Eucheumatoids Post-harvest

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.

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.

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.

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.

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.

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.

Due to the different color varieties, post-harvest processes in the Caribbean islands include additional steps before drying. Farmers bleach gold seaweed by placing it directly under the sun, sometimes covered with plastic sheeting, to enhance appearance and secure quality. Seaweed is graded from A to C, from highest to lowest. In St. Vincent and the Grenadines and in Grenada, farmers rinse seaweed with freshwater to remove impurities and salt—purple and green varieties before drying, and gold after bleaching.

Moisture content is not formally measured; farmers judge dryness visually and by feel, aiming for a crispy, non-sticky texture that signals market readiness. Drying usually takes around three days under good conditions and is often carried out at farmers’ homes, which limits capacity and leaves crops vulnerable to sudden rainfall. Some farmers have built joined drying beds, but surveillance remains in several areas a major issue, as stealing of biomass that is drying is not unusual. 

Laying seaweed to dry remains the most widespread approach. Farmers use beaches, yards, or raised platforms where sunlight and airflow are abundant. This method allows easy handling of large volumes. For gold seaweed, bleaching under plastic sheeting is often integrated, enhancing uniformity and appearance before grading for market sale.

Hanging seaweed lines is practiced mainly for purple and green varieties to protect their natural pigments. The method minimizes ground contact and contamination, using shaded, ventilated areas or tree branches for suspension. This slower, indirect drying process helps preserve color vibrancy and texture, ensuring a premium product presentation.

On the islands, culture lines remain in the sea after harvest and are typically cleaned every two to three cycles. Sometimes they are brought to farmers’ homes and soaked in chlorinated water for cleaning. After about three years, lines are usually fully replaced.

Upon harvest, the initial focus in both Venezuela and Brazil is cleaning the biomass and selecting quality seedlings for the next cycle. Post-harvest processes vary significantly by region and product destination. In Brazil, most seaweed is sold and processed fresh for liquid extraction into biostimulants, with only the residuals being dried. Producers  in Santa Catarina and Rio de Janeiro prioritise harvesting within 45 days to prevent biofouling, as cleaning incrusted algae significantly raises costs. In contrast, Venezuela primarily sun-dries its seaweed for export. The exporting companies have implemented strict quality control, ensuring seaweed is clean and standardised before processing. 

Upon harvest, the initial focus in both Venezuela and Brazil is cleaning the biomass and selecting quality seedlings for the next cycle. Post-harvest processes vary significantly by region and product destination. In Brazil, most seaweed is sold and processed fresh for liquid extraction into biostimulants, with only the residuals being dried. Producers  in Santa Catarina and Rio de Janeiro prioritize harvesting within 45 days to prevent biofouling, as cleaning incrusted algae significantly raises costs. In contrast, Venezuela primarily sun-dries its seaweed for export. The exporting companies have implemented strict quality control, ensuring seaweed is clean and standardized before processing. 

Bio-stimulants are the main market for Brazil's seaweed industry, leveraging a liquid extraction process that is both rapid and efficient. This operation is highly time-sensitive and relies on fresh, clean algae, requiring biomass to be processed within 48 hours of harvest to preserve its valuable bioactive compounds.

The primary method in Brazil is a simple mechanical, cold-press extraction. The seaweed is ground into a pulp and then pressed to separate the liquid, yielding about 1,000 liters of raw extract from 1.3 metric tons of fresh algae. The residual 15-20% of solids are dried and increasingly sold as a functional ingredient for inoculants, which are live-microorganism bioinputs increasingly utilized in Brazilian agriculture.

Meanwhile in Venezuela, also TIDE has built a  600 m² processing plant for extraction of a biostimulant to diversify income beyond raw material exports. With a capacity of receiving 5 tonnes of fresh seaweed every 150 minutes, the new facility, which is only 10 minutes by truck from most cultivation sites, can produce 10,000 litres of pure Kappaphycus extract each day for their biostimulant line. 
 

This method is predominant in Venezuela, where seaweed is spread on beaches or open areas near farm sites. The company TIDE operates a 300 m² concrete drying facility capable of processing one ton every two months. The technique relies entirely on solar exposure and is susceptible to weather delays, creating potential bottlenecks during rainy periods. Under good conditions the sun-drying typically achieves a 10:1 wet-to-dry ratio over three days. 

Post-harvest maintenance is systematic across both countries. Venezuelan operations perform regular line cleaning and rope tightening. In Brazil, Santa Catarina conducts comprehensive cleaning every six months using high-pressure equipment, while Rio de Janeiro implements full system maintenance - cleaning structures, ropes, and tubes on raft systems.