Science towards a clean and developed environment (5)

Text of an Inaugural Lecture delivered at Yaba College of Technology by Dr. Adeleke Atanda Abiodun, B.Sc.(Hons.)(Unilorin), M.Sc.(Unilorin), Ph. D. (UNAAB).

CONTINUED FROM MONDAY 13/07/2015

Table XXII: Inhibition of Bacterial Isolates by Cosmetic Clay Extracts

The findings revealed that the content of Pb determined in the facial cosmetics was greater in black antimony than calabar stone.

The study also showed that the continuous use of calabash chalk for cosmetic purposes could result in an increase in the trace metal levels in human body beyond acceptable limits.

We however recommended that efforts should be made at enlightening the users and the general public on the dangers involved in the use of clay material contaminated with heavy metals.
Climate change and global warming

Global warming and climate change refer to an increase in average global temperatures. Natural events and human activities are believed to be contributing to an increase in average global temperatures. This is caused primarily by increases in “greenhouse” gases such as Carbon Dioxide (CO2);

A warming planet thus leads to a change in climate which can affect weather in various ways. In a nutshell: global warming is the cause, climate is the effect. Global warming is defined as the increase of the average temperature on earth. And as temperature increases so do natural disasters. Over the last 100 years, the average air temperature near the Earth’s surface has risen by a little less than 1 degree Celsius, or 1.3 Fahrenheit.

Abidun

It doesn’t seem that much does it? Yet this warming is at least responsible for the conspicuous increase in storms, floods, and raging forest fires we have seen in recent years, says scientists.

Their data show that an increase of one degree Celsius make the Earth warmer now than it has been for at least a thousand years. The top 11 warmest years on record were all in the previous 13 years said NASA in 2007, and the first half of 2010 went down in history as the hottest ever recorded.

Projections from the UN Climate Change body the Intergovernmental Panel on Climate Change (IPCC) say that global surface temperature will probably rise a further 1.5 to 4.8 degrees Celsius during the 21st century. The huge range of estimates is due to the amazing complexity of our Earth’s climate system and the uncertainty about whether, mankind will fight this warming or continue with business as usual.

In the past climate change was triggered by changes in the sun’s energy output, the changing position of continental plates, or the rotating axis of the Earth itself.

Many plants and animals were able to adapt to these slowly changing their habitat according to the comings and goings of glaciers. According to the most recent UN assessment, 20 to 30 percent of Earth’s plant and animal species face extinction if the world warms by 1.5 and 2.5 0c.

Scientists inform that the global warming we now experience is not a natural occurrence and that it is not brought on by natural causes. They say that responsibility lies with humanity’s carbon emissions.
Greenhouse gases

Six main greenhouse gases are Carbon dioxide (CO2), methane (CH4),which is 20 times as potent a greenhouse gas as carbon dioxide) and nitrous oxide (N2O), plus three fluorinated industrial gases: hydro fluorocarbons (HFCs), per fluorocarbons (PFCs) and sulphur hexafluoride (SF6). Water vapour is also considered a greenhouse gas.

Renewable energy

Briefs on Energy
Bioenergy is renewable energy made available from materials derive from biological sources. Biomass is any organic material which has stored sunlight in the form of chemical energy.

As fuel may include wood, wood waste, straw, manure, sugarcane and other by products from a variety of agricyltural process. In its most narrow sense it is a synonym to biofuel , which is fuel derived from biological sources.

In its broader sense it includes biomass, the biological used as a biofuel, as well as the social, economic, scientific and technical fields associated with using biological sources of energy.

One of the advantages of biomass fuel is that it is often a by-product, residue or waste – product of other processes, such as farming, animal husbandry and forestry. In theory this means there is no competition between fuel and food production, although this is not always the case.58

The biofuel, fuel derived from biological sources burning is environmentally friendly compared to other fuels like oil and coal. Its ash content is only about 2.5% against 30 – 50% of coal, and it contains very little sulfur. Since it burns at relatively low temperatures, it produces little nitrous oxides.

Biogas is gaining ground as a promising form of renewable energy used to generate electricity, heat and make biofuels. Focus on climate change and the need to minimize organic waste in landfills has led to an increasing interest for biogas production.
Production of biogas from kitchen waste and chicken dung

Madam Rector Ma, sewage to some is ‘nothing to do with thing’ but to others especially to the scientists, it’s a gold mine. Sewage is mainly liquid waste containing some solid produced by humans which typically consists of washing water, faeces, urine, laundry waste and other materials which goes down drains and toilets from households and industries

It is one type of waste water that is a major or potential source of pollution especially in urban areas. It is estimated that pollution of drinking water due to faeces is by far the biggest cause of death worldwide. Sewage is a complex matrix, with many distinctive chemical characterics. These include high concentration of ammonium, nitrate, phosphorus, high conductivity (due to high dissolved solids), and high alkalinity with pH typically ranging from 7 and 8. Trichlorometanes are also likely to be present as a result of past disinfection 59.

Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Biogas originates from biogenic materials and is a type of bio fuel. One type of biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as biomass, manure or sewage, municipal waste and energy crops. This type of biogas is comprised primarily of methane and carbon dioxide.

Of all renewable energy, biogas holds the exciting prospects, in the sense that biogas serves as a waste disposal mechanism, power generating medium and a source of fertilizer 60. Biogas generation is a proven technology both in Nigeria and the world at large.

Madam Rector Ma, the primary objectives of this research is to design an effective biogas reactor, using local materials and to convert the sewage into biogas using a digester. This is because the fuel situation in Nigeria is disturbing and requires a practical, affordable and reliable solution.

From environmental point of view, the application of biogas as an energy source can not alleviate the energy crises caused by the depletion of fossil fuels, but also contribute to green house effect prevention, as there is a zero newly formed carbon dioxide production 61, 62.

The observed increase in globally averaged temperatures since the mid – twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations via the greenhouse effect. These gases consists largely of production of combustion for man quest for energy, CO2 and the likes methane, chlorofluorocarbons (CFCs), react with the ozone layer.

The ozone layer is a layer in earth’s atmosphere which contains relatively high concentrations of ozone (O3). Aside from the global problems of greenhouse warming, Nigeria has her own peculiar energy challenges. Nigerians and businesses operating in the country spend a lot of money to buy energy to cook. To make matter worse 80% of rural dwellers in Nigeria use fire – woods to cook their food thereby emitting tons of greenhouse gases in the process, and further polluting the atmosphere 63.

There is therefore, a need to design an energy system that will not further contribute to global warming, cheap and affordable for everyone especially rural dwellers and that has a simple technology that can be easily deployed anywhere.

The thrust of the study border on conversion of sewage to biogas in other to generate heat for cooking: this will afford both city and rural dwellers of Nigeria the privilege of using their waste to cook. The primary objectives of this research shall be to design an effective biogas reactor using local materials and to convert the sewage into biogas using a digester.

Kitchen wastes were collected from eateries around Yaba College of Technology, such as Finicky, Mr. Biggs, and Vigny and from fruit seller. The cow dung and chicken manure used were collected from a nearby farm. A metal cylinder which is locally fabricated was used as a digester with both inlet and outlet. The inlet to the cylinder allows waste to be poured in, while the outlet controls the maximum loading of the digester.

Any excess loading of fresh waste from inlet will force out effluents from outlet. Aluminum foils paper was used to wrap the cylinder in order to keep the temperature inside the cylinder at about 370C. The foil prevents the digester from loosing heat to extreme conditions in the atmosphere.

The kitchen waste was separated from materials which may be toxic to the bacteria in the digester and other materials that are not bio-degradable were separated. Five (5) Kg of kitchen waste which include rice, vegetables, fruits waste were grounded using grinding machine into a fine paste with about eight (8) litres of water. The mixture was allowed to stay under aerobic condition in a container for about eight (8) days.

It was pasteurized at 600C. Nine (9) kg of cow dung previously staled was diluted with fifteen (15) litres of water. Filtration was done using a bucket sieve after which the whole mixture was poured into the digester so as to keep it under anaerobic conditions for gas generation.

The four key biological and chemical stages of anaerobic digestion are:
Hydrolysis which occurred when the insoluble organic polymers such as carbohydrates, cellulose, proteins and fats are broken down and liquefied by enzymes produced by hydrolytic bacteria. Carbohydrates, proteins and lipids are hydrolyzed to sugars which then decompose further to from carbon dioxide, hydrogen, ammonia and organic acids. Proteins decompose to form ammonia, carboxylic acids and carbon dioxide. During this phase, gas concentrations may rise to levels of 80 per cent carbon dioxide and 20 per cent hydrogen.

Acidogenesis occurred when the organic acids formed in the hydrolysis and fermentation stage is converted by acetogenicmicro organisms to acetic acid. At the end of this state, carbon dioxide and hydrogen concentrations begin to decrease. This stage is where there is further breakdown of the remaining components by acidogenic (fermentive) bacteria. Here wastes are created along with ammonia, carbon dioxide and hydrogen sulphide as well as other by products. This process is similar to the way that milk sours.

Acetogenesis occurred when simple molecules created through the acidogenesis phase are further digested by acetogens to produce largely acetic acid as well as carbon dioxide and hydrogen.

Methanogenesis is the terminal stage of anaerobic digestion, here methanogens utilize the intermediate products of the preceding stages and converts them into methane, carbon dioxide and water. It is these components that makes up the majority of the biogas emitted from the system. Methanogenesis is sensitive to both high and low pHs and occurs between pH 6.5 and pH 8.0.
Figure: Processes involved in anaerobic digestion

The remaining, non digestible material which the microbes cannot feed upon along with any dead bacterial remains constitutes the digestate. Digestate is the solid remnants of the original input material to the digesters that the microbes cannot use. It also consists of the mineralized remains of the dead bacteria from within the digesters. Digestate can come in three forms: fibrous, liquor or sludge.
The relationship between the amount of carbon and nitrogen present in organic materials is expressed in terms of carbon / nitrogen (C/N) ratio. A C/N ratio ranging from 20-30 is considered optimum for anaerobic digestion.

The gas was collected using a tyre tube which was connected to rubber hose joined to the regulator. Gas chromatography analysis was carried out. The gas which is produced by anaerobic digestion known as marsh gas, sewage gas, dun gas, or biogas is about 70% methane (CH4) and 29% carbon dioxide (CO2) with insignificant traces of oxygen and sulfurated hydrogen (H2S) which gives the gas a distinct odour.
Table 2:

We therefore concluded from the analysis that methane is present at a higher percentage in the biogas which made it combustible. As such care should be taken on how we dispose our wastes so as to avoid the release of the poisonous gases into our environment. We advocated that methane production can be used in running vehicles, generators and some other internal combustible engines. We found also that methane exhibit reduced soot formation over gasoline, reduced engine maintenance and wear with extended oil change intervals, increased spark plug life, resulting to an extended engine life.

Considering the economic situation of Nigeria, if biogas plant are installed across every rural homes in Nigeria and also in urban homes, the available fuel from the nation grid will cut down overhead costs and stimulate the economy thus brings about economic benefits. In addition to this, and for biogas generation we advocated that; an alternative energy source like biogas should be encouraged for use especially in urban areas in other to reduce the quantity of carbon dioxide in the environment, this would take care of the environmental threat from the burning of firewood, but it also solve the problem of kitchen waste and animal waste management in the diary-production town, and that production of biogas has a double benefit because the plant’s digestive fluids are used as a liquid fertilizer which may be utilized as a resource, hence the use on agricultural farms.

Biodiesel oil from thevetia seed oil as Ethyl Ester: Analternative to diesel fuel
Madam Rector Ma, in my quest to finding solution to energy needs in Nigeria, I investigated the possibility of obtaining biodiesel oil from Thevetia seed. The thevetia peruviana (Yellow Oleander) is a dicotyledonous plant found growing abundantly in the tropics and temperature regions. Based on its ability to grow everywhere it is planted, it is mostly used as an ornamental tree to decorate compounds, homes, offices, public places etc.

Many developing countries had no indigenous oil reserves, and in the few countries that have they are not well managed. Scarce foreign currency is therefore required to provide fuel for transportation, agriculture and other essential services. Liquid fuels are a vital necessity for farming and the supply of nourishment in both highly developed and under developed countries. Modern mechanized food production systems are known to be sensitive to energy shortages as was demonstrated in the early 1970s.

Agricultural equipment often uses small diesel engines either to generate electricity in absence of main supply from the public source or directly for water pumping, milling, grinding etc. although agriculture and industry use diesel powered engines for many purposes, but the supply of diesel fuel is limited. The utilization of alternative fuels and their domestic production therefore deserves attention, particularly when considering the possibility of bottle-necks in fuel supply especially in times of a crisis 64. The most important energy used in agriculture is diesel fuel.

However, numerous recent publications have dealt with convenient alternatives to it, in particular the use of vegetable oils. Some vegetable matter yields oil as a natural product while fuel is produced by distillation in others. The use of vegetable oils as fuel for diesel engines is not a new concept 65, 66, 67, 68, 69. However, since the invention of the diesel engine, the development of this type of engine has been based on the availability of petroleum-derived diesel fuel, which in turn, has been tailored to meet the needs of the current engines. Vegetable oil fuel permits acceptable short term engine performance. Peterson reported that the most important properties of whole vegetable oils affecting engine durability were viscosity and degree of fatty acid unsaturation 70.

According to Pryde viscosity could be reduced by heating the vegetable oil to sufficient temperature or by converting the vegetable oil to the simple esters of methyl, ethyl or butyl alcohols 71. Esters are often used as fuel because they have lower viscosity and enhanced fuel properties when compared to unadulterated vegetable oils. The chemical transformation of triglycerides into methyl or ethyl esters has been suggested and the use of these esters as diesel fuel has been examined 72.

In carrying-out the production of biodiesel fuel from Thevetia seed, the characteristics of the Ethyl and Methyl ester of Thevetia seed oil was determined. The Thevetia seeds used for this study were collected randomly from the thevetia plant from selected locations in Lagos State. We extracted thevetia oil from the seeds, purified the extracted oil, and carried out quality assessment of the Thevetia oil. Thereafter, we prepared methyl, ethyl esters from the oil samples. Transesterification is the process of producing a reaction in a triglyceride and an alkanol / alcohol in the presence of a catalyst to produce glycerol and fatty acid esters.
Transesterification reaction

O
CH2 – O – C – R CH2OH
O O
CH – O – C – R + 3CH3OH H+ CHOH + 3R-C
O OCH3
CH2 – O – C – R CH2OH

Triglyceride Methanol Glycerol Methyl ester

The viscosities of the prepared ester samples were determined using Viscometer in line with ASTM 445on Diesel fuel. The density, flash point, pour point, smoke point, cloud point, sulphur and the cetane number of the produced ester samples were determined. The saponification value, non saponifiable matter, iodine value, and acid number of the extract, methyl and ethyl esters including a standard diesel fuel were determined by standard methods, on triplicate samples ASTM 1988;73 British Standards Institution 1989a, b74; British Standard Institution 1990 75.

The result showed that the value of the moisture content got for T. peruviana seed oil was 5% was rather too high when compared with the standard values obtained for other oil. The high value recorded was probably due to inadequate drying of the seeds and weather when the seeds were collected.

The saponification value of 280.5 was higher than for other common vegetable oil, and fat probably reflected higher quantity of the fatty acid present in the oil, since the saponification value is a measure of mean molecular weight of the fatty acids.

The refractive index (1.465) conformed to those of the other vegetable oils hence reveals that the extracted oil was pure. Refractive index is a measure of the purity of oils. Iodine valve is a measure of the degree of unsaturation of oils. In general, the greater the degree of unsaturation, the greater is the ability of oil to become rancid through oxidation 76.

The iodine value of T. peruviana seed oil (77.9) was between valves obtained for other vegetable oils in Nigeria. Acid value is a measure of free acid present in the oil which is also a measure of extent to which glyceride in the oil have been decomposed by lipase action. Decomposition is known to be accelerated by heat and light and is usually accompanied by free fatty acid formation.

The acid value (35.9) was rather too high when compared with those of other edible vegetable oils. The high acid value recorded made the oil obtained from the plant unfit for human consumption but usable industrially, as well as a biodiesel fuel. The work carried out in 2002 revealed that T. peruviana seed oil as being poisonous 77.

Comparable properties of esters derived from T. peruviana seed oil is shown in Table X. The results showed that the esters had corresponding lower values for the various parameters determined compared to the crude T. peruviana seed oil.

Also, the moisture content, saponification value, iodine value, acidic value and unsaponifiable value of the methyl ester were considerably higher than those of the ethyl ester.

These values are important to the long term storage properties of the fuel and in how they affect engine performance 78.Table 1. Comparative properties of Crude T. peruviana seed oil and its methyl and ethyl esters

The results of viscosity of the crude T. peruviana seed oil, seed oil esters, and standard diesel fuel are shown in Table Y. irrespective of the temperature, the viscosity of crude T. peruviana seed oil was significantly higher than those of its methyl and ethyl esters and the standard diesel fuel.

The result also showed that the viscosity of the ethyl ester was slightly lower than those of the methyl ester of the seed oil.

On the other hand, the viscosities of the seed oil esters were very close to those of the diesel fuel irrespective of temperature under consideration. In the light of promising results obtained with T. peruviana seed oil esters, a suitable basis existed for comprehensive tests of the oil esters as a substitute for diesel fuel.

• Abiodun is of the Department Of Chemical Sciences, School of Science, Yaba College of Technology, Lagos.

Table 2. Comparative viscosities (Centistokes) of crude T. peruviana oil, its methyl and ethyl esters with those of standard diesel oil

Table IX: Standard Values for Some Vegetable Oil