A Wee Solution To Traffic Pollution

Published on Thursday, 27 January 2011 10:16

	By Robin Whitlock Follow @RobinWhitlock66

In 1992, NBC News reported that a 37 year old earthquake victim in Egypt had been found alive beneath a pile of rubble and that he had survived by drinking his own urine. This is the kind of story that tends to turn people's stomachs as most imagine that urine is highly toxic, or at best unhealthy, when actually it isn't at all. It's purely a means for the body to extract substances that it does not need at a particular time. Sometimes, in circumstances when access to water is denied, urine can save lives.

Other Uses for Urine

Apparently, urine has other uses besides that of being a life saver in catastrophic situations. Ninety-five percent of it consists of water with another two and a half percent being urea and the remainder a mixture of various substances including enzymes, minerals, salts and hormones [1]. It also contains phosphorus which is essential to food production. Phosphorus is therefore the subject of great concern currently as stocks of this chemical are in decline worldwide.

The enzymes in urine can be of great use to medicine. This is because enzymes act as catalysts; that is to say they produce chemical reactions. This is why they are essential to metabolism within the human body as without them the speed of metabolism would be too slow for the host organism to remain alive [2]. Urea is also called carbamide and is an organic chemical compound which is produced when the body metabolises protein. It is found in many species besides humans and can also be produced artificially with the aid of various other inorganic compounds [3].

Urine used for Hydrogen Production

Researchers from Ohio University's Russ College of Engineering have discovered a way in which urea can be processed into hydrogen for use in hydrogen fuel cells. They have developed a urea wastewater electrolyzer which can directly convert urine into hydrogen [4]. This is important because hydorgen is a very clean energy source and increasingly is being seriously considered as a viable replacement for oil and petrol in motor vehicles.

At present most of the hydrogen available for use in such a manner has to be obtained from reforming natural gas. However, small amounts can be generated using water electrolysis in order to separate the oxygen from the hydrogen in the water so it can then be utilised. A fuel cell is essentially a device which uses electrolysis by electrochemically converting hydrogen and oxygen into water, thus producing electricity as a by-product. The way in which a fuel cell differs from an ordinary battery is that unlike the battery, which has the various chemicals required for the conversion stored inside it, the fuel cell is fed by a constant stream of chemicals flowing through it. In the vast majority of the fuel cells currently in use, the chemicals concerned are hydrogen and oxygen [5].

In the same way as a battery, a fuel cell has two electrodes called an anode and a cathode. In the fuel cell the hydrogen passes over the anode where it is forced through a platinum-coated catalyst which converts the hydrogen into protons and electrons. These flow out of the cell in different directions; the protons pass through an electrolyte but the electrons flow through an electrolytic membrane to the cathode where they are combined with oxygen to produce water [6]. It is the action of the splitting of the proton from the electron that produces the electricity and therefore generates the heat.

As a result the byproducts are electricity (and therefore heat) and water [7]. The most popular kind of fuel cell, and the type that has most potential as a renewable energy device, is the polymer exchange membrane fuel cell (PEMFC). The membrane in such a cell is a thin plastic membrane which is permeable to protons when saturated but does not admit electrons. Since each fuel cell produces only a small amount of voltage the cells have to be stacked together into a single functioning unit when used to provide power for homes and vehicles [8].

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The device developed by Ohio University operates through the electrolysis of urine in an alkali medium to extract the urea. In this design, a low-cost gel is used in contrast to the normal potassium hydroxide. In removing the urea, hydrogen and ammonia are produced. Another way in which the urea fuel cell differs from a normal fuel cell is that in this instance a nickel catalyst is used instead of the normal platinum which has been shown to be ineffective when electrolyzing urea. The new technology is so far the only way in which hydrogen can be produced directly from urea; it has widespread potential being ideal for use as an isolated unit capable of producing energy from human excreta. This would be of great benefit in isolated communities such as military garrisons which currently spend over $7 millon on energy. Another benefit in such circumstances would be a drastic reduction in the amount of human sewage, the processing of which is currently responsible for the release of several million tonnes of greenhouse gases.

Further Research

Further research on urea-fuelled systems is being carried out at Heriot-Watt University by Dr Shanwen Tao and his assistant Dr Rong Lan [9]. The two scientists have developed a prototype Carbamide Power System which operates using urea-fuel cells and the project has attracted a £130,000 grant from the Engineering and Physical Sciences Research Council to aid development. Dr Tao's colleague, Dr Robert Goodfellow said in an article for the BBC News website that the technology "converts the urea within urine directly into water, carbon dioxide, nitrogen and, more importantly, electricity." Unlike the research conducted at Ohio, Dr Tao's fuel cell research therefore constitutes a one-step process in which the electrolysis directly converts the urea into electricity.

Normal hydrogen fuel cells contain an ionic-conducting membrane that separates the hydrogen from oxygen. However, the big issue with fuel cells is cost - hydrogen is a highly flammable gas and is therefore difficult to store and transport cheaply. The gas may be stored within a medium, for example light chemicals such as ammonia, methane and methanol etc [10]. This explains the enthusiasm for research on urea as an alternative to conventional hydrogen.

A urea system would eliminate the requirement to transport hydrogen and would therefore be much cheaper. Given that hydrogen may be stored in ammonia, it can also be used to produce cheap ammonia fertilisers, the carbon dioxide currently used for this process being obtained by carbon sequestration from the atmosphere. Urea fuel cells will therefore assist in the stabilisation and reduction of greenhouse gases as well being able to fuel the transport of the future. One such fertiliser is Ad-blue, a urea solution developed by the European AdBlue-urea-SCR project and it is this that is the target fuel for the new urea fuel cells. The new urea fuel cell, being developed by Strathclyde University, according to Commercialisation Manager Gillian Fleming is dual functioning as it is also able to be used with hydrogen if necessary. The university's aim is to have an 80-100 cm² fuel cell available for testing by May 2011.

Additional benefits arise once the urea has been removed from urine, since the remaining liquid could be purified into drinking water. "So in theory you could be drinking your own waste product" said Dr Goodfellow [11].

Sally Magnusson, the well-known BBC Anchorwoman and presenter of Songs of Praise, has recently written a book about urine and its potential uses called The Life of Pee – The Story of How Pee Got Everywhere. She expects that the adoption of the new technology is not going to be as simple as it might sound, largely down to attitudes towards bodily wastes among the general public. Recently appearing on STV's programme, The Hour, she said that the general conception of anything to do with pee was as a sort of 'grubby vice'.

"It's because we don't like bodily wastes" she told the programme's presenters, "we have this sort of squeamish-ness about the whole thing." Yet she suddenly got interested in the subject and discovered that there are a great many stories about urine and what it has done for us within the context of our social history over thousands of years. "Within living memory, in this country" she says, "in Britain, there were horses and carts going round people's houses, especially in the wool-producing areas and there were people handing out buckets of urine to be taken away to fool the cloth."[12]

According to Sally around a quarter of the energy produced by Britain's largest coal-fired power station is used for treating urine, removing the nitrogen before the stuff goes into rivers where it could kill off fish by over-fertilising aquatic life. In Denmark there is a company that is helping to solve the problem caused by large amounts of pig urine from farms by using it to manufacture plastics and various products including lipstick. Urea also has a number of medicinal purposes, for example soldiers used to use it to treat wounds and fishermen apply it to cuts. This is because urea has got very strong antiseptic properties.

"Nasa uses it to create drinking water for astronauts" Sally says, revealing another property of urine that could be of interest to aid agencies working in drought-stricken areas of the world.

So, it seems that the future is bright, but more amber-yellow than orange.