With our food chains set to be stretched to bursting point we need to come up with new ways to reduce waste. Chris Smith and Ginny Smith spoke to environmental entrepreneur Jason Drew from South Africa about his buzzy idea to closing a loop in fish farms.

Chris - Jason, what's your solution to the food problem in the future?

Jason - It's just taking one particular part of the food chain and beginning to close loops. So, closing food cycles like we're doing in business to drive sustainability and what we're doing is really launching what we call the nutrient recycling industry. So, we take it for granted today that we should recycle our tin, our plastic, our glass. And what we do is we recycle what are otherwise waste nutrients. So in particular, we take wastes from slaughter houses, our industrial slaughter houses and indeed from other waste food sources, and reconvert those into usable proteins using in particular, 2 or 3 different species of fly.

Chris - When you say 'waste', that would be slaughter house waste, what would happen to the material that you're currently calling 'waste' if you weren't to get your hands on it?

Jason - Well, a lot of it goes into landfill, a lot of the blood. I mean, if you slaughter a million chickens which isn't a lot every month, that's a quarter million litres of blood that would otherwise get poured into effectively only just dams, lakes of blood. The problem is, the haemoglobin then settles out and begins to affect the water table over a period of time.

Of course, using the fly to recycle those waste nutrients, we create an entirely natural animal protein and you know, that's why flies have for years been eaten for millions of years by fish and by chickens. You know, a trout leaping out of a stream is after a fly. A tilapia in the bottom of the pond is looking for fly larvae or mosquito larvae. And so, it's a natural food. Larvae is a natural food for chickens and fish. And instead of using the roughly third of our fish that we take from our seas in our industrial and agricultural processes, we can just recycle those waste nutrients and convert them back into a good, natural animal protein to put back into our farming operations.

Ginny - So, how exactly does this work? Can you talk me through the operation?

Jason - In its very simplest form, we have a very large cage full of flies. We've taught the flies to lay their eggs all in one place. We take those eggs out of those cages and we keep a proportion of those eggs back to put into our breeding stock. Our breeding stock is fed on human grade food, on milk powder, sugar and yeast, and a few other goodies.

We then feed the eggs on the waste from the slaughter houses in the abattoirs and 1 kilo of eggs will turn into about 380 kilos of larvae or protein if you take away the constraints in nature, it will stop that happening. So, on a decaying carcass in the bush, different types of flies would land on it, different stages of decomposition and they'd be eaten by passing birds or indeed, that fly off and be eaten by a fish from a stream. So, what we're doing is, we're copying that natural process in closing the loop.

Chris - How much energy do you think that you can extract back out that would otherwise go to waste? Can we put some numbers on this, Jason? What sort of difference can your approach make, using this, I think very interesting technique?

Jason - Our food conversion ratios depends on the waste sources. It's about 2.5 to 1. So, if we take 2.5 tons of waste, we end up with about a ton of larvae which on chemical analysis is, from an amino acid composition perspective is identical to that of fish meal, plus or minus a few percent. So, it has all the growth factors that you need to make your chickens grow, to make your trout grow, to make the salmon grow.

So, we make 2.5 tons of waste to make about a ton of larvae or protein. And the reason this has become available as a business opportunity is that the price of fish meal has risen substantially over the last 5 to 8 years from a sort of stable price range of around $600 to about $2,000 today per ton. So, every ton of fish meal that we don't have to take from the seas because we replace it with mag meal is a good thing we're doing and our large scale factory coming on line later this year. It's targeted to make 100 tons of wet larvae a day, which is about 28.5 tons of dry larvae a day.

Ginny - So, what are the fish currently being fed on? You mentioned fish meal.

Jason - Fish meal is really predominantly pelagic fish that are fish specifically to create an animal protein, so it can then go to the feeding of monogastric animals. So, our fish, our chickens, our pets, and other single-stomached entities who need or have always traditionally naturally had animal proteins part of their diet. So what we're doing is just replacing the unnatural protein which is fish meal with a natural protein.

We sort of gave up fishing in about 1950 and started catching because with sonar we just went to catch the fish in the seas. And we've been exploiting that natural resource to a point of breaking it and we're all aware of the issues facing our seas around the world.

Chris - Can I just bring in Tim at this problem because I think Tim, how does this sort of factor with where you're coming from in terms of growing enough food to supply people? This must be music to your ears.

Tim - Absolutely. I've been talking to somebody recently about this sort of idea because what we're doing is recycling something into something that's very usable and be usually around fish meal and collecting fish from the seas in an unsustainable way, and turning that into a food for other fish to eat becomes kind of crazy, and a real stopping point in the chain of production of fish. So, if we can do things like this, it allows us to carry on growing fish protein and that takes some of the pressure of converting land to producing animal protein or plant protein on land.

Ginny - So, we're also joined tonight by Steve Sugden from Water for People who is working on a similar idea to Jason's but using a slightly smellier option. So Steve, you normally work on sanitation issues. How did you start thinking about the food chain?

Steve - If you take a city like Dar Es Salaam with a population of 3 million, you've got 75% of that population that are actually pit latrine users. When the pit latrine is full, it causes a problem to a householder who then normally have to employ manual pit emptier to empty the pit waste and that gets put on to the nearest piece of land or drain. This causes huge public health problems. The last time I was there in an area of Dar Es Salaam, the health officials thought they had endemic cholera.

So, the whole idea is, can we change our attitudes from seeing this as human waste, can we actually see it as an asset? Quick calculations will say that around 560 tons of human waste are produced every day in Dar Es Salaam and can we actually use that as a source of organic matter, as our source of energy to increase food production?

Chris - Talk us through actually what's involved then Steve? What do you do to rescue back that waste in the same way is doing it with blood? You're using something a bit less pleasant perhaps. What is involved in your technique?

Steve - There's two possible ways. One which you can actually do it to the household which is more difficult, for the fact that you've got to keep inoculating the pit latrine with more fly larva.

So, the preferred method that we're looking at is actually, developing pit emptying services, taking it to a nearby transfer station and then using black soldier fly which is, I think really an extension of what Jason was talking about, and using black soldier fly to actually eat the waste. The black soldier fly from the early work that's being done has a 42% fat content and a 30% protein content. And as I say, can be used as fish meal or even for making the fat content for making biodiesel.

Chris - So Jason, this is sort of complimentary to what you're doing. Can you team up with Steve and the two of you come up with the solution that means you can make the best of both worlds, both stuff that goes down the loo and stuff that goes in his landfill?

Jason - They're always nutrients and what we need to do is get busy using these waste nutrients, reconverting them to something useful, and get busy repairing the future.

Chris - Final word from Tim. Where do you see this going?

Tim - I think we need to get a lot smarter about re-using this stuff like these guys have been saying. I went to a farm in China a couple of years ago where they had pigs and the pigs producing muck and the muck was then used to farm earthworms, and the earthworms went into fish food, and the remainder of the muck went onto the field and it became a very closed system, and incredibly efficient in terms of yield production which is quite unlike most of our industrialised agriculture.