How can seaweed heat my home?
DEPENDING on its colour, seaweed is classified as red ( Rhodophyceae), brown ( Phaeophyceae) and green ( Chlorophyceae). In Ireland, approximately 500 species of seaweeds have been documented within these three classes. Seaweed can be harvested from beaches, or cultivated in “seaweed farms”. Globally, production of seaweed was estimated at 19 million tonnes in 2010, with the Japanese kelp species, Saccharina
latissima/Laminaria japonica accounting for 99pc of that. China is the world’s biggest producer of seaweed, at over 11 million tonnes annually.
In Ireland, seaweed production is much smaller, around 45,000 tonnes annually and it is mainly used as fertiliser and as a source of alginate, a gum-like compound widely used in the food, pharmaceutical and cosmetic industries.
Seaweed is highly valued as a property in food because it is a valuable source of minerals and vitamins. Seaweed extracts can be found in a wide range of everyday products such as toothpaste, shaving foam, ice cream, cheese, body products, printing inks and even beer.
Seaweed also represents a huge and renewable resource for the generation of bio energy, the term for energy derived from organic materials such as plants, animals, wood or waste.
Despite all its benefits, when it accumulates in large quantities on our beaches, seaweed can represent a big nuisance. It can make access to beaches difficult, while the presence of seaweed in the water and the rotten-egg type smell that follows its decomposition (caused by the production of hydrogen sulphide (H2S) tends to drive people from beaches.
Many people regard decomposed seaweed as waste product, but for others it is a valuable resource. After harvesting, seaweed can be subjected to a biological process called anaerobic digestion, which means that it takes place in an oxygen-free environment. This process is very similar to human digestion, which happens in our stomach, thanks to the action of a series of different bacteria.
When seaweed undergoes anaerobic digestion, the bacteria produce a biogas that is about 60pc composed of methane (CH4). When the biogas is stripped of by-products of the anaerobic digestion process, other than methane, the result is another gas called biomethane. This is composed of about 97pc-98pc methane – and is similar to natural gas used to generate heat, electricity and also as transport fuel.
Among all seaweeds, one seaweed family particularly suitable for this kind of process is the Laminaria spp., which is very easy to see while walking along the beach, but maybe without being aware of what amazing resource it represents!