Flying, for business or pleasure, has long been seen as one of the biggest carbon villains. As airports gear up again after Covid it's clear not every business wants to keep meetings online or holidaymakers settle for a staycation.

But what if we could fly without the guilt? Tom Heap meets some of the pioneers of zero carbon flight: hitching a ride with Harbour Air in Canada who have retrofitted one of their planes to fly on electric battery power; visiting the equivalent of the Batcave with a Bristol company making EVTOLs - electric vertical take-off and landing vehicles - which could see us zipping between cities; and asking about the use of sustainable aviation fuels. Dr Tamsin Edwards joins him to discuss how much carbon dioxide - and more - this could potentially save.

Produced in association with the Royal Geographical Society. Special thanks for this episode to Dr Andy Jefferson from Sustainable Aviation and Tim Johnson from the Aviation Environment Federation.

Producer: Anne-Marie Bullock

Nuclear power should be a powerful ally in the fight against climate change but cost and safety issues hold it back. Could a new generation be safer and cheaper? Tom Heap meets the team behind the molten salt reactor that can use nuclear waste as fuel and is claimed to be significantly cheaper and safer than current reactors.

Ian Scott was a senior scientist at Unilever, pioneering research into skin-ageing, but when he retired from the field of biological sciences he became fascinated by the costs of nuclear power. Why had nuclear electricity- which we'd once been promised would be 'too cheap to meter'- become one of the most expensive forms of energy generation. The answer lay with the safety mechanisms that have to be built-in to reduce the risk of another Chernobyl or Fukushima. If he could develop a system that would be much safer then it would, almost certainly, be much cheaper.

Scott's central idea- to use molten salt as a coolant rather than water- caught the eye of energy authorities in Canada and Ian's company, Moltex, has plans to build its first reactor in New Brunswick. Significant safety concerns remain, with some in Canada concerned about Moltex plans to use spent fuel from conventional reactors and others raising fundamental issues about the corrosive qualities of molten salt and the generation of radioactive tritium

Tom visits the Moltex laboratories and climate scientist, Tamsin Edwards, gauges the potential impact on greenhouse gas emissions.

Producer: Alasdair Cross

Produced in association with the Royal Geographical Society. Special thanks for this episode to Professor Ian Farnan and Dr Eugene Shwageraus from the University of Cambridge.

Biochar is an idea thousands of years old but one that seemed to have been (foolishly) lost by many along the way.

Like charcoal, biochar is made by baking wood in the absence of oxygen and then quenched. It can then be ground down and worked into the soil to improve fertility and crop yields. It's believed to have been applied thousands of years ago in the Amazon, to generate the Terra Preta.

The biochar locks in much of the carbon captured by the trees and stabilises it. Tom meets Forester Dave Faulkner and his team at Whittlewood to see the productions process in Northamptonshire.

Meanwhile, Josiah Hunt experimented with the process in Hawaii and now supplies across California. As well as capturing carbon and improving the soils, he says they're removing liability wood to reduce forest fires and are helping to produce green electricity.

Can this ancient process help bring new hope?

Producer Anne-Marie Bullock

Produced in association with the Royal Geographical Society. Special thanks for this episode to Professor Stuart Haszeldine and Dr Ondřej Mašek from the University of Edinburgh and the UK Biochar Research Centre.

Concrete blocks are the foundations of the modern world but they could be greener. Tom Heap meets Colin Hills and his team turning waste dust and carbon dioxide into building materials.

Professor Hills of the University of Greenwich has developed a technique that mimics natural processes, using carbon dioxide as a glue to form stone aggregates from waste dust left behind by heavy industry. The spin-off company, Carbon 8 Systems, has compressed the process into a shipping container and now makes building materials in the UK and France with this clever carbon-munching technique. Colin's colleague, Nimisha Tripathi wants to adapt the system for the developing world, choosing waste from her native India- things like pistachio shells and banana skin- to make a tailored range of building products relevant to the region in which they're made.

Tamsin Edwards of King's College London joins Tom to consider just how much carbon dioxide we can remove from the atmosphere by developing this new generation of bricks and mortar.

Produced in association with the Royal Geographical Society. Special thanks for this episode to Professor Paul Fennell and Dr Rupert Myers of Imperial College London and to Professor Karen Scrivener of École Polytechnique Fédérale de Lausanne.

How to improve mass catering for the planet. Tom Heap considers how changing the menus in schools, hospitals and the armed forces could help in the fight against climate change.

Andy Jones, chair of the Public Sector Catering 100 Group, explains how his own farming family background informs his drive to reduce the amount of meat served in canteens and increase the choice of vegan and vegetarian options. Tom visits hospitals in Nottingham to see the drive in action and joins climate scientist, Dr Tamsin Edwards to consider the carbon impact of a broader shift from beef to beans.

Producer: Anne-Marie Bullock

Produced in association with the Royal Geographical Society. Special thanks for this episode to Dr Rosie Robison from Anglia Ruskin University and to Dr Tara Garnett and Dr Peter Scarborough from the University of Oxford.

From clothes to cars and buildings, all our new 'stuff' takes energy and resources to produce. If we want to cut down the use of high carbon materials like steel and cement then we need a new attitude. We need to think about sharing more and valuing what we have, we need products that are designed to last longer.

Tom Heap meets Aisling Byrne from clothing app NUW. Concerned about the impact of fast-fashion on the environment, she found that lecturing friends who loved fashion didn't change their minds or behaviour, so she's designed a clothes-sharing app for people to put unwanted clothes into new hands and get the excitement of something 'new' in return. It can stop the demand for brand new products at the top end and avoid landfill at the other end. Professor Julian Allwood of Cambridge University expands on how much our desire for bigger and better is impacting on resources and how behaviour change needs to come sooner rather than later.

Producer: Anne-Marie Bullock

Produced in association with the Royal Geographical Society. Special thanks for this episode to Dr Mike Tennant of Imperial College London, Dr Sonali Diddi of Colorado State University, Professor Jana Hawley of the University of North Texas and Professor Sandy Black of the London College of Fashion.

A big weight and a very, very deep hole. The team behind Gravitricity think they have found a solution to a serious problem with renewable energy. As we rely increasingly on wind and solar energy the risk rises of the lights going out when the wind doesn't blow and the sun doesn't shine. We can solve the problem with energy storage but batteries are expensive and don't last very long. As Tom Heap and Tamsin Edwards hear, the answer could lie with a deceptively simple pulley system. Put an enormous weight at the bottom of a mineshaft. When you have lots of wind or sun, use the electricity to pull the weight to the surface. When you're short of power, release it and send a huge surge of energy back into the grid.

Producer: Alasdair Cross

Produced in association with the Royal Geographical Society. Special thanks for this episode to Professor Stephen Peake from the Open University and Dr Hugh Hunt from the University of Cambridge.

Heating our homes can be expensive and draughty old housing stock leaches carbon dioxide. But making homes more energy efficient can be a costly upheaval and is therefore often done piecemeal. Tom Heap meets the team from Energiesprong who are proposing a new model - retrofitting modern technology like insulating 'wraps' around the house, replacing roof tiles with solar panels and fitting ground source heat pumps into old housing stock. It's done on scale and on a whole-house basis to keep costs down with the aim of creating net zero energy homes but also to create 'kerb appeal' so that neighbours will want to 'keep up with the Joneses'. Tom is joined by climate scientist Tamsin Edwards to discuss whether tackling inefficient, poorly insulated housing head-on can provide great gains for people and planet.

Producer: Anne-Marie Bullock

Made in association with the Royal Geographical Society. Special thanks for this episode to Kate De Selincourt, Professor Stephen Peake from the Open University, Professor Gavin Killip from the University of Oxford and John Palmer from Passivhaus Trust.

Soil is brilliant at capturing carbon dioxide and keeping it out of the atmosphere. But what if we could make it do an even better job? On a farm overlooking the broad River Tay in Perthshire they've sprinkled the fields with the waste product from quarrying. Nature does the rest - using the rockdust to pull carbon dioxide from the air and store it in the soil. With the help of Rachael James from Southampton University, Tom Heap and Tamsin Edwards check out a technique that could be applied to millions of hectares of the world's farmland.

Producer: Alasdair Cross

Made in association with the Royal Geographical Society. Special thanks for this episode to Professor Heather Viles of the University of Oxford, Professor Larissa Naylor and Dr Adrian Bates from the University of Glasgow, and Dr Phil Renforth of Heriot-Watt University.

Giant fans are sucking in fresh air from the Swiss Alps and Iceland's frozen interior, capturing the carbon dioxide and turning it into fizzy drinks or burying it deep underground. Tom Heap gets up close to the extraordinary Climeworks device at the Science Museum in London and talks to the team that's developed it to ask if they've designed the solution to climate change or created a potent symbol of our failure to cut carbon emissions? Dr Tamsin Edwards of King's College London joins Tom to crunch the numbers.

Producer: Alasdair Cross

Produced in association with the Royal Geographical Society. Special thanks for this episode to Dr Samuel Krevor and Professor Nilay Shah of Imperial College London and Professor Jon Gluyas of Durham University.