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The problem with water hyacinth November 17th, 2019 by

The Pantanal wetland, shared by Bolivia and Brazil, is the size of a small sea. In the Pantanal it rains for six months, followed by a half year drought. During the rainy season the rivers overflow their banks, creating a seemingly endless sheet of shallow water reaching to the horizon. In the dry season the water retreats to the river courses. There are few trees in the Pantanal, but there are dense stands of a delicate-looking purple flower, the water hyacinth.

In the twentieth century, gardeners innocently spread the water hyacinth to Asia, Africa and elsewhere. Water hyacinth has striking blue flowers and was used to adorn ornamental fountains. But it escaped and was soon clogging lakes, ponds and municipal water supplies.

Water hyacinth is such a survivor that you can drain ponds, let the plants dry out and burn them – then watch them grow again when the pond is refilled. It’s not surprising that control options are limited, particularly in open water, such as lakes and rivers.

The plants can be hand removed, by people willing to do heavy labor in the mud, cutting and dragging water hyacinth to the shore. Even this drudgery only works if you repeat it every year.

When the water hyacinth is removed, people tend to leave it in heaps at the edge of the water, where it is unsightly and gets in the way.

I recently saw another solution for water hyacinth in Benin, in West Africa. At Songhai, a training center in Porto Novo, they harvest water hyacinth, chop it, mix it with manure and use it to make methane (biogas) for cooking. Songhai also keeps a large tank of methane to run an electrical generator when the power is out.

Making biogas isn’t for everyone, as we saw in a previous blog. The Moreno family in Peru has trained people for years to make biogas from guinea pig manure, but few if any of the trainees later made biogas at home. For this to happen you need to buy equipment, provide labor, and pay close attention to managing the microorganisms that ferment the organic matter and give off the gas.

I liked the Songhai method because they don’t just remove the water hyacinth. They treat it like raw material and they make something with it.  But I wondered if using it to make biogas was profitable. A more detailed study is needed to gauge its potential to make money. The Songhai solution has one key advantage: the water hyacinth does not need to be dried, a plus because the big heaps of flesh plants hold retain a lot of water.

Water hyacinth is a water thief in some of the thirstier parts of the world. Finding uses for it may help to defray the costs of weeding it out.

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Scientific name

Water hyacinth is Eichhornia crassipes.

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