Many potential savings are not yet realized

As energy costs continue to rise, energy efficiency in aquaculture becomes an increasingly important topic. And addressing the topic of energy efficiency isn’t just about the power requirements of individual devices; it means taking a holistic view of all processes that require energy... because sustainable production also means producing more fish with less energy.

Climate control systems ensure that constant indoor air conditions prevail in RAS. This cross-flow heat exchanger reduces heat requirements by around 50%.

The production, distribution and preparation of our food require large amounts of energy. On average, about one quarter of the energy requirements of developed countries are used for this. The production of protein-rich foods, i.e. meat and fish, require a particularly large amount of energy. It is not really possible to name any accurate figures on how much energy is needed to produce a fish in aquaculture because such data are highly dependent on various different factors such as the farming method used or the prevailing climatic conditions. The nutritional requirements of the fish species in question play just as important a role as the efficiency of breeding, which in turn depends very much on the farm’s management, genetic improvements achieved for the species through specific breeding regimes, or health management. It can be said, however, that for the most important production techniques in aquaculture, feed today accounts for the largest share of costs. And for the farming of some fish species feed accounts for nearly two-thirds of production costs.

One way to combat the increasing pressure from rising feed costs would be to increase the production of herbivorous or omnivorous fish species such as carp or tilapia. However, demand for these fish species is not high in Western markets. Aquafeed manufacturers thus often choose another way and are in the meantime including more and more plant materials in their feed. Although this requires a lot of knowledge and particular expertise, it is still a good way to reduce energy input during the farming of carnivorous species such as salmon, and it makes production more environmentally friendly and more sustainable.

In comparison with other methods for the production of protein-rich food aquaculture already comes off quite well today. To produce one kilogram of beef, for example – depending on method and region – between 35 and 50 MJ are necessary (all figures based on kg live weight). For pork, energy requirements vary between 16 and 20 MJ/kg. This corresponds approximately to the per kilogram energy requirement within fisheries, which during the last two decades has increased approximately six-fold due to the rise in fuel costs and longer journeys to the fishing grounds. Concrete data on energy use in aquaculture are only available for a few species and they vary greatly… from 17 to 20 MJ for the production of one kilogram of pangasius, to 18 to 27 MJ/kg of tilapia. It must not be forgotten, however, that compared to agricultural production methods, aquaculture is still relatively young and so still has large optimization potential. If it were possible, for example, to achieve the standards of the best farms everywhere in aquaculture, this would already enable enormous improvements. And global aquaculture has huge savings potential from an energy perspective, too. One could, for example, make good use of the nutrients contained in the supposed "waste" from fish farming facilities. This could be for the production of other foodstuffs so that aquaculture would then generate more protein with the same energy input. These possibilities must be developed further in the coming years in order to achieve higher sustainability.

Already today, a number of aquaculture facilities are undergoing "energy screening" to track down any latent reserves and possible savings. They call in specialists to analyze their energy balance, their consumption of water, electricity and heating energy and set these against the company’s output and product throughput rates. Although this requires considerable effort, it pays off very quickly. Sometimes, all it takes is a few small changes to noticeably improve the profitability of production.


Waste of energy as the price of alleged safety

A project that the German Development Corporation GTZ carried out jointly with Thai shrimp farmers a few years ago showed where reserves are also to be found. In Thailand’s intensive shrimp farms energy costs account for approximately one-quarter to one-third of production costs. It was noted that paddlewheels and pumps ran continuously, even when this would not be necessary. The aim of the project was to analyze the cost structures of the farms and identify opportunities for savings. First, they looked for key performances, i.e. those factors that cause costs and can be influenced selectively – a kind of " benchmarking," in which not only bare costs, but also the efficiency of the systems was considered, in other words, whether the costs and the benefits were in a reasonable relation to each other. The costs were each assessed per kilogram of shrimp produced in order to make the companies comparable. The analyses revealed that aerators accounted for around 80% of energy costs, making them the biggest energy consumers. If they were only used when actually needed, the energy costs could be reduced significantly. To control the switching on and off of the aerators as needed, however, meant taking regular oxygen measurements. Unfortunately, many farmers shy away from the necessary investments for this. Apparently they would rather pay a little more per month for diesel and electricity than invest a large amount of money in one go in the monitoring of oxygen.

Aerators offer huge savings potential. Modern systems usually require less maintenance, are more powerful, more reliable and more energy saving than technically obsolete units.

Many aquaculture facilities, especially in developing countries, lack a power management policy, and the technology used is often outdated and not very effective. Already with modern aerators and pumps that have a higher level of efficiency, energy consumption could be reduced measurably. Sometimes costs can even be saved simply through a slight reduction in production intensity. Farmers who do not use their ponds at the upper limit of capacity don’t have to ventilate them so intensively. The risk of losses decreases, and farming is optimized. And after all: what is the benefit earning a bit more if the gain is offset again by exponential cost increases? The project therefore also developed calculation models to find the point at which production quantities, costs and revenues are in a reasonable proportion to each other. Sometimes, it is already possible to increase efficiency simply by producing a little less.


Combining aquaculture with renewable energy sources

Another way to reduce energy costs is to use renewable energy sources, which come from "natural resources", for example solar, wind, precipitation, geothermal, or tidal, as well as agricultural raw materials or waste. Renewable energies have become much more significant due to the dramatic rise in crude oil prices and the ongoing climate change and they are considered to be particularly sustainable. Anyone who meets their energy requirements using such sources only improves the ecological balance of their operation, however, and not its energy efficiency… that is at least as long as they continue to use just as much power as before, albeit from other sources. A more efficient energy use would means producing the same or even a larger amount of fish with less energy.

Compared to terrestrial farm animal production, aquaculture releases only small quantities of CO2 into the atmosphere and proportionately only contributes minimally to the global greenhouse effect. This was proven in the study ”Blue Frontiers : Managing the environmental costs of aquaculture" that the World Fish Center carried out on the basis of life cycle analyses in aquaculture. According to this study most of the energy needs are not accounted for by aquaculture itself, but by the peripheral area of feed production. In some species feed production can account for up to 90% of total energy consumption. Nevertheless, like agriculture, aquaculture is under strong social pressure to improve its sustainability and reduce its impact on the environment. One way to achieve this objective would be the stronger integration and use of renewable energy, particularly bio-energy. The multi-year integrated EU research project BIFFiO, in which scientists from Norway, the UK and Germany as well as small and medium sized enterprises from the aquaculture, agriculture and bio-energy sectors are involved, is to examine how waste from fish farms and animal farms can be used intelligently either for obtaining energy, or as fertilizer. When the project comes to end in October 2016, it will make an important contribution to the EU’s objective to meet 20% of the Community’s energy needs with renewable sources by 2020.

Elsewhere in the world, too, people are looking to make use of renewable energy. Already in July 2008, the U.S. State of Hawaii adopted a law (HB 2261) which includes a loan programme for aquaculture operators and farmers working in projects with renewable energy from water and wind power to photovoltaics or the production of methane, bio- diesel and ethanol. Loans can be provided for a maximum of 85% of project costs over a period of up to forty years.

Simple shade netting over the ponds of this natural system, in which cold-loving trout are produced, keeps the water cool even in summer.


Closure of material and energy cycles

Closed circuit systems which are also called recirculating aquaculture systems (RAS) have particularly large potential for energy savings and thus also for efficiency improvements. In such systems, the circulating water is kept constantly in motion using pumps, which require considerable amounts of energy. The water must be continuously cleaned with mechanical and biological filters, disinfected with ozone or UV light, "degassed" i.e. CO2 removed and re- oxygenated. When RAS are operated in regions with temperate climates they also often have to be heated as well, particularly in winter. Because these processes require energy, the investors today mostly try to combine their RAS with plants for producing renewable energy. Biogas plants are frequently chosen because they provide not only electricity, but also considerable amounts of waste heat. Some biogas plants can even utilize the sludge produced during fish production, so that at least partially closed material and energy cycles between RAS and biogas generation arise. The heated cooling water of conventional thermal power plants also offers good possibilities for a more energy efficient aquaculture because they enable optimal growth conditions year round for the fish in the farm’s tanks.

Combining aquaculture with other methods of food production also seems promising with regard to the efficient use of energy. Aquaculture facilities do not only produce fish but also slaughter waste, nutrient-rich water, sludge and CO2 from the fishes’ respiration. It is possible to make good use of such components within integrated systems. The simplest case would be, for example, to spray the nutrient-rich water ("liquid fertilizer") which flows out of the fish tank onto agricultural land or to use it for irrigation of vegetable crops. The operators of aquaponic systems even try to link fish and plant production directly. Such systems, however, are highly complex and so very difficult to control if both farming areas are to be equally productive. Even the CO2-enriched warm air from warm-water RAS could be put to good use by passing it, for example, into a greenhouse, where it could then be used by plants during photosynthesis. Many plant operators also put heat exchangers into isolated RAS to keep the energy within the system for as long as possible and not to lose it to the outside.

This cascade of high temperature heat pumps next to an RAS for zander fry heats 6 m³ water to approximately 80°C, which is stored overnight in two buffer tanks.

Despite all efforts, however, it cannot be ignored that the demand for electric power and other energy forms is increasing in aquaculture, which of course leads to an increase in production costs and in turn to a poorer CO2 balance on the farms. According to calculations by the Danish Aquaculture Association the rearing of just one kilogram of rainbow trout currently devours nearly 1.7 kWh. The Association sees this high value as a challenge for aquaculture and has set a goal to reduce the energy requirements of trout production to 1 kWh per kg. With an annual production of 35,000 tonnes that would mean annual financial savings of 17.1 million DDK and a CO2 reduction of 13,400 t. Attempts are now being made in a research project to find methods for aeration, degassing and water movement that are more energy efficient than the currently preferred method of air-lift pumps ("mammoth pumps").


Better ecological balance through recycling of process waste

It is also possible to improve the efficiency of fish production in aquaculture by finding ways to use the accumulated fish waste to economic benefit. One possibility is as fish meal and fish silage, another is further processing it to biodiesel, which can be used either in its pure form or as an additive to conventional fuels. This has long been more than a mere idea: diesel from fish waste is already being made and used commercially in several regions of the world, for example in Canada, the USA, Vietnam and Honduras. The energy content of the fish biodiesel is 6% lower than in mineral fuel. One litre of biodiesel can be produced from one kilogram of fish waste and biodiesel is on average about one US dollar cheaper per gallon than conventional petroleum diesel. The production of fish biodiesel, which is usually done by transesterification from fish fat, is not too complicated. During the process, in addition to biodiesel, glycerol is also produced as a by-product and this can be further processed to soap. The remaining fish waste can even be processed into fishmeal, although the value of this meal is not high because a lot of high-energy components have already been extracted.

Anyone who is not wanting to look at the energy efficiency of individual components but rather to examine the efficiency and sustainability of the whole process chain in aquaculture often makes use of life cycle assessments (LCA ) . With their help, it is possible to assess accurately the impact on the environment at every stage of the product life "from the egg to the edible product". The energy balance does not only allow statements to be made about how environmentally friendly the system is but also enables one to locate crucial weaknesses within the system. And it is precisely these hotspots which through changes and modifications or slight adjustments can bring about the greatest promise of success. Water consumption and land usage are just as much part of this as the main energy consumers feed, transport, infrastructure of the facilities and the processing of the produced fish.

In the same proportion as aquaculture’s energy dependence increases, the number of ways to improve the eco-balance and energy efficiency of production systems also increases. The aim is generally to generate as much fish as possible with as little energy as possible. Often it helps already to stop using old, inefficient energy-intensive techniques and replace them with new, more efficient equipment. This can be especially worthwhile where aerators are concerned, with new systems usually requiring less maintenance, being more powerful, more reliable and more energy saving than old units that were purchased many years ago . There is also enormous potential for savings in the field of lighting where traditional light sources can be replaced by light-emitting diodes (LEDs). These modern light sources are known for their long service life and extremely low power consumption while maintaining the same light output. For special purposes in aquaculture there are now even submersible LED lights that can be used underwater.

In aquaculture, as in other industrial sectors, sharing experiences among professional colleagues is the easiest and cheapest investment. And one should take advantage of every opportunity to do this, because increasing energy efficiency does not only benefit individual companies but every single one of us. We all share the consequences of using fossil fuels and increased CO2 emissions, climate change and environmental damage. For this reason alone, when using or choosing a particular technology one should always consider its necessity and its energy requirements very critically. Sometimes setting up a simple shade net over a pond will achieve the same effects as elaborate, energy-intensive filtration systems or cooling systems.