Cultivation of algae - marine recources.pdf

Algae Cultivation MAT703F Marine Resources ARNAR ÞÓR SKÚLASON FACULTY OF FOOD SCIENCE AND NUTRITION What is algae? Algae are aquatic, photosynthetic organisms They are not all closely related, even belonging to three kingdoms...

Algae Cultivation MAT703F Marine Resources ARNAR ÞÓR SKÚLASON FACULTY OF FOOD SCIENCE AND NUTRITION What is algae? Algae are aquatic, photosynthetic organisms They are not all closely related, even belonging to three kingdoms Most microalgae belong to the kingdom Protista but cyanobacteria belong to the kingdom Bacteria and seaweeds belong to Plantae They do not look similar and can range in size from around 5m to 50m Generally algae are split into micro- and macroalgae Although sometimes controversial, cyanobacteria are generally included with microalgae which is fitting regarding cultivation and use in food Macroalgae is more commonly known as seaweed Seaweeds are split into three phylum Image: Example of a phylogenetic tree, the Phaeophyta (brown algae), Rhodophyta (red algae), and Chlorophyta (green algae) coloured boxes represent algae. Species belonging to Chlororophyta are more closely related to land plants than algae from the phylum Phaeophyta Seaweed lifecycle Seaweeds have a complex lifecycle and can grow both in haploid (n) and diploid (2n) forms Haploid forms are called gametophytes and come in male and female types (or +/-) Male and female forms can look identical or vastly different, depending on the species Diploid forms are called sporophytes Sporophytes and gametophytes can look identical or vastly different based on species Image: Life cycle of Ulva spp. Image: Life cycle of kelp (e.g., Saccharina latissima). Why algae? Sustainable Require little to no land or freshwater No need for pesticides or weed killer Binds CO2, reducing acidification of the ocean Nutritional They can contain complete proteins Can be a source of omega-3 fatty acids (source of omega-3 in fish for example) They are often rich in fiber, vitamins and minerals Bioactivity Various bioactive compounds have been found in algae Functional compounds Popular gelling compounds from seaweeds include, agar, carrageenan and alginate Popular coloring from algae includes phycocyanin (blue) and phycoerythrin (red) Various compounds with pharmaceutical and therapeutic applications including antibiotics, hormones, enzymes, and neurotoxic compounds can be produced by algae Why cultivate algae? Wild sources of algae can be depleted if over-harvested To supply increasing demand, cultivation is therefore needed Various methods for algal cultivation are used all over the world but the optimal method for cultivation depends on location, species and use/market The environmental footprint of algae is less than for other foods, including land grown vegetables Exact footprint depends on species and cultivation method Image: Relative resource use per ton of edible protein. From WWF presentation at Arctic Algae Conference. Examples of products containing algae Factors that affect algal growth Algae require water, light, CO2, nitrogen, phosporous and other nutritional elements to grow The amount of available nutrients impacts algal growth, as well as the ratios between certain elements Different species have different preferences but generally the requirements are similar Algal growth depletes nutrients in the medium as it grows, affecting seasonality in natural conditions. Require regular nutritional additions in cultivation tanks. Light intensity, and spectrum affect growth as well as the light-to-dark period Both too high and too low intensity can lead to destruction in many species Optimal spectrum is different between species but also between life stages Light conditions don’t only impact growth but also the composition of the algae, including concentrations of pigments and bioactive compounds Temperature, pH, and salinity affect growth Differs between species but also within a species, based on where samples are collected Optimum is usually not far from conditions at natural growth sites Movement Needed to replenish nutrients and provide even access to light but too much movement can cause stress or even destruction Cultivation methods – Microalgae Wild harvest Microalgae can be harvested wild History of spirulina has for example been traced back to the Aztecs harvesting it from the surface of Lake Texcoco in the 16th century Spirulina is still wild harvested in Chad, where the knowledge has been passed down from mother to daughter for centuries (if you want to know more: https://www.fao.org/4/y5118e/y5118e09c.pdf) Note that Spirulina is quite large for a microorganism (1-10 m in diameter but up to 500m in length) making it easier to harvest from wild sources. It also prefers alkaline conditions which limits the growth of many other organisms, reducing the risk of contamination Spirulina harvest in Chad. Photos by Marzio Marzot from the FAO Report: The Future is an Ancient Lake, 2004. Outdoor cultivation Algae can be grown outdoors in ponds Similar to wild harvest But in man-made ponds (e.g. circular or raceway shaped) They are actively maintained, e.g. by stirring and adding nutrition Much of the world’s spirulina harvest is cultivated in outdoor ponds Chlorella can also be grown outdoors but it is more difficult and the market is smaller so it is not as common Haematococcus pluvialus is also cultivated in outdoor ponds, but that is done in combination with indoor bioreactors Outdoor ponds are cheap and require minimal housing, equipment, and electricity Natural sunlight fuels the growth which is cheaper than artificial lights but in turn not as stable. Outdoor ponds are open to the elements leading to variation in conditions due to weather and can lead to excessive loss of fresh water due to evaporation Outdoor ponds are also at a high risk for contamination Images of raceway ponds used for growing Spirulina and Haematococcus pluvialus at Cyanotech. Outdoor cultivation in tanks Cultivation of microalgae is sometimes conducted outdoors in tanks Some are open and function like ponds Others are closed, clear tanks (or bags) Tanks are easier to clean than ponds Closed tanks reduce the risk of contamination Closed tanks reduce the effects of weather by protecting water levels from evaporation and rain Having the tanks outside provides sunlight for growth, reducing the need for expensive lights and electricity Sometimes these tanks are even kept in greenhouses for some additional control over conditions while maintaining access to natural sunlight  Bioreactors Highest level of control possible but at the highest cost Can be closely monitored and maintained in every aspect Use artificial light which can be controlled in regard to intensity, day length and spectrum (color) Nutrients can be monitored and adjusted regularly (easier in a closed system) Air bubbling is often used to move the culture around and to add CO2 to the culture Continuous and consistent production possible all year around With such a high level of control the quality of the cultures can be maintained at a much higher standard E.g. Vaxa Technologies grows Spirulina with CPC (blue pigment) content of aprox. 18% compared to the 2-5% of CPC in competitors (outdoor cultivated) Spirulina. (The numbers are based on inhouse methods.) Algalíf also has an unusually high concentration of astaxanthin in their Haematococcus culture compared to the industry standard, due to the high level of control in their systems. Photobioreactors at Vaxa (top) and Algalíf (bottom) Cultivation methods – Seaweed (Macroalgae) Wild harvest Very common all around the world to have a history of collecting and eating at least certain species of seaweed In Scandinavia and around the British isles Palmaraia palmata (dulce or söl) is the most well known example of this Can be done from the shore at low tide requiring next to no equipment and minimal training Wild harvest using boats is also possible and better for species growing at greater depths Contamination can be an issue, especially in the form of heavy metals Microbial contamination is however a low risk Grazing can be a problem Many animals, e.g. fish and molluscs, enjoy eating seaweed which impacts their growth and health as well as lessening the quality Wildlife must be monitored so that resources are not depleted when harvesting regularly and in large amounts There is a limit for how much can be produced this way Algal bloom harvest When excessive amounts of nutrients from farming make their way to the ocean, they can lead to surges in algal growth called algal blooms The species likely to grow are e.g. cyanobacteria (can be toxic) and seaweeds of the genus Ulva Algal blooms can have a devastating effect on their environment by depleting other organisms of light and oxygen Algal blooms can also affect tourism, especially when seaweeds flood beaches Solutions to mitigate the problem of certain algal blooms include harvesting the algae using specialized boats Nearshore cultivation Seaweed cultivation in countries close to the equator is generally done close to shore in nets or on lines and using simple anchors or rafts This type of cultivation requires no boats or complex equipment and utilizes free, natural sources of nutrients and light Weather affects the yield but closeness to the shore provides protection Vast amounts of agar comes from seaweed cultivated in this way Much of it is cultivated close to the equator, sundried, and shipped to Europe for processing Offshore Seaweed cultivation on ropes a few kilometers from shore (most often 1-2 km) The conditions are quite extreme restricting which types of seaweed can be cultivated Large and robust kelp species most common Possibilities for large scale farms Boats needed to attend the farms At least for deploying and harvesting Seasonal business, 1-2 harvests per year Fishing boats can be used for seaweed farming during the off-season, inspiring creative solutions E.g. Atlantic Sea Farms in Main, USA https://youtu.be/dbTYbXN9qIc Image from Ocean Rainforest Onshore cultivation Seaweed can be cultivated in tanks on shore Tanks provide shelter from the waves and provide the possibility of adjusting nutrient composition in the seawater Having the tanks outside provides sunlight for growth, reducing the need for expensive lights and electricity Maintaining such a farm is more expensive than an offshore or nearshore farm and requires more land Used more commonly for research than commercial cultivation Image from Sea Grant In-house cultivation As with microalgae: Highest level of control possible but at the highest cost Can be closely monitored and maintained in every aspect Use artificial light which can be controlled in regard to intensity, day length, and spectrum (color) Nutrients can be monitored and adjusted regularly (easier in a closed system) Air bubbling is often used to move the culture around and to add CO2 to the culture Continuous and consistent production possible all year around Most types of seaweed are not feasible to cultivate in this manner as is More feasible when cultivating in this manner for extraction of specific high-price compounds or for some niche market Image by Arnar Þór Feasibility increases with lower cost of electricity Skúlason, taken at Hyndla Note that cultivation of gametophytes and seedlings is generally done in- ehf. Ulva fenestrata house and seeded on twine or rope which is deployed for further growing in lava-filtered cultivation in the ocean seawater. Cultivation in conjunction with other industry Seaweed can be used for cleaning wastewater from in-land aquaculture It can remove CO2 and nitrogen compounds from the wastewater and add oxygen Cleaning with seaweeds can reduce the risk of algal blooms from releasing the untreated waste into nature while producing seaweed which could be used for feed or other production Rearch is ongoing, species include Ulva spp. and Palmaria palmata Cultivation of seaweed off-shore is sometimes done in conjunction with other aquaculture, e.g. fish or shellfish cultivation. The seaweed provides shelter, re-oxygenates the water and removes CO2 and other waste which increases the yield of other cultivated species. Generally done using Kelp or other large brown seaweeds. It has also been proposed as part of offshore windmill farms, among other aquaculture Example – Seaweed as biofilter