Crotalaria is a genus of flowering plants in the legume familyFabaceae (subfamily Faboideae) commonly known as rattlepods. The genus includes about 500 species of herbaceous plants and shrubs. Africa is the continent with the majority of Crotalaria species (approximately 400 species), which are mainly found in damp grassland, especially in floodplains, depressions and along edges of swamps and rivers, but also in deciduous bush land, roadsides and fields. Some species of Crotalaria are grown as ornamentals. The common name rattlepod or rattlebox is derived from the fact that the seeds become loose in the pod as they mature, and rattle when the pod is shaken. The name derives from the Ancient Greekκρόταλον, meaning "castanet", and is the same root as the name for the rattlesnakes (Crotalus).
Crotalaria species are used as food plants by the larvae of some Lepidoptera species including Endoclita sericeus, Etiella zinckenella and Utetheisa ornatrix. The toxic alkaloids produced by some members of this genus are known to be incorporated by Utetheisialarvae and used to secure their defense from predators.
Current and potential uses
Food and health
Crotalaria is a genus containing unique foods because of their rich nutrient content including starch, protein dietary fiber, oligosaccharides, phyto-chemicals and minerals. Their nutritional contents contribute to many health benefits to human beings. To ensure the survival and optimal cultivation of these plants, they are often selected for resistance to diseases, yields and nutritional quality.
There are several species of Crotalaria that are popularly consumed by human populations throughout the world. The wild and domesticated landraces of Crotalaria tetragona, colloquially known as “Tum-thang,” are grown and eaten by the tribal communities of the Mizoram state of North-east India. The flowers and pods of Crotalaria tetragona are eaten as vegetables, the flowers and buds are used as garnishing, and the seeds are eaten as pulse. In the Lake Victoria basin of East Africa, the wild and cultivated lines of Crotalaria brevidens, also known as “mitoo,” are harvested and eaten as a leafy vegetable in many popular cuisines. Its wide consumption is mainly due to its nutritional value as a rich source of β-carotene, which is a precursor of vitamin A.Crotalarialongirostrata, also known as "longbreak rattlebox" or “chipilín,” is found in Guatemala, El Salvador, and Oaxaca and is a popular addition to many local dishes. The edible portions of the plant are the leaves and shoots, which are cooked and served as a leafy green vegetable or desiccated and utilized as an herb. The comestible foliage contains high amounts of calcium, iron, thiamine, riboflavin, niacin, and ascorbic acid, while the seeds and roots are considerably toxic.Crotalaria longirostrata is considered a “noxious weed” in the United States since it is avoided as a source of consumption by many animals and since its seeds shatter and spread over a wide range.
Australian species of the Crotalaria genus have the capacity to be cultivated into potential grain crops that are adapted to dry environments, nutrient poor soils, and low-input agricultural systems. Australian Crotalaria species also show many suitable traits of harvestibility, including an upright growth habit, a low tendency to dehisce and shatter, the bearing of its fruits and flowers at the ends of branches, and large to moderate seeds.
Several species of Crotalaria are presently being cultivated for suitable traits that are not directly related to human consumption. Crotalaria juncea, also known as sunn hemp, is currently grown throughout the tropics and subtropics as a source of green manure, lightened fiber, and fodder. Crotalaria juncea is also being considered as a potential source of cellulosic ethanol for biofuel.
Sensitivity to water supply levels
To analyze the differences in crop yield of Crotalaria in different regions, samples of Crotalaria brevidens and Crotalaria ochroleuca were taken from each setting and analyzed for crop yield under different water supply conditions. The results of the study show that Crotalaria plant height was extremely sensitive to water supply, and significantly led to a decrease in the shoot heights and leaf sizes in these two species, which ultimately meant lower crop yield. As a result, it can be said that Crotalaria was proven to grow better in regions with more adequate water supplies (ex.- they are predicted to grow better in swamplands than in deciduous bush land).
The primary source of toxicity for many species of Crotalaria is the presence of pyrrolizidine alkaloids, which are poisonous to birds and large mammals. The two kinds of pyrrolizidine alkaloids that are found in Crotalaria plants are monocrotaline and spectabiline. They can be found in the leguminous seeds, foliage, stems, or roots of Crotalaria plants. Species with higher concentrations of pyrrolizidine alkaloids yield greater toxic effects compared to those with lower concentrations. In addition, species that contain only monocrotaline are more poisonous than species that contain only spectabiline at equal concentrations within the seeds, leaves, stems, or roots. There are no confirmed species to this date that contain both spectabiline and monocrotaline; a Crotalaria plant can only have either one or the other. Thus, plants that are less toxic and therefore more appropriate for human consumption carry only low concentrations of spectabiline. According to one study, species that display the greatest toxicity include Crotalaria spectabilis Roth,C. retusa L.,C. alata Leveille, and C. quinquefolia L. Species that are least toxic include Crotalaria australis Bak. Ex Verdoorn,C. maxillaris Klotzsch,C. spbaerocarpa,C. juncea L, and C. brevidens Benth., among many others.
Alkaloidmonocrotaline, a pyrrolizidine alkaloid, the main toxic principle of Crotalaria spectabilis, is used to induce experimental pulmonary hypertension in laboratory animals. Larvae of the Ornate moth feed on the plant and re-purpose the poisonous compound as a defense, excreting it when they are threatened by potential predation.
- Crotalaria pallida pollen may cause an allergic reaction in humans, including swelling of the eyes and face, a rash on the neck and shoulders, and itching. Symptoms may take up to a week to clear.
•Crotalaria longirostrata and Crotalaria pumila are tropical legumes domesticated since pre-Columbian times. They cover a wide range of uses such as: food and refreshing drink for humans, cover crop or green manure, improvement of fallows, paper elaboration, medicinal plant and honey production (melliferous species). Due to their high protein contents, Crotalaria longirostrata and Crotalaria pumila were further studied to observe potential improvements in the diets of those who consume it. In an experiment, this species of plant was collected in 5 communities of the state of Veracruz. In comparing the relative protein content of each plant, it was found that the cultivated plants with the largest leaves were the most protein-rich, while the plants with the smallest leaves had the least amount of protein. This has important agricultural implications because these plants can be selected specifically for larger leaves in order to yield maximal protein content. Both of these plants are also considered to be valuable genetic resources, and studies suggest that they co-evolved within certain geographic regions. To affirm this, a cytological study between the two species was conducted, and it was found that their chromosomes are very similar in shape and size. The highly symmetrical nature of these two karyotypes suggests a close phylogenetic relationship between the two.
•Crotalaria brevidens and Crotalaria ochroleuca are leafy vegetable species found to be cultivated in western Kenya. Several tribes known to reside in the country, including the Luhyas, Luos and Kisiis tribes, have been reported to have an extraordinarily high number of these species in comparison to other plant species in their communities. Over time, the Luhyas, Luos and Kisiis have selected both of these species of plants to have high yields. Alongside, this, Crotalaria brevidens and Crotalaria ochroleuca can be used as cover crops. Furthermore, they have also been selected by these Kenyan tribes to have high tolerance to disease and poor soil. Both of these serve as indications that the food production systems of each tribe evolved with the emphasis of vegetable cooking.
List of species
Crotalaria comprises the following species:
STORM’s latest achievements, as well as other useful resources will be shared in this section.
STORM articles and papers
“Operational Demand Forecasting in District Heating Systems Using Ensebmles of Online Machine Learning Algorithms,” Energy Procedia, Volume 116, June 2017: p.208 – 216. (scientific paper)
“Status of the Horizon 2020 STORM Project,” Energy Procedia, Volume 116, June 2017: p. 170-179. (scientific paper)
“Operational demand forecasting in district heating systems using ensembles of online machine learning algorithms” Award-winner at the 15th International Symposium on District Heating and Cooling in Seoul, South Korea, September 2016. (scientific paper)
“Release the Energy” – NODA’s Patrick Isacson discusses the relationship between digitalisation and district heating and cooling systems, October 2016 (article in Horizon 2020 Projects: Portal magazine)
“Storm Project lands award at DHC symposium” – DHCNews.co.uk, November 2016
“STORM Generic Controller Spans the Generations“, December 2016 (Interview with STORM coordinator Johan Desmedt in EU Research magazine)
“STORM project wins award for research excellence at DHC2016” – BuildUp, December 2016
“The Future of District Heating and Cooling Networks – Intelligent Controllers Based on Machine Learning Algorithms,” HOT COOL magazine N. 1, 2017
“Digitalisation of DHC – Optimising a Demand Driven System,” EuroHeat&Power Magazine, English Edition, Vol 14 IV/2017
Project communication materials
Project public deliverables
- D1.1 Report on classification of DHC networks and control strategies
- D2.1 Simulation platform configuration
- D3.2 Controller framework compatibility report
- D3.3 STORM controller evaluation report
- D5.1 Final report on the performance of the STORM controller
- D6.2 Economic assessment of business models for DHC networks operators
- D6.4 Report on STORM international and local dissemination activities
- D6.5 Report on education modules for universities of applied science in Europe
- D6.6 Report on training courses for professionals (proceedings of 5 training seminars)
What is DH?
District heating (DH) is a system for distributing heat for both residential and commercial heating requirements (space heating, hot water). The fundamental idea is to either recycle surplus heat from other processes which would be wasted otherwise or to have centralized/decentralised heat generation units which can meet a certain heat demand. DH systems produce medium – steam, hot water or chilled water which are then distributed to end-users. As a result, end-users do not need heat generation units such as boilers or furnaces. Numerous benefits can be achieved by connecting both residential and commercial sectors to DH network such as improved energy efficiency, fuel flexibility, enhanced environmental protection, decreased costs and reliability.
Further information: District Energy Explained, Euroheat & Power
Delivering the Energy Transition: What Role for District Energy, ECOFYS study commissioned by Euroheat & Power, 2016
District Heating, Wikipedia
Different generations of DH systems
Over the last decades, DH systems have been developed by introducing new technologies and by increasing energy efficiency. These changes have had a wide range of consequences which resulted in four different generations of DH systems in terms of technology, heat distribution, medium, circulation systems etc. Starting from the 1st generation where the heat carrier was steam, the last, 4th generation of DH provides low temperature DH systems with water at 30-60°C, depending on requirements. Apart from the heat carrier, circulation systems have changed from steam pressure and central pumps only to more sophisticated central and decentralised pumps. Another important development can be found in substations and radiators (heat exchangers) where floor heating and low-temperature radiators will be used.
Further information: Project description Strategic Research Centre for 4th Generation District Heating Technologies and Systems (4DH), 2012
4th Generation District Heating (4GDH): Integrating smart thermal grids into future sustainable energy systems, Henrik Lund, Sven Werner, Robin Wiltshire, Svend Svendsen, Jan Eric Thorsen, Frede Hvelplund, Brian Vad Mathiesen, 2014
Technologies used in DH systems
There are various heat sources which can be used for generating heat in DH systems including combined heat and power (CHP) plants, heating plants which can use biomass or fossil fuels, geothermal heat, solar heat, heat pumps and heat-only boilers. It should be mentioned that these sources can be combined for more efficient DH systems such as combining CHP units with heat-only boilers or heat pumps. Another component of DH systems is, mainly thermal, energy storage, which is used for storing excess energy. For the STORM project, geothermal systems and heat-only boilers are deployed. When it comes to geothermal DH systems, heat is extracted from the ground by creating drilling wells which is then used for meeding space heating demand or hot water preparation. In a system like this, no fuel is required since extracted heat is applied for medium preparation. On the other hand, heat-only boilers need fuel for generating heat. However, with the development of this technology, high energy efficiency can be achieved in a sustainable way by using bioenergy.
Further information: Developing Geothermal District Heating in Europe, GeoDH project, 2014
Control, automation and monitoring in DH systems
An important segment of DH systems operation are control, automation and montoring withing the system for the most efficient working load. DH controlers and system can provide trouble-free and energy-efficient network operation. Control valves, actuators and sensors in combination with proper communication within the system can ensull that all requirements are met in the most efficient, cost-effective way as fast as possible. Moreover, with the development of technology, it is possible nowadays, with the sophisticated systems and forecasting, to predict heat demand to be met by DH system. By doing this, peaks and requirements can be predicted and modelled accordingly which results with great flexiblity, automation and control.
Further information:District Heating and Cooling – A Vision towards 2020 – 2030 – 2050, DHC+ Technology Platform, 2012
Smart Heat Grid – How Does it Work?, NODA Intelligent Systems
Smart District Heating and Cooling, Energy Research Knowledge Centre – SETIS, European Commission, 2014