new North Sea and it's right underneath our feet", he said, hoping tech like this could be used to assuage the ongoing energy crisis.

Diversification of energy markets - using as many different energy sources as possible - may be important for the energy transition. If the energy comes from different sources, disruptions are less likely to create the kinds of calamitous effects seen during cyberattacks or natural crises.

This, in effect, makes the supply chains more resilient while also helping more companies get involved. As Ives said, many alternative fuels can make use of existing energy infrastructure such as gas pipes.

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Wärtsilä claims green grass is carbon neutral in that the CO2 it absorbs whilst growing is released back into the atmosphere when the methane is burned - the CO2 was already present but does not add extra to the air. Fossil gas, by comparison, releases CO2 that is not in the atmosphere now, meaning that it is a net addition to atmospheric CO2.

“As a company committed to helping decarbonise the industries we serve, we are delighted to be involved in this exciting green energy project. In addition to its technological advantages, our Puregas CA50 biogas upgrading plant provides the customer with the lowest total cost of ownership, which is central to our product development”, said Steven Scott, the Sales Manager for Biogas Solution at Wärtsilä Gas.

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