HOW much does carbon dioxide weigh?

Not a lot, right? It is a gas, after all: in a year, an average human breaths out 380kg of the stuff – just over a third of a tonne.

In the past 12 months, Oxford's Low Carbon Hub has saved 541 tonnes of carbon dioxide gas from going into the atmosphere.

That's just under the weight of 100 African elephants.

The figure is one of the many astounding statistics the hub has calculated for its first ever Social Impact Report.

Among the others are the fact that the group now has enough solar and hydro plants to power 853 average homes every year.

That is power that has all been made possible with community investment, donations and grants in just five years since the group started operating.

In a statement about the report, the hub said: "We’re really pleased to share our first ever Social Impact Report.

"A big part of the feedback from our first stakeholder survey was that people wanted more information not only about what we do at the Low Carbon Hub, but also how we’re doing, and so we’ve produced this report showing our progress against four indicators: planet, people, prosperity and perception.

"The report illustrates how much we've achieved over our first five years."

Since 2012, the Low Carbon Hub – now based at offices in Park End Street – has installed a total of 36 renewable energy installations around the county.

Those include 24 solar power arrays on the roofs of schools and the recently-completed £3.2m Sandford Hydro plant in the Thames just south of the city.

In fact, every year since 2012, the group has doubled its power generation capacity.

In 2016/ 17 alone, the group installed 1.6MW worth of new capacity and generated 1,552,027kWh of electricity, saving 541 tonnes of carbon dioxide emissions.

However when Sandford Hydro starts turning properly this winter, when the level in the Thames rises high enough to start pushing its giant Archimedes screws, the hub will be able to generate more than 2.6mkWh of energy – enough to power 853 average homes – and save 1,188 tonnes of CO2 from the atmosphere.

All of this has been possible by persuading average people to invest some of their wages in a greener, more sustainable future.

To date, that investment stands at just over £3.4m and rising.

The hub's CEO, Dr Barbara Hammond, is delighted with the achievements so far, but already looking forward to what can be accomplished in the next five years.

She said: "We are just at the start of our journey and want to achieve so much more, but we’re proud of the progress we’ve made during our first five years.

"Thank you to the many individuals and organisations that have worked with us to make this possible."