Cooking and Climate Change around the world
Posted on December 6th, 2015

Dr Hector Perera            London

Climate change is a critical challenge facing humanity.  According to the 2007 report from the Intergovernmental Panel on Climate Change, rising global temperatures will very likely increase the frequency and intensity of heat waves, droughts and heavy rainfall events, adversely affecting agriculture, forests, water resources, human health and settlements.  These events will impact many people around the world, and will disproportionately affect the poor in developing countries.

Inefficient Cooking Contributes to Climate Change

Nearly three billion people around the world burn coal or solid biomass (including wood, charcoal, agricultural waste, and animal dung) in open fires or inefficient stoves for daily cooking and heating. Unfortunately some Sri Lankans as well still using this wood stoves for cooking that means they are also contributing to climate change. One must visit a fire wood stove kitchen to understand the difficulties inside such a kitchen. Honestly I am surprised how our Kussi Ammas cooked our meals so tasty in such conditions. When fire wood burns you will see yellow flame that shows it is incompletely burnt. The smoke, dust, ash and smell of different gases from fire wood give a really complicated atmosphere inside this firewood stove kitchens. In addition to the health burden from smoke inhalation, burning solid fuels releases emissions of some of the most important contributors to global climate change: carbon dioxide, methane and other ozone producing gases such as carbon monoxide, as well as short-lived but very efficient sunlight-absorbing particles like black carbon and brown carbon.  Unsustainable wood harvesting also contributes to deforestation, reducing carbon uptake by forests. We had fire wood from our own garden but many people depend by buying mainly rubber plant wood for cooking. Now the things have changed for better, too difficult to find fire wood stove houses except in very rural areas. I have seen some people still use gas cookers while it gives out yellow flame instead of clear blue flame that means even if there are energy efficient gas cookers are there, some people hardly clean the cooker to give a completely burnt gas flame that is blue flame. The gas cookers must be regularly cleaned so that it burns gas efficiently.

Residential solid fuel burning accounts for 25% of global black carbon emissions, about 84% of which is from households in developing countries.  In South Asia for example, where more than half of black carbon particles come from cooking stoves, black carbon also disrupts the monsoon and accelerates melting of the Himalayan-Tibetan glaciers.  As a result, water availability and food security are threatened for millions of people.  These problems are compounded by crop damage from ozone produced in part by cook stove emissions and from surface dimming, as airborne black carbon intercepts sunlight.

Clean cooking can help address climate change

Many of today’s more efficient cook stoves have been shown to reduce fuel use by 30-60%, resulting in fewer greenhouse gas emissions and reduced impacts on forests, habitats, and biodiversity.  Recent evidence also demonstrates that advanced (efficient and low emission) cook stoves and fuels can reduce black carbon emissions by 50-90%.  Since the atmospheric lifetime of black carbon is only a few days, reducing black carbon would bring about a more rapid climate response than reductions in carbon dioxide and other long-lived greenhouse gases alone.

Studies show that controlling both short-lived climate pollutants and long-lived greenhouse gases can increase the chances of limiting global temperature rise to below 2° C, a long-term international goal for avoiding the most dangerous impacts of climate change.  In a series of recent reports, the United Nations Environment Programme emphasized the importance of introducing clean-burning biomass cook stoves and substituting traditional cook stoves with those that use modern fuels to mitigate climate change and improve air quality simultaneously.

Two broad categories of change are the dominant features of how a system responds when heat energy is added to it.  The warming effect is a physical change and the amount of temperature rise per unit of heat added depends on the substance(s) in the system.  The heat capacity of a substance is what we use to calculate this.  The heat capacity reflects the way heat energy increases the speed of various kinds of motion of the atoms and molecules in the system.  It is not a simple idea, but is simpler than what happens if chemical changes also occur.

Endothermic and exothermic reactions

Chemical changes are the second way heat is involved and in the simplest case a reaction is either endo or exothermic, meaning that as it progresses it either absorbs or gives off heat. In burning methane or cooking gas, first heat is absorbed that is an endothermic reaction but as it progress it gives out so much heat than the heat put in so it becomes an exothermic reaction. That means breaking bonds needs an initial heat but in making bonds it gives off heat. This endothermic and exothermic conditions are also applied in cooking.

When we add these ingredients, they react with others due to absorption of heat then break some bonds that is an endothermic reaction then some bonds recombine with others making new compounds then they are exothermic reactions that is they release heat. Spices react with other spices and with chicken to form new compounds for which no heat is required because they release the absorbed heat. Most of the times these British TV chefs just keep on heating or add more heat even when heat is internally automatically created. I sometimes make use of this principal in my kind of scientific energy saving cooking. When heat gives out they are exothermic reactions. We have to make use of these conditions and use less energy in cooking when it reaches a certain condition. I assume that could be at thermodynamic equilibrium condition. This would be better explained with respect to an actual cooking demonstration than just limited to words only because many of you who read this would not understand exactly what I am writing here.

London journalist Dr Tilak Fernando

I mentioned this before as well to the London journalist then Dr Tilak Fernando as well admitted that the process has been demonstrated for his benefit as well, in his own residence. I explained in such a simple way even his loyal servant understood. Before that I demonstrated and explained in simple words in three occasions to about 50 people in an apartment block in South of Colombo. One cannot say that I didn’t explain what the secret behind my scientific energy saving cooking is all about.

Once I visited with my wife to see a good friend who holds a responsible position in ITN TV then they invited us to stay for dinner. I knew if we refused to accept that invitation that would be an insult to them so we had to accept even we didn’t planned to stay for dinner. Then I asked the lady, may I have the opportunity to cook at least one thing that is rice. I invited their 12 year old daughter to watch exactly how I cooked rice. She kept telling that she has to watch the TV so she needs to hurry up and go.  I showed her how much water was taken for a certain amount of rice and allowed it to come to boiling point while I washed rice. Then I added rice and allowed it to boil, then started the froth dribbling out of the lid. I showed her how to reduce the temperature so that froth didn’t fall down into the cooker. Once it is adjusted she ran off to watch the TV but as she went I asked her to come back just to turn off the heat. In the meantime we were talking with his dad then she ran downstairs to switch off the cooker then again she again ran upstairs to watch the TV. Her mum was busy with preparing one or two other dishes. Once they were ready she served the rice and to my surprise she admitted there was no burnt rice. I was thinking that my method was simple enough even for a 12 year old child to understand.

Second law of thermodynamics

If you have ever made candy you know that the temperature rise is not linear but that it occurs in stages.  It is fun to watch the way the temperature of a mixture of butter, sugar and water progresses as you go through the various stages to the final, hard crack stage.

If I had been heating pure water, the temperature rise would have been almost linear until the boiling point was reached.  Then a new phenomenon, evaporation, would change the way the heat was being used.  The latent heat of vaporization rather than the heat capacity of water would now play a role in the way the heat being added at a constant rate was affecting the temperature.  With candy, the cooking is a chemical rather than just a physical change and things are much more complicated.  That is why there are different stages. Similarly cooking chicken curry has lots of chemical changes.

The cooking example also explains “tipping points” or irreversible changes that can also involve positive feed-back loops.  Certainly heating water is reversible.   You can heat the water and cool it back down and be back where you started from as far as the water is concerned.  The environment has been changed irreversibly in the process as the second law of thermodynamics dictates.

In the case of the cooking of the toffee not so.  Once the chemical changes occur, the sugar, water, and butter are no longer the same substance similarly cooking chicken curry. At each stage the system goes through profound chemical changes that cannot be reversed.  You actually create a new substance. When we added a few spices such as cinnamon, cloves, coriander, chilli powder, pepper, garlic, ginger, curry leaves, lemon grass to flavour and cook chicken, those ingredients reactions with chicken to form a completely different substance in flavour and that cannot be separated into individual spices or ingredients again. Anyone can detect by smell of cooked chicken curry that is formed due to a very complex chemical reaction or by a series chemical changes. It does not happen at one stage but takes a long time that is why chicken and other curries are cooked for a certain length of time. One question, why our beautiful Sri Lankan ladies keep on opening the lid, stir the chicken curry several times. May be because they get a secret beauty therapy from the cooking aroma, who knows. Sometimes when the walk about, they smell like real Tandoori chicken. Ladies, why not follow my scientific energy saving cooking technique? Then they can save energy and stop any cooking any aroma depositing on them while cooking. Your comments are welcomed

One Response to “Cooking and Climate Change around the world”

  1. Tilak Says:

    It is really sad to see why my good friend cannot understand the fact that only exposing his chemistry knowledge will not help him to get anywhere with his ‘ secret’ recipe , but he has to be realistic in getting whatever his ‘secret’ is patented.

    All what observers have seen is that the technique of cooking ( in special stainless steel) utencils, covered completely with lids during the process of cooking and reducing the heat level! To any simple mind it stands to reason but let Dr. Perera reserve his thermodynamics and chemistry knowledge for the time being and come out in a simple form ( except reducing the flame) what his secret is. Unless he does that he can cry till the sun rise from the west and the moon loses it splendour, but he will only get frustrated more and more to the point that readers will not be interested to read about his articles on ‘ cooking’ or energy saving.

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