The recycling revolution and the whereabouts of our waste are hot topics this week as David Butler describes a new technique for recycling water, Rebecca Weymouth lifts the lid on what happens to our domestic waste, Peter Barham reveals why plastic is so difficult to recycle, and Richard Thompson discusses how waste plastic threatens the environment. In Kitchen Science Derek turns old chip oil into biodiesel, and from making fuel to running on empty, Anna Lacey asks Andrew Prentice how humans cope with famine.
In this episode
Beating The Cluck Out of Food Poisoning
Researchers at the University of Arkansas are administering probiotic "good bacteria" - similar to the yoghurts on sale in the health food store - to chickens in a bid to cut food poisoning due to bugs like salmonella and campylobacter. Every year in the UK at least 10 million unfortunate victims end up locked to a loo seat thanks to something they ate, and poultry is a common culprit. That's because chickens and other birds often carry pathogenic bacteria which, if the meat is not carefully prepared, can infect the consumer. To combact the problem researcher Billy Hargis is giving his birds a dose of probiotics. The idea is that the good bacteria will compete for nutrients and resources, pushing out the harmful gut pathogens. To isolate them in the first place the team collect the natural bacterial flora from healthy chickens, confirm that the bugs they have isolated can compete effectively against the pathogen, grow them up and then administer them to chicks in their feed and water. Also adding prebiotics - substances which encourage the growth of the good bacteria - to the diet helps to maintain a thriving intestinal population. At the moment the researchers are currently working to achieve the perfect cocktail of good bacteria, but the fruits of their labours have now been embraced by a number of commercial poultry farmers eager to cut the levels of food poisoning bacteria in their produce.
How To Make a Monkey Yawn
Have you ever noticed how yawning is contagious. Just talking about it is making me want to yawn! Animals other than humans can also yawn, but scientists have shown for the first time that monkey yawns are contagious, just like human ones. Scientists at the University of Stirling in Scotland showed stumptail macaque monkeys videos of other monkeys yawning. They found that this set the macaques off yawning and scratching, much like your average bloke in the morning, while videos of non-yawning monkeys had no effect. Although we still don't know why yawns are contagious, we now know that other animals can catch them too.
- New Horizons Mission
New Horizons Mission
with Dr Alan Stern, Southwest Research Institute, Boulder, Colorado
Alan - New Horizons is a NASA planetary mission that was just launched on the 19th January to make the first reconnaissance of Pluto and then hopefully on to Kuiper belt objects as well. The mission is the fastest space craft ever launched but because of the great distance will take about nine and a half years to reach Pluto before going on into the Kuiper Belt. So it's arrival will be in the summer of 2015. When it arrives, it'll be studying Pluto's system with cameras, spectrometers and other instruments to give us a very good view of what kind of a system this is. We'll look at how the different bodies are put together, what they're made of, their geology and study their atmospheres.
Chris - What does this actually add in addition to some interesting and intriguing findings of Pluto? What will it add to our understanding of that segment of our solar system?
Alan - I think most importantly we've discovered in the last decade something that was completely unexpected. That is that there's a whole new class of object out there. These are miniature planets or so-called 'ice dwarfs', which vastly outnumber the rocky terrestrial planets and the four gas giants. Instead of four of each of those, we think that there are hundreds of these ice dwarfs. Pluto was the first one discovered and is probably the best-known example. So this is going to give us our first handle on what this very populous class of body in our solar system is all about.
Chris - And is it just because they're so far away that they're so difficult to see, even with telescopes like Hubble? Do we need to send a raft there in order to look at them more closely?
Alan - That's exactly right. Pluto, the brightest of this population, is itself 50 000 times fainter than Mars and 100 times smaller in the sky. Even over 75 years, we've only been able to eke out a very small amount of information.
Chris - Do you think there are any surprises lurking out there?
Alan - It's an embarrassing but true statement that across the solar system as we've visited new types of bodies, we've typically found that our expectations way underestimated the richness of nature. So I expect very much to be surprised.
- Surviving Famine
with Anna Lacey interviews Professor Andrew Prentice, London School of Hygiene and Tropical Medicine
Andrew - Famine is usually defined as a catastrophic shortage of food of such immensity that it's associated with very high mortality levels.
Anna - But how come so many people actually come through famine and survive?
Andrew - Let's start thinking about how the body manages in metabolic terms. The first thing it needs to know is how fat or thin it is, and so there's a hormone that tells the brain that acts as a fuel gauge. When the brain realises that it's very short of food, it starts to save energy, use up body fat, protect the major organs and hence protect survival. There are very clever mechanisms by which this is orchestrated and also some very terrible ones, for instance, cannibalism.
Anna - How come we haven't evolved similar mechanisms for dealing with lack of water, especially as lack of water and lack of food due to drought are often quite highly correlated?
Andrew - That's a very difficult question and one which I haven't thought about before. I guess one explanation is that humans have been clever enough to dig wells. So even if there may not be enough water for the crops, they are generally able to get enough to drink.
Anna - If famine has been such a driving force in evolving what we like and what we eat and how we deal with food, how come we need such a range of foods in order to be healthy? Why can't the Atkin's diet, say, be enough?
Andrew - I think we need to separate out survival and optimal growth and development. If you look back at mediaeval times or people who live in small cottages and hit their head on the beams all the time, you will realise that people were much smaller. So although you could hang on in there and survive, there's a big difference between that and growing optimally, having optimal brain function and optimal survival. That's where the quality of diet is really important.
Anna - While we're on the subject of diets, obviously obesity is becoming a big problem nowadays. Are these adaptations that we've had in the past causing us more problems than just obesity?
Andrew - I think obesity is the obvious where we've got a complete mismatch between our modern environment and our very ancient metabolism that has evolved to survive famine. Diabetes is also though to be a consequence of our evolution against famine because it is associated with the propensity to lay down fat very quickly. So in times of feast we lay down fat and that is regulated by insulin. And then during times of hunger and famine, we use up that fat again.
Anna - Do you think our bodies are going to evolve to deal with fat in the same way that we've evolved to deal with famine?
Andrew - I think that's an absolutely intriguing question. It's a difficult one to answer. To some extent you can argue that evolution has stopped now. We're not trying to have many children and so the fact that it takes a fat woman a lot longer to conceive two children than it takes a thin woman to conceive two children doesn't make much odds. So my feeling is that we won't evolve back again.
- Water Usage And The Green Roof Water Recycling System
Water Usage And The Green Roof Water Recycling System
with Professor David Butler, University of Exeter
Chris - Tell us about your work.
David - I'm very interested in water and reusing water because at the moment we use a lot of water and we waste it in my opinion. We've been looking at ways to reuse water where we can.
Chris - Have you got any figures up your sleeve as to roughly how much water we do use on the average day in the average household here in the UK?
David - The average person uses about 150 litres per day. Now if you imagine 150 one litre bottles sat on your table, that is an awful lot of water. Of that 150, we only drink maybe a litre or so.
Chris - To put that in perspective, if I was someone in Africa, how much water would I use in a day, assuming that I don't live in on eof the big cities?
David - 10 litres maybe.
Chris - So therefore we're actually 1500 per cent over what we actually need to get by.
David - That's absolutely right.
Chris - So we have a terrifically wasteful culture. What's your solution?
David - My solution is to try and reuse water that we've already used once before. We can take water from our showers or baths and try and get it back to a quality that's suitable for, let's say, flushing a toilet. Why do we need to flush our toilets with drinking water?
Chris - It's always surprised me. Is it just because it would cost the environment so dear in laying down a second set of pipes to deliver slightly less pure water to every house?
David - Yes and it's very expensive. Some places in the world where they are very short of water do that. But we thought it might be worthwhile looking at whether we could recycle water at the smaller scale rather than the larger scale.
Chris - So what is your solution?
David - It's to try and treat this grey water using a low-tech solution. You plant vegetation, plants and flowers into a gravel bed, maybe on top of a large building on a flat roof and trickle this grey, once-used water through it. We then use these natural processes to get it back to a suitable quality.
Chris - Ok, that's the theory behind how you set it up. But what's happening if you zoom in to the small scale? What are these plants doing and what is the gravel doing to clean the water? David - In the gravel you're getting a build up of micro-organisms that will remove some of the polluting material. The roots of the flowers will also open up the pores and draw in oxygen as well.
Kat - What sorts of polluting materials are these?
David - They're oxygen-demanding material. If you put this water straight into the environment, it would suck the oxygen out of rivers and so on. We don't really want to be flushing our toilets with that sort of water.
Chris - So in other words it would suck the oxygen out the environment because it would promote the growth of bacteria due to the phosphates and things in it. It's also bacterially laden too.
David - yes, and we're actually asking our bacteria to grow at a specific point and we're making them a nice environment in which to do that.
Kat - My mum does things like putting the washing up water out in the garden and I've often wondered whether you could put a plastic tub in the shower and catch some of the water that you don't wash with. Is that not so good to put on the garden?
David - Well I wouldn't really recommend putting it on your tomatoes for example.
Chris - In case someone's peed in the shower! But how does it actually work?
David - There's no problem at all with water with pee in it and unless you've got an infection, it doesn't have bacteria in it. And anyway, the water that we're dealing with would be very low in urine concentration.
Chris - So what you would then do would be collect the water that comes from a certain set of appliances such as a washing machine and pipe that off separately to the flower bed.
David - Yes, to the flowerbed on the roof and trickle it through there.
Chris - So you have pump it up?
David - Yes, and that's going to consume energy, which is the negative side of this.
Chris - Why is it on the roof?
David - To save space and then we can use gravity to get it back down into the building.
Chris - So it trickles down through the plants. How much water can this flowerbed process?
David - This can more or less process all the water we need for flushing our toilets and that is about a third of the total amount of water we use individually.
Kat - Does it collect rainwater as well?
David - Yes, that's another option. We can certainly collect rainwater and rainwater is of better quality than this grey water. We've certainly been looking at techniques for recycling that as well. You do need a big tank to collect rainwater if you want a good secure supply.
Chris - Is the water that comes out safe?
David - It's safe for flushing the toilet and I think it's safe for doing garden irrigation, but I wouldn't water my tomatoes with it.
Chris - Do you need a special type of plant that you need to do this or will any old plant do?
David - Well this is exactly what we're trying. We're trying local species of plants to see how well they do and that's why this system is under development. We want to see which plants will do what.
Chris - And what size flowerbed do you need to process the output from a standard family?
David - Well more or less you need a couple of square metres for each individual.
Chris - That's not much.
David - No, that's not a lot and that's why we think that this is a promising technique.
Chris - What about in winter time though when the whole thing freezes?
David - That's a good question. It shouldn't freeze because grey water will be warm from your showers, and we also collect the water in a tank in the house and store it. But we are a little bit concerned that some of our plants will die off in the winter so we're looking for hardy varieties that will grow throughout the season.
Chris - Interestingly, in China they're trying to prepare air quality for the Olympics. China has air quality that's so bad that on over 150 days in the year Beijing has air unfit for humans to breathe. They're trying desperately to try and improve it, so they're implementing a series of roof top gardens. They have a particularly hardy type of grass which they're planting on all their high rise buildings in an attempt to use it like the lungs of the city.
David - I think these green roofs are very important and promising for the reason you mention and we can also use it to treat our grey water, our rainwater, and they are insulating as well.
- Recycling Domestic Waste
Recycling Domestic Waste
with Rebecca Weymouth, Cambridgeshire and Peterborough Waste Partnership
Chris - Recycling. It's something that I've only recently really started taking seriously now that I know what I know about what's happening to our planet. But what actually is the point of recycling? Does it all add up to a benefit for the planet?
Rebecca - It really does and every little helps. People may think that they don't have that much rubbish and is it really worth me putting that one can in the bin. But it really is worth recycling all the materials that the councils ask you for.
Kat - So what types of things can actually be recycled?
Rebecca - It depends on where you live, so do check with your local council. The classics are obviously paper, glass, cans, garden waste and plastics in some areas.
Kat - What about things like clothes and electrical equipment?
Rebecca - Clothes are obviously another classic. They're more traditionally recycled through taking them to a local supermarket and they can go directly to benefiting charities as well. Electrical equipment is an exploding market and can be recycled if you take them to your local site and they get taken off to specialist reprocessors. They can break them down, take out all the plastic metals and separate them for recycling.
Kat - You hear these stories that some people recycle glass or newspaper and it actually costs more environmentally and in terms of energy than making it from scratch. Is this really the case?
Rebecca - No it's not. The paper industry and the glass and metal industries rely heavily on second hand materials because there's huge energy savings from recycling. For instance, recycling aluminium cans saves 95% of the energy it would take to use primary resources. You get huge economic and energy savings from using recycled materials.
- Problem Plastics
with Dr Peter Barham, University of Bristol
Chris - What actually is a polymer?
Peter - A polymer is a long molecule of atoms that are joined together to make a string of mostly carbon.
Kat - And how do you get different types of plastic? You get very hard plastics in bottles and flimsy plastics in bags.
Peter - Basically it depends on what you hang on the side of the chain. You can have different atoms on the side of your polymer chain. For instance you can make polyethylene, which is very floppy plastic.
Chris - Now what is a biodegradable plastic? Is it true to say that this could be in the ground for a hundred thousand years and therefore we should use a biodegradable plastic? What's the difference between the two and how they work?
Peter - A lot of this is definition and you have to be careful. Strictly speaking, a biodegradable plastic is one which will degrade, or disappear back to carbon dioxide and water if left in the atmospheric zone, whereas other plastics won't. Plastics like polythene is actually biodegradable because if you put it in the ground it will disappear in a hundred thousand years or so.
Chris - one thing I have actually noticed is that in the old days, plastic bags form supermarkets were actually quite reliable. You could put things in them and keep them for a long time and they wouldn't go off. But recently I've noticed that when I go to put stuff in the boot of my car and carry things around, that the ultraviolet light in the sun coming through the window are breaking the bags down into pieces of shrapnel. Is that true?
Peter - Well I don't know what you have in the back of your car! Most plastics can be degraded by ultraviolet but I'm surprised that much ultraviolet would get through the windows of your car in the first place. It's more likely that there's something in the back of your car.
Kat - What should we do about the huge number of plastic bags? Is there any solution to the plastics that we're putting into the environment?
Peter - The problem with plastic bags and all plastics is that recycling is not really a very good option. The trouble is that there are so many different plastics that unless you know exactly what you're recycling, you can't do much with it. So with plastic bottles, there are only a few different types. If they say PET on the bottom you know what they are and you can turn them into something else like fibre-fill for soft toys or duvets. But if you take plastic bags, they are made from a wide range of things. There's PVC, polyethylene, polypropylene and mixing up those makes an awful mess that's totally impossible to recycle.
Chris - So how are we now getting round the problem and making nags we can recycle? How do they work?
Peter - Basically any bag would be recyclable if you knew exactly what was in it. The only way you can make that work is if you are a supermarket that takes back the bags that you give out. This way, you know what's in them and you could send them to be recycled. As soon as you get one or two foreign bags in there from something else, it will completely ruin your machinery and the processing won't work. It's a terrible shame.
- Effect of Plastic Particles on The Environment
Effect of Plastic Particles on The Environment
with Dr Richard Thompson, University of Plymouth
Chris - it's well known that a hell of a lot of plastic bags get used every year. The figure that was published a few years ago was that a trillion plastic bags alone are used annually and go into the millions of tonnes. A lot of it ends up in the sea.
Richard - Yes, a lot of plastic products are produced annually. Obviously quite a lot of that material goes into landfill and small quantities are recycled. However quite substantial amounts do enter the environment as litter or debris. It's estimated that about eight million items of litter go into the sea every day, and much of that is plastic.
Chris - And when it gets into the sea, what does it do? Does it bob around or does it break down?
Richard - Most of it is found floating on the surface. The majority of plastics are buoyant or neutrally buoyant so we find them on the surface or we find them on strand lines where they are washed up on shores throughout the world from the poles to the equator. We also find lots of plastic on the deep sea bed as well now. As plastics stay in the sea, they become fouled by marine organisms and this alters the overall density of the plastic object so that plastics that floated when they first entered the sea become negatively buoyant and sink to the seabed.
Kat - You mentioned marine organisms. Are there things in the sea that actually eat plastics?
Richard - Quite a lot of organisms will eat plastic. Usually what happens is that creatures seem to mistake plastic for what they might normally eat. To a turtle, for instance, a floating plastic carrier bag might look similar to the jellyfish it might usually eat. To a sea bird, small coloured fragments of plastic on the shoreline might well be confused for the food items that those birds may normally be eating.
Kat - It's a big problem not only with animals in the sea but animals in general. I remember seeing some terrible footage of some birds with rings from the top of beer cans stuck round their necks. Is that a problem as well and physically affecting animals?
Richard - There's a range of different problems. There's the physical problems you mentioned of entanglement and that can be for birds and particularly for marine mammals as well. Fish also get caught up and tangled. There are also problems if creatures eat plastic, such as leading to suffocation or blocking the digestive tract.
Chris - One thing the Japanese have been looking at is what happens to these tiny particles of plastic when marine organisms begin to filter and eat them. They have a theory that these tiny particles of plastic may be bio-concentrating, or in other words accumulating toxins and then leading those toxins to enter the food chain.
Richard - That is entirely possible. The mechanism that has been shown in the work in Japan is that plastics, when they're floating at the sea surface, will be very attractive to hydrophobic contaminants. Chemicals that have entered the marine environment from other sources, such as DDE, are hydrophobic in nature and will latch onto the surface of buoyant objects rather than be in the seawater. And so floating plastic debris can accumulate some of these contaminants to several orders of magnitude more concentrated than those chemicals were in the surrounding seawater. They are mopping up contaminants. Of course the question is when you have these concentrated contaminants, is there any danger of these contaminants coming off perhaps in a different circumstance such as the guts of an organism?
Chris - Are you worried?
Richard - I'm concerned about it and it's certainly something that we're working on at the moment at the University of Plymouth.
- Why do eggs make things rise when they're baked, and why does yeast make dough rise?
Why do eggs make things rise when they're baked, and why does yeast make dough rise?
When you make a cake, you mix together fat, sugar, flour and eggs. To make the batter, eggs have a very important property that means they can emulsify things. In other words, eggs contain lipoproteins that can stick fat into a liquid. So you mix together fat, flour and sugar and make a cake batter. When you put it in the oven, the fat melts and the air that's been beaten into the cake expands into the gaps. This makes the cake rise. The protein that's in the egg whites solidifies and holds the whole cake structure as a stable thing. This means that when it comes out the oven, it doesn't just flop down. If you've got baking powder in there as well, that releases carbon dioxide which is another gas that expands and makes the nice big gaps in your lovely fluffy cake. That's why eggs make things rise. They make everything stick together and then hold it together as a solid protein structure. The yeast story is similar. Yeast is a type of fungus and when you warm up your bread mixture of flour and water, they create carbon dioxide. That creates the holes in your nice fluffy bread and a little bit of alcohol too!
- How does a chameleon change its skin colour so fast?
How does a chameleon change its skin colour so fast?
It's pretty well known how chameleons change their colour. Lots of people think they change colour to match in with their surroundings but it's not actually true. Chameleons change colour to signal to other chameleons what kind of mood they're in. The usual calm chameleon is a pale green colour. So when you see them in Madagascar and Africa which is actually where they're most common, they're that light pale green colour. If you warm them up and put them into a bad mood, they can flash red and yellow and all kinds of funny colours. When they get a bit frisky, they also change colour to attract a mate. But how do they actually do that? It's all down to a very clever system that's not dissimilar to a television screen. In a chameleon's skin, they have these things called chromatophores and these are tiny cells that are laden with pigment. In a normal cell, the pigment is locked away in these tiny vesicles or pouches inside the cell. When a signal comes in from the nervous system or a chemical in the bloodstream, they cell discharges that pigment and it spreads out in the cell and causes the cell to change colour. Depending on which sets of these chromatophores get discharged, then the chameleon changes colour accordingly.
- Why can some plastics be recycled, but not others?
Why can some plastics be recycled, but not others?
Here in Cambridgeshire and Peterborough, we only accept plastic bottles for recycling, and that's the guidance we give our public. Basically, the reason we ask for bottles is because they are made from three different types of plastic which we know that we are readily able to recycle. These are PET, PVC and HDPE. So if you stick to bottles the likelihood is that it will be one of those three types of plastic.
- Why issue biodegradable bags that refuse collectors won't take away?
Why issue biodegradable bags that refuse collectors won't take away?
That's a difficult one. I'm surprised that he's been told that because all supermarkets usually have recycling schemes now so that you should be able to take your plastic bags back to the supermarket so you can get them recycled regardless of whether they're biodegradable or not. The best thing to do in the first place is not to use plastic bags, or take them back and reuse them so you don't get this build up of plastic bags in your kitchen drawer. Best of all is to get a bag for life or a reusable bag.
- What happens to syringes and how do they get recycled?
What happens to syringes and how do they get recycled?
Actually they don't anymore. Historically we did reuse syringes and those are the ones made of glass, but nowadays it's much cheaper to make them out of plastic. They then end up on the beach of course and Richard Thompson has to pick them up in his marine ecology studies.
- If the ice caps melt, will there be enough land left for us to live on?
If the ice caps melt, will there be enough land left for us to live on?
If you wanted to define whether there would be enough land, you could give everyone a metre-squared of the Isle of Wight for the moment but that's not really survivable. In terms of the poles melting, people say it's really bad news if the poles melt, but it's not. If the North Pole disappeared tomorrow, there wouldn't be any change in sea level. The reason for that is that it's entirely made of ice and ice is floating. As you know, ice is made of water and weighs the same as water. The amount of water level change is proportional to displacement so if the North Pole melted we wouldn't be in much trouble. The real worry is ice on land, so that's Greenland and the South Pole. If that melts, we are in trouble. Predicted sea level rises for the next 100 to 200 years is anything from a few centimetres maybe to as much as seven metres over the next 700 years. But it's not just the melting of the water. If the planet warms up, things will start to expand. Just the getting warmer effect is enough to make the water expand a bit and to increase in depth. In fact, the melting of the ice on Greenland alone is contributing to about a 0.5 centimetre rise in ocean levels everywhere every year.
- Is recycling sent by boat actually environmentally sound?
Is recycling sent by boat actually environmentally sound?
I don't think that's true. I know that there are a number of plants up and down the country. It's a stage process so you have reprocessing plants and mills. The UK paper recycling industry is big on its own so it doesn't need to import or export wood from outside. Often there is an amount of recycled material that is exported, such as green glass, because we just don't have the market for it in this country in terms of the glass production. But the transport costs are offset by the energy saved by recycling in Europe.
- We're on an island surrounded by water. How come we've got a water shortage?
We're on an island surrounded by water. How come we've got a water shortage?
I guess what you're talking about is why we don't use seawater to drink. We could and it's perfectly possible from a technical point of view but it's going to cost us a lot of money and a lot of environmental damage to do it. It uses a huge amount of energy. People in dry places like Las Vegas pipe in water over very long distances which costs a lot on pumping costs.
- Why are we not allowed to put shredded paper in the recycling bin?
Why are we not allowed to put shredded paper in the recycling bin?
I believe it's because small shreds of paper would clog up the paper reprocessing system but I think it depends on your local authority and the paper mill it goes to. Of course you can also compost shredded paper, which is a nice alternative.
- How to anti-diarrhoea tablets like Imodium work?
How to anti-diarrhoea tablets like Imodium work?
The answer is that anti-diarrhoea tablets like Imodium contain a version of morphine and they're a morphine-like drug which has some morphine-like effects without all of the morphine effects. It doesn't make you fall asleep or make you feel high for example. One side effect of morphine or morphine-like drugs such as heroin is that it switches off the bowel. In other words it converts motility or movement through the bowel into backwards and forwards mixing motions. That's why people who tend to take a lot of morphine for pain or due to being a drug addict get very very constipated. What scientists have been able to do is to find which bit of the morphine molecule works and makes that effect, made a molecule that mimics that effect and put it in a tablet form.