Seeing waste from food processing as a resource

Saturday 1 October 2011 12:13PM (view full episode)

Waste from food processing is on a scale that could be a resource for whole industries. Sao Paulo produces large quantities of orange juice and the peels amount to ten million tonnes of waste each year. New processes using low level microwaves allow chemical components to be extracted from the peel. James Clark sees this century as one of transition from petroleum based chemistry to renewable feedstock based chemistry.

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Robyn Williams: James Clark is Professor of Green Chemistry at the University of York, and he is pioneering a system using microwave ovens, not unlike the ones you have at home, to extract useful chemicals from organic waste, masses of waste. We chuck, in Britain say, 6 million to 10 million tonnes of carbon residue away, equivalent to how much is taken from oil to run a chemical industry. Could there be a better way?

James Clark: Indeed yes, I'm suggesting that actually we could do a classic closed loop of using food waste, waste from one industry, and use that as the feedstock for another industry for making chemicals.

Robyn Williams: And the idea is that you have those wastes all in one place so you don't have to transport them. Where are the biggest piles of waste in the world?

James Clark: Brazil of course is really the food growing area for large parts of the world these days, so Brazil is particularly interesting. They have enormous quantities of citrus waste, of nut waste, of banana waste and so on. But there are also very large concentrations in China, in India, in southern Europe, and even if you go to countries like the UK, if you think about earlier in the supply chain then of course we grow a lot of cereals, and the cereals themselves generate a lot of waste, the straws, the husks and so on, which aren't used for very much at the moment, and they can also be a good feedstock for this process.

Robyn Williams: Give me an idea of the scale of what is left, say, in Brazil of oranges, orange peel?

James Clark: Orange peel, we estimate about 10 million tonnes of waste in the Sao Paulo region, that's on a fairly concentrated area where most of the world's orange juice comes from, about 10 million tonnes of waste.

Robyn Williams: And what do they do with it now?

James Clark: A small amount is used for animal feed but the bulk of it is burned because otherwise it putrefies and becomes a problem.

Robyn Williams: What is the microwave technology you're talking about that is going to release these chemicals?

James Clark: We're familiar with microwaves in a cooking sense, and we discovered that microwaves, if operated at low enough temperatures, can actually give you controlled chemistry, and they are capable of activating the cellulose, which is present in almost all plants, including peel, and then that activation triggers a series of chemical processes which allow you to extract the chemical value from the peel.

Robyn Williams: Low temperatures? How low?

James Clark: We operate below 200 degrees.

Robyn Williams: And what about the scale of the machine? Can it be on a small household level, or can it be on an industrial scale as well?

James Clark: We have a scale operating at the moment which is more or less the same as a typical household microwave, a slightly different design but essentially a similar size. But you can also make them up to multi-tonne per hour scale. The largest microwave process operating that is similar to what we would require that I have seen operated about six tonnes per hour.

Robyn Williams: And you can go up to 20 tonnes.

James Clark: We've seen it designed for up to 20 tonnes per hour, that would work certainly.

Robyn Williams: And are these omnivorous machines? Can you put in oranges, cereal, you name it, as long as it's organic?

James Clark: Indeed, because as long as there are some cellulosics in there, the whole process is triggered, and yes, you could feed any biowaste, and it could also be paper waste, cardboard waste as well as food waste.

Robyn Williams: And how do you get the chemicals out?

James Clark: Continuous extraction. So the idea is that chemicals typically are relatively volatile, so as you actually decompose the biomass inside the microwave, you strip off, you evaporate the chemicals as they are formed.

Robyn Williams: And has the chemical industry said that they'd be willing...are they interested in such a supply of chemicals?

James Clark: The chemical industry is beginning to realise that they can't rely on petroleum as the conventional feedstock for their chemicals. So slowly but surely they are beginning now to look for renewable sources of chemicals.

Robyn Williams: So you think it is actually economically feasible to do this sort of technology of recycling?

James Clark: We've proven that energy-wise you can take about 10% of what you make and use that as a fuel to drive the entire process, so energetically it is certainly efficient. The same applies to the carbon. Yes, we do think it's sufficient enough to operate commercially, yes.

Robyn Williams: And how long have your pilot plants been operating?

James Clark: Our semi-scale facility is operating as from the end of this year. So we've been working on a slightly larger than lab scale normally, but by the end of the year we will have a pilot scale facility which operates at tens of kilograms feed per hour.

Robyn Williams: And presumably this can be adapted around the world?

James Clark: We were very keen to actually see this is supplied wherever, as I said, there's a good source of local biomass. So we're talking to people in Brazil, China, Vietnam, and hope that they can set up similar demonstrators there.

Robyn Williams: And of course this won't be conflicting with any of the regular food supply, it will be augmenting it.

James Clark: Absolutely, because we don't take food-grade material, we take any waste that people otherwise would put into a landfill or burn. We think we can get much greater value back by our process.

Robyn Williams: Most organic waste is not in one place, it is distributed. What if there was a presumably thought of this...a scheme for collecting it together for the convenience of the extractor?

James Clark: I think it's wherever there is a, for example, we're talking to shopping centres, there's enough concentration there to make it viable. I would think it could also be viable, say, for an apartment building where there's enough waste coming together to make the process efficient. An individual household, that's pushing it a bit, but I think once you get a group of them working together, I don't see why collectively you couldn't take their biowastes, have this process available to then give some value to their wastes.

Robyn Williams: You did mention that of course in the oil industry you've got an enormous amount in the way of plastics and other chemicals coming out of it, I think 10% of the oil may be used in that way. What about coal, where we come from in Australia, gigantic supplies of coal? Do you imagine that we might have a chemical industry where we don't actually burn the stuff, we actually extract what we need from it?

James Clark: Personally I always think that burning is the last thing you do. I think you should always look to extract the chemical value first, and then of course you can burn the residues. And yes, coal is rich in chemicals, and why not, coal is an old biomass essentially, and it is certainly a good source of certain types of chemicals.

Robyn Williams: Okay, so that's the plan. What's going to happen next? You say you've got a pilot that is taking off, what do you imagine might be happening in, say, two, five years time?

James Clark: I would hope in two to five years time we have a network of these demonstrator facilities around the world, wherever there is an interesting concentration of biomass, and that we would also be seeing the first commercial units. They might be in a large farm, they might be at the docks, they might be at a food processing company. We can make these units now, they are proving to be energy efficient, we can see the value for what you can generate. So I see no good reason why they can't be commercially operating in the two to five year timescale.

Robyn Williams: On a scale to rival the chemical industry as it stands?

James Clark: That will take time. To me this is a century of transition from petroleum-based chemistry into renewable feedstock-based chemistry.

Robyn Williams: Thank you very much.

James Clark: You're welcome.

Robyn Williams: James Clark, professor of chemistry at York, with a new basis for a chemical industry.


James Clark
Professor of Chemistry
Director The Green Chemistry Centre
University of York
Heslington York UK


Robyn Williams
David Fisher

Comments (1)

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  • Philip Mitchell Graham :

    02 Nov 2011 3:57:43pm

    Fascinating how none of the pro nuclear lobby have nothing to say abut this.