Making the most of waste from energy plants 

Bottom ash is a by-product from waste-to-energy plants. Containing large amounts of minerals as well as ferrous and non-ferrous metals, it could be a significant source for secondary raw materials. For instance, some metals found in bottom ash are precious and/or listed as critical raw materials. But recycling materials from bottom ash is hampered by hazardous substances and sub-optimal recovery. Reuse of the mineral fraction is also restricted due to contamination with hazardous substances. This LIFE project plans to improve the recovery of heavy nonferrous metals and the quality of the mineral fraction, using a full-scale treatment facility. Its approach will allow the recovery and recycling of materials that would otherwise be lost or recycled for low-quality applications.













Project objectives

This project aims to demonstrate an integrated, full-scale treatment facility for the different fractions of bottom ash; as each fraction has its own environmental challenges. By demonstrating the technical and economic feasibility, the project contributes to the objectives of EU environmental policy and the circular economy. The objectives are directly aligned to the aims of LIFE. By focusing on an integrated approach, the project will recycle and recover materials that will otherwise not be recovered – or recycled in low-quality applications.

Heros is an innovative recycling company that is specialized in bottom ash recycling. Heros treats 750 ktonnes/year of bottom ash. With its current installations, Heros performs in line with state-of-the-art; and better than EU-average. However, Heros has the ambition to push innovation further and aims for an integrated process for the treatment of the different fractions.

The project will aim at a treatment capacity that consists of 2 integrated processes.

Equiash process: treatment of the 0-2 mm fraction: carbonization, washing and mineralization to remove hazardous substances (cap: 92.000 tonnes).

Jig process: upgrade to the existing wet treatment plant (for 2-16 mm fraction), improving HNF metal recovery and quality of mineral fraction. The upgrade concerns adding three jigs; one for the coarse fraction (2-16 mm) and two for the clinging fine fraction (0-2 mm) (cap: 150.000 tonnes).

The objectives are to demonstrate:

  • Optimal treatment and disposal of hazardous substances from the various fractions of bottom ash slags.
  • Increase of metal recovery from bottom ash slags to 96% for Fe and 88-93% for NF-metals, including investigating the increased recovery of Critical Raw Materials (e.g. Sb).
  • Improved quality of the treated mineral fraction to enable free application of the recycled mineral fraction for civil engineering purposes.

When demonstration results are positive, the project will be a showcase for the recycling of bottom ash. With the current installed WtE-capacity and planned capacity in several Member States, it is expected that bottom ash will remain an important, potential source of secondary raw materials. By demonstrating the innovative method, this project can help shape the development of environmental policy of the EU community by demonstrating what is technically possible (best practices) and what kind of reductions in environmental impact and resource efficiency are realistically attainable.


A. Preparatory actions:

During the preliminary phase, Heros starts with detailed engineering for the permitting procedures. Basic engineering will be carried out before the official start of the LIFE project and will not be part of this application. After detailed engineering, the project can acquire all relevant permits necessary to start the construction of the installation.

B. Demonstration actions:

The project will demonstrate the optimal and integrated treatment and recycling of all fractions of bottom ash. Demonstration actions are necessary to show what is technically possible (best practices) and what outcomes are realistically attainable.

B1: Construction of fully integrated demonstration process:

  • B1.1 - Construction coarse fraction metal recovery
  • B1.2 - Construction Equiash
  • B1.3 - Construction fine fraction metal recovery

B2: Commissioning and testing fully integrated demonstration process

  • B2.1 - Commissioning and testing coarse fraction metal recovery
  • B2.2 - Commissioning and testing Equiash
  • B2.3 - Commissioning and testing fine fraction metal recovery

B3: Demonstration of ASH 2 MATERIAL process

Three sub-actions are necessary to demonstrate the three process components:

B3.1 and B3.3 - Demonstration of the coarse and fine fraction metal recovery (WASI-NF: Upgrade of the existing 2-16 mm fraction wet treatment plant, improving metal recovery). 

Heros currently operates a state-of-the-art wet treatment facility (WASI). This plant removes salts and hazardous substances efficiently from the bottom ash and will be upgraded to further enhance the wet recovery of metals and the quality of the mineral fraction.

Within the existing set-up, additional separators will be placed that will explicitly target the Heavy NonFerrous (HNF) from the 2-16 mm fraction. This will also target the HNF fraction in the limited 0-2 mm fraction that still is clinging to the 2-16 mm fraction.

B3.2 - Demonstration of the Equiash process (i.e. treatment of the 0-2 mm fraction):

Separated fine fraction (0 – 2 mm) will be transported and introduced into the demonstration installation. The installation will consist of 4 specially designed bunker with dedicated systems for the carbonization and washing processes.

B4: Final evaluation of process and market strategy

Final evaluation of the project and its results, including a cost-benefit analysis. Based on this, optimisation steps and an engineering package for production facility will be developed. Also, a market strategy based on market and stakeholder analyses, a replication plan and a business plan for market launch will be developed.

C. Monitoring the impact of the project actions

Monitoring actions are necessary to ascertain and validate the environmental and social benefits of the project. Main objectives of the monitoring actions are: (1) define project indicators from a technical and environmental point of view and monitor them along the lifetime of the project, including a Life Cycle Assessment (LCA); (2) define project indicators from a socio-economic point of view and monitor them along the lifetime of the project. 

D. Communication and dissemination actions

The results of the project will be disseminated to various stakeholders: waste-to-energy industry, policy makers and authorities, customers of building material and metals, technology suppliers, the general public. Specific communication and dissemination actions involved are notice boards, project website, layman’s report, and organization of events, production of brochures, papers and publications.

E. Project management and monitoring

These actions consist of the overall project management, networking with other projects, drafting of an After-LIFE plan, performing an audit and compiling indicator tables on the quantitative and qualitative data of the process.

Sustainability of the Project Results

Heros is fully dedicated to innovation in bottom ash treatment. This project is at the core of its ambition. Heros has drafted a long-term strategy for its sustainability; focusing on: (1) project continuation; (2) replication and transfer.


After successful demonstration of the technology, the project will provide a robust economic business case. Heros strongly believes in the high technical and market potential of this project. Relying on the sustainability of the achieved results in terms of technical and economic viability, Heros will not only continue the exploitation of the project after the project’s completion, but double the plant’s capacity.

In addition, Heros will continue to study possible improvements and optimization to ascertain the full potential of the integrated process. This research involves collaboration with other industries and research partners. Possibilities to increase and diverse market and valorization possibilities of the recovered materials will be continuously analyzed. Activities will be conducted in close collaboration with end-user stakeholders (construction, metallurgical sector). These actions will be covered by Heros’ own resources.

Replication and transfer:

The replication potential of this bottom ash treatment project is promising. Heros will take all necessary measures to ensure the materialization of this potential. A distinction could be made between three layers of replication actions. The first focuses on Heros and other subsidiaries of the REMEX group, the second focuses on the entire European WtE and bottom ash sector and the third on the general public. Heros will communicate about the project, results and the technological innovations implemented. To ensure replication of the project, Heros will also develop information on the economic and environmental performance of the demonstrated project (based on cost-benefit analysis and lifecycle assessment performed in the project).





Update January 2021


Metal Recovery of the coarse fraction in the wet treatment facility


Heros currently operates a state-of-the-art wet treatment facility (WASI). The plant removes salts and hazardous substances from the bottom ash very efficiently. This plant is upgraded to further enhance the wet recovery of metals and quality of the mineral fraction.

This technology is called jig. After the washing drum and screening process, the coarse mineral fraction is passed on to a jig. This fraction - which still contains valuable heavy non-ferrous metals – is swirled in water by a pulsating water flow. The metals sink faster than the ash and collect at the bottom of the jig from which they are discharged through an adjustable weir. The remaining mineral fraction is passed on to a mixing drum. Here it is merged in a fixed ratio with the washed sand fraction.

The metals recovered during the washing process include copper, zinc, lead, stainless steel and small amounts of gold and silver. These valuable non-ferrous metals go to melters and metal processing companies. Using such recycled metals in metal production means a lower carbon footprint, thereby reducing greenhouse gas emissions from metal production.


Administrative data:

Project number: LIFE18 ENV/NL/000436
Project acronym: LIFE ASH 2 MATERIAL
Project title: Integrated full-scale treatment facility for different fractions of bottom ash ensuring safe use as secondary material

Coordinating beneficiary: Heros Sluiskil B.V.

Contact: Mr. Michiel Stokla (M.Stokla@heros.nl)