Recycling diatomaceous earth waste: Assessing its physicochemical features, recovery techniques, applications, viability and market opportunities

Diatomaceous earth (DE) is widely used in industrial filtration processes, such as in beer, wine, and oil refining, producing significant amounts of diatomaceous earth waste (DEW) as a byproduct. DEW has been explored for various recycling applications, including adsorbents, filters, insecticides, and as a raw material for hydraulic and alkali-activated binders and clay-based ceramics. Despite its potential, the recycling process for DEW remains underdeveloped. This article presents a comprehensive review of the technological, economic, and environmental aspects of DEW recycling, including risk classification by regulatory agencies, alternative recovery methods, and potential pathways for recycling into various products. Given the limited data on DEW generation, an estimation of Brazil’s DEW output is also provided. The recycling potential of DEW is critically assessed through the CPQvA methodology, which follows a structured sequence of analysis: (i) classification (legislation and standards), (ii) potentiality (physical and chemical properties), (iii) quantity and viability (production and disposal concerns), and (iv) application possibilities based on existing literature. To critically analyze the potentiality of DEW, experimental results are also presented for DEW from a Brazilian brewery and compared with global samples. This includes comprehensive chemical, physical, and thermal analyses. Additionally, thermal treatments at 400 °C, 500 °C, and 1000 °C were applied to investigate the removal of volatile compounds and the restoration of its original properties. The results are in-depth discussed and compared with DEW and raw DE data from the literature. • DEW mainly contains silica with variable crystallinity. • DEW traits vary by source and beneficiation. • Recyclability depends on amorphicity and volatile content. • Thermal, chemical, and biological recovery processes can restore DEW properties.