Biogas Fermenter in Vietnam Welded with TWINNY

Success Stories30 May 2022

In rural Vietnam and many other areas of Asia, people still cook with fossil fuels, such as bottled gas. Read this article to find out how Leister is supporting an international research team in its search for a more environmentally friendly alternative.


Gregor Studer, Manager Marketing Services, Leister Switzerland

Silke Landtwing, Manager of Corporate Communications, Leister Switzerland

Vietnam enchants with dense rainforests, green rice terraces, and unique sites that are part of the UNESCO World Heritage. We think of the famous Halong Bay and Phong Nha-Ke Bang National Park.


The Mekong Delta in southern Vietnam is a vast maze of rivers, swamps, and islands with floating markets, Khmer pagodas, and villages surrounded by rice fields. This area offers the ideal starting position for the production of biogas. Why? Read on.

Biogas plants for self-sufficiency in rural areas

For decades, people in rural areas in Asia, Africa, and South America have been using bottled gas or firewood for cooking. This is also the case here in Vietnam. Different biogas plants offer an environmentally friendly alternative. The biogas is usually produced from pig manure in a microbial fermentation process. This requires a constant pig population of five adult animals to produce enough biogas for the daily cooking needs of a farm household.

An international research team now wanted to find out whether biomass or a mixture of biomass and pig manure could be used to generate biogas as an alternative. The goal was to develop a low-cost biogas fermenter using biomass from rice straw waste and water hyacinth as feedstock. Both are available in virtually unlimited supply in Vietnam as well as in many other parts of Asia.

Years of international research and funding

Already in 2013 and 2014, extensive laboratory experiments were conducted under the supervision of leading scientists from Aarhus University (Denmark) and Can Tho University (Vietnam). These experiments clearly showed that rice straw and water hyacinth are excellent substrates for biogas production. In addition, the researchers found that the biogas yield was about 50% higher when the biomass was used in co-digestion with pig manure. (Co-digestion is the joint fermentation of solid biogenic waste with liquid substrates such as sewage sludge or manure).

Fermenter welded from geomembrane

Farm-scale trials pursued the development of a long-lasting, low-cost biogas plant as an alternative to traditional brick domes.

Here are two pictures of such brick domes. The picture on the right clearly visualizes the effort and resources involved in the construction of a brick dome.

The new solution should allow easy and cheap installation of the fermentation equipment by farmers and should not require expensive construction. For this purpose, a fermenter with an inlet and outlet nozzle was formed from a conventional plastic geomembrane (HDPE), in which the bio substrate ferments under solar radiation. The resulting biogas reaches another reservoir (gas storage) via a pipeline. From there it is then used for cooking. When it came to airtight welding of the geomembrane, the research team needed expert knowledge of plastic welding from Leister.

Leister automatic welding machine TWINNY is best suited for this job

The project research team first contacted Leister's Danish sales and service partner Bergstrom Plastteknik A/S.

After some clarifications and tests, it was evident that the round welding of the HDPE geomembranes for the inlet and outlet of the fermenter worked best with the TWINNY. By the way, you can see this inlet and outlet nozzle in the picture.

The TWINNY automatic plastic welding machine was designed by Leister for civil engineering, pool construction, mine construction, and film welding in landfill construction and is versatile in use. Due to its intuitive user guidance, even inexperienced users can quickly start working with the TWINNY professionally.

This was also an essential criterion in this project. Jan Bentzen, Associate Professor from Aarhus University is pleased with the success: "Thanks to the competent cooperation with Leister, we quickly found the best solution for welding the Biogas reactors made from HDPE in a high-quality and above all airtight manner."

Lots of potential for the construction of small biogas plants in the Vietnamese Mekong Delta

Now that the project has been scientifically proven to work, nothing stands in the way of building small-scale biogas plants from HDPE geomembranes in rice-growing regions. In Vietnam's Mekong Delta alone, there is currently estimated to be the potential for 17,000 agricultural biogas plants. The investment cost is about 400-450 USD and the fermenter has a lifetime of at least ten years.

Environmentally friendly and sustainable alternative

Such biogas plants significantly reduce the demand for fossil fuels. They are a cost-efficient, environmentally friendly, and sustainable alternative to bottled gas.

The new biogas fermenters are also a good option in economic terms. This is because they have to be installed and maintained, which has a positive impact on the order situation of small companies as well as creating new workplaces.

The living standards of the rural population also rise. Because it is obvious that the self-produced biogas saves costs in cooking and at the same time protects the environment.


The picture shows a newly developed biogas fermenter in operation on a Vietnamese farm in the Mekong Delta.


A Vietnamese farmer connects his gas stove to the pipe (gray plastic tube) of his own biogas plant.