Post-harvest
Once the harvested biomass is brought to shore, a process has to be applied quickly due to the high water content of most species.This step is not always carried out by the farmers and the level of sophistication varies between seaweed species and its designated application.The processing conversion factor is an important measure to take into account when evaluating crop and the processing yield.
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Eucheumatoids
Once the harvested seaweed is brought to shore, it often has to be cleaned from filamentous algae, oyster spat or other epibiotic organisms that may attach to the seaweed in certain seasons. Farmers have developed different methods to get rid of those.
At this point, the farmer also selects the portion of the harvest that is best used for seedlings for the next cycle. The key to a successful seaweed harvest is producing good quality seedlings for the next cycle. Normally, younger plants that are robust and free of ice-ice syndrome and endophytes are selected as seedlings for the next cropping season.
Up to a quarter of the harvested biomass may be kept by the farmer as seed material for the new cycle.
On Nunukan Island in Indonesia, farmers use a high pressure water hose to spray off most of the unwanted material, in this case mainly oyster spat.
Removing filamentous algae is highly labour intensive since it needs to be removed by hand.
On Nunukan Island, some farmers strip the seaweed from the cultivation lines using. Although this process is faster than untying every plant individually, the seaweed is broken into smaller pieces, which is usually a lower quality parameter.
The speed of tying not only depends on the tying method and the skill of the individual, but also the social circumstances.
Drying the seaweed
In the Eucheumatoid industry, the majority of biomass is dried by the farmers. The wet-to-dry ratio may be as low as 6:1 when it leaves the farm, but by the time the raw dried seaweed is dried to the export-quality level of 35% moisture content, the wet-to-dry ratio is about 8.5:1.
Numbers may vary between cultivars, farm locations and seasons, but are known as general industry standards.
Sun-dried seaweed not only significantly shrinks in size and weight, but also in the natural colouring.
Under good weather conditions, meaning sunshine, crops usually take 2 to 4 days to dry. During the rainy months of the wet season, the process can take up to 7 days.
Drying is often a major bottleneck as it requires ample space and – especially during the rainy season – time. Different methods of drying will be applied given the space availability. Generally speaking, there are several ways to lay the seaweed or hang the seaweed.
Laying to dry
When seaweed is laid out, it is either placed directly on the ground, on a fish net or on a rack / bed type platform. For seaweed farming communities at sea, the plants are dried on the available space on their stilt houses or on dedicated drying platforms at sea.
Seaweed laying on the ground in Janaeponto, South Sulawesi, Indonesia.
Close to Semporna, in Malaysia, the drying platforms are usually an extension of the houses on stilts.
The farm site is sometimes only a few meters away from the drying platforms.
On Rote Island in Indonesia, there are drying beds in public areas, such as the beach. Theft is not a problem here.
The harvested seaweed is spread out and dried under the sun for a couple of days.
A tarp is typically used to cover the seaweed every end of the day or on rainy days.
Hanging to dry
Farmers told us that hanging the harvested seaweed lines above the ground was the best drying method. Doing this ensures that the seaweed dries quickly and prevents it from getting contaminated from lying on the ground.
The seaweed can easily be dried by hanging it up on the same lines it had been attached to.
Drying racks surrounding stilts houses in Semporna region, Malaysia.
In Bantaeng, South Sulawesi, the community has build drying racks that all seaweed farmers can freely use.
In Sabah, the Malaysian government trialed solar-powered sun drying ‘ovens’. However, the farmers prefer the coventional sun-drying method.
Treatment of culture lines
Cleaning the culture line after each cycle not only keeps the material intact, it also reduces contamination from disease, epiphytes or similar impurities across farm cycles. When PE ropes remain in ocean environments, they are prone to biofouling. There are several different ways the farmer cleans the ropes:
In Bantaeng Regency, South Sulawesi in Indonesia, farmers smash used lines on wood in order to remove any unwanted residues on the line.
On Nunukan Island, in Indonesia, it is common practice to rub the lines to get rid of any unwanted residues. Farmers struggle in particular with small oyster spat in certain seasons.
On Rote Island, in East Indonesia, the cleaning is done by simply rubbing parts of the rope on to each other. A fairly time intensive task.
Close up picture of the lines that are treated post-harvest.
Cleaning the ropes can also be done in between cycles at sea.
Laying the lines under direct sun light for a day or two will also help to limit biofouling. Takalar, South Sulawesi.
Explore another seaweed species:
Eucheumatoids | Saccharina | Undaria | Pyropia | Gracilaria
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