Wasted Energy and its Recovery

The idea of taking energy from waste suggests there is a fundamental fault in our manufacturing and industrial base. For it causes us to state the obvious; the waste should not be there in the first place. Leaving essential packaging aside, for nobody wants to receive damaged goods, the vast majority of operational processes create unwanted products. But to demand that this should not happen is not easy. The laws of physics state that no such machine or useful energy convertor can boast of being 100% efficient, meaning you never get as much out as you put in. We can try to minimise the waste by making our machines as efficient as we possibly can, thereby cutting the cost of consumed energy and reducing the waste that nobody wants.

Daily waste products have increased dramatically over the last forty years for a variety of reasons and is fast becoming a big problem. Products have been manufacturered without any regard to the effect that the excess waste packaging has on the environment which has given us the problems arising today.

Consumer pressure resulting from media awareness has forced manufacturers to bow to consumer demand. Conservation is now treated as a resource and not so much of a saving particularly by the utility companies like electricity, gas and water.

Bio-technology could answer many of our problems in the future. With the demand for paper ever increasing, which all ultimately ends up as waste, coppice and other wood farms might supply the short term answer until the demand on the wood industry levels out. This growth sustainable industry could greatly benefit from current research into what type of quick-growing trees are available and to where these farms could be placed to make optimum use of the suns energy and available water.

So what are the real practical alternatives and what can we do at home to make use of the energy in discarded waste apart from recycling bottles for the community.

Liquid Waste
Just consider how much hot or warm water we quite casually discard down the drain without a thought of the usefulness it could be to us. 1kg of water will release 4200Joules of energy when it drops by 1 Celcius. That is equivalent to a single bar electric fire being run for just over 4 seconds.. You probably remember that from your school Physics lesson, but something that perhaps is not commonly known is that water holds far more energy than most other substances for every kilogramme and every degree.

It needs a lot of energy to bring it to the boil! In fact, water is a most peculiar substance. According to other similar chemical substances, it should be a gas at room temperature. Thank goodness it isn't.
One way to extract the heat from water and thus deprive the rats in the sewer of a nice warm bath is to store it in a central site at ground level . All hot water wastes from baths showers, sinks washing machines and dishwashers, could be fed into the tank.

If space is at a premium it could be an idea to build the storage tanks around the bath if space permits with control electronics to discharge the water at room temperature down the drain. If the tank is within the house, heat can be extracted naturally through the use of cooling fins or if heat is to be removed more quickly, a heat exchanger could be installed. The natural place for an insulated tank with heat exchanger is at ground level so all hot outlets can be gravity fed.

Cooling water down from a bath from say 60 Celcuis to 10 Celcius could extract about 42MJ of energy. This is the equivalent of the 1kw fire on for 700 minutes.
A heat exchanger could be the basis for a warm air ducting system in the house, taking in the cooler air and returning warm.

Another serious consideration in these days of changeable climatic conditions is whether the water is discharged into the sewer anyway. In the summer months when the garden is dry, the cooled water could drain out through a divertor valve under gravity or pumped into leaky ground pipes to water your prize plants. Control electronics would detect a preset water temperature from a thermal probe and open a valve to discharge the water into the sewer or on to the garden.

Solid Wastes
For years now domestic household waste has been dumped in Land-fill sites and covered over when it's full without any regard for collective problems that arise as a result of mass indiscriminate dumping. The problem of 'leeching' is a very serious one if the site was not lined in the first place. Rainfall washes through the site and deposits toxic chemicals into underground water channels that eventually build up concentrations in our drinking water.

Organic waste products produce gas on these tips. The mixture of methane and carbon dioxide eventually finds its way up to the top and escapes. A few landfill sites once finished have had this resource tapped to power local machinery either on the site or close to. This controlled method of drilling into the rubbish to release and use the gas is by far the safest thing to do, otherwise if left, methane has been known to build up just below the surface providing a real risk of explosion, particularly if houses have been built on old sites.
Some new dumping sites have been prepared by lining the hole with plastic sheet. This prevents leeching and ensures that the eventual gas supply, once tapped can only come out of the bored hole.

Mixed solid wastes are more of a problem and becomes an expensive exercise when a substantial investment has to be made in sorting machinery. Whilst this cannot be avoided, it can at least be reduced by pre-sorting our rubbish at source. This is not common practice in Britain as yet but the time may be coming when commercial, environmental and even legal pressures will require us to do so. We might start by returning to incentive schemes.

Large scale producers of waste like hotels or industry could gain a reduction in their business rate if they adopt such a policy. They could also benefit from lower energy bills after a payback period on bought treatment plants to recycle waste and /or Combined Heat and Power units. CHP not only provides much needed heat and electricity but can also benefit from exported electricity to the National Grid sold on the open market. Incentives should also apply to the individual like guaranteed cash return for collected glass bottles.

Sadly, Britain lags behind many countries in the recycling stakes. Holland has three bins for collecting glass, metal and the rest of the rubbish. The effort involved in taking your sorted rubbish to specialised skips is too much to bear for a lot of Brits so it might make sense to sort right at the point of disposal. Future Utility rooms in modern houses might have a hi-tech disposal unit that ends up with three or more shutes for waste materials, bagged and ready for collection. For those with a really lazy disposition, a single chute, for all waste could be available with electronic sorting.

Rubbish treatment is a complex and at present somewhat expensive operation to sort completely mixed rubbish into its component parts IF the vast majority of household rubbish has already been sorted and then collected, the cost of reprocessing could be reduced. Reprocessed bio-fuels are created at some plants by pelleting the burnable waste and bagging it. The heat or calorific value of pelleted waste is only about half that of coal and so would require a greater storage volume. Burning the recycled fuel in a more efficient manner will go some way to compensate for this difference. Sulphurous emissions are also below 10% of the emissions from coal.

Incineration of household waste is a contentious issue. Whilst providing heat for nearby housing estates and generating electric power is an arguement for conservation and recycling energy, it still can produce plenty of airborn pollutants if not dealt with in the proper way. There have been many complaints over smells, and sooty smuts landing everywhere resulting from low temperature burning. Even more worrying are the toxic gases that are colourless and odourless. Again these can be dealt with if incinerated a higher temperatures.

So much for conflagration of waste, but what about less violent methods of treating rubbish?

Biological activity has very often been neglected in the part it can play to reclaim some of the sun's energy. Getting rid of garden refuse is now considered to be a weekend chore in todays urban garden, with miriads of journeys to take the garden clippings to the dump. Your friendly dustman will not take such things. So in view of the all-embracing tiny garden, where having a bonfire can be antisocial and dangerous, an alternative might be to shred up the twigs, branches, leaves and household organic waste for quick composting to redistribute back on the land. This is the natural way to put back energy into the soil.

Another alternative, if there is a big pile of waste chippings from lopped branches is to make use of the liberated heat generated inside. Useful heat can be extracted from generated inside from the moist pile of chippings by embedding a copper water pipe in the form of a coil or layered zig-zagging throughout the body of the heap. The greater the metallic surface area the water can pass through using as long a pipe as posible with heat conducting fins, the hotter will be the outcoming water. When all the heat energy has been extracted, the pile can be composted and fresh waste can be added.

Another area that might be considered is the use of chemical enhancement of bio-degredation, extracting the heat at a faster rate and producing a valuable by-product called wood alcohol or methylated spirits. There is a huge potential market for methanol as it has been shown that a car engine can run on this, the most simple of alcohols. A point to bear in mind here is firstly the expense of the chemical used might defeat the object of the exercise and an excess of any reactive compound be it organic or otherwise might produce unwanted pollution.

During WW2 and for many years after, another collecting system was in operation. The Rag-and-Bone man would principally give you a small financial return for unwanted garments or rags. The recycled rags were used mainly for the manufacture of good quality paper when combined with wood pulp. This trading died in the late sixties as we entered the throwaway age. The fact remains that nowadays, old clothes just go to the scrap heap. If you are a caligrapher and handy with quil or ink pen you might like to make your own paper or parchment from rags.

Gaseous Waste
Domestically speaking, loosing a lot of hot air is indeed a problem unless arguements prevail in the household. The retention of warm air in the house has been greatly discussed over the years by the usage of insulation and it we will not delve into it further.

The principal source of hot gas waste is from gasfire boilers and real grate fires. Great efforts have been made over the years by boiler manufacturers to improve the efficiency of such machines and it is true to say the waste heat output has been vastly reduced. But the real test is whether you consider the heat output could be reduced.

Could the output benefit from a heat exchanger to lower the temperature of output flue gases without impeding the flow of burnt gases from the boiler? The same goes for open fires, the chimney lining and brick acts as a storage radiator throughout the use of the fire.

Heat is slowly lost to the chimney cavity and out the top. Could a heat exchanger be used in the chimney breast to remove the waste heat by warming cool air from the room on one side and passing it out on the other? A difference in temperature and therefore pressure is required to get air to move in the first place.The greater the differences, the greater the movement of air will be.