Torwash Produces Biofuels from Sewage Sludge and Other Wet Waste

In principle, the Torwash reactor can handle all waste streams, as long as they are organic. The dirtier and wetter, the better, because that is where the most profit can be made. The company's slogan is: Waste, too Good to Waste. The start-up aims to convert all organic waste into sustainable chemicals and fuels, creating circular products that can combat climate change. Both here and in developing countries.

Energy Carrier

Now that Minister Jetten has stopped subsidizing the burning of wood as biomass, the biofuels from Torwash can serve as a sustainable alternative. Eneco will be the first customer to burn pellets made from sewage sludge in its biomass plant in Groningen. These pellets will come from the first demo factory that Torwash is building at a wastewater treatment facility in Brabant. “What we produce is an energy carrier,” say project leader Pavlina Nanou and Torwash's CEO Levien de Legé.

TNO Spin-off

The inventor of the Torwash technology is TNO's Jan Pels. He devised a method in 2004 to make fuel from wet grass with the same quality as clean, dry wood pellets. Over the years, he developed technology that can work with nearly all waste types—from food waste to autumn leaves, sewage sludge, digestate (a residue from manure or plants after digestion), sugar beet tops, mushroom compost, slaughter waste, manure, straw, water plants, or plastic. You name it, Pels has probably tried it. It almost always involves wet waste and by-products that companies have to pay to dispose of. His TNO colleagues Pavlina Nanou and Levien de Legé were just as enthusiastic about the promising technology. Normally, TNO licenses the technology to suitable companies that commercialize it. But this time, the three opted to start their own spin-off. In 2020, they founded Torwash BV, in which TNO holds a 25 percent stake.

Better Fuel

The technology employs hydrothermalysis and is suitable for creating useful applications and fuels from various types of waste. “It seems like a huge cloud of different materials, but it is all organic material. Our process works the same for all applications,” De Legé explains. “We break down molecules in chains that contain oxygen, which happens in water, by heating the water to a high temperature without bringing it to a boil. This occurs in a high-pressure reactor—kind of like a pressure cooker. We have overheated water. The cutting process breaks the material apart partly and extracts oxygen. That is released as CO2, which is just enough to cause interesting chemical properties—namely, it becomes much easier to dewater. The material becomes water-repellent instead of holding onto water. Additionally, the oxygen and salts are removed, making it a better fuel. So it doesn’t matter what you throw in, as long as it’s wet and dirty. That kind of waste often costs the most to process. We simply make nice, clean pellets from it, just like you buy for your stove.”

Sewage Incinerators Could Shut Down

In principle, Torwash can work with anything, but you have to start somewhere. That’s why the choice was made to process sewage sludge from wastewater treatment plants in the country. It contains a lot of water and is currently being dried and burned in waste incineration ovens like those of HVC in Dordrecht and SNB in Moerdijk. Over 1.5 million tons of sludge per year, costing 150 million euros. Torwash thought that was a waste because that sludge is not waste but a raw material. “Sludge is very difficult to dewater but becomes completely hydrophobic after our process. We can then use a mechanical press to extract most of the water. If this is applied on a large scale, the sludge incinerators in the Netherlands could be shut down,” says De Legé. “The existing dewatering methods leave sludge with still 80 percent water, and you transport that to a sludge incinerator in a tanker. Essentially, you’re burning water.”

Fully Circular

Torwash can extract the water and turn sewage sludge into combustible pellets or dry cakes. The removed water is efficiently digested into biogas, making the entire process energy-neutral. Phosphate from the sludge can also be recovered. The water goes back to the treatment plant and then into surface water. Thus, there is no waste left, making the entire system fully circular.

Demo Factory Under Construction

The process has already proven effective during extensive testing at the Almere waste treatment plant in collaboration with the Zuiderzeeland Water Authority. The produced biofuel and biogas turned out to be excellent for sustainable energy production. That’s why Torwash chose to scale up. Together with TNO and various water authorities, the start-up has begun building a demo factory twenty times larger at the wastewater treatment facility of Waterschap Aa and Maas in the Land of Cuijk. “Here we’re going to prove the technology on a larger scale of 500 kilograms of sludge per hour,” says Nanou. “We will process 10 percent of their sludge stream in our facility, which includes a Torwash reactor and a filter press. We will produce beautiful dry cakes, from which we can create any desired shape. Eneco will use these chunks in its biomass plant for demolition wood in Delfzijl. That’s just a limited amount. What we produce will pass through there in ten minutes.”

Ten Times Larger

The factory is half-funded with a DEI+ (Demonstration Energy and Climate Innovation) subsidy. The demo factory is expected to be operational this summer. The next step is to make that factory ten times larger and process 5,000 kilograms of sludge per hour. The modular design has already taken that into account, allowing new reactors to be added to the existing setup. By 2027, Torwash reactors should be available for sale. Initially for small wastewater treatment plants, then for all types of installations.

Using Agricultural Waste Around the Equator

The technology is also applicable in agriculture, where many waste streams remain unused. Not in the Netherlands, where most agricultural waste is recycled. But around the equator, there is a vast amount of food being grown. “All the by-products from coffee plantations, palm oil plantations, and sugar cane plantations are just rotting away there. With our process, you could perfectly convert that into combustible pellets for fuel. That way, you wouldn’t need to use wood,” says De Legé. Torwash would love to partner with a sugar factory to process all waste into pellets. An added benefit: if agricultural waste goes through the Torwash reactor, it is also more suitable for fermentation into bioethanol, a future raw material for bioplastics. “But it’s very difficult to secure funding for these types of projects. That’s why it’s not our priority. We are focusing on developing the sludge business case,” he says.

Recycling Dirty Plastics

Plastic waste can also be processed in the Torwash reactor. Currently, the majority of plastic in the Netherlands is burned as household waste. What gets recycled often ends up in low-quality applications, such as fence posts. “That option is at least as interesting,” say Nanou and De Legé. “The cut we make in the material also applies to bioplastics, often with biological polyesters. For example, biodegradable plastic like PLA is reduced back to its building blocks. That represents true recycling. The advantage of our process is that the waste does not need to be clean. Food scraps, metals, and other plastics simply sink to the bottom.”

However, it is a requirement that a good recycling system for biodegradable plastics is established. Currently, no one wants it. Composters don’t want it because it composts too slowly, and sorting facilities don’t want it mixed with other, sturdier types of plastics. That's why processing PLA in the Torwash reactor could stimulate a new collection and recycling system.

Green Chemistry Accelerator

Torwash has received help and guidance from the Green Chemistry Accelerator in recent months, which is an acceleration program by the Green Chemistry New Economy platform (GCNE), Invest-NL, and the Regional Development Companies (ROMs) in the Netherlands. Experts within the program assist green chemistry startups with a tailored plan to achieve their main goals in one hundred days. This customized support also facilitates the financing of pilots and demo factories. The five selected startups will conclude the program on February 16 with a meeting at Change Inc. in Amsterdam. In total, five startups were selected for the program. Besides Torwash, they include ETB Global, Paques Biomaterials, Relement, and Susphos—promising game changers in the greening of chemistry.

Step by Step

During the program, Torwash learned to focus on the short term. Nanou: “We had to set our priorities to move forward and consider what we really needed to work on in the next three months. That helped us figure out what steps to take to further develop our business model. The coaches and experts were immensely helpful in that regard. By posing questions to other entrepreneurs who have already gone through this, we keep making progress step by step.”