What is Green Cooking?
Posted on June 23rd, 2012

Dr Hector Perera      London

If you can cook more environmentally friendly manner in your kitchen, then it can be regarded as green cooking. When I said environmentally friendly manner, it should not unnecessarily pollute the atmosphere and not waste energy carelessly. The question is do we use energy efficiently in cooking?  You’ll find ways to cut down on energy consumption in the kitchen that means cut down the wastage of gas or electricity used for cooking. If we burn less gas or electricity, naturally less carbon dioxide is given off that means less pollution of the atmosphere.

CH4        +       2O2    —–ƒÆ’†’   CO2  +   2H2O  + heat

The term stoichiometric ratio describes the chemically correct air-fuel ratio necessary to achieve complete combustion of the methane gas as a fuel. This equation changes with the type of fuel.

If someone asked me to write a stoichiometric equation for the combustion of firewood as a fuel, it can be done but not quite simple as for hydrocarbons. I must say we cannot always stick to rule but try not to be careless about fuel. When fuel is burnt there is always carbon monoxide due to incomplete combustion and this is a wastage of fuel but cannot be easily totally avoided still one can cut down the wastage.

 As a result, you’ll not only save money on your energy bills, you’ll also benefit by knowing that you’ll be releasing far less carbon dioxide or even monoxide than you used to, and that the air you’ll breathe in your environment will be cleaner. Some people not even cared even to ventilate the kitchen by opening a window to let some air into the kitchen. When the cooker is on, it burns fuel with oxygen in the air or we call it oxidation which can be full or partial combustion.

If I asked you, have we not changed the way of our life styles over the decades or within the last few years, you will agree to some extent. Definitely I have changed the way we live and along with other things have changed to some extent. Just look at little towns including Gampaha which is my parent’s home town, it has changed a lot than a few years ago. It’s too much to describe the changes that took place in a few years, new and wide roads, new tall buildings, over head bridges with duel carriage ways, banks, shops and supermarkets we never thought about. Mobile phones are something new, now even ten year old children know how to use them.

Some people now live in apartments in high story buildings. In Sri Lanka, in the past these types of living and buildings were limited to cities like Colombo, Kandy and a few other cities but now it’s coming up in everywhere. Who knows quite soon Gampaha and suburb cities would like carbon copies of Manhattan in America?  I still remember a few years ago, Battramulla and the surrounding areas were nothing but marshy lands but now look at the world of difference, with modern high rise buildings, supermarkets, wide roads then picturesque Parliament.

One thing for sure once they started to live in these types of dwellings, they cannot follow the traditional firewood stove cooking.

 I must admit even we had these types of firewood stoves at home with a large coconut land. I have noticed many people have houses in coconut lands.  In England these types of houses in large gardens are a luxury, they called them detached houses, only the rich and wealthy people still live in these places but the people in the urban areas in Sri Lanka have no value, they just take it for grant. We had the traditional method of cooking on three stone cooking fire. It is the cheapest stove to produce; requiring only three suitable stones of the same height on which earthenware cooking pots are balanced over the fire in cooking rice and curries. I never had to cook at home in this type of kitchens but occasionally went to see how they cooked. The smoke, dust, heat, blackened walls are just part of the kitchen, didn’t see any difference.

 However, this cooking method also has many problems,
smoke sometimes vented into the home, instead of outdoors, causing health problems. According to the World Health Organization, “Every year, indoor air pollution is responsible for the death of 1.6 million people – that’s one death every 20 seconds.” Definitely we must change the traditional firewood type of kitchens into something healthy type of kitchens and cooking.
With these traditional firewood kitchens, fuel is wasted, as heat is allowed to escape into the open air. This requires more labour on the part of the user to gather fuel and results in faster deforestation, if wood is the fuel being used.
 Only one or two cooking pots can be used at a time.
The use of an open fire creates a risk of burns and scalds. I am sure you must have noticed sometimes firewood or coconuts shells burst into fire dangerously. Especially when the stove is used indoors, cramped conditions make adults and particularly children are susceptible to falling or stepping into the fire and receiving burns. Additionally, accidental spills of boiling water may result in scalding and blowing on fire to supply air to burn firewood may discharge burning amber, hot ash, heat, smoke causing eye, ear and throat injuries.

Another concern with traditional wood fires is the inefficiency of fuel consumption. Traditional open pit wood fires are very efficient at turning wood into energy, but inefficient at transferring the released energy into the cooking vessel. Most of the released energy in the wood is wasted heating the surrounding air rather than heating the cooking vessel. The inefficient transfer of energy requires the use of more wood, which has to be harvested from the surrounding environment, to buy from the shops which sell firewood then causing environmental stress.

Something must be done

The main way to improve the fuel efficiency of the stoves we use is to improve the heat transfer from the fire to the cooking vessel. Most importantly, the hot air and gas released from the fire must contact the cooking vessel over the largest possible surface area. This is accomplished through the use of a pot skirt that creates a narrow channel forcing hot air and gas to flow along the bottom and sides of the cooking vessel. Heat transfer can also be increased by using wide pots. Increasing the speed of the hot gases that flow around the pot can also improve heat transfer. One thing for sure these traditional firewood stoves cannot no longer be used in the modern apartment dwellings. There is no need to stick to the traditional firewood stoves; there are plenty of gas and electric cookers, single or double ovens, grills, extractor fans and many more facilities at a finger tip. There are far too many modern gadgets to make the life easier.

I have observed how the people cook with gas and electricity. To my surprise most of the time, some energy is just wasted than making the proper use. Do they waste due negligence, carelessness or unaware of the wastage? Sure they know any type of energy means money that means they have to buy or pay for it or somebody has to meet the expenses of the fuel. Unlike in the past, the present day people do not have to waste time in collecting firewood or buy them, in a way they do not understand how fortunate they are but sadly they waste some of the energy. This is the point I always addressed in order to achieve fuel efficiency. Any comments please, perera6@hotmail.co.uk

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