In Java, Indonesia, tofu residues are converted into green energy!

Posted on 23 August 2016.

In the village of Kalisari on the Indonesian island of Java, the liquid from pressing the tofu made on site is recovered and recycled. It produces biogas that is converted into 100% green energy.

On the island of Java in the Indonesian archipelago, tofu production is an ancient tradition. In the village of Kalisari, 150 small producers have been transforming soy milk into tofu for generations.

To become tofu, soy milk is curdled with coagulating enzymes (salt or acidic ingredients) and then pressed. The recovered liquid can then be converted to biogas.

Curdling soy milk with a coagulant (salt or acid ingredients) results in the famous white paste which is then pressed, drained and cut into small cubes. It is this very acidic liquid recovered at the end of this operation which is the focus of a pilot recycling project.

Placed in one of the digesters that have been installed in the village with some water, the "whey" ferments and through an anaerobic digestion process is transformed into biogas in the tanks and not released into the atmosphere. Biogas then powers steam turbines that generate electricity for furnaces, stoves and lighting in the village. The five digesters are now operating at full capacity and each provides green energy for one hundred homes.

There are several advantages. First, if left in the open air tofu liquid waste emits methane, a greenhouse gas that is twenty times more powerful than carbon dioxide. And as the very acid tofu residues are often poured into the gutters, they pollute rivers, deplete agricultural land and damage Indonesia’s rice fields.

Recovering and recycling these residues is therefore of benefit to the environment but also has a practical use for the locals. The most immediate is to provide them with a source of energy that is three times cheaper than LPG and above all is available immediately - a considerable advantage on an island where energy supplies are uncertain.

A useful, virtuous approach

Supported by the local government and by the Dutch non-governmental organization Hivos, which is particularly involved in renewable energy development projects in Indonesia, the experiment conducted in Kalisari is exemplary.

It has to be said that according to the Global Carbon Atlas 2014, the archipelago of 1700 islands, which is home to some 250 million people, is the seventh largest emitter of CO2 in the world. The country has set itself the goal of producing a quarter of its energy from renewables by 2025.

Waste recycling therefore represents a major challenge and the potential for tofu residues is significant in one of the regions where it is produced in large quantities.

In Kalisari, the success of recycling tofu liquid is such that the demand is now outstripping supply. Villagers are eagerly awaiting a new digester that will increase biogas production and supply energy to other small producers. The local government has an ambition - to become an energy efficient village with no pollution.