Light, cost-effective, and efficient--the textile reactor takes its place on the recycling landscape
When I meet Mohammad Taherzadeh, Professor of Biotechnology at the University of Borås, at his office, he is just in the process of planning a collaboration meeting with a university and some companies in Australia about the research on the textile reactor and what can be produced in it. Since the prototype stage at the University of Borås and the development of different models and sizes at the partner company F.O.V. Fabrics AB, the reactor has been introduced in several countries worldwide, mainly for the production of biogas.
Let's take it from the beginning. Research on waste recycling, such as wood residuals, agricultural or household waste, by converting it to bioethanol and biogas, has been going on for a long time at the university, but what has been used are fixed reactors made of stainless steel or glass. On a larger scale--for example, purification plants--the bioreactors are made from concrete.
Quick info about the textile reactor
To date, the textile reactor has been tested in different markets in the world, and the technology has evolved along the way. The latest market tested is India, where the company F.O.V. has established a subsidiary that supplies reactors with volumes from five cubic meters to 300 cubic meters. Approximately 30 reactors have been established and technical trials are being carried out with the researchers at the University of Borås.
Possible area of use can be anywhere organic waste is produced, from a standard kitchen with gas stove, fruit markets, forestry and agricultural industries to the food industry and restaurants.
Five cubic meters corresponds to a hot tub while 300 cubic meters corresponds to a swimming pool 25 meters long and four swimming lanes wide.
Research on the textile reactor is conducted in the field of resource recovery. Doctoral projects on the textile reactor have also been carried out at the University of Borås by Solmaz Aslanzadeh (doctorate 2014), Karthik Rajendran (doctorate 2015), Ramkumar Nair (doctorate 2017) and Lukitawesa Lukitawesa (doctorate anticipated in 2019).
Read more about research in resource recovery at scrr.se
A chance meeting between Mohammad Taherzadeh and Fredrik Johansson, business developer and partner in F.O.V., who has technical textiles as a specialty, sparked the idea of a textile reactor.
"Why not a reactor made of textile material, we thought. We saw some interesting benefits, such as being easy to move. In our research field, we are experts in the fermentation processes for the production of biogas and ethanol, for example, and F.O.V. specialises in technical textiles, so we combined our focus," says Mohammad Taherzadeh.
The meeting led to a research collaboration in which the research team in the field of resource recovery would develop the technology to convert waste to biogas and bioethanol by anaerobic digestion or fermentation while continuing to develop processes for various applications. The company would contribute the textile material and the design of the reactor itself.
The research team specified the requirements for the reactor. In addition to low weight, it must still have the proper properties, such as being impermeable and able to withstand different substances, such as the chemicals and microorganisms that will work in the reactor. Externally, it must handle different kinds of weather and climates, and it must have a long life span.
A first prototype of the reactor saw the light of the day in 2014. It was a triangular and pyramidal creation, for stability. Over a few years, it was tested in several research projects. First, attempts were made to produce biogas with kitchen waste in the lab environment, then later with manure. The results were excellent.
From F.O.V.'s side, a potential market in, for example, agriculture in Europe was noted, but the cold climate was a problem. The reactor, which is meant to be placed outdoors, needs heat so that the microorganisms in it will thrive. Initially, it would be better to try it out in tropical climate. Taherzadeh turned to potential partners for research collaboration in different countries with the right weather conditions.
"We contacted both higher education institutions and companies in search of research collaborations in Vietnam, Indonesia, and Brazil," says Mohammad Taherzadeh.
Prior to stage 2--to test the reactor in an outdoor environment--a different design was chosen. It was shaped as a lying bag, more suitable for a larger scale reactor.
The researchers fed the reactor with different types of waste and tried different mixtures to get as good a production of biogas as possible. They also tested reactors of different sizes to produce the desired technical characteristics. Today, textile reactors have been developed and established in several locations around the world to produce biogas on both small and large scales, ranging from a few cubic meters to 300 cubic large reactors. They are used so far mainly in agriculture.
Europe is still interesting as a possible market for the reactor and the researchers have turned their eyes towards Sweden with its colder climate.
"In countries with tropical climates, the wet anaerobic digestion process works well, as the material that the reactor is filled with is mixed with water to form a watery sludge and we do not need to add heat. The same process works less well in a cold climate, because then the bacteria in the reactor will freeze and die. That's why we are now looking at a method of dry digestion, where we reduce the amount of fluid and work for there to be better insulation. Our lab scale tests look promising and we are ready to test on a large scale," says Mohammad Taherzadeh.
But it doesn't stop there. Research on the textile reactor has entered stage 3--to find new applications for it. In new projects, it is now being tested for the production of things other than biogas and bioethanol. Mohammad Taherzadeh tells about a project with fungi.
"A reactor is basically like any other vessel. What it produces depends on what you put in it and what microorganism is used in it. Right now we are trying to grow fungi in the reactor. It is the same kind of fungi we have used in several other projects, Ascomycete, a kind of fungus that is also used as a foodstuff in Asia. We are investigating whether we can grow it in the reactor to use in new products, such as for the production of animal feed."
The textile reactor is then filled with vinasse, a residual from sugar and ethanol production. The fungus grows in the reactor and will then be used for the production of animal feed. At the University of Borås, experiments are being carried out in lab environments, and in India pilot trials are being conducted; the results look promising.
The fungus grows in the reactor and will then be used for the production of animal feed.
Another ongoing project is to develop an entirely new material for the textile reactor itself, which today consists of a thick fabric of composite material with a sealing layer on the inside that keeps the fabric impermeable. The new material should consist of a thinner textile layer that becomes impermeable through a new method. It is completely recyclable and does not release any hazardous substances. The goal is to close the recycling circle as well as to ensure that the material that the textile reactors consist of can be recovered when the life of the reactor is complete.
One of the research projects in which the textile reactor has a key role is on the reduction of the use of water in the anaerobic digestion process and the improvement of the environment within the reactor for the microorganisms that produce biogas. Another is about improving the technology of the reactor, and a third is on producing a whole new textile material for the reactor itself. The experiments are conducted at the university's research lab for biotechnology and polymer technology.
Regina Jijoho Patinvoh, who earned a doctorate in Resource Recovery in December 2017, has been working on a research project on a dry digestion process for biogas production using microorganisms that can handle acid-poor conditions.
We go down to the lab where she has her workplace. On a workbench there's a grey bag with an opening that is closed with a long zipper. Through it, cattle manure is added to the reactor together with straw mixed with sewage sludge from a water treatment plant. The sewage sludge contains microorganisms that accelerate the decomposition process of the waste material in order to form biogas. By using sewage sludge, you do not need to add water to the process. Through a hose, the gas is drained to another container. During the process, she takes samples to control the quality of the gas and how much gas is produced.
Water shortage is a major problem in many countries. This method is a good option in those cases.
The aim of the research project was to investigate the potential of the textile reactor with regards to the dry digestion process. Regina Jijoho Patinvoh did this by gradually increasing the amount of solid waste material and reducing the volume of liquid in the reactor as much as possible without the digestion process being stopped.
"In many countries, water shortage is a major problem. That's why this method is a good option. We can reduce the amount of liquid and simultaneously also use a smaller reactor, making it easier to take care of the remaining by-products. It will be economically advantageous," she says.
The by-products remaining when the maximum amount of biogas has been obtained can then be used as organic fertilizers, as they contain important nutrients for vegetation. And the textile reactor can be used over and over again. Once one round of waste has been processed in the reactor, new material can be added for another round of digestion. In this second round, the process time is shortened and a greater yield of biogas is produced.
"This is due to the fact that the microorganisms that produce biogas in the reactor need time to adapt to the new environment that the substrate and the reactor make up. They are just like we people who need some time to get used to new environments," she explains.
She is pleased with the results. The textile reactor has the proper properties, it is impermeable so that no gas leaks out, and it does not release any harmful substances during the fermentation process. It is robust and easy to handle. In the long run, the goal is for the dry digestion process to be used on a large scale. The method is suitable for small farms, but it is also possible to couple together several textile reactors to work in parallel for continuous biogas production.
One day, Regina Jijoho Patinvoh hopes that textile reactors will also be used in her home country, Nigeria.
"Actually, the reactor can be used there already. The climate there is perfect, no heat is needed, the technology is simple, and the reactor is cost effective."
Doctoral student Alex Osagie works to develop and improve the technology around the textile reactor. In the biotechnology lab, he picks up a reactor made of transparent plastic. It is used to visually study what is happening inside.
"I introduce various functions to the reactor, for example to control the temperature and to mix the material in it. This in order to best provide the microorganisms that work in the reactor an optimal climate to produce the substances we want. Another part of my research is about analysing and calculating the strength of the textile reactor to determine how safe it is to use, especially in large scale applications."
He shows how he works with the translucent reactor. In it, either those microorganisms that need air to live or those who do not can work. In both cases, the material you add to the reactor needs to be mixed around so that it does not lie on the bottom, because then the microorganisms will not eat and cannot function.
"The textile reactor can be fed with different types of material depending on what is to be produced. In ethanol production, sugar is added. Then we use yeast for a fermentation process. And for biogas production we supply different kinds of waste. Then we use microorganisms that handle acid-poor conditions in the digestion process," he says.
He can regulate what should be inserted into the reactor via perforated hoses inside the reactor. It can either be a substrate based on different types of waste to those microorganisms that work without air, or he feeds air into the reactor for those organisms who need the right amount of this to thrive. The challenge for this research is the complexity of the areas of application themselves.
"At the lab level, we can see that the technology works well, but more research is needed before it is time for production in large scale textile reactors. Technically, the textile reactor can be of great importance to the processing industry. The installation time is short, textile reactors can be used in any kind of space, both small and large, and they are perfect if you want to test new applications. They provide a great deal of flexibility."
It is possible to reduce the use of environmentally harmful binders.
From polyamide to polyamide--a material made of waste to handle waste, and then reused to become a new material. That's how doctoral student Mostafa Jabbari describes his research project with the textile reactor. He is improving the material that today's textile reactors are made of. In addition, he is developing a whole new material, which is lighter, stronger, and completely recyclable.
He shows the way into the polymer research lab and picks up a bag of textile waste in polyamide, some thin pieces of cloth, also of polyamide, a bottle of a viscous solution, scissors, tape, a glass sheet, and a water bath.
At the beginning of his research, he based his work on the existing material that today's textile reactors are made of with the goal of improving its thermal insulation properties. The microorganisms in the reactor must have a stable climate with an even temperature, even if temperatures outside the reactor it run between cold and hot. When the reactor is to be used outdoors, it must withstand different types of weather and sunlight. Next, he went further to the reactor's internal climate. By adding antibacterial properties, he wants to create a climate where the microorganisms used in the fermentation processes thrive and can work. Now he is going another step further and is developing a whole new material for the reactor.
By using waste from the textile industry, the goal is now to develop a composite consisting of a single polymer, polyamide, which is completely recyclable.
"We have created a process for manufacturing the material for the reactor in an environmentally friendly manner by developing a solution of polyamide that stretches like a thin film on plain thin fabric, also of polyamide. The film makes the fabric impermeable so that it does not let through gas, for example. In this way, the use of environmentally harmful adhesives between the textile and the sealing layer in the reactor wall can be reduced," he explains, demonstrating how it works.
It's therefore not about developing an individual material, but about a new concept for developing self-protecting composites for completely recyclable materials.
The method is still in its infancy and as yet the new material is not ready for use in a textile reactor or any other possible product.
Mostafa Jabbari, however, is very pleased so far and in a few years he hopes that the material can be used for future textile reactors, but also for other products such as furniture and interior decoration in cars.
Text Solveig Klug
Illustration Michèle Harland
Photo Suss Wilén och Mostphotos
Translation Eva Medin