The Economist : Energy Consumption

America was the world’s biggest consumer of primary energy in 2009, using 2.18 billion tonnes of oil equivalent (TOE), according to BP’s latest statistical review.  This was 5% less than in 2008, and contributed to a recession-driven decline of 1.1% in the world’s energy usage.

China’s energy consumption continued to grow last year, increasing by 8.7% to only 5m TOE less than America’s.  Since 1999, China has more than doubled its consumption.  By contrast, America (like many other rich countries) used less energy last year than it did a decade earlier.  But despite these trends, the average American still used four-and-a-half times as much energy last year as the typical person in China.

Reference : http://www.economist.com/node/16322840?story_id=16322840

The Economist : Energy From Human Waste

WHERE there’s muck, there’s brass—or so the old saying has it.  The cynical may suggest this refers to the question of who gets what, but thoughtful readers may be forgiven for wondering, while they are recovering from the excesses of Christmas in the smallest room in the house, what exactly happens when they flush the toilet.  The answer is encouraging.  Less and less waste, these days, is actually allowed to go to waste.  Instead, it is used to generate biogas, a methane-rich mixture that can be employed for heating and for the generation of electricity.  Moreover, in an age concerned with the efficient use of energy, technological improvements are squeezing human fecal matter to release every last drop of the stuff.  Making biogas means doing artificially to faeces what would happen to them naturally if they were simply dumped into the environment or allowed to degrade in the open air at a traditional sewage farm—namely, arranging for them to be chewed up by bacteria.  Capturing the resulting methane has a double benefit.  As well as yielding energy, it also prevents what is a potent greenhouse gas from being released into the atmosphere.

Several groups are testing ways of making the process by which faeces are digested into methane more efficient.  GENeco, a subsidiary of Wessex Water, a British utility company, uses heat.  Instead of running at body temperature, the firm’s process first stews the excrement at 40°C for several days.  It then transfers the fermenting liquid to a tank that is five degrees cooler.  This two-tank system produces more methane than conventional methods because different strains of bacteria, which chew up different components of faeces, work better at different temperatures.  The result of giving diverse groups of bugs a chance to operate in their ideal environments is, according to Mohammed Saddiq, GENeco’s boss, about 30% more methane from a given amount of excrement.  In Germany a team at the Fraunhofer Institute in Stuttgart, led by Walter Trösch, is using a different approach. Dr Trösch has reduced the amount of time it takes to digest sewage from two weeks to one, by employing a pumped mixing system.  This works faster than traditional methods for two reasons.  The first is that stirring the sludge causes methane to bubble to the surface faster.  From the bacterial point of view, methane is just as much of a waste product as faeces are from the human viewpoint.  Encouraging this poison to escape allows the bacteria to survive longer and thus produce yet more methane.  The second reason is that mixing the sludge moves bacteria away from chunks that they have been digesting and on to “fresher” material that has not had as much bacterial contact.  The result is a quicker digestion of the whole.  The Fraunhofer pump system, which has already been deployed in 20 sewage plants in Brazil, Germany and Portugal, needs to operate for only a few hours a day, so does not require a large amount of energy…..

The consequence of techniques such as these is that an ever-larger proportion of sewage is being used as a raw material for energy generation.  Germans already process about 60% of their faeces this way, and the Czechs, Britons and Dutch are close behind.  GENeco reckons the figure in Britain by the end of 2010 will have leapt to 75%—enough, when converted into electricity, to power 350,000 homes.  And the latest thinking is to improve yields still further by cutting out the middle man.  Faeces are food that has been processed by the human digestive system to extract as much useful energy as possible.  An awful lot of waste food, though, never enters anyone’s mouth in the first place, and this is an even more promising source of biogas.  In America in particular numerous sewage plants have begun processing undigested food in large quantities over the course of 2009.  This is the result of a collaborative policy by the country’s Environmental Protection Agency and its Department of Energy, to encourage the recycling of waste food in this way.  In Britain, alas, public policy actually discourages such activity.  Waste-water facilities there must pasteurise food scraps before they are processed, according to Michael Chesshire, the head of technology at BiogenGreenfinch, a company that modifies sewage digesters to use food scraps.  That is a serious waste of brass.

Reference : http://www.economist.com/sciencetechnology/displaystory.cfm?story_id=15172621

Global Emissions Culprits

Also check out this related graphic.

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The Economist : Desalination Breakthrough

THERE is a lot of water on Earth, but more than 97% of it is salty and over half of the remainder is frozen at the poles or in glaciers.  Meanwhile, around a fifth of the world’s population suffers from a shortage of drinking water and that fraction is expected to grow.  One answer is desalination—but it is an expensive answer because it requires a lot of energy.  Now, though, a pair of Canadian engineers have come up with an ingenious way of using the heat of the sun to drive the process.  Such heat, in many places that have a shortage of fresh water, is one thing that is in abundant supply.  Ben Sparrow and Joshua Zoshi met at Simon Fraser University in Vancouver, while completing their MBAs.  Their company, Saltworks Technologies, has set up a test plant beside the sea in Vancouver and will open for business in November.  Existing desalination plants work in one of two ways.  Some distil seawater by heating it up to evaporate part of it.  They then condense the vapour—a process that requires electricity.  The other plants use reverse osmosis.  This employs high-pressure pumps to force the water from brine through a membrane that is impermeable to salt.  That, too, needs electricity. Even the best reverse-osmosis plants require 3.7 kilowatt hours (kWh) of energy to produce 1,000 litres of drinking water.

Mr Sparrow and Mr Zoshi, by contrast, reckon they can produce that much fresh water with less than 1 kWh of electricity, and no other paid-for source of power is needed.  Their process is fuelled by concentration gradients of salinity between different vessels of brine.  These different salinities are brought about by evaporation.  The process begins by spraying seawater into a shallow, black-bottomed pond, where it absorbs heat from the atmosphere.  The resulting evaporation increases the concentration of salt in the water from its natural level of 3.5% to as much as 20%.  Low-pressure pumps are then used to pipe this concentrated seawater, along with three other streams of untreated seawater, into the desalting unit.  As the diagram explains, what Mr Sparrow and Mr Zoshi create by doing this is a type of electrical circuit.  Instead of electrons carrying the current, though, it is carried by electrically charged atoms called ions.

Salt is made of two ions: positively charged sodium and negatively charged chloride.  These flow in opposite directions around the circuit.  Each of the four streams of water is connected to two neighbours by what are known as ion bridges.  These are pathways made of polystyrene that has been treated so it will allow the passage of only one sort of ion—either sodium or chloride.  Sodium and chloride ions pass out of the concentrated solution to the neighbouring weak ones by diffusion though these bridges (any chemical will diffuse from a high to a low concentration in this way).  The trick is that as they do so, they make the low-concentration streams of water electrically charged.  The one that is positive, because it has too much sodium, thus draws chloride ions from the stream that is to be purified.  Meanwhile, the negative, chloride-rich stream draws in sodium ions.  The result is that the fourth stream is stripped of its ions and emerges pure and fresh.  It is a simple idea that could be built equally well on a grand scale or as rooftop units the size of refrigerators.  Of course, a lot of clever engineering is involved to make it work, but the low pressure of the pumps needed (in contradistinction to those employed in reverse osmosis) means the brine can be transported through plastic pipes rather than steel ones.  Since brine is corrosive to steel, that is another advantage of Mr Sparrow’s and Mr Zoshi’s technology.  Moreover, the only electricity needed is the small amount required to pump the streams of water through the apparatus.  All the rest of the energy has come free, via the air, from the sun.

Reference : http://www.pheedcontent.com/click.phdo?i=c03d296d65b0c7a30e1f0d5e9e07374c

FT : Walking The Green Talk

Scary requirements -

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Reference : Financial Times, Sep 24th 2009