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2.1 Petroleum Consumption

The fishing industry uses fuel in each of its sector activities, namely catching, processing and marketing (transport). In both small scale and large investment fisheries, the catching sector probably consumes the largest amount of fuel, with transport second and processing last. The fuel demands of the small scale processing sector are relatively light with the exception of some freezing and canning enterprises which serve the export market.

As with most other industry we have developed our fisheries in such a way that they are almost wholly dependent on fossil fuels. Accordingly the fishing industry has suffered along with other industry, from the recent increases in fuel prices. In recent years (1973 to 1980) fuel costs have more than trebled. Today knowledgeable economists and oil men warn us that those price rises are but a small foretaste of what is to come during the 1980–1990 decade. In ten years time the availability of oil at any price may be in question, we are told, not by environmentalists or politicians, but by a major oil company1. The following graph illustrates the average fuel price rises in fishing ports in England from 1974 to 1979.

1 Thought for Fuel. World Fishing, Vol. 27, No. 10. October, 1978.

Figure 3

Figure 3

The first and obvious course of action to reduce fuel costs is to consume less fuel. Reductions in consumption can be effected in many ways, and most of these changes in equipment and operations cost much less than investment in alternative fuel production necessary to make up the difference. A massive increase in the average engine horsepower installed in fishing vessels at all size ranges has taken place in the last 30 years. Few fishermen or vessel owners would claim that the increase in power is necessary for fish capture. Rather it is necessary to keep up with the competition. Most fishermen would gladly use lighter powered engines if all others in their region did likewise. Some prototype low-powered vessels are already in use such as the “Jobstar” of Tauranga, a 15 metre 70 hp refrigerated troller/liner1.

1 “Designed for Low Energy Use Per Kilo of Fish”. Commercial Fishing, Vol. 18, No. 9, Auckland, New Zealand, September 1979.

Fuel consumption has to be looked at in relation to fish caught. A recent study by the Institute of Fishery Technology in Trondheim indicated that otter trawlers used four times as much weight of fuel to catch one ton of fish, as local coastal gill net and line vessels. The coastal vessels also employed more men relative to weight of fish caught.

Table 1. Fish catches (Norwegian vessels) relative to fuel consumption and crew size
Fishing MethodCatch Per Man Per YearTons of Fuel Used Per Ton of Fish Caught
Coastal; net and line30– 40 tons0.075
Offshore; long line40– 50 tons0.140
Distant water factory ships90–110 tons0.290
Offshore; fresh fish trawlers90–110 tons0.370

The above table counts only the fuel used in the actual fishing operation. It does not consider the fuel consumption necessary to construct the vessels and their equipment. This factor is causing an escalation of capital costs in fishing.

2.2 Reducing Energy Requirements

Fuel consumption by fishing boats and transport vessels can be reduced in the following ways.

  1. by installing engines of lower power range
  2. by installing heavier, slow speed engines
  3. by using more efficient propellers or by installing nozzles
  4. by reducing overall speed requirements
  5. by supplementing propulsion power with sail

Alternative (a) is possible if fishing methods with low energy consumption budgets are selected in preference to those requiring high energy budgets. These methods are discussed in the section on fishing vessels. As indicated above, from the Norwegian study, reductions of up to 75 per cent in fuel consumption may be possible.

1 Endel, A. Institute of Fishery Technology Research, Use of Energy in Norwegian Fishing Operations, 1979. From Fishing News International, Vol. 18, No. 7. London, July 1979.

A comparison of published fuel consumption rates by major engine manufacturers indicates that alternative (b) could result in a saving of up to 20 per cent on fuel. This saving is modest, but not insignificant. The heavier engines also have a longer life, resulting in a saving on capital investment over the longer period.

Alternative (c) could result in reductions of around 10 per cent in fuel bills, by obtaining more efficient propulsion. A recently introduced 2 pitch propeller has, it is claimed, reduced fuel bills by over 20 per cent1.

Alternative (d) would require a change in the mental attitude and in values, on the part of fishermen the world over. But the results could be striking. It takes relatively little power to drive a vessel at a speed of 6 knots. An increase of the power to produce 8 knots would be significant but not excessive given a good hull form. Beyond 8 knots, considerable increases in power are needed to bring the speed up to 10 or 12 knots or more. How much of the additional speed is really necessary? The advantages of speed need to be weighed against the escalating costs of the fuel and machinery required to obtain those speeds.

Alternative (e) is discussed in the section on fishing vessels. It is a reasonable compromise that might be acceptable in both developing and industrialized countries. Many fishermen on the west coast of America use both sail and power on their vessels.

2.3 Alternative Fuels

The possibility of using fuels other than diesel oil or gasoline is being explored by many groups today and some of their findings are quite encouraging. Synthetic fuels may soon be produced and they may provide a large part of industrial requirements in some countries. Biogas can be used to fuel diesel engines or gasoline engines. Diesel oil substitutes from vegetable oils may also be on the market shortly. Gasoline engines may be run on alcohol, natural gas or biogas. Small scale fishermen in rural areas could easily be made self sufficient in alcohol and methane gas fuels. A Swiss firm, Motosacoche S.A. now markets a 10 hp kerosene engine which they claim will use 2.3 liters of kerosene per hour as opposed to 3.5 liters of gasoline for a conventional petrol engine. This would result in a 50 per cent saving in fuel costs. Other models are available, ranging from 3.5 hp to 18 hp.

2.4 Alcohol

Alcohol fuels can be produced from grain, root crops, or from wood. From wood we can make methyl alcohol or “methanol” which is the commonly used type of alcohol in industry. From vegetable crops we can produce ethyl alcohol or ethanol. When produced for industrial purposes, ethanol is usually treated with toxic substances to make it non-potable.

1 Ref. Newage Engineers, Significant Fuel Savings with Propeller System. World Fishing, August 1978. See also Trawler Skipper Chooses New Propeller System, Western Fisheries, Vol. 98, No. 5. B.C. Canada, August 1979.

The actual process of making alcohol varies with the raw material. Sugar must be formed first and this may require heat and acids for most raw material apart from sugar cane and sugar beet. The sugar is made to ferment by adding yeast and the fermented liquor is distilled to produce alcohol.

Table 2. Processes for producing alcohol

Table 2

A one-hectare field might yield 2.5 tons of grain a year. This could produce 900 liters of ethanol. A similar sized woodland area might yield over 8.5 tons of wood a year which could produce 950 liters of methanol plus a large residue of wood for direct burning.

Alcohol may be mixed with gasoline but some engines today are running on pure alcohol with no adverse effects though speed and power may be reduced. Some countries are embarking on “alcogas” programmes to substitute 15 per cent of all gasoline requirements with alcohol. One can operate a vehicle on gasoline mixed with up to 40 per cent alcohol with no noticeable loss of speed or power. A simple unit is necessary to vapourize the alcohol and separate the water from it.

Coconut oil has been used as a diesel substitute for many years. It requires very little modification so its properties are very close to those of diesel oil. There are a number of programmes currently under way to modify coconut oil for use as a gasoline substitute. Peanut oil is used as a diesel substitute in some parts of Thailand. While these vegetable oil may be adapted for use as fuel, it may not be wise or feasible to use them to a large degree as the raw material is also an important and vital part of the region's food supply.

2.5 Biogas

Biogas or methane is produced when organic matter is made to decay under anaerobic (without oxygen) conditions. This is usually done in a digester which can be a fairly simple and relatively small apparatus. Almost any kind of organic matter may be used. Those richest in energy include kitchen garbage, animal and chicken manure, vegetable crops, and paper. The methane gas (CH4) is produced along with about 30% carbon dioxide (CO2) by the biological processes involved in anaerobic digestion. The waste material from a biogas digester makes a useful fertilizer.

In most literature on the subject, the term “biogas” refers to the raw gas produced which includes CO2 and other gases. The term “methane” is used for the pure CH4 gas. Each 10 m3 of biogas is equal in calorific value to about 6.2 m3 of methane, 5.5 m3 of natural gas, 7.0 liters of gasoline (petrol) and 6.2 liters of diesel.

Several precautions should be taken if one attempts to produce methane for the first time. Operators must learn how to use a starter brew to generate the biological activity, how to dilute and agitate the mixture, and how to control the pH level. The first batch of gas produced must not be used as the original air in the tank can form an explosive mixture. Otherwise the generation of biogas involves few technical or safety problems1

Most questions on biogas by possible users relate to the amount of fuel that they can expect from a given amount of organic material. The following table might provide some indication. The figures are based on the production rates of efficient digesters.

Table 3. Biogas production: volumes obtainable from waste matter
Type of WasteWater DilutionVolume of Gas per Wt. MaterialGas Produced per Animal per Day
Pigs× 30.4 – 0.5 m3 /kg0.24 m3
Cattle× 20.1 – 0.3 m3 /kg0.22 m3
Poultry× 40.3 – 0.6 m3 /kg0.014 m3
Human & kitchen wastesvariable0.3 – 0.7 m3 /kg0.028 m3

Depending on the raw material and the digester efficiency, we can obtain from 300 to 600 m3 biogas for each ton of organic matter. Grass and foliage can be used and some groups are experimenting with large plantations of water hyacinth, kelp and algae.

1 Clarke, R. Technological Self-Sufficiency. Faber, London, 1976.

Comparing it to other fuels, Chesshire1 states that a continuous gas production rate of 14 m3 per day will generate 1.0 kw of electricity continuously given an engine efficiency of 25 per cent. Remember that the digesters require some heat for operation in cooler climates and this may be taken from the gas produced.

Biofuels hold great promise for integrated systems in fishing villages where they can be used for a variety of purposes related to fish catching, fish processing and fish farming.

The Gobar Gas Institute in Uttar Pradesh, India, has since 1957, done an enormous amount of work in biogas research and development. Some 9,000 gas digesters have been installed in India. The smallest one, for village use generates around 3.0 m3 of biogas per day from 10 kg of dung2. The yield is sufficient for the cooking needs of a 7-person household. In 1976 the unit cost about 1,500 rupees or just under $200. This is considered expensive for village people, but it is a permanent and relatively efficient installation. If it saved 2 liters of kerosene per day, it would have saved its initial cost in less than 18 months (at $0.20 a liter).

Simpler village units can be put together, but their efficiencies are low. For this reason many advocate communal use of larger digesters. These might usefully be included in integrated systems for fishing villages.

On a regional scale one might compare a biogas and fertilizer system based on over 26,000 small villages with a coal-based industrial plant of slightly greater cost. The village units require no foreign currency, they create over 100 times as many jobs, and they make a net energy contribution 6 times greater than that of the industrial plant. This is better illustrated in diagram form3. (See Figure 4).

1 Chesshire, M. Methane on the Farm in How to Use Natural Energy. NEC, London, 1978.

2 Meynell, P.J. Methane: Planning a Digester. Dorset, England, Prism Press, 1976.

3 Two Ways of Increasing Fertilizer Production. Liklik Buk, MCC, Papua New Guinea. Probably based on Reddy, A.K.N. Power to the Poor. Institute of Science, Bangalore, India. Date unknown.

Figure 4

Comparison of industrial and organic, large scale and small scale fertilizer production

Figure 4

An excellent example of successful application of a biogas and fertilizer production system is seen in the Maya Farms and processing plants of Felix Maramba in Angono near Manila. The manure from 15,000 pigs and 6,000 ducks is converted into fertilizer and biogas. The system yields over 1,300 cubic meters of gas per day. Some of the fertilizer waste is purified and used for animal feed. The system provides about 50 per cent of the farm's power requirements and 30 per cent of its animal feed. It eliminates almost completely the need for pollution control devices. Installed in 1972 at a cost of $92,000 the system currently saves the farm and plant some $87,000 annually1.

Possibly the major world example of small scale biogas production is found in China where there are reported to be seven million units in operation. In China biogas is not so much a by-product of a waste disposal system as a comprehensive, controlled method of recycling resources, producing energy and supplying fertilizer. It is also believed to promote the health of rural people as it destroys pathogens that might cause disease. Producing fertilizer from composts of organic waste is an ancient Chinese practice. After 1950 attempts were made to produce biogas as well as fertilizer. In 1978 a breakthrough was achieved in the development of a process to ferment the materials in an airtight and watertight container. The methane gas produced is collected and used as fuel for stoves, lamps and engines2.

Figure 5


Figure 5

1 Fuel and Feed on the Farm. Newsweek, Vol. XCIV, No. 12, Sept. 17, 1979.

2 Crook, M. & Van Burean, A. A Chinese Biogas Manual (translation). London, Int. Tech. Publ., 1979.

Figure 6

Figure 6

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