Connect with us

Features

Managing Food crop pests without compromising yield and environment

Published

on

By DR. Chandrasiri Kudagamage

Insect pests cause substantial damage to our food crops. Insecticides are normally applied to combat them. However, dependency solely on insecticide for pest management has resulted in various undesirable environmental and human health problems. Human health is affected by the consumption of food with insecticidal residues. Also, the destruction of friendly insects such as pollinators, predators and parasites, is among some of environmental effects of indiscriminate use of insecticides. Long-term persistence of some chemicals in the environment and frequent exposure to these chemicals may also result in different forms of cancers. Sri Lanka ranks very high as regards pesticide-related health hazards and around 20,000 poisoning cases are reported per year and of them 1,600 are fatal. Seventy percent of them were related to suicide. (Registrar of Pesticide)

With the development of herbicide resistant crops like soya bean, corn and wheat the use of total weed killer glyphosate has increased and become most widely used herbicides in history. Farmers, in 2014, sprayed enough of the chemical to cover every acre of cropland in the entire world with nearly a half- pound of the herbicide, according to a 2016 study published in Environmental Sciences Europe. With this intensity of use glyphosate is likely to cause problems and as a result, this herbicide is being increasingly scrutinised for human health impacts. Scientists say it also could be altering the wildlife and organisms at the base of the food chain.

DDT was a widely used insecticide during post world war times. The popularity of this insecticide was due to it less acute toxicity. However, it was subsequently known that this insecticide accumulated in the fat layer of fish and mammals. It was banned in 1970s in our country. However, the use of insecticides continued and many farmers believed chemicals are important input for reducing yield losses.

Undesirable effects of chemicals came to be realised worldwide shortly after the wide use of agro-chemicals in post-world war times. Famous environmentalist and a marine biologist by profession, Rachel Carson in her book, ‘Silent Spring 1962’ highlighted the bad effects of indiscriminate use of chemicals. This inspired grass root environmental movements and others to highlight these effects in various forums. Carson did not anticipate a total ban on pesticide. However, she predicted consequences of over use of chemicals on biodiversity and target pests developing pesticide resistance etc. This led to establishment of environmental protection agency(1970) by an executive order from US President Richard Nixon. The purpose of this agency was to protect human health and environment. Similar legislature also being adopted in our country. The pesticide law 33 of 1980 was enacted to regulate import, manufacture, distribution and use of agro-chemicals in Sri Lanka.

 

Alternative Approach

 

To address the above issues new concept of pest management popularly known as Integrated Pest Management or IPM was launched and it evolved into an Eco-friendly and economical pest management tool. This approach has been recognised as a policy for the management of pests by successive governments. However, enough funding in the form of manpower, funding for conducting research, laboratory and analytical facilities has been limiting. This has slowed the progress of IPM in pest management in several crops.

The primary objective of IPM is to develop an economical eco-friendly pest management package where pesticides are used as the last resort when other control measures fail and the pest population exceed a certain threshold called the economic threshold. IPM integrate well with other available control methods and can be applied to any ecosystem such as crop based, home garden, greenhouses and domestic pest control.

Following globalisation and transboundary movements of food and with the increase of demand for diverse food, there has been a concern for contamination of food with various pathogens and chemical residues. Hence agriculture practices need to be introduced to minimise these effects. Recently-introduced Good Agriculture Practices (GAP) fulfil this requirement and goes beyond the scope of IPM.

IPM has various components such as mechanical control (use of bags for fruit fly control), use of resistant varieties, biocontrol (use of predators, parasites and microorganism) and legislative and quarantine (banning of imports from infested country).

 

IPM experience with major food crops

 

There are about five or six major insect pests in our staple crop rice. These pests infest different stages of the crop. Among the pests, rice brown planthopper (BPH) and rice gall-midge play an important role causing low to high of damage depending on the prevailing climate. Due to the cultivation of resistant varieties the incidence of rice gall-midge was very low compared to the times when susceptible varieties were cultivated. With respect to rice brown planhopper , the first resistant variety was introduced to farmers in 1980s. Although resistant varieties are ideal as an insect management method, evolution of new strains that can attack these resistant varieties remain a problem. This has happened with respect to gall-midge resistance where resistance broke down in rice varieties cultivated in the 1980s. However, rice breeders and entomologists were able to introduce a new resistant variety by 1984. There are reports of breaking down of this resistance in the recent times. This indicates importance of constant attention in monitoring resistance, management of resistance and finding new sources of resistance. The availability of molecular genetic tools make it easy for the incorporation novel forms of resistance, which is more stable.

The pests that attack at the seedling stages such as thrips are best approached by following correct planting time as heavy infestation is observed in late planted crop. With respect to rice bug which infest crop after flowering, use similar planting time in a Yaya, weeding around the bunds before weeds flower are important non-chemical methods

Although IPM in rice is fairly successful, it is not widely applied in vegetables and other crops. A study conducted by the Department of Agriculture (DOA) in four major vegetable growing Districts in Sri Lanka showed that 85% of farmers in the Badulla District applied pesticides to their crops before the appearance of any pests or symptoms. In the Nuwara-Eliya District this was recorded at 66%. This shows that chemical controls are used even before pest damage has exceeded economic threshold levels and the use of pesticides as a precautionary measure has become common.

Cucurbit fruitfly and melon fly infestation is the most common limiting factor in the cultivation of cucurbit crops for local consumption and export. The melon fly lays eggs deep inside the fruit. The emerging larvae feed inside the soft tissue. This results in fruit dropping and decay. The larvae pupate in soil. Insecticide control is difficult since larvae feed inside the fruit and avoid direct contact with insecticide. In the export consignment, if a single larva is present the whole consignment can get rejected. Therefore, alternative control strategy based on IPM concepts are required. There are several strategies such as bagging of fruits, collection of crop residues and decaying and fallen fruits into a black polythene bag which help to destroy the larvae due to heat developed inside the bag. Together with these cultural methods, application of protein bait is an innovative approach to control this pest. The female flies are attracted to protein substance and consumption of protein help to mature their eggs. Proteinous material prepared from locally available substances are mixed with soft insecticide and applied to leaves instead of fruits. To reduce the amount of insecticide used application to few spots of the crop is sufficient to reduce the female melon fly population. For more effective results these IPM methods need to be applied on wide area basis such as Yaya or cropping area.

Mealy bug was reported to infest papaya fruits in different parts of the country in the late 1980s. This insect is a invasive pest rapidly infesting many species crops. However, main host is papaya. Due to its rapid multiplication rate and wide host range insecticide control is not successful. In other countries where this insect was found, the population of mealy bug is kept at lower level because of the action of the predators and parasite. DOA has already released a effective parasite obtained from United State Department of Agriculture’s Animal and Plant Health Inspection Service parasite rearing facility, in areas where this pest was found.

In Dec. 2018, another pest Fall Army Worm was observed infesting maize in all major maize growing areas. It was also found to infest sugar cane. This pest is native to America. Outside its native habitat it was first found in Central and Western Africa in 2016, and then quickly spread to sub Saharan Africa and in 2018 it was reported from many Indian states. It is a good example of trans boundary movement as the adult moth is capable of flying hundred of kilometres per night. Also, in the absence of native parasites and predators, other control methods based on IPM concepts need to be developed. Initially, experience of small farmers of South America, where the pest is endemic will be valuable tool for the development of control methods. However, research and farmer awareness programme is of paramount importance to develop more realistic management programme for this new pest.

Taking IPM into farmers’ fields

Many believe the concepts developed in IPM is too complex for the average farmer to understand because it involves counting, record keeping and various calculation for economic threshold determination. Hence, farmers need to be introduced to simpler approach to study the crop growth, pest infestation and natural enemy abundance. This is achieved by a group-based learning process. This is known as the Farmers’ Field School. According to this method around 20- 25 rice farmer groups collectively, study the progress of their crop from establishment to harvesting. For this farmers meet together once a week and observe their fields and share their experience with respect to growth of the crops and those factors that limit the growth including the action of pests, and abundance of natural enemies, etc. Depending on the outcome of the observation of their fields, decision will be taken to take action if the pest population grows up. This is a learner centred process where the agriculture instructor is only a facilitator. The impact of this programme was felt by the increases in yield, reduced insecticide use and favourable bio-diversity factors like abundance of predators and parasites.

Apart from government extension, NGOs such as Sarvodaya, CARE and Sri Lanka Red Cross have provided their support on IPM by conducting training programmes on IPM, but, focusing mainly on paddy.

 

Pesticide Management

A comprehensive pesticide control procedure in the form of pesticide law 33 of 1981 is in existence in the country, but enforcement is low due to several reasons. Often advice regarding pesticide selection was given by the pesticide seller in the village. As a result farmers may select the wrong pesticide, Over use of pesticide is common. They do not use correct dose and dilution. Often they apply pesticide even before appearance of the pest. Also, they do not follow correct post harvest interval. Although, provisions are available to mitigate these shortcomings via the pesticide law, the best way to tackle is through farmer training based on a good extension program.

Under the pesticide law, every product imported to the country has to be registered. Further field monitoring and enforcement of correct use, laboratory testing for quality and residues, imports regulations in the form of banning and restricting the pesticide are carried out. Over the years, the use of WHO Class1 pesticides has been prohibited and these products banned.

Instead of conventional pesticide, there are several specific pesticide registered in the country having low toxicity to humans. Some of these products affect insect hormone system and hence specific to them. Also, available in the market are several neem based botanical pesticide which are effective particularly on caterpillar pests. Additionally, there are bacterial insecticides which result in gastric problems in insects. Insect become sick and die when they consume leaves treated with these insecticide. These insecticides act on few species of insects and easily break down when exposed to light and other environmental factors. Hence, these products are not very popular with farmers although they are safe and environmentally friendly. For these specific pesticides, there are opportunities for use in home gardens and in greenhouses

 

Future development and promotion of IPM

There are several shortcomings in the development and implementation of IPM. There is a dearth of trained extension workers to deal with large number of farmers involved in crop production. To address this issue, leader farmers can be trained in IPM methods and they can be used to train other farmers in a Yaya or in a village. The government extension workers can be facilitators in this training programme as explained above with respect to Farmers’ Field School method of training. However, more intensive training programme for extension workers covering many aspects of IPM and successful experience of IPM particularly from rice IPM programme needs to be integrated into their training curriculum. Farmer field school programme has been adopted in many countries the world over and the knowledge is shared in the form of reports, videos, manuals, field guides and podcasts. Hence there is lot of avenues to incorporate relevant information in the training curriculum of the extension workers in our country.

Consumer awareness of environmental and health hazards of pesticides and particularly of the persistence in the environment needs to be created to reject food contaminated with pesticides. For this facilities for pesticide residue analysis needs to be improved.

Field demonstration of IPM methods with the involvement of researchers, extension workers and farmers needs to be established. By following IPM methods used in these demonstration, farmers can pick up the most appropriate IPM methods to test in their fields. More investment is needed to promote innovative research such as melon fly control as explained above. Participatory IPM trials and development of simplified IPM packages for major pests and diseases are also necessary for popularising IPM among farmers.

Globalisation of trade and travel, and introduction of improved planting materials can cause accidental introduction of pests. Papaya mealy bug and fall army worm are recent examples of such pest introduction. Facilities available at the plant quarantine station need to be improved for identification of pests of quarantine significance.

There is also an increasing interest in utilising information technology in agriculture to help extension advisers and other intermediaries in delivering up to date information to farmers to manage their crops. Development Mobile Apps that work offline for early warning and surveillance of pests helps farmers make quick decisions for the management of pests.

Author is Former Entomologist, FAO Rice IPM project’s Research coordinator, Director Horticulture Research and Development Institute and Director General Department of Agriculture



Continue Reading
Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Features

An air of discontent prevails

Published

on

We have had a series of “Avurudhu parties” here in Aotearoa. No shortage of Kavum, Kokis, Athiraha, and even Wali Thalapa. Buffalo curd available locally and of course imported treacle in abundance. Yours truly has assumed the role of a fly on the wall during these festivities and gleaned much information, worth talking about.

First to get on to the Pearl, the talk of the botched-up vaccination plan and running out of the second dose of vaccine. Bizarre permutations as to what would happen if the second dose was not available on time and to who would be press-ganged into getting the “dodgier” types of vaccine from China and Russia, etc. The possible repercussions of getting a second dose of another type of vaccine to the original, the speculations of which left me rather glad that the general populace of Aotearoa has not been vaccinated to date. The talk moved on to the Easter bombings and the recent comments by leaders of the Roman Catholic church as to the possible perpetrators of the attack. Some increasingly obvious conclusions as to those responsible for the planning and funding of same are being reached by those other than some of us who dared to voice our opinions over a year ago! This combined with the increasing and very rapid unpopularity of the person they elected to high office hoping he was genie of the magic lamp type, and the possible reverse of Hong Kong that could take shape on the reclaimed land near the Colombo port, does not bode well for an already dubious future. By reverse of Hong Kong, I mean Hong Kong is trying to hold out as a bastion for democracy, whilst the proposed port city seems to be modeled on the opposite!

Moving on to Aotearoa, the rest of the world seems to be praying for a leader such as our own Jacinda Ardern, but the fat cats of Aotearoa are getting rather sick of her. Those who own multiple houses and have been setting off their interest payments against their taxes due to a loophole in the law that has now been plugged are grumbling. The fact that most young people can’t afford to buy their first houses due to rich people and property developers snapping up all available property, happily funded by banks who are only interested in the bottom line, is of no consequence to them. The fact that this could lead to so much discontent that it could even lead to armed insurrection doesn’t bother them. They seem to have forgotten that we have had almost no deaths and hardly any Covid 19 cases in our community when they say that the lockdowns, we underwent were too excessive and how the economy and business sector has suffered. These very people throng the stadia during the rugby and cricket games and enjoy music concerts with gay abandon. Megacorporations are not happy about the restrictions that are coming on with regard to the use of Liquid Petroleum Gas (LPG) due to environmental concerns. To top it all off I had a lecture from my 13-year-old daughter about how I am being “led by the nose” by Jacinda Ardern and her propaganda! Where she got that from could only be from her elder brothers whose get rich quick schemes have seen a setback due to certain leftist policies coming in from the Labour government that is in power with an absolute majority.

I laugh to myself and think about other examples I have seen of self-proclaimed pundits never being content with their lot. My education was in a very large Government school. As a perfect and a member of some sports teams we handled the administration and some of the governance of this school. Later in life when my children were attending a private school I got involved in the Executive committee of the PTA of that school. The “problems” faced by the private school and the vast dramas that were involved in trying to solve those problems were laughable when compared to those faced by even us, senior students (a much lower level in the administration) of the Government school.

It led me to believe that people always grumble. They are never content with their lot and there is always someone plugging their case and trying to sow the seeds of discontent among the populace. If those living in Aotearoa, in the present situation and well aware of the chaos and mayhem that is prevailing in the rest of the world are dissatisfied, when will anyone be satisfied? Everything is relative and one should try to step outside the confines of one’s own situation and look at the broad picture. In the words of learned barristers, I rest my case!

This week’s missive will not be complete without a tribute to the memory of Prince Phillip, the Duke of Edinburgh. He lived through some of the best and worst times of human existence on this planet and conducted himself impeccably. He showed his humanity and his failings, with a few bloopers down the line but most of those had an undercurrent of humor and couldn’t really be construed as offensive, despite the best efforts of the media and others to make them so. He served as consort to her Majesty the Queen with loyalty and aplomb and he leaves behind an enviable legacy in the world of conservation and youth affairs. It is hoped that his heirs will be up to the task for they face a task which in cricketing terms could be classed as coming into bat after the great Sir Vivian Richards had just scored a century, in his prime. Something very difficult to surpass in skill and entertainment value. Unfortunately, the Duke made just 99. May he rest in peace!

 

Continue Reading

Features

We have much to learn; and emulation is no disgrace

Published

on

“Imitation is the sincerest form of flattery that mediocrity can pay to greatness.” said Oscar Wilde who, through sharply ironic wit, often proclaimed the absolute truth.

Cassandra quotes him today as she wants to point out how much we in Sri Lanka can benefit by reaping some ideas from the recent royal funeral in Windsor. And she does not excuse herself for placing stress on our mediocrity as juxtaposed with greatness. Nationalists may shout themselves hoarse and bring down a few more majestic trees by decrying the comparison. They can justifiably claim we have a cultural heritage of two and a half millennia but have we remained cultured, following faithfully and correctly the four great religions of the world? A loud NO from Cass, echoed by millions of others. Though Britain’s development of the English language, culture, arts and science was later than our civilization, they outstripped all countries at one time and are again elevated, while we are poised on bankruptcy, with the begging bowl in hand and thugs and thieves as legislators. We in Sri Lanka are mediocre if not degraded against the greatness shown by the Brits in many spheres. This is no Anglophile speaking but a dame who was born when the Brits were leaving us to govern ourselves and grew up with our statesmen doing a jolly good job of it; Sinhalese, Tamil, Burgher, and a few Muslims taking the lead graciously and effectively with complete honesty, to serve the people. They maintained and improved our country so it was admired by others and even some desiring to imitate Ceylon as Singapore’s Lee Kwan Yew admitted. And where are we now? Except the Rajapaksa family from Medamulana, wearing rose tinted glasses or with eyes shut by arrogance, and their followers and throngs of sycophants, others see our country and our people for what it, and the people, really are. No need to elaborate.

 

The funeral of Prince Philip juxtaposed against customs here

The low-key funeral observing all Covid-19 restrictions was noteworthy for being utterly devoid of bombast and vainglory. It was dignified and moving. Cass wonders how many of her readers watched the funeral on Saturday 17, late evening here. Prince Philip had detailed all arrangements from the Navy being prominent and other Forces joining in plus the substitution of the gun carriage with a jeep he had helped design. The horse carriage he was adept at racing was stationed close by the entrance to the chapel. He has bequeathed it to the daughter of his youngest son and Sophie; the Wessexes having been very close to him and the Queen.

The entire proceedings proved first and foremost that the royal family observed strict pandemic restrictions like mask wearing and physical distancing. There was no one rule for them and another rule for us, thus proving beyond doubt that England (usually), and more so the Royal Family (definitely) are a country and an institution despising double standards. The monarch decreed and abided by the same regulations that have restricted everyone else in the UK, sharing their fate. An anecdote is relevant here. The Queen learned that lesson long ago. She was 14 when her mother said, after Buckingham Palace was bombed in September 1940, that she “could look the East End in the face now.”

Do all our people follow rules common to everyone? Oh! My heavens NO! There are differentiations according to layers in society. Shangri La would host a party for a hundred when only 30 are allowed to gather. During the height of the first wave when restrictions were strict, SLPP electioneering saw hordes thrust together and baby carrying, patting heads and hand clasping mostly by Mahinda Rajapaksha sans a mask. He has a charismatic bond with the masses but that needed to be curbed. Sajith Premadasa’s meetings were strict on physical distancing and mask wearing.

Only 30 were invited to the extremely solemn and yes, beautiful funeral service at Windsor Chapel. This meant eliminating even close relatives of the Family; but it was done. The Queen sat distanced from her daughter and sons and their spouses. Her now diminutive figure seated alone emphasized the loneliness she must be feeling after a close and successful marriage of 73 years.

This brings to mind our First Ladies. Cass steps out bravely to say that Elina Jayewardene was a gracious lady of restraint and dignity, the only perfect consort so far. Cass remembers Hema Premadasa beating her breast (true) and crying over the coffin of her late husband’s remains – in the true sense of the word – at the Prez’s funeral at Independence Square. There is dignity in restraint of even tears over a death in public. Among the women Heads of the country, the mother completely beat the daughter in dignity and ability.

We Sri Lankan women are now much more restrained in our mourning at funerals. Time was when widows even hoarsely wailed their sorrow, coiled and roiled with grief, and begged the dear departed “To look once more; say one word.” Cass in all the expressed grief of such funerals suppressed her laughter with difficulty. How would it be if the corpse obliged?

The choir at the funeral of Prince Philip was just four – one woman and three men. But their singing resounded in the high vaulted, completely majestic, centuries old church. The lone kilted piper within the Chapel evoked much. The service itself was short, just a Reading, prayers and listing of the multitude of honours bestowed on the Duke of Edinburgh, whose medals and decorations were on display beside the alter. The Archbishop of Canterbury, Justin Welby, and the Dean of Windsor, David Conner conducted the service.

To conclude, the Duke of Edinburgh had advised and laid stipulations on a simple funeral with the necessary pomp and pageantry but low key and very unostentatious. The actual funeral was even more low-key with mourners requested not to be on the streets or place flowers. The latter they did in all the residencies of the Royal Family in appreciation of a man who faithfully stood by the Queen and in his own way gave service to the nation.

Coming back to Free Sri Lanka, we seem to stress on that first word Cass inserted to the country name, even in these dire times of no crowds. And the worst is milling crowds are apparently encouraged to boost popularity of certain VVIPs by sycophants and by the preference/orders of the VVIP himself.

Consider the funeral of Minister Thondaman: crowds in Colombo and all VIPs wishing to register their presence before the body, and then the commotion at the actual cremation Up Country. Consider this year’s Sinhala New Year celebrations which were very dignified at the President’s residence but were inclusive of all traditions and a large gathering in the PM’s home, even raban playing by the Second Lady, and milling crowds outside.

 

Roller coaster ride of the country continues

Cass is relieved she had a topic to write on; namely that we should emulate the manner in which the much admired Duke of Edinburgh’s funeral was conducted, abiding by his stricture of it being low key and the country’s Covid restrictions. Our leaders especially must accept the saying I quoted at the beginning.

The country continues its roller coaster bumpy ride with some crying out the country is being sold to the Chinese, we will be a colony of theirs after they occupy the Port City; and others in remote areas sitting down for days on end, some near 100 days, drawing attention to the human elephant conflict. Much is touted about the Bill relating to the rules to govern the Port City.

Cassandra listens to all, and is somewhat warned and frightened, but cannot comment. However, one matter she speaks about loud and clear. The people must be told the status quo of the pandemic – daily numbers catching the infection and numbers dying. This is not for interest sake or ghoulish appetites; but to know how things are so we relax a wee bit or shut in more stringently. The Covid-19 Task Force, or the Health High Ups (not Pavithra please) should tell the country of the true situ of the pandemic as it holds the country in its grip. We want to know whether the grip is tightening or weakening. Please give us daily statistics. This newspaper announces total numbers. No help. Are we expected to jot down figures, subtract, and give ourselves daily infection and death statistics? No! It goes to prove that other matters – political slanted, ego boosting and economics – are more important than warning, containing the pandemic, and saving lives.

Continue Reading

Features

Do you pump Octane 95 Petrol to your car to get better performance?

Published

on

If your answer is YES, this article is for you

Dr. Saliya Jayasekara.

Senior Lecturer Department of Mechanical Engineering
University of Moratuwa

Many passenger vehicles, including three-wheelers and motorcycles are fueled by octane 95 gasoline when octane 92 gasoline (petrol) is available at a lower price. 

Otto engine (petrol engine) is an internal combustion spark ignition engine invented by a German engineer Nicolaus Otto in 1876 and used in most of the light weight vehicles including cars, three wheelers and motor bicycles. Otto engines can burn most of the hydrocarbon fuels (including hydrogen and ethanol) that can mix with air by evaporation (low boiling point). But the combustion characteristics of different hydrocarbons are not the same when burned inside an engine. If an Otto engine is designed for a particular fuel, it would not perform similarly with a fuel that has a different chemical composition.

In a well-tuned Otto engine run on gasoline for which the engine is designed, the combustion of the gasoline (petrol) / air mixture will continue smoothly from the spark plug to the piston head by igniting successive layers of the mixture as shown in Figure 1 (a).

If low grade gasolines are used, the combustion of some of the air/ fuel mixture in the cylinder does not result from propagation of the flame front initiated by the spark plug, but one or more pockets of air/fuel mixture explode (Detonate) outside the envelope of the normal combustion front as shown in Figure 1 (b). This detonation can cause severe damage to the piston and the head of the engine while deteriorating thermal performance of the engine (low efficiency)

Gasoline is a petroleum-derived product comprising a mixture of different hydrocarbons ranging from 4 to 12 carbon atoms in a carbon chain with the boiling point ranging of 30–225°C. It is predominantly a mixture of paraffins, naphthenes, aromatics and olefins. Additives and blending agents are added to improve the performance and stability of gasoline. The engine designers learned that straight-chain paraffin have a much higher tendency to detonate than do branched-chain paraffin.

The tendency of a particular gasoline to detonate is expressed by its octane number (ON). Arbitrarily, tri-methyl-pentane, C8H18 (iso-octane) is assigned an ON of 100, while the straight-chain paraffin n-heptane, C7H16 is given an ON of zero. Hence, a fuel sample with the same anti-detonation quality as that of a mixture containing 90% iso-octane and 10% n-heptane is said to have an ON of 90. Gasoline is made up of a mixture of mostly branched-chain paraffin with suitable additives to give an ON in the range 90 –100. It was also learned through experiments that the ON of a gasoline blends (e.g. gasoline and ethanol) can be calculated by using weighted average ON of each compound. Most importantly, the octane number has nothing to do with the heating value (Calorific value) or the purity of the fuel.

Engine thermodynamics show that engines with a high compression ratio offer higher thermal performance than engines with a low compression ratio. These engines having high compression ratio require high octane gasoline (for example octane 95) to avoid detonation. However, using gasoline having higher octane ratings for the engines designed for a low octane rating (for example, 92 octane) would not provide an additional benefit or loss, other than increased fuel cost.

Therefore, it is important to know the designed octane number of the engine before fueling (refer owner’s manual of the vehicle). For example: the minimum ON requirement for two and three wheelers in south Asia is 87 (The World Bank). Most of the Toyota, Honda and Nissan models including hybrid engines recommend 92 octane gasoline.

Dr. Saliya Jayasekara received the B. Sc. degree in mechanical engineering from university of Moratuwa in 2001, and the M.Sc. and PhD degrees in decentralized power generation systems from Royal institute of technology Sweden and the Melbourne University Australia in 2004 and 2013 respectively. He has well over 13 years of national and international experience in design and installation of centralised/decentralised power plants, boilers (utility/package) and heat exchangers. Currently he is serving as a senior lecture at University of Moratuwa, a visiting lecturer and fellow at Deakin University Australia.

Continue Reading

Trending