Ever thought about the carbon cost of a packet of crisps? At CCM Technologies they think of little else. Their revolutionary fertiliser offers a big step to carbon-free snacking.

Waste from crisp factories or from sewage treatment works can be routed and treated to form the basic building blocks of new fertilisers that can be spread on the ground to grow a new harvest of potatoes- or any other crop we need. The system avoids waste and takes a big cut out of the carbon emissions of traditional fertiliser production. Tom Heap tours the CCM fertiliser plant on the outskirts of Birmingham and discusses the carbon benefits with Dr Tamsin Edwards of King's College London.

Producer: Alasdair Cross

Researcher: Sarah Goodman

Produced in association with the Royal Geographical Society. Special thanks for this episode to Dr Kate Schofield from the University of Plymouth and Dr Abigail González Díaz from the National Institute of Electricity and Clean Energy.