A greener crisp: new fertiliser to cut CO2 by 70%

How much carbon is in the humble crisp? If you take into account the carbon footprint for growing the actual potatoes, it’s a reasonable amount. Nevertheless, it could soon be 70% lower! That’s because crisp-makers “Walkers” have adopted a new chemical process that recycles waste carbon dioxide and potato skins and turns them into fertiliser. Developers CCm are intending - initially - to capture carbon dioxide from a nearby brewery while they set everything up at the crisp factory, and then embrace other sectors of the food and drink supply chain later on. Phil Sansom heard how it works from CEO Peter Hammond...

Peter - Walkers have agreed to be the first users of our technology in the food sector, transforming waste from the crisp factory in Leicester into a fertiliser material, which can then be used to grow more potatoes to supply next year's crisps.

Phil - What's the point? Don't we already have fertiliser?

Peter - You do. But unfortunately, fertiliser is a very energy intensive material to produce, and doesn't necessarily reach plants in the way that you might hope. So one way and another, it has a very high carbon footprint.

Phil - What's this technology then? How does it work?

Peter - What we do is use carbon dioxide to stabilise nutrients that are contained in waste materials from the Walkers factory in Leicester. Those waste materials predominantly come from potatoes - it's the skins - but it's also carbon dioxide that's produced in the plant.

Phil - Can you give me any insight into how that works? Because obviously carbon dioxide: that's something that everyone's trying to get rid of, but it's not an easy, easy task.

Peter - No, that's true. Carbon dioxide is quite unreactive, and so that makes it a difficult customer to get rid of. However, we're very lucky in waste materials that one of the chemicals that's actually relatively freely available in them is ammonia. And that ammonia very much likes to react with carbon dioxide. The first step then is this capture of the CO2 by the ammonia that's held in the liquid. We have to add some additional materials, particularly ones that are high in calcium, and also some nitrate material, so that the ammonia that's held there is transformed into ammonium nitrate, which is a really good plant nutrient. And the whole system is stabilised by the creation of calcium carbonate; chalk to most of us. And that helps literally glue the whole system together.

Phil - So I've got my waste and carbon dioxide going in, and then I've got my ammonium nitrate and calcium carbonate coming out the other end?

Peter - Absolutely. All stuck on to the organic substrate underneath, which comes from the potato skins.

Phil - Does it work well enough to make a good amount of fertiliser? And then does that fertiliser itself work well enough?

Peter - It certainly does. We've actually been testing it for the last six years now. And we found that across the board, we can attain the same yield and growth patterns that you would see with conventional fertilisers, so that's been very encouraging from the start. But also we started to see additional benefits in the soil, which are due to our adding these additional materials that wouldn't be delivered with normal fertiliser materials.

Phil - Now, Peter, you also said that sort of the point of all this is dropping carbon emissions. What sort of carbon emissions come out of your process? Obviously you said carbon goes in, but does carbon go out, and how does that compare to fertiliser at the moment?

Peter - Typically a ton of nitrogen based fertiliser will generate between three and a half and six and a half tons of CO2 for every ton of material that's produced.

Phil - That's a lot.

Peter - Yeah, it is. That figure is now dropping down to less than half a ton of outputs from our process. And the reason we can do that is we're simply drawing those materials that normally have very energy intensive production routes. We're recovering those from what are currently regarded as waste streams, and it actually stops them being waste materials.

Phil - Is that just a drop in the ocean, or is that something to write home about?

Peter - No. It's that use of fertiliser that makes agriculture have such a huge greenhouse gas impact. There's a lot spoken about the methane from cows and that sort of thing, which is obviously significant, but the largest input is coming from the use and misuse of fertilisers.

Phil - If I just take a sample out... I've got my lunch here. Right, this ready salted crisp: how much savings is there on it compared to how bad it was for the environment before?

Peter - At least 70%.

Phil - At least 70%?

Peter - In two years time, it will be a hundred percent better than it was before.

Phil - I'm going to tuck in with pride.