Tag Archives: energy

Going down the drain

In the latest of our blogs linked to The Rubbish Collection, Curator Sarah Harvey talks to Nick Mills, Waste Innovation Manager at Thames Water about what happens to our sewage and what the future holds for wastewater.

Sarah: What do Thames Water do with our sewage?

Nick: We have 350 sewage works and 68,000 miles of sewers across our region, which stretches from East London to the Cotswolds in the west. Last year, we removed and treated 4,369 million litres of sewage from 15 million customers. At our 350 sewage works we treat the sewage to remove contaminants and return it safely to the environment, it is often cleaner than the water in the river.

Sarah: What happens to the end products of the processing?

Nick: The main end-product of the sewage treatment process is something called sludge. This energy rich by-product is put to good use in anaerobic digestion, producing renewable energy that helps power our treatment sites. The digested sludge is then recycled to agricultural land.

Sludge having been put through a Bucher press to reduce liquid content © Thames Water

Sludge having been put through a Bucher press to reduce liquid content © Thames Water

Sarah: What are the biggest challenges you face in dealing with our sewage/ waste water?

Nick: London has outgrown its sewer system. The Victorian sewers are in great condition, but simply not designed for today’s population. They were designed for just over two million but are used today by just over six million. The proposed Thames Tideway Tunnel will stop tens of millions of tonnes of raw sewage flowing into the Thames every year via the outfall system. It is a must-do job. We can’t keep treating the Thames as a sewer.

The Lee Tunnel © Thames Water

The Lee Tunnel © Thames Water

Sarah: What are the strangest or most difficult things to deal with that people throw down the drains?

Nick: ‘Bin it – don’t block it’ is our campaign to end the misery caused by fatbergs. Leftover cooking fat and oil poured down the sink will set hard. This creates stinking, pipe-blocking fatbergs beneath your house or in your street.

A sewer flusher in London digging out a fatberg © Thames Water

A sewer flusher in London digging out a fatberg © Thames Water

Wet wipes are another big no-no because they are made of plastic. They don’t break down like toilet tissue, clinging to fat and clogging up the system. If drains get blocked, what you flush can come back up through your toilet or even your sink.

Sarah: What can consumers and organisations do better?  Is there a top 3 list of things people could do differently to help?

Nick: Our message is simple, if it’s not water, toilet tissue or poo, please… ‘Bin it – don’t block it’.

Sarah: What do you think the industry will be like in 20 years’ time? What are the new innovations and technologies that you are exploring at the moment?

Nick: In 20 years’ time I can see the wastewater industry becoming a net energy producer, by employing more efficient processes and increasing energy recovery. Combining advanced anaerobic digestion and technologies like pyrolysis, large increases can be made. Our Innovation team are busy demonstrating this at the moment. Phosphorus, a finite resource essential to life as we know it, will be recovered at every major sewage works and sold competitively as a fertiliser to farmers, this has also been demonstrated recently at our Slough sewage works by the Innovation team.

Innovation works at Slough © Thames Water

Slough sewage works © Thames Water

Sarah: What did you think when you first heard about Joshua Sofaer’s The Rubbish Collection project?

Nick: I think it is great. It shows the harsh reality of waste, but at the same time reveals the great work that people do behind the scenes to keep society moving. I hope it will encourage a new generation to start what is a very interesting and rewarding career as there are huge challenges yet to be solved.

Phase 2 of Joshua Sofaer’s The Rubbish Collection runs at the Science Museum until 14 September 2014.

Rubbish that powers homes and builds roads

In this week’s blog linked to The Rubbish Collection, Curator Sarah Harvey looks at some of the materials that are on display in the exhibition.

The second phase of Joshua Sofaer’s The Rubbish Collection art installation has involved tracing the journeys of the Science Museum’s rubbish, to find out where it goes, and how it is processed. This has enabled us to work out what materials to bring back for display, and in what quantities, to represent 30 days’ worth of Science Museum waste.

A giant claw lifting general waste into the incinerator at the Energy from Waste plant © Science Museum

A giant claw lifting general waste into the incinerator at the Energy from Waste plant © Science Museum

Rubbish leaves the museum via a variety of different companies but the vast majority is taken by Grundon Waste Management. It goes to their site at Colnbrook, near Heathrow, which holds three centres; a transfer station, a Materials Recovery Facility and the Lakeside Energy from waste plant, co-owned by Viridor Waste Management.

The interior of the Lakeside Energy from Waste plant © Science Museum

The interior of the Lakeside Energy from Waste plant © Science Museum

Today I’m going to focus on the materials on display from the Energy from Waste plant. When you think of an incinerator that burns rubbish you might picture a dirty, sooty, very smelly and unpleasant place, but it’s actually an extraordinary, almost clinically clean building (except for the container where the rubbish is held), and it’s surprisingly beautiful with a giant claw grabbing up to six tonnes of rubbish at a time to feed the incinerator fires.

Inside the incinerator at the Lakeside Energy from Waste plant © Science Museum

Inside the incinerator at the Lakeside Energy from Waste plant © Science Museum

All the Science Museum general (non-recycled) waste goes to Lakeside to be incinerated. Four products come out of that process: energy, incinerator bottom ash, air pollution control residue and clean air. The largest output is energy, with the plant providing enough to power 50,000 homes per year. We have calculated that the energy produced by incinerating one month of Science Museum waste is enough to light one of our gallery bulbs for nearly 24 years.

Bottom ash aggregate and recyclable metal as it comes out of the Energy from Waste plant © Science Museum

Bottom ash aggregate and recyclable metal as it comes out of the Energy from Waste plant © Science Museum

The energy is produced by burning the rubbish for approximately 3 seconds at 950 degrees centigrade, which is long enough to combust most materials. At the end of the process, incinerator bottom ash is left over. This ash still contains large pieces of metal which are separated and sent to be recycled, and the ash itself is left to ‘mature’ so that chemical reactions can take place that lower its pH value. This aggregate is then used in the construction industry, primarily in road building. You could be driving on your old rubbish.

Bottom ash aggregate (left) on display in Phase 2 of The Rubbish Collection © Katherine Leedale

Bottom ash aggregate (left) on display in Phase 2 of The Rubbish Collection © Katherine Leedale

One of the most remarkable things about the incineration process is that the air that comes out of the plant is actually cleaner than the air that goes in. This is because it is very carefully filtered to contain the toxins released during burning. The filtered ash is known as air pollution control residue (APCr). Historically this toxic ash would have been contained in hazardous waste landfill, but new technologies and research are now finding uses for it. Grundon have invested in a company called Carbon8 who use carbon dioxide to neutralise the toxic heavy metals and materials, making them permanently non-hazardous. This safe ash can then be used as an aggregate and, alongside other recycled materials including wood, makes the ‘Carbon Buster’ carbon-neutral breeze blocks we have on display in The Rubbish Collection.

Carbon Buster breeze blocks in Phase 2 of The Rubbish Collection © Katherine Leedale

‘Carbon Buster’ breeze blocks in Phase 2 of The Rubbish Collection © Katherine Leedale

It’s been very encouraging to find that the Science Museum rubbish is producing some useful and valuable products through incineration. However, one of the big findings from our documentation of the Museum’s waste was that there is still a lot of recyclable material ending up at the incinerator. Those materials retain much more value when they are recycled so by continuing to improve and refine our recycling systems, and through new initiatives like separating our food waste, we hope in the future to decrease our general waste further.

Phase 2 of Joshua Sofaer’s The Rubbish Collection is now open at the Science Museum and runs until 14 September 2014.

A hundred years of the quantum atom

Alice Lighton, content developer for our Collider exhibition, writes about the history of quantum physics. Colider: step inside the world’s greatest experiment opens in November 2013 with a behind-the-scenes look at the famous CERN particle physics laboratory. 

A few years ago, a friend asked a question that took me somewhat by surprise. “Alice,” he said, “is quantum physics right, or is it just a theory?”

At the time I was in the midst of a physics degree, so my initial response was “I hope so!” Quantum physics matches up to experiment extraordinarily well – it is often called the most accurate theory ever. But the question, and subsequent conversation, made me realise how little many people know about the subject, despite its profound impact on modern life and the way we think about the universe.

This year is the centenary of the publication of one of the theories that laid the foundation for our understanding of matter in terms of quanta – packets of energy. According to quantum mechanics, light is not a wave, but lump of energy called photons. Max Planck came up with the idea at the end of the 19th Century, though he considered his light ‘quanta’ a useful model, rather than reality.

Niels Bohr

Niels Bohr, one of the founders of modern physics.

One hundred years ago, in 1913, the young Danish researcher Niels Bohr sent a paper to the Philosophical Magazine in London that used these quanta to solve a serious problem with theories about the atom. At the time, scientists thought the atom was like a solar systems; electrons orbit a nucleus of protons and neutrons. But anything that moves in a circle gradually slowly radiates energy, and so moves closer to the centre of orbit. Eventually, electrons should fall into the nucleus of the atom.

But they blatantly don’t, otherwise everything in the Universe would collapse, and we wouldn’t exist. Bohr proposed that electrons could only sit in discrete orbits or distances from the nucleus – and therefore when electrons change orbit transitions between orbits emit only emit energy in discrete packets (quanta), not gradually. The electrons therefore stay put in their orbits, and don’t fall into the nucleus of the atom.

A hydrogen atom is made from one electron orbiting a proton. Photo credit: flickr/Ludie Cochrane

Bohr was the first to show that packets of energy could successfully explain and predict the behaviour of atoms, the stuff that makes up you and me. His results were only approximately correct, but a big improvement of previous theories.

Generations of scientists have built on Bohr’s insight to understand and create the modern world. When my friend asked whether quantum physics worked, I pointed at his laptop. Computers, nanotechnology, and the Large Hadron Collider owe their existence to the physics that began with Bohr’s generation.

The CMS experiment at the Large Hadron Collider tries to work out the rules governing the sub-atomic world. Photo credit: CERN

Bohr’s original papers are clear and comprehensible, a beautiful read for physicists. The mathematics involves nothing more difficult than multiplication and division, yet the philosophical implications are immense. Max Planck never fully accepted quantum physics; neither did Albert Einstein, despite winning a Nobel Prize for his work on the subject.

Bohr also won a Nobel Prize for his quantum theory, but his work did not stop. He founded the Niels Bohr Institute, a centre of theoretical physics in Copenhagen, worked on the Manhattan Project developing the atomic bomb, and continued to make contributions to quantum mechanics.

And he has a lovely link to the exhibition I’m currently working on, about the Large Hadron Collider. Bohr was influential in the founding of CERN, the Geneva laboratory that is home to the LHC. If he had his way, the LHC would be in Denmark, but other scientists objected – Northern Europe was too cloudy, and had too few ski resorts, for Italian tastes.