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Salt production using Plastic sheets

Table salt (sodium chloride) is an important product in the coastal areas for household and industrial uses and especially for fish processing like salted-fish drying, fish sauce (patis) and fish paste (bagoong). Salt production can be done by family members who do not brave the high seas for fishing. Housewives, youth and children can undertake the work. The production technique being advocated here puts idle and barren open coastal lands into productive use and minimize mangrove destruction from the pond-tile method of producing salt.

Traditionally, the coastal provinces in the Philippines with the Type 1 climate of distinct dry and wet seasons, like Paranaque, Bulacan, Pangasinan and Occidental Mindoro, are the biggest producers of salt. However, due to the conversion of salt ponds into subdivisions and prawn culture in the 1980's in the first three provinces, Occidental Mindoro is now the number one producer of salt. Salt production, using plastic sheet, is now recommended for various coastal areas, regardless of the type of prevailing climate. It is also about 80 percent less expensive than the traditional pond-tile method. The plastic ponds can be provided with roll-over plastic cover in case of rainfall.

Climatic types of the Philippines

Salt-making unit using plastic sheet

Sea water contains 30-40 g of salt per 1000 cc or 1 liter (30-40 kg of salt per 1000 liters). One kilo is about 1 liter.

The plastic ponds have a perimeter frame of 5.0 cm thick lumber (preferably coco lumber where wood lumber is expensive) with varying widths.

The plastic sheet should be black, with thickness of at least .025 mm. Seawater evaporate 2.62 cm more quickly on black color than on white or light color which reflects sunlight.

It is recommended that one-unit plastic pond shall consist of two units rectangular evaporation ponds measuring 12.0 × 6.0 × 0.6 m; two units pre-crystallization rectangular saltbeds measuring 12.19 m × 6. 10 m × 38.10 cm; and, four units crystallization square saltbeds, measuring 6.0 m × 6.0 m × 7.50 cm.

Provide strong posts where the lumber frames are nailed. Hold the plastic sheets in place with thumbtacks.

Proposed small-scale plastic-solar salt production

The land should be well-leveled and cleared of all plants and sharp objects (stones, nails, coral, stumps) that can damage or make hole to the plastic sheet. The land should also be wellcompressed before the frames are placed.

1. Usually, three sets of ponds are needed— evaporation, concentration and crystallization)

2. The position of the different ponds should be gradually sloping towards the lower elevation or drain.

Process of sea water evaporation pond

3. Transfer the sea water more easily to the evaporation pond with the use of manual-type centrifugal pump or pedal pump (used for irrigation) anchored to a wooden platform. This is recommended for a small-scale production of two to four production units. The pumped water shall pass through a wooden or bamboo canal to the evaporation pond. This is done to elevate the flow of sea water to the salt production site by using wooden post where the canals are attached.

Precrystallization process

4. Leave the water in the ponds to evaporate.

5. After reducing the initial volume to one half, siphon off or transfer the brine to the concentration pond. The evaporation time to one half the initial-volume level depends on light intensity, air movement and size of pond. Siphoning can be done with the use of plastic hose with 1.27-1.59 cm hole in varying numbers.

Crystallization process

Crystallization pond

Salt heap space

6. Leave the brine solution in the concentration pond to further evaporate until its initial volume is reduced to one third.

7. Then, siphon it off or transfer to the crystallization pond or saltbeds. Use plastic hose of 1.27-1.59 cm diameter for siphoning. A pail or bucket can also be used but it is labor-and time-consuming. Attach two water faucets of 1.59 cm size between evaporation and concentration if the elevation of the source is higher.

8. Leave the brine in the crystallization pond to evaporate further until it is reduced to one third of its original level. At this time, salt crystals begin to form when the brine is almost evaporated.

· Better-quality salt is obtained when the seawater is filtered through a cotton cloth before transferring to the different evaporation ponds. This is to remove impurities.

· While a salinometer can be used to measure the concentration of salt in the brine, the best indicator for practical purposes is the reduction in the level of the brine solution.

9. Collect the salt crystals and expose them further to sunlight to dry in small heaps.

Harvesting process

Economies of production

The three sets of ponds (evaporation, concentration and crystallization) in the production unit measure 144 sq m each or a total of 432 sq m per unit. The 1991 cost estimate using black plastic sheets, coconut lumber and manual pumps, was about P15.00 per square meter or a high estimate of P7,000 per unit.

At an assumed production of 150 days per year at 20 kg, the expected gross income is P18,000 per unit in about five to six months' thee. Considering that the initial capital cost is deducted from the first year, a three-year period (the least expected lifespan of the unit) can yield at least a gross income of P54,000 per unit, with an initial capital of P7,000.00. This is about 200-250 percent ROI per year. The normal practice of contract sharing is 60 percent for financier and 4() percent for salt producer.

Small-scale salt production can be promoted through public investments by wage-earners who have at least P7,000.00 savings per year to be invested in the so-called "adopt a fisherman family" public-investment scheme. Salt production is a practically risk-free venture that can give high profits.