Recycling sewage sludge ash while producing sustainable concrete

EasyMining, Ragn-Sells, Technical University of Denmark (DTU), Ramboll, and BIOFOS are working together on a state-of-the-art technology to build a sustainable future with circular economy, minimize waste, reduce CO2 emission, recover the life-essential resource phosphorus, and produce environmental-friendly concrete.

Phosphorus is a crucial element for all life forms and every cell of every living organism contains phosphorus. However, it is a limited resource which is primarily extracted from rock phosphate. The global reserves are concentrated in a few countries like Morocco and Western Sahara.

The EU is highly dependent on phosphorus import, and EU has therefore included phosphorus on their critical raw material list, and recycling of phosphorus is therefore high on the EU agenda.

World-leading phosphorus recovery technology

One of the waste sources globally with the highest phosphorus content is sewage sludge, and many countries in Europe are making new legislations demanding mono-incineration of sewage sludge and recovery of phosphorus from the sludge ash.

EasyMining is currently building full-scale plants (in Sweden and Germany) to recover phosphorus from sewage sludge ash through their Ash2Phos technology. These plants will, for example, treat sewage sludge ash from Sweden, Germany and from BIOFOS in Denmark.

In the Ash2Phos process, sewage sludge ash is dissolved in hydrochloric acid (ambient temperature, no pressure). Phosphorus, iron and aluminum are separated from the leach solution by precipitation steps in a unique combination. Thereafter, the solution is neutralized and treated to remove heavy metals. The recoverable elements are separated into three products: pure calcium phosphate (e.g. typically <0.1 mg/kg cadmium), ferric chloride and aluminum hydroxide.

These products can be used as raw materials in the existing fertilizer industry and for production of coagulants, which creates a closed loop. The recovered calcium phosphate can be processed into NPK fertilizers, ammonium phosphates, superphosphates, as well as into feed phosphates.

The sewage sludge ash contains a fraction which is non-acid soluble meaning that about 50-60% of the ash ends up as a silicate sand residue, and EasyMining wants to find a solution for this silicate sand residue to avoid landfilling it, and to contribute to circular economy and a sustainable future.

Silicate sand residue as cement replacement

This silicate sand residue can be used as cement-replacement in concrete. DTU Department of Civil Engineering (DTU-byg) and Ramboll have extensive experience from previous investigations in using similar kind of silicate sand residue as a cement substitute in concrete, which is a sustainable and economical solution for recycling the silicate sand residue. Earlier results show the possibility to replace up to 30% of cement in concrete with silicate sand residue without compromising the quality of the concrete. This sustainable concrete will get a red-ish color due to the high iron oxide content in the silicate sand residue.

Because cement production has a high CO2 food print, up to 1.2 tons of CO2 can be saved for every 1 ton of silicate sand residue used in concrete. This will have a huge impact of the global carbon footprint, since more than 8% of the total CO2 emission for the entire world comes from concrete production.

People worldwide are trying to find a way to make concrete production more sustainable, and this is a solution. We are therefore, for example, investigating how much of the silicate sand residue from the Ash2Phos technology that can replace cement without compromising the quality and streamline the cement substitution process.

Future potentials

Ramboll will perform a market analysis to investigate which markets are ready for this sustainable concrete, and find potential future partnerships, who wants to be part of this first green concrete. Ramboll will, for example, be in contact with cement and concrete manufacturers, companies (producing e.g. facades and tiles), construction firms, architects, etc.

All partners expect that a full-scale production can be ready by 2023-2024, and it is expected that this project will expand to other countries in the world besides just Sweden, Denmark and Germany.

This article is jointly produced by the project team including representatives from EasyMining, Ragn-Sells, Technical University of Denmark (DTU), Ramboll, and BIOFOS.


EasyMining’s circular nitrogen removal technology secures 19 MSEK

EasyMining has been granted a 19 MSEK investment from the European Union’s LIFE programme for commercializing its patented method for removing nitrogen from sewage water. The circular solution enables water treatment facilities to capture nitrogen and put it to use as a fertilizer, thereby reducing emissions of greenhouse gas.

– We are happy and honored to have the EU invest in our innovation, contributing to making nitrogen removal circular in Sweden and Europe. EasyMining’s technology puts to use the nitrogen compounds we have already produced, and helps to reduce marine eutrophication, says Anna Lundbom, who has headed the LIFE programme application process at the Ragn-Sells Group.

The technology has been developed and patented world-wide by Ragn-Sells’ innovation company EasyMining. Water with a high nitrogen content, for example in municipal sewage treatment facilities, is treated with an agent which crystallizes the nitrogen and causes it to precipitate. The nitrogen is then extracted from the crystals and may be used again in agriculture, where nitrogen is one of the key nutrients in commercial fertilizer. This offsets the need to produce virgin nitrogen compounds, thereby reducing the climate footprint of farming.
– When waste-water treatment plants use our method, they reduce their emissions of nitrogen compounds to nearby water, they reduce their climate footprint, and they save tax payer money. They do this by recovering nitrogen, a valuable nutrient, and making a real contribution towards a circular economy, says EasyMining CEO Jan Svärd.

Today’s nitrogen removal methods commonly release the nitrogen back into the air instead of recovering it. These methods typically use bacteria to separate nitrogen from the water, which also causes emissions of nitrous oxide (laughing gas), a powerful greenhouse gas which speeds up climate change 300 times more efficiently than carbon dioxide. The adsorption agent which crystallizes the nitrogen in the Ragn-Sells process is neither emitted nor consumed, but continually reused.
The project is a partnership between EasyMining, Denmark’s largest waste-water treatment company BIOFOS, Lantmännen, and Ragn-Sells’ Treatment & Detox business area. In the first phase of the project, the construction of pilot facilities is planned, and in three years, the patent will be ready for full commercialization. In addition to the use in waste-water treatment facilities, the method will also be used to treat runoff from landfills.

Through the LIFE programme, the European Union is allocating 3.4 billion euros to environmental and climate-related projects between 2014 and 2020.

Fact sheet: The process EasyMining’s nitrogen removal process is chemical in nature, as opposed to the bacterial methods commonly used in waste-water treatment plants in Sweden and Europe today. Water with a high nitrogen content, such as the water produced from de-watering of sewage sludge, is treated with an adsorption agent, which causes the nitrogen to crystallize and precipitate. Next, the nitrogen is extracted from the crystals and may be used again, while the adsorption agent is circulated back into the process.
The method can be used on any water which contains ammonium. The EU-backed project encompasses use in waste-water treatment facilities as well as runoff from landfills. Additional possible use includes treatment of manure, and liquids from biogas production facilities.

For more information, please contact
Jan Svärd, CEO, EasyMining, +46 70 978 64 74,

Ragn-Sells Media Services,+46 70 927 24 00,

Ragn-Sells board visits EasyMining in Uppsala

The board of Ragn-Sells had a very successful visit at EasyMining to view the new finalized pilot facility in Uppsala as well as discussing the upcoming Ash2Phos full-scale factory.