Green plants and algae absorb carbon dioxide
Some novel solutions are suggested to cope with the twin problem of global warming and increasing energy needs. Global warming has arisen due to climate change, which, in turn, has come about due to the increase in greenhouse gases, notably carbon dioxide. These gases trap incoming solar radiation and heat up the earth and its atmosphere.
One direct result of this is the melting of polar ice and glaciers, leading to a slow and steady rise in sea level. At this rate of rise, it is apprehended that low-lying coastal areas and islands might be flooded and swamped off.
How has this happened? Not because of natural causes (as some would fondly assert), but due to our burning more and more organic fuel — coal, wood, oil and petroleum.
The way humanity has been guzzling energy during the last century has led to significant rise in the levels of atmospheric carbon dioxide. The gas would not go away from the earth, since (unlike hydrogen or helium) it is too heavy to be pulled out of the earth’s gravity. Hence the greenhouse effect, global warming and sea level rise.
Some look to ways of ‘fixing’ or using up the carbon dioxide. One great way is provided by Mother Nature herself — photosynthesis. Green plants and algae absorb carbon dioxide and water, and convert them, using sunlight, into carbohydrates.
Hence the suggestion: plant more trees, create more efficient algae and spread them all over. They should sponge off the man-manufactured carbon dioxide and reduce global warming.
Not a bad idea, but the scale involved is humongous. The amount of land that can be used for this is not much, since we cannot usurp areas growing food grains, or where people live in dense groups.
Deserts and arid zones are one possibility. Hence the attraction to certain desert plants such as jatropha and jojoba. They not only help siphon off carbon dioxide but also produce oil that can be used as what has come to be called as ‘biodiesel.’
Indeed, many governments and companies promote such biofarming a bit too eagerly; we need to stop and think of what areas are being taken up (or over), addition to the greenhouse gas burden through biodiesel burning, viability of the oil as an all-purpose fuel and so forth.
There is a spirited and informed debate on this issue, on the Internet.
Focus has also turned to coastal areas and mudflats near the sea, where the salinity does not allow farming of the usual food crops.
But there are plants that grow and flourish here. One such plant is salicornia, also called sea asparagus, or umari keerai.
In the U.S., one Dr. Carl Hughes of the Environmental Research Lab of the University of Arizona (and head of the non-profit Seawater Foundation) has keenly advocated propagating it. He has suggested diverting seawater inland into coastal lakes where salicornia can be farmed.
Why salicornia? First of all, its tips are edible, not just by animals but also by us. The plant yields oil that is edible (rich in polyunsaturates), and usable as biodiesel. The September 5, 2003 issue of The Hindu carries an informed report, by its Agriculture Correspondent, on salicornia.
And salicornia is a better photosynthesizer than wheat and some other grains. It uses what botanists call the C-4 pathway, converting the captured carbon dioxide first into compound containing four carbons (oxaloacetate), using the enzyme PEPCase.
Wheat can only convert the same gas into a one carbon less, C-3 molecule (phosphoglycerate), using the enzyme RUBISCase.
Salicornia (like sugarcane) laps up carbon dioxide better, does so in saline water, and gives oil (or biodiesel, if you wish).
The Central salt and Marine Chemicals Research Institute (CSMCRI) at Bhavnagar, Gujarat, has been working on salicornia (and jatropha too) for some time now. Its Director, Dr. Pushpito Ghosh, points out that apart from the oil, the plant produces several other valuable products.
Indeed, he suggests using salicornia oil, not neat, but as a blend with others, since this way it keeps better and also it suits our tastes better.
One other interesting product that comes out of the plant is its salt, which contains a small but nutritionally adequate amount of potassium.
CSMCRI has also found a nitrogen- fixing microbe that is symbiotic with salicornia, which is salt-tolerant; a double whammy of carbon and nitrogen fixing set up in one. And they have taken a patent on a molecule that the plant produces which is antibacterial.
This is all well, but would it not be very useful if we could grow food grains that are salt-tolerant? That would be a boon to tsunami-hit and brackish areas. Professor HY Mohan Ram of Delhi reminds us of such a rice variety that used to be grown in Kerala.
The Manila-based International Rice Research Institute (IRRI) has a stock of 40 strains of rice, which can tolerate salty growing conditions. Some of these varieties are currently being evaluated at Karnal in Haryana.D. BALASUBRAMANIAN