Question of the Week
What information can you give me on fish emulsion and turning fisheries waste into a useable fertilizer?
Answer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service. I am pleased to provide you with information on fish-based fertilizer manufacturing.
Fish wastes include fish renderings, fish offal, and spoiled fish. These organic wastes are quickly decomposed by microorganisms and are "highly putrescible," meaning they can quickly begin to putrefy and stink if they are not handled properly. Anaerobic conditions increase the potential for putrefaction. Degradation compounds that cause malodors include ammonia, hydrogen sulfide, dimethyl sulfide, mercaptans, indoles, skatoles, and phenols. In addition, highly putrescible organic wastes combined with anaerobic conditions are conducive to the development of pathogenic microorganisms such as salmonella and E. coli.
Thus, there are special considerations for handling fish wastes to avoid putrefaction, malodors, and pathogenic contamination.
Fisheries' wastes can be converted into organic fertilizers through composting and through manufacture of fish-based fertilizers such as fish emulsion, fish hydrosylate, and fish solubles. In fact, I suggest that you consider both composting and fish-based fertilizers as options for handling local fish wastes. The following will focus on fish-based fertilizers, but I am also listing a few resources on composting of fish wastes.
There is limited technical documentation on the preparation of fish emulsion, fish hydrosylates, and fish solubles. Nevertheless, I think you will find the following items and resource listings helpful as a starting point.
The following excerpt is from a fact sheet on organic fertilizers, published by The University of Alaska Fairbanks Cooperative Extension Service, and contains a description of marine by-products used as organic fertilizers.
In Alaska, marine by-products can be a major source of nutrients. The forms are diverse, varying from fish to the shelled forms such as oysters, crabs, lobsters, and sea urchins. By-products used in agriculture are classified as liquid, dry, and fresh or frozen scraps.
Fish emulsions and oil are the main liquid by-products. To make fish emulsion, or fish hydrolysate, fish scraps are ground, digested with the enzyme papain, de-oiled, the bones screened out, and then the emulsion can be pasteurized in a dehydrator or spray-dryer to form spray-dried fish hydrolysate.
Fish soluble nutrients (FSN) are included in the "family" of fish emulsions, but are made as a byproduct of fish meal. The basic FSN manufacturing process consists of cooking the fish, pressing out the liquid, extracting the oil, evaporating some of the liquid, and acidifying to stabilize the mass. Reduction of stress at time of transplanting is one beneficial plant response to the application of the family of fish emulsion products.
Bone meal and oil are often by-products of the emulsion process. Bones are dried and ground into a meal. Bone meal is also screened from coarsely ground, dried fish meal. Fish bone meal has shown promise as a fertilizer derived from a marine byproduct as it contains Na for responsive crops, and micronutrients not present in standard commercial NPK fertilizers. Salmon bone meal and white cod bone meal are currently being used in Alaskan agriculture in small quantities. Research using salmon bone meal on potatoes and lettuce has been conducted by the University of Alaska. Analysis of Alaska salmon bone meal and white cod bone meal is given in Table 3.
Source: Organic Fertilizers, The University of Alaska Fairbanks Cooperative Extension Service. http://extension.uaf.edu/ces/publicationsdb/catalog/anr/FGV-00349.pdf
A brief description of fish emulsion is provided in the following newsletter from the University of California's Sustainable Agriculture Research and Education Program (UC-SAREP), published in 1991.
Fish Emulsion. Fish emulsion is a secondary by-product of the fish meal industry. After removal of the solids (which become fish meal) and the oils (which go to oil products manufacturers), the remaining wastewater is usually evaporated to about 50 percent solids, making a thick, viscous end product that is bottled and sold as fish "emulsion." Since the oil has been removed, the term "emulsion" is not completely accurate. "Fish solubles" would be more appropriate, being the nonoil and nonsolid portions of the fish. As sold in gardening sections and in nurseries, this type of fish fertilizer contains about five percent nitrogen, one percent phosphate and one percent potash. The high cost and low nutrient value of fish emulsion, and handling and application problems make it impractical for use in most commercial-scale farming operations. Fish emulsion is practical as a foliar applied fertilizer for high-value crops, including ornamental greenhouse plants. It can rapidly "green up" foliage when used for foliar feeding.
Source: Marine By-Products as Fertilizers,Chaney, David, Components Newsletter, UC-SAREP Winter 1991 (Vol. 2, No. 1) www.sarep.ucdavis.edu/newsltr/components/v2n1/sa-10.htm
The following review, "Utilisation of Marine By-Products," published in the September-October 2003 issue of Electronic Journal of Environmental, Agricultural and Food Chemistry, contains descriptive text on fish protein hydrosylates using enzymes.
Hydrolysates can be defined as proteins that are chemically or enzymatically broken down to peptides of varying sizes. Chemical and biological methods are most widely used. Biological processes using added enzymes are employed more frequently and enzymatic hydrolysis is promising because it results in products of high functionality and nutritive value. Fish protein hydrolysates can be made in two ways. The first depends on the digestive enzymes of the fish itself while the second method is based on the hydrolysis of the raw material with added commercial enzymes (Mohr, 1978). The autolytic process depends on the action of digestive enzymes on the fish itself. Today much of the fish flavour, fish soup and fish paste products available on the market are prepared by enzymatic hydrolysis (Shoji, 1990). Protein hydrolysates can be used as emulsifying agent in a number of applications such as salads dressing, spreads, and emulsified meat and fish products like sausages or luncheon meat (Badal and Kiyoshi, 2001). Enzymatic hydrolysis has several advantages over other processing methods for recovering protein from under utilized fish biomass and fish by-products. However the hydrolysis process often leads to bitter taste in the product. The bitterness restricts the practical uses of these hydrolysates. The presence of bile in hydrolysis of whole fish and fish viscera may also cause bitterness in fish protein hydrolysates.
Source: Utilisation of Marine By-Products, T. Rustad, Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway. Electronic Journal of Environmental, Agricultural and Food Chemistry Vol. 2, No. 4. September-October. 2003.
The following e-mail from Neal Van Milligen with Kentucky Enrichment Inc. describes a low-tech method for preparation of fish emulsion that can be adapted to small community projects. The e-mail is in response to a query from ATTRA seeking information on fish emulsion. The method Neal describes is similar to fish fermentation methods used by the EM (Effective Microorganisms) and IMO (Indigenous Microorganisms) systems in Japan and Korea.
We have found rather simple methods to produce a fish emulsion for liquid fertilizer applications. It seems that many fish processing byproducts (heads, bones, skin, unused meat and offal) contain the necessary microorganisms to process themselves. This is not always true but often is. The byproducts should be ground up rather finely and placed in a sealed vessel (a jar or 55 gal drum, for example) and left in their own juices for about 7 days. After a couple of days the lactic acid and other materials produced by the microorganisms will reduce the pH to about 4.5 or even slightly lower. This will remain for about 3 days and then gradually return to about pH of 6. The process is complete if the pH remained low enough for long enough to render ineffective all of the bacteria, etc in the mixture.
Controlling the pH is a matter of controlling the growth and life of the bacillus and other microorganisms. The trick is when the naturally occurring microorganisms are insufficient to cause the lowering of the pH and additional bacteria must be added. It takes some skill to determine how much of what kind has to add.
The resultant mixture should be pathogen free and stable for up to 2 years if done properly and left in the seal container. When ready for use the liquid is filtered out and the solids used for one of many applications we can recommend. We have a proprietary blend of ingredients we use to eliminate the fishy odor that usually comes from this process making the fertilizer more acceptable to home owners and farmers.
The Vietnamese farm group we work with has also told us about the Vietnamese fish sauce produced in nearly every village near the coast in Vietnam. They make a human food using a very similar technique with whole fish. Each village has its own recipe and are very proud of their sauce.
If you have some one or group interested in the details of this emulsion process for their own project we would be happy to work with them. We can assist in the equipment needs, technical issues and marketing. In some cases we can provide financial assistance to support the project. We are already involved in this process in the USA and Nicaragua. We would be pleased to work in these or other areas of the world.
Regards, Neal Van Milligen, Kentucky Enrichment Inc.
The following excerpt on salmon hydosylate is taken from a brochure published by the Alaska Salmon Byproduct Utilization Project.
What is Salmon Hydrosylate?
- Protein which has been "enzymatically" digested
- A viscous liquid: like chocolate pudding with an odor of fresh fish and vinegar
- It is 58% water and 42% solids
- The solids are comprised of:
- 32% protein – soluble & insoluble
- 7% lipids/fats (Omega-3 salmon oils)
- 3% ash: calcium from bone
The Five Main Processing Steps
- Grinding—fresh salmon and waste
- Heating—scraped surface steam heat exchange
- Digestion—breakdown of solids with enzymes
- Evaporation—concentration by water removal
- Acidification—stabilization for spoilage control
Source: Salmon Hydrosylate, The Juneau Economic Development Council
The Food and Agriculture Organization of the United Nations, in Rome, Italy, publishes several technical papers, bulletins, and circulars that address fisheries’ wastes, wastewater, post-harvest handling, and by-product utilization. The following documents address the chemical and biological characteristics of fish fermentation, fisheries wastes, post-mortem stages of decomposition, and treatment methods.
Waste from Processing Aquatic Animals and Animal Products: Implications on Aquatic Animal Pathogen Transfer. FAO Fisheries Circular No. 956
Wastewater Treatment in the Fishery Industry. FAO Fisheries Technical Paper No. 355 www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/003/V9922E/V9922E00.HTM
Freshwater Fish Processing and Equipment in Small Plants. FAO Fisheries Circular No. 905 FIIU/C905
Quality and Quality Changes in Fresh Fish. FAO Fisheries Technical Paper No. 348 www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/V7180E/V7180E00.HTM
Fermented Fish in Africa. FAO Fisheries Technical Paper No. 329
Based on the aforementioned documents and resources, I hope you can gain a better sense of what is involved with processing of fish wastes into fish-based fertilizers.
Composting Fish Wastes
Composting of fish wastes is another approach you may wish to explore. Large-scale composting facilities commonly use tractor-based turning and mixing equipment to manage the process. Compost windrows are built by mixing fish wastes into large volumes of carbonaceous material (i.e., sawdust, straw, leaves) to achieve an appropriate C:N ratio. The moisture should be approximately 50%. A goal is thermophilic heating of the compost pile to achieve destruction of pathogenic organisms and bio-chemical decomposition of the parent raw organic matter. The end result is a humus-like product called compost.
This is a brief description of composting. There are many excellent publications and technical documents on making compost, the composting process, managing compost facilities, and compost quality. ATTRA has a publication titled Farm-Scale Composting Resource List, which you can request.
The following documents (below, in Resources) address the specialized nature of fish waste composting. Again, the highly putrescible nature of fish wastes requires specialized handling procedures to avoid putrefactive anaerobic conditions, malodors, and pathogenic concerns.
Here a few key practices and management strategies that can be especially important in composting of fish wastes and related offals.
- A hard-surface compost pad that prevents percolation and runoff of compost leachates.
- Readily-available carbonaceous feedstocks (e.g., sawdust, leaves, shredded wood wastes) to immediately incorporate and cover incoming fish wastes.
- Commercial-scale equipment and composting processes to promote thermophilic composting and PFRPs, "processes to further reduce pathogens."
- Microbial inoculants and topical deodorizers to control odors and flies, and to facilitate bioremediation (e.g., Effective Microorganisms from EMRO-USA; GONE from R.B. Morris Co., Inc.; BAT products from RKB Enterprises, Inc.)(2, 3).
- Compost fleece blankets, also known as compost covers, to shed rainfall and prevent leaching, and to promote a protected environment conducive to microbial processes (eg., TopTex, Compostex, and related brands available through Autrusa/Imants USA, Champlain Valley Compost Co., and Midwest Bio-Systems)(5).
- Laboratory tests to verify no detectable pathogen levels in compost, as well as compost quality. See the ATTRA resource list titled Alternative Soil Testing Laboratories (6) for details.
1) State Composting Regulations
McEntee Media Corporation: Recycling and Composting Online
3) RKB Enterprises, Inc.
625 Maury Ave.
Norfolk, VA 23517
4) Champlain Valley Compost Co.
245 Ten Stones Circle
Charlotte, VT 05445
5) Midwest Bio-Systems
28933 35 E. Street
Tampico, IL 61283
6) Alternative Soil Testing Laboratories
ATTRA – National Sustainable Agriculture Information Service
7) Information Note on the Composting of Organic Waste from Seafood Processing
Bord Iascaigh Mhara, Irish Sea Fisheries Board
Infonote Series No. 2
8) On-Farm Composting of Fishery By-Products
Prince Edward Island Department of Agriculture and Forestry
9) Implementing Fishery-Based Compost Applications: The Next Step
Florida Sea Grant Extension Program
10) Biodegradability and Nutrient Analysis During Crawfish Processing By-Products and Rice Hull Composting; Composting in the Southeast - Proceedings of the 1998 Conference
11) Composting Fish By-Products: A Feasibility Study, BC Agricultural Composting Handbook, British Columbia Ministry of Agriculture and Food
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