Summary of Key Points
Policy requirements call for the national proportion of hazardous waste landfills to be reduced to less than 10% by 2030, with fly ash (the residue from waste incineration, which is classified as hazardous waste) being targeted for increased resource utilization. This shift shifts the focus from primarily using landfills to prioritizing recycling, opening up new markets. However, this business is not simply about turning waste into treasure; there are three critical considerations that must be addressed: who will pay for the treatment, what will become of all the resulting products (including residues), and whether costs can be matched with revenues. While landfilling remains a legal option, it has dropped from being the default choice to a last-resort solution. The demand for resource utilization is essentially driven by the narrowing of landfill options.
I. Policy Forces Fly Ash to Find New Paths, but Landfilling Is Still Not Completely Abandoned
In the past, many cities would directly bury fly ash in landfills after stabilizing it. Now, policies require a reduction in the use of landfills (for example, Shanghai aims for zero landfilling by the end of 2026). Nevertheless, the reality is that most fly ash is still being landfilled: in Chongqing, 200,000 tons out of 210,000 tons of fly ash generated in 2024 were buried; in Quanzhou, nearly all 100,000 tons of fly ash generated in 2025 were landfilled.
Why? Because landfilling is still legal and compliant (as long as it meets the standards), it's just no longer the preferred method. The increase in resource utilization is not due to a sudden surge in demand for products but rather because landfill options are becoming increasingly limited—new incineration plants must plan for the disposal of fly ash, and old plants need to find alternative solutions. Therefore, the starting point for fly ash resource utilization is a necessity, not a desire to produce recycled materials.
II. Fly Ash Is Hazardous Waste, and Resource Utilization Must Meet Safety Standards
Fly ash is classified as "hazardous waste (HW18)" due to three toxic components: heavy metals (such as lead and mercury), dioxins (carcinogenic substances), and high levels of chlorides (which can affect product quality and the environment). Any resource utilization technology must address these issues:
- Washing with water can remove chlorides, but this generates high-concentration brine that needs to be treated to avoid new pollution.
- Pyrolysis can break down dioxins, but the remaining heavy metals and residues still need to be managed.
- High-temperature melting can convert ash into a glassy solid to stabilize the heavy metals, but this process is energy-intensive and costly for flue gas treatment.
- Co-utilization in cement kilns (using fly ash as raw material for cement production) requires dechlorination, and it depends on whether nearby cement kilns are willing to accept it.
Even if the treated products meet standards, they cannot be used indiscriminately—for example, they cannot be used in sintered bricks, as dioxins may be re-generated during the sintering process. Resource utilization is not about giving a new name to the waste; it involves breaking down a major hazardous waste issue into smaller, more manageable problems, each of which must be addressed thoroughly (such as how to dispose of the brine and where to store the residues).
III. Treatment Fees Are the Foundation of the Business, while Product Revenue Is Additional
Many people think that fly ash resource utilization generates profits from selling products, but this is incorrect. The first source of revenue comes from treatment fees. For instance, in Yiwu, the cost for treating fly ash in 2025 was 1,669 yuan per ton; in Yixing, the proposed fee for the "washing + pyrolysis to produce rock wool" process is 2,180 yuan per ton.
Why pay? Because companies must cover costs related to hazardous waste transportation, pollution control, energy, chemicals, and residue disposal—these expenses do not disappear just because the products can be sold. Treatment fees ensure that fly ash is legally disposed of, while product revenue helps reduce overall costs (for example, selling the extracted salt can mitigate losses). The essence of fly ash resource utilization is selling a service, not recycled materials.
IV. No Single Technology Is Suitable for All; It Depends on Local Conditions
No single technology solution works for every situation; local factors must be considered:
- Washing + Cement Kilns: Suitable for areas with nearby cement kilns, but dechlorination must not affect cement quality, and the transportation distance must be limited.
- Washing + Low-Temperature Pyrolysis: Used in Shanghai's Liming project to produce potassium chloride, sodium chloride, and detoxified ash, requiring additional water treatment and salt separation equipment.
- High-Temperature Melting: Can stabilize heavy metals but is energy-intensive and requires a stable market for the resulting products (such as rock wool).
- In-Site Co-Utilization: Washing fly ash before returning it to the original incinerator is suitable for plant upgrades, but it may not accept waste from other sources.
Therefore, technology choices are localized—cement kilns are preferred in areas with a cement industry, melting processes are chosen where energy costs are low, and other solutions may be necessary in regions without related industries.
V. The Success of the Business Depends on a Complete Closure Loop and Financial Sustainability
Building a production line is easy, but making a profit requires careful consideration of four aspects:
1. Source of Fly Ash: Is the supply stable? Are the chloride and heavy metal levels within acceptable limits? Is the transportation distance reasonable? Can treatment fees cover all costs?
2. Pollution Control: How will the brine generated be managed? Will flue gas emissions meet standards? Where will the residues be disposed of? We cannot turn one hazardous waste into another more difficult-to-manage form.
3. Product Quality: Is the purity of the produced salt sufficient? Can the detoxified ash be sold to cement plants? Are downstream customers long-term partners or just trial users? Without a market for qualified products, they will become inventory.
4. Net Costs: Treatment fees plus product revenue minus transportation, energy, labor, and depreciation must result in a profit. For example, the Liming project in Shanghai invested over 80 million yuan; it's not just about purchasing equipment but also ensuring a complete supporting system.
Only when all these aspects are balanced can the business be sustainable. Policy creates demand, but ultimately, financial viability determines success.
In Conclusion
Fly ash resource utilization is not a romantic story of turning waste into treasure; it's a practical business driven by policy requirements, cost calculations, and a closed-loop management of materials. Companies that succeed must secure a stable supply of fly ash, choose the right technology for their location, properly manage all products (including wastewater and residues), and accurately account for every expense. Otherwise, even if the products meet standards, the business will not be viable.