Turning The Smell Of Rotting Garbage Into An Alternative Renewable Energy Source
Rubbish dumps are usually considered the last resting ground for unwanted and unusable waste, but a valuable resource lurks in the rot. Energy in the form of gas is emitted by the waste as it decays and increasingly it is being harnessed and put to use.
Landfill gas has been converted into electricity, steam and even automotive fuel in some countries and some of these applications are being explored in India.
Until recently India’s city’s waste was tipped in such a haphazard fashion and with so much burning at the tip, that no landfill gas could be collected. But, now things are starting to change, and although in far too many places there is still inadequate control, there is a welcome trend toward compliance with the nation’s Waste Rules 2000. This means that the new secure landfills required by these rules will produce landfill gas which can be captured as a profitable “green” energy source.
However, the desire to put the gas to good use is not simply one of tapping into an unused resource. Landfill gas is made up of several gases and chemicals which are potentially flammable and harmful to health.
The main component is methane which is highly "explosive if it is allowed to concentrate in a confined space. It is odourless and colourless and can also asphyxiate people if it is inhaled in sufficient concentration and there is not enough oxygen left for us to breath.
The other main components are carbon dioxide, which is also an asphyxiant, and "trace organics" which are a number of chemical compounds present in very small concentrations but which nonetheless can be toxic. They also give the landfill gas its unpleasant smell.
Waste degradation in landfills produces landfill gas in large quantities, and the gas continues to pour out for very many years. In fact we know that the gas can last for 15 to 30 years after a landfill is closed, because there are enough old landfills now that have been doing just that for the scientists to have measured this to be happening.
Let me put it another way, waste management experts now predict that the production of gas from the average modern landfill such as those complying with the Waste Rules 2000 will mean a net mass loss of about 18% assuming 150 cubic metres per hour of landfill gas at 1.15kg/m3 is created by each tonne of waste. Now when you consider that the average landfill these days contains 5 to 10 million tones of waste this is a huge amount of gas.
In other words, nearly one fifth of the whole landfill will be converted into gas by the fermentation organisms in the landfill over the 15 to 30 year period quoted. In fact more gas will flow at a slower rate even after that, but we don’t have any landfill sites in the world which are as old as that yet to be able to know for sure.
All this gas would create special problems in India where so many people live or work near closed landfills. Most of the large landfills are close to or within urban areas.
Consequently most nations have introduced a number of measures to ensure people are not exposed to the dangers of these gases. They have been monitoring the gas output and, at closed landfills where the gas output has weakened, trenches have been dug to around the waste to intercept the gas before it can migrate off the site and get into houses.
At more recently closed landfills, and older parts of current landfills, wells have been installed to extract the gas and burn it off at very high temperatures so that it will not harm the environment. But whilst these measures are necessary for safety and environmental reasons, it is a waste of a good resource.
In recognition of this, most countries have regulations in which their Environmental Protection Departments require operators of all old landfills to at least extract the gas and flare off (burn) the gas. Burning the gas is much better than just letting it escape although it is a terrible waste of energy not to use landfill gas to meet energy needs.
Burning the gas, provided that it is burnt in a controlled fare stack which holds the burning gas at a high temperature with plenty of air for long enough, will not only produce a smokeless flume (chimney gas), but it also consumes all those “trace organics” in the landfill gas which give it such a characteristically unpleasant smell and may of which are toxic.
However, once the operator of a landfill has been required by government regulators to spend a lot of money to collect and extract the gas, it is really not difficult to find uses for the gas, and many manufacturers now produce reciprocating engines which when coupled to a generator will produce electricity which they can sell very profitably into the local electricity grid.
By doing this these operators are using the landfill gas as an alternative fuel, and it is a very green fuel, because each kilowatt created will in most nations replace oil or another fossil fuel which would have been burnt in a power station and causing a net greenhouse gas emission. But, even better is the fact that the carbon dioxide emitted from the landfill gas after burning is about 20 times less damaging as a greenhouse gas than the effect of the un-burnt methane.
The developed nations which signed the Kyoto Protocol have decided that it is so important for the avoidance of the worst effects of climate change that emissions such as that from escaping landfill gas are reduced that the have agreed to pay the less developed nations like India if they will reduce their carbon emissions, and one way is by landfill gas flaring and use of the landfill gas as alternative energy, as we have just described.
This payment system is called the Clean Development Mechanism or CDM for short, and India will benefit from payments from the industries of the developed nations, from this market fund, when the new Waste Rules 2000 landfills are developed and are filled with waste over the next few years.
It is easiest to convert the gas to electricity because it is then more manageable and safer to handle. However, using it as an alternative fuel is more efficient, although the gas must first be cleaned, there must be adequate storage facilities and rigourous safety controls apply to taking gas off the landfill site.
However, if you do avoid burning it at the landfill you can certainly create automotive fuel from it. We know that this is possible because the Swedes and the Fins are already doing it, and plan to become self sufficient by using solely alternative renewable and non-fossil fuels within the next 20 to 30 years.
So, landfill gas may smell really bad, but its clever use creates a double benefit. A bad (even toxic) smell is destroyed and a useful energy resource provided.
India will do well to follow the best waste managers in the world in massively reducing the tonnage of waste sent to landfill in every way possible, but where this is not possible, or even where it is not possible yet, the landfill gas from landfills should be used as an alternative fuel. This enables the operator/owner of the gas rights to obtain the benefits of being paid Carbon Credits by the developed nations participating in the Kyoto Protocol.
Contact Steve Last by using the “Contact Us” page form on this web site if you require any LANDFILL GAS MANAGEMENT assistance, and have a project in mind for which we can quote prices for you.
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