Exploring the potential of converting washed-up seagrass (Posidonia banquettes) into biofuel

Despite the fact that the most sustainable way to treat Posidonia banquettes is to actually leave them untouched, it is understood that beach managers are forced to remove them under specific circumstances. Even so, the second-best practice would be to remove them temporarily from selected beaches at the beginning of the summer period and return them to the same beaches before the winter period. In addition, the use of heavy machinery should be avoided and more sustainable ways to remove them should be used.

Nevertheless, if returning them before the winter period is not an option, their use as renewable energy sources should be explored to be able to at least take advantage of their potential instead of just throwing them away in dumpsites. Wanting to contribute to the effort to tackle the climate crisis and promote the use of renewable energy sources, the Municipality of Larnaka is looking for innovative proposals to turn Larnaka Posidonia banquettes from a problem into an opportunity. The goal is the sustainable use of seagrass to bring mutual benefits to the citizens and the environment.

Posidonia oceanica is a marine plant, endemic to the Mediterranean, which forms large underwater meadows. Posidonia meadows (Priority habitat: ‘1120’, Habitat directive: 92/43/EEC), provide food and refuge to many marine organisms and are very important for the sustainability of local marine biodiversity. Posidonia drops its leaves, mainly in late summer and early autumn, and the washed ashore leaves; erroneously called “phytzia” (algae) in Cyprus, accumulate on beaches sometimes forming large banquettes.

Posidonia leaves, mixed with sand and rhizomes, can create formations along the beach that are called banquettes. Posidonia banquettes, act as natural wave barriers, thus reducing the coastal erosion, while at the same time support and promote the formation of new habitats, such as sand dune systems. Furthermore, their presence in an ecosystem increases the budget of nutrient resources. 

There is a general negative perception about the origin and aesthetical quality of such habitats, commonly associated with waste, which is a misconception. Unfortunately, the negative perception, forces local managers to remove Posidonia banquettes from the beaches, often using heavy machinery. Their removal, a costly practice, limits all of the advantages mentioned above, often causing further damage to highly valued habitats such as sand dune systems. 

Larnaka, as a coastal city, relies heavily on tourism due to the ideal climate and excellent quality of organized and non-organized beaches. However, in order for the beaches to meet the excellent conditions of the (erroneously) acceptable perceived standards, painstaking and costly efforts must be made to remove the large quantities of dead leaves of seagrass (Posidonia oceanica) that wash ashore every year.

The gulf of Larnaka has patchy areas of Posidonia oceanica meadows, and dead leaves of the seagrass naturally wash ashore on sandy beaches every year from early November to early April. Every year, the Municipal Authorities with their crews remove the seagrass from the beaches, which in the end are thrown away. On average, more than 10 tons of seaweed are removed each year at a total cost to the Municipality of an average of € 120,000.

 Entity proposing the challenge:

Municipality of Larnaka