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Advances in Agriculture, Sciences and Engineering Research
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© Science Education Development Institute, 2013
Volume 3 (1) Jan.: 656 - 667, 2013
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ISSN: 2276 - 6723
THE UTILIZATION OF FISH AND FISH FARM WASTES IN BIOGAS PRODUCTION: “A REVIEW”
K.E NNALI and A.O OKE
Department of Fisheries and Aquatic Resources Management, College of Natural Resources and Environmental
Management, Michael Okpara University of Agriculture, P.M.B 7267, Umudike, Abia State, Nigeria
Corresponding author: [email protected]
ABSTRACT
The production and utilization of biogas from anaerobic digestion of fish and fish farm wastes provides
many environmental, social economic and health benefits to the fisherman, fish farmer, fish
industrialist, consumers and the society as a whole. With environmental issues such as the greenhouse
effect and correct waste disposal methods gaining much attention throughout the fishing community,
the concept of controlled anaerobic digestion is perhaps a much overlooked example of a way to reduce
greenhouse gas emissions and provide a better waste disposal method for organic fish waste in fish
farms, processing and packaging centres. It is a diversifying sector of fishery and aquaculture
management, due to its enormous global benefits in mitigating the effect of greenhouse gases.
Utilization of the internal value chain of biogas production enhances local, economic capabilities,
safeguard jobs in rural fishing ports and zones. It improves fish processing and storage due to easy
sourcing of biogas fuel for smoking of fish and fish drying. It has contributed to improving the standard
of living, economic and social development of rural fish farmers. Also, biogas from fish, fish waste and
fish farm waste when digested can be used significantly to produce electricity and other valuable
sources of energy compared to fossil fuel. Using renewable resources in a sustainable way, fish and fish
farm waste for biogas production facilitates the closure of the carbon and nutrient cycles in the natural
water bodies housing the fishes. Fish and fish waste can join forces in reducing the energy dependency
on fossil fuel which is depleting the ozone layer, thereby contributing greatly to the much noticed
global warming phenomenon. This review summarizes and evaluates the current knowledge of
utilization of fish and fish farm wastes in biogas production and the potential for further utilization in
aquaculture and fisheries sub-sector of the economy.
KEYWORDS: Biogas production, fish and fish farm wastes, bio-fertilizers, anaerobic digestion, biodigester, greenhouse gases, digestate.
INTRODUCTION
With environmental issues such as the greenhouse effect and correct waste disposal methods gaining much
attention throughout the fishing community, the concept of controlled anaerobic digestion is perhaps a much
overlooked example of a way to reduce greenhouse gas emissions and provide a better waste disposal method
for organic fish waste in fish farms, processing and packaging centres [6].
The production and utilization of biogas from Anaerobic digestion provides many environmental, social
economic and health benefits to both the fisherman, fish farmer, fish industrialist, consumers and the society as
a whole [10]. It is a diversifying sector of fishery and aquaculture management, due to its enormous global
benefits in mitigating the effect of greenhouse gases. Utilization of the internal value chain of biogas production
enhances local, economic capabilities, safeguard jobs in rural fishing ports and zones. It improves fish
processing and storage due to easy sourcing of biogas fuel for smoking of fish and fish drying. It has contributed
to improving the standard of living, economic and social development of rural fish farmers. Fishermen who
have embraced the biogas innovation, tends to spend less cost in heat energy generation for post-harvest
processing. The biogas from fish, fish waste and fish farm waste when digested can be used significantly to
produce electricity and other valuable sources of energy compared to fossil fuel. In this way, fish biogas project
can create new markets for fisheries and aquaculture sector. Using renewable resources in a sustainable way,
fish and fish farm waste for biogas production facilitates the closure of the carbon and nutrient cycles in the
natural water bodies housing the fishes. Fish and fish waste can join forces in reducing the energy dependency
on fossil fuel which is depleting the ozone layer, thereby contributing greatly to the much noticed global
warming phenomenon.
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What is biogas and its composition?
Biogas is a by-product of the biological breakdown of organic waste in an anaerobic condition [5]. Anaerobic
condition is practically achievable in a biological setup when air tight containers are used to accommodate
biodegradable materials in the presence of the desired anaerobes. Usually, this biodegradable materials e.g.
organic farm waste contains bacteria and fungi spores. These are biological inoculants that trigger breakdown of
macro-molecules to micro molecules. The result of this, is the simultaneous biological breakdown and
respiration which quickly uses up the available oxygen thereby creating an anaerobic condition that forces all
the aerobes (microorganism that need oxygen) to die off [2]. The anaerobic organisms emerge and biologically
degrade the waste in an anaerobic condition to produce the much celebrated methane biogas. Anaerobic
digestion or decomposition is a complete biological process in which anaerobic bacteria and fungi decompose
organic waste in an environment of no oxygen to produce methane biogas. The major products of anaerobic
digestion are biogas and bio fertilizer. The bio-fertilizer is the digested substrate residue commonly called the
“digestate”. The biogas has an analytical composition of methane 55 – 65% carbon dioxide 35 – 45% nitrogen 6
– 3% hydrogen 0 – 1% hydrogen sulphide 0 – 1% [10]. Usually there are two broad phase in biogas production;
the aerobic and principal anaerobic phase. The aerobic phase is at the initial experimental period when the living
organisms (aerobes) are still present. As the respiration and bio degradation takes place, there is oxygen
depletion and carbon dioxide production. Soon the oxygen finished and this leads to death of the aerobic
microbes paving way for a hundred percent takeover of the anaerobic microbes which eventually produces the
methane gas component of the biogas.
In the global fishing industry there are millions of tonnes of fish wasted due to poor perseveration and storage
facility. Fish is a highly perishable meat with high grade of essential amino acid. With the soft tissue structure of
fish it is prone to microbial attack. The living fish has many pathogens that are beneficial and non-beneficial to
the fish. At death this microbes couples with the digestive enzyme starts degrading the fish tissue at a very fast
rate. This degradation rate is due to the softness and proximate composition of fish. Bacteria and fungi multiply
rapidly at an environment of good substrate. This makes fish a good substrate to incubate bacteria and fungi that
can be used to kick start biogas production from fish and fish farm waste. By the anaerobic digestions, the
significant amount of methane gas emission resulting from the uncontrolled anaerobic decomposition of organic
waste into the atmosphere will be reduced [9]. The production of biogas will reduce dependency on fossil fuel
thereby reducing carbon dioxide emission. The world today is under serious threat of drastic climate change
which was triggered by depletion of the ozone layer by greenhouse gas emission.
Anaerobic digestion definition and processes
Anaerobic digestion is a biological process making it possible to degrade organic matter by producing biogas
which is a renewable energy source and a sludge used as fertilizer. Controlled anaerobic digestion is by no
means a radical or new concept. Large scale industrial digesters and small domestic digesters are in operation in
many places around the world. The purpose of all these digesters is to produce combustible biogas which can be
burned to provide energy for a whole range of uses. The production of biogas is carried out in the environment
in a natural way (e.g. gas of marshes - vegetable and animal matter decomposition where the formation of
bubbles at water surface can be observed). In the absence of oxygen (anaerobic digestion), the organic matter is
degraded partially by the combined action of several types of micro-organisms. A succession of biological
reactions (see fig. 1) led to the formation of biogas and sludge. The bacteria which carry out these reactions exist
in natural state in the liquid manure and the anaerobic ecosystems; it is not necessary to add more, they develop
naturally in a medium without oxygen.
Hydrolysis:
The organic macromolecules break up into simpler elements-solid waste thus is liquefied and hydrolyzed in
small soluble molecules (e.g. the cellulose is transformed into soluble sugars such as glucose or cellulose) [9].
Acidogenesis:
This process transforms these simple molecules into acids of weak molecular weight such as lactic acid and
volatile fatty-acids from 2 to 5 carbon atoms [9]. In parallel are produced low-weight molecular alcohol, such as
bicarbonate ethanol and molecular hydrogen.
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Acetogenesis:
The products resulting from fermentation require an additional transformation before being able to produce
methane. It is here that intervene the acetogenes reducing bacteria and the sulfato-reducing bacteria, producing
hydrogen sulphide (H2S) [9].
Methanogenesis
The ultimate phase during which two types of methanogenes bacteria take over the first ones (acetogenes)
reduce methane acetate, CH4 and bicarbonate. The second ones reduce methane bicarbonate [9]
Disadvantage of Fossil In Relation To Biogas
(1) Fossil fuel on production produces air and gas pollution which introduces large quantity of carbon
compound into the atmosphere. This gaseous introduction causes acid rain; heavy metal presence in drainage
water and aquatic bodies. Bio gas production is environmentally friendly as no gas is introduced into the
atmosphere on production. It is environmentally friendly as the ecosystem is not adversely affected [11]. These
fish and fish farm waste introduction is for the bio-digester inoculation. Bacteria are greedy in nature and
reproduce actively under favorable condition. This is the natural mechanism that continuously sustains
methanogensis in the biogas digester. The biogas digester is also called “a fermenter” and it has three main
sections.
1
Substrate and holding tank
2
The processing and mixing tank
3
Biogas collection and holding tank.
Biogas is basically insoluble in water [7]. Some of the fish farm wastes are dead fishes, unwanted aquatic plants
and animals, earthen pond sludge.
Importance of Biogas Production from Fish Wastes
(1)
It is a renewable energy source.
(2)
Its production is an environmentally friendly process with little or no hazards associated.
(3)
Biogas is a cost efficient tool and approach for greenhouse gas reduction in the world.
(4)
Protection of the natural water environment as its production does not lead to aquatic and
environmental pollutions.
(5)
It helps reduce air and gas pollutions in industrial farms.
(6)
Its production is cheap recycling of organic waste that could be harmful to human existence.
(7)
The organic residue of biogas plant is use as a bio fertilizer
(8)
It brings economic benefits to the farmers.
(9)
Creates jobs and brings local development.
(10)
It prevents and regulates livestock infections.
Agricultural production benefits of Fish biogas
(1)
Cheep slurry storage.
(2)
It reduces cost of transportation of organic waste.
(3)
Its an odour regulated production.
(4))
It helps regulate pathogen and disease vectors e.g. flies in fishing ports
(5)
It lessens methane gas emission into the atmosphere.
(6)
NPK bio fertilizer production with less leaching strength
(7)
The gas produced is used to generate heat in the farm for fish smoking.
(8)
The gas can be converted to other forms of energy as so desires.
Fish and
Fish farm waste in Biogas production
The activities that characterize the fish processing sector depend on the type of fish being processed and the
desired final product. Fish processing today broadly consist of removing the edible parts of fish and preserving
them for consumption [11]. Then what happens to the non-edible parts? Before now they are buried and used for
compost formation. This is good but has not gone unnoticed with its attendant environmental and health
challenges. The main fish processing stock includes, cod, tuna, herrings, mackerel, anchovy, pilchard, salmon,
pollack, hake, haddock. Products for human consumption range from whole fish to fillets especially products
which may be sold frozen or preserved [11]. Wild caught marine fish processing facility are typically located at
commercial point or harbor while for aquaculture products, the processing activities are washing, gutting,
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Advances in Agriculture, Sciences and Engineering Research: Volume 3 (1) Feb.: 656 - 667, 2013
heading, cooking, cooling, pressing, drying and packaging. Each of these processing stages has an industrial
waste associated with it. These industrial waste e.g. the head, guts, fin, scales, are goods inoculants for the
biogas plant. They can be digested alone or used as an inoculants to fasting or catalyze digestion process. Fatty
fishes as herring are skinned by pulling them over a freezing drum. After fish evisceration, it is used as a
substrate in a bio-digester to produce methane biogas. Usually fish produce methane gas but is preferably used
in bio digestion inoculation. This aids mass digestion of other non-easily degraded organic materials.
Bio-digestion and mechanism
The motive behind the use of bio digestion is usually related to waste management and energy production. The
bio digestion is brought about through the aid of a bio-digester. A bio-digester is a setup in which bio digestion
can take place and the products duly harnessed. The materials digested are agricultural waste, food waste, fish
wastes, human wastes, organic waste etc. The biogas from a bio-digester is used to produce heat and electricity
in the various fish farming location which is usually in non-residential zones [7]. An added benefit to biodigester is the leftover high grade organic fertilizer (bio-fertilizer). There are several models of bio-digester used
globally to achieve same result e.g. floating drum (see fig.4), fixed drums (see fig.5). These types are typically
designed for single families and small communities. Bio-digester provides serious solutions to waste
management and energy generation. Some are made of polyethylene tube or plastic drums with are tight
conditions.
Mechanism of bio-digester
The digestion process begins with bacterial hydrolysis of input material substrate to digest or break it down to
insoluble organic polymers such as carbohydrates for other bacterial like the acidogenic bacterial to convert the
sugar and amino-acid to carbon dioxide, hydrogen, ammonia and organic acid while acetogenic bacteria covert
the organic acids to acetic acid. Finally the methanogenic bacteria convert the acetones to methane gas. All this
processes are brought about by archea population which plays an indispensible role in anaerobic digestion. As
the gas is been produced by effervescences there is pressure build up at the top of the bio-digester. The substrate
been digested will gradually be liquefied. This produces a relatively semi-solid sludge. The sludge is high in
nitrogen, phosphorus and potassium. These are good sources plant nutrients [1].
Advantages of bio-digester
1
The materials are easy to fabricate and source
2
Easy to install, usually with small space.
3
Low cost of machine or setup installation of digester
4
It has a very simple mechanism of operation
5
The cost of maintenance is minimal.
Bio-digestion does not require sophisticated equipment and technology [1]. In general bio-digesters helps
improve animal husbandry and aquaculture by cleansing the environment of slaughter houses and septic tanks.
Usually, the contents of fish ponds drainage helps control environmental pollution associates with disposal of
fish pond sludge and slurry. The sludge is the solid component of a fish pond comprising of dead fishes, fish
fecal matter, unused feed in the water. These solid components cause drainage blockage and causes pathogen
infection. Usually this activated sludge is used as a biomass substrate to feed the bio-digester to produce, biogas
and bio-fertilizer (an organic fertilizer of high nutritional value for fish pond and folder crop
Fish and Fish farm wastes
Usually fish is preserved to prolong its freshness and nutritional composition. To achieve this, the elements and
components that can introduce microbial decomposition and spoilage in the fish are immediately removed to
produce a less pathogenic substrate fit for human consumption [11]. Fish canning and fish related industry, the
heads guts (GIT), fin and scales are removed and they constitute wastes. These wastes are used as biomass
substrate for the bio-digester. The fish farming operation is still another waste producing industry Due to decline
in capture fisheries. Aquaculture has been positioned to meet the global fish demand. The work plane for the
actualization of fish production capacity led to the resolution in the global fish production. Usually in a fish
pond, the unused feed, fish faecal matter and dead fish couple with Zooplanktons and phytoplankton in the
water sediment heavily at the bottom. The long time sedimentation cause fish pond sludge formation, the sludge
at drainage of the pond is converted by evaporation it and using it as a biomass substrate for a bio-digester in
fish biogas production [11]. The sludge in its watery form has to be activated by concentration and possible
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removing the pathogen in it to become fish pond activated sludge. This activated sludge is used as bio-digester
inoculants or biomass substrate. The aquatic plants and weeds which before now have been of no economic
importance are now used to combine with the activated sludge to form a biomass substrate for a bio-digester for
the production of biogas and bio-fertilizer.
Socio-economic Impacts of Fish Biogas Production
Biogas productions from fish waste have some social benefits when compared to use of fossil energy source.
Most of these social impacts are related to jobs creation and financial base expansion of fishermen and fish
farmers [11].
Employment opportunity
The development of fish waste bio-digestion and biogas production in some fishing communities will create
means and source of financial livelihood for some unemployed people (Plate 1).
Health Issues
Fish biogas plant is also known as fish waste treatment plant. It directly contributes to a better hygienic
condition of the fish producing settlement and community. The utilization of the bio-fertilizer residue from the
digested waste in fish pond fertilization improves pathogen control and veterinary safely. When compared to
untreated manure and slurries. The standardization of the digestate is by the retention of some thermopiles
digestion temperature, pasteurization or pressure control. In all this cases it is to inactivate pathogens, weed
seeds and control of other biological hazards. The waste management associated lapses has been the open door
to global epidemic levels. New diseases emerge traceable to one pathogen or the other in relation for improper
waste management .The fish and fish processing industry is not exempted from waste management production
and lapses. The fishing industry is faced with large spoilage of fish before final fish processing and package.
The processing industry having waste like fish head, fins, guts and scales are possible digestible waste of
importance. This waste is converted to finance of and economic resources to the farms. The biogas generated
from the waste will be used to produce heat for fish smoking, drying and preservation. This lowers the cost of
fish processing, preservation and storage. The innovation of fish biogas production or fish waste bio digestion
has tremendously helped the environment in fishing communities. The world is under treat by the ozone layer
depletion due to much carbon burning and drastic depletion of the global forest vegetation for fire wood [12]. If
all the fishermen and fish farmers in every fishing community will embrace fish waste bio digestion to produce
biogas (methane) which can be used in fish processing and preservation. The fishermen and fish farmers will
spend less money on heat generation. Reducing consumption of forest biomass will be every good tool for
creating sustainable forestry resources for the future.
Environmental Impacts of Fish Biogas
Due to its several advantages, biogas exploitation can contribution to their energy, agriculture, aquaculture,
water ways and water body management. Fish biogas production apart from its energy content can be an
effective waste management method providing a natural high quality fertilizer for crop cultivation and
environmental protection (reduces emission) of particulate matter and nitrous oxide and contributes to
greenhouse gas (GHG) mitigation. However the environmental impact of biogas production and exploitation
needs careful consideration towards more sustainable fish waste management [11].
AIR AND GAS EMISSIONS
Utilization of fossil fuels such as lignite, hard coal, crude oil, natural gas converts carbon, stored for millions of
years in the earth’s crust and releases it as carbon dioxide CO2 into the atmosphere. An increase of the current
carbon dioxide (CO2) concentration in the atmosphere causes global warming as carbon dioxide is a greenhouse
gas (GHG) [3] The combustion of biogas also releases CO2. However the main difference when compared to
fossils fuel is that the carbon in biogas was recently taken up from the atmosphere by photosynthetic activities
of the plant. The carbon cycle of the biogas is thus closed within a very short time in comparison with carbon of
one million and several years. Biogas production by fish anaerobic digestion reduces emission of methane (CH4)
and nitrous oxide (N2O) from storage and utilization of fish waste, fish manure and animal manure as compost.
The GHG potential of methane is twenty three fold and N2O 296 higher than carbon dioxide [3]
On the other side careful attention is needed for fish biogas production in order side to ensure complete and high
quality gas combustion. Leakage should be avoided from the gas digester to avoid explosion in the fishing zone
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ENERGY BALANCE
Most fishing and fish processing locations are usually in remote and undeveloped locations lacking such basic
amenities like electricity. So energy sourcing and production become a major challenge. The challenge is greatly
seen in the fish processing and storage lapses. The integrated fish and fish waste biogas project will generate the
much needed energy for fish preservations. The gas energy in its potential form is used for fish processing and
storage [11]. Nowadays, the experiment and experience has shown that when the mass and energy balances have
been properly collaborated and optimized that nothing is a waste. The lower the biogas input on biogas plants,
the lower the impact on the environment.
SOIL FERTILITY
The use of fish waste materials from biogas production and the utilization of the gas which basically has no
residue will increase the soil heavy metal content and carbon content. The bio fertilizer on the field has been
beneficial to crop plant production. The bio fertilizer efficiency is due to it homogeneity and high nutrient
composition, soil fertilization in which the bio-fertilizer improves the soil texture, soil structure and soil
nutritional composition [8].
FISH AND FISH FARM WASTE MANAGEMENT
One major advantage of biogas production is the ability to transform fish waste into valuable resource in a
fishing community. The nature of waste greatly produced in a fishing location will determine the possible
outbreak of diseases either to the aquatic, livestock or human population of that place. Usually indiscriminate
disposal of fish waste will serve as good substrate for pathogenic invasion of the locality under consideration.
Biogas production from fish waste contributes to reduce the volume of fish waste and cost of waste disposal, it
reduces waste odour by 80%. [12]
Bio-Fertilizer Application
Fish biogas plant is not only a supplier of energy. The digested biogas, bio-fertilizer also called the digestate is a
valuable source of renewable plant nutrient [12, 4, 5]. It is rich in nitrogen, phosphorus potassium and
micronutrient. It is usually in liquid, sludge or dried form as desired by the end users. This is used in liquid form
in company of irrigation water, it is applied prior to the ploughing of the soil or in most case it is dried in some
places as desired for easy application [4, 5]. The storage and application of liquid fertilizer reduces compost
flies, unpleasant odor associated with compost formation.
REFERENCES
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Mechanical Engineering, BUET, Dhaka, 2008.
[2] .Gebaur, R., Mesophilic Anaerobic Treatment of Sludge from Saline Fish Farm with Biogas Production, Bioresource Technology, 2004, 93, pp. 155-167.
[3] Gebaur, R., Eikebrokk, B., Mesophilic Anaerobic Treatment of Sludge from Salmon Smolt Hatching,
Bioresource Technology, 2006, 97, pp.2389-2401.
[4] ICEBET, Agricultural biogas production in Denmark, (Institute of Chemical Engineering, Biotechnology
and Environmental Technology). University of Southern Denmark, 2009.
[5] Lanari, D., Francis, C., Biogas Production from Solid Wastes Removed from Fish Farm Effluents, Aquat.
Living Resour., 1998 11(4), pp.289-295.
[6] Mata-Alvarez, J., Macé, S., Llabrés, P., Anaerobic Digestion of Organic fish Wastes. An Overview of
Research Achievements and Perspectives, Bio-resource Technology, 2000, 74, pp.3-16.
[7] Marchain, U., Gelman, A., Braverman, Y., Reducing Waste Contamination from Animal-Processing Plants
by Anaerobic Thermophilic Fermentation and by Flesh Fly Digestion, Applied Biochemistry and
Biotechnology, 2003, 109, pp. 107- 115
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Advances in Agriculture, Sciences and Engineering Research: Volume 3 (1) Feb.: 656 - 667, 2013
[8] Mashandete, A., Kivaisi, A., Rubindamayugi, M., Mattiasson, B., Anaerobic Batch Co-digestion of Sisal
Pulp and Fish Wastes, Bioresource Technology, 2004. 95, 19-24.
[9] McDermott, B. L., Chalmers, A. D., Goodwin, A.S., Ultrasonication as a Pre-Treatment Method for the
Enhancement of the Psychrophilic Anaerobic Digestion of Aquaculture Effluents, Environmental Technology,
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[10] Milono, P., Lindajati, T. Aman, S., Biogas Production from Agricultural Organic Residues. The First
ASEAN Seminar-Workshop on Biogas Technology, Working Group on Food Waste Materials, 1981 pp. 5265.e,
[11] Salam, B., Islam, M., Rahman, M.T., Biogas from Anaerobic Digestion of Fish Waste. International
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[12] Santana A., Proud, B., The Production of Biogas from Cattle Slurry, the Effects of Concentration of Total
Solids and Animal Diet, Trop. Anim. Prod.,1980, 5(2), pp. 130-13
Fig. 1. Anaerobic digestion diagram. Source: Institute of Chemical Engineering, Biotechnology and
Environmental Technology (2009).
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Fig.2. The concept of centralized (joint) biogas plant Source: Institute of Chemical Engineering, Biotechnology and Environmental Technology (2009).
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Fig.3. Linear sequence of bio-digestion Source: Institute of Chemical Engineering, Biotechnology and Environmental Technology (2009).
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Fig.4. Source: Institute of Chemical Engineering, Biotechnology and Environmental Technology (2009).
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Fig.5. Source: Institute of Chemical Engineering, Biotechnology and Environmental Technology (2009).
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Plate1. FISHERMEN IN UGANADA PRODUCING BIOGAS
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