STORY Power Generation

The root plant using plant roots

Posted on February 27, 2019 by Matthias Peer, Images by Matthias Peer

Biogas plants in Thailand not only supply good air but also save money for their operators.
Nakhon Ratchasima, Thailand

In Thailand's agricultural heartland, biogas plants make more than just good business sense. In the villages of Nakhon Ratchasima they are also eliminating an annoying odor problem.

The winter months used to be anything but pleasant in the area surrounding Prayut Vitthayanukorn's factory in the Thai province of Nakhon Ratchasima. The entrepreneur can remember this very well. Strong north winds used to blow over its waste water reservoir, taking the stench of sulfur straight into the neighboring communities. “We used to get a lot of complaints about it,” says Prayut. He shows us old pictures of the plant: a murky, foaming liquid can be seen. For him, it was clear that this could not be allowed to continue.

Prayut Vitthayanukorn is the founder of the company General Starch Limited which processes root tubers of the cassava plant into starch.

Environmental protection takes priority 

His home country of Thailand is an emerging country, and economic growth is still often at the expense of the natural surroundings. But Prayut chose to take a different approach: He made environmental protection a company priority. In fact, he turned his waste water problem into a tangible benefit – with the help of a biogas plant. He was one of the first industrialists in the region to use this technology, but now many are following his lead. That said, southeast Asia's second-largest economy still has some catching up to do in terms of promoting biogas plants.

Prayut's factory is located in northeastern Thailand – an agricultural area seldom visited by tourists. He makes his money from an agricultural product: he processes the root tubers of the cassava plant, also known as manioc, into starch. His company, General Starch Limited (GSL), supplies this powder Native Tapioca and Modified Tapioca Starch by the ton, mainly abroad, generating over 100 million dollars in sales per year. The starch ends up in foods such as sauces and doughs, and also in industrial products like paper and plasterboard.

In the early morning, it is still dark as the trucks of the cassava farmers line up outside the factory gates. The trucks are color-fully painted and loaded to the brim with many tons of root material. One of these vehicles belongs to Chainart Rakkaserm. The 55-year-old's field is ten kilometers away. Today, he's bringing in 7 metric tons. He drives his truck onto a weighbridge to determine the exact weight of the produce and then parks on a kind of lifting platform that tilts diagonally downwards at the push of a button, tipping the load out and allowing it to fall down a shaft and onto a conveyor belt. This is where the cassava roots begin their industrial odyssey– the factory processes around 800,000 tons each year. 

Colorfully painted trucks piled full with cassava roots on the way to Prayut Vitthayanukorn's factory.

Biogas from waste water 

Before the roots are turned into powder, they go into a washing machine. The milky waste water flows through pipework into an outdoor basin where it is covered by a black tarpaulin and, from a distance, is reminiscent of a giant air mattress. Beneath the dome of the tarpaulin, microorganisms turn the contaminated water into biomethane. The gas is extracted and cleaned – and is then used as the factory's most important source of energy. The plant produces around 90,000 to 100,000 cubic meters of biogas every day, half of which is used by Prayut to heat steam boilers. The steam is used to dry the roots – a process which used to require oil to be burned. The use of biogas not only helps to protect the environment by reducing the use of fossil fuels, it also pays off financially: Prayut says he saves a quarter of a million baht per day, somewhere around 6,000 euros. 

Under the black tarpaulin, micro-organisms process the wastewater from the cleaning of the cassava tubers into biomethane.

But that's not all. The 67-year-old co-founder of the company, who created GSL in the early 90s together with some business partners, lets his son Kamolpat demonstrate the heart of the plant: General Starch produces its own electricity in the factory's own power plant. Kamolpat, who will one day take over the running of the family business, hands out earplugs to his visitors before further ado, because things are about to get really loud: behind the soundproof door are four mtu Series 4000 engines. The control room is decorated with Buddhist drawings and prayer flowers intended to bring luck to a challenging task. The engines are indeed very audible, and run thousands of hours a year without interruption. 

Electricity accounts for 20% of production costs

General Starch Limited's products are in global demand, with 80% exported over the globe, where cassava powder is used as a cheaper alternative to potato starch. The comparatively poor potato harvest in Europe this year will further increase demand for this alternative product from Thailand. As a result, Prayut's factory is running 24/7, powered largely by electricity, which normally accounts for anywhere up to 20 percent of production costs, according to Prayut. His in-house power plant helps him reduce this cost by a significant amount. The mtu engines, which have been in operation since 2016, give him a capacity of 8 megawatts – power which help GSL reduce drawing the electricity (approximately 80%) from the national grid. According to the company, this reduces the factory's electricity bill by around 160,000 euros per month. Prayut is also able to use the waste heat given off by the engines to power 
a cooling system.

mtu Onsite Energy's combined heat and power plants enable GSL to save 160,000 euros a month in electricity costs. GSL also uses the waste heat to supply the cooling system with power.

Company power plants like this are now more common in the province of Nakhon Ratchasima, which is usually referred to by its inhabitants as Korat. This is partly down to the efforts of Thai engineer Prasit Pornsaksit who supplies energy-efficient turnkey solutions to companies in his home country through his company MSM. “In Thai agriculture, biogas plants are now in demand in many places,” said Prasit. “But it is cassava processing that produces by far the most waste water. This means it is also possible to use biogas to fuel engines with power outputs in the 1.5 to 2.0 megawatt range.”

One of Prasit's customers in the cassava trade now has eight mtu engines in operation. They generate a lot more electricity than the factory needs for its own requirements. The owner sells the surplus to the power company and receives feed-in tariff payments in return. “This is a worthwhile business,” said Prasit. However, the model is not currently available to other companies. The Thai government has suspended additional purchases of renewable energy for the time being. The reason given by the authorities was that they feared electricity prices would otherwise rise. Previously, suppliers of renewable energy received a generous premium on top of the market price as an incentive.

Prasit is in favor of foregoing the subsidy but reopening the power grids. He reckons that electricity generated from biogas would pay for itself even without the subsidies. Rolling these out could go a long way towards helping protect the environment.

He can see great opportunities for biogas, for example, in Krabi in southern Thailand, one of the most popular holiday destinations in southeast Asia due to its superb beaches and idyllic islands. But local residents fear that the unique natural surroundings of the area could be damaged by a coal-fired power station currently being planned. The project to supply the much-visited region with urgently needed power has been a matter of dispute for some years now. Biogas could go a long way towards alleviating the power bottleneck. Krabi may not have any cassava factories, but there is no shortage of palm oil mills. “Their waste water is an excellent source of biogas,” enthused Prasit.

Economic benefits secondary 

In Korat, Prayut describes biogas as indispensable for the success of his business. However, he emphasizes: “The economic benefits were secondary to me from the very beginning. My primary concern was to find a solution to the environmental problems.” The positive contribution that General Starch Limited wants to make in the region can also be seen in a field near Chainart's farm. The cleaned and treated waste water from the Cassava factory is sprayed onto the ground in thin jets from plastic pipes. It is used here to irrigate a General Starch reforestation project. Banana trees and herbs are already growing here. There are also plans for a small mushroom farm. Prayut ultimately wants the site to become a kind of natural supermarket for local residents, where everyone can help themselves free of charge.

From Chainart's point of view, the factory's reputation has been greatly enhanced by the owner's initiatives. He says it gives him much more than a reliable living, but that the negative aspects of starch production have also now been eliminated. “In the past, the winter stench literally got up our noses,” he recalls. “But fortunately, that's now a thing of the past.”

Point of contact

Norbert Maier
+49 821 7480 2396