Spent Mushroom Substrate and Electric Arc Furnace Dust Recycling by Carbothermic Reduction Method

Author: mycolabadmin
4/3/2022
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Summary

Scientists discovered that leftover material from mushroom farming can replace expensive coal-based chemicals used in recycling steel furnace waste. By heating this mushroom waste, they recovered valuable zinc while reducing carbon dioxide emissions by 23,000 tons per year. This innovative approach solves two environmental problems at once: it recycles agricultural waste that would otherwise be landfilled, and reduces emissions from industrial metal processing.

Background

Spent mushroom substrate (SMS) is an agricultural waste exceeding 300,000 tons annually in Taiwan with limited recycling channels. Electric arc furnace dust (EAFD) is toxic industrial waste containing valuable zinc that is currently processed using expensive metallurgical coke as a reducing agent, generating significant CO2 emissions. This study explores simultaneously recycling both wastes using SMS as a biomass-based alternative to coke.

Objective

To investigate the feasibility of using spent mushroom substrate as a reducing agent to replace metallurgical coke in the carbothermic reduction of electric arc furnace dust for zinc recovery. The study examines the effects of torrefaction, volatile matter content, and carbon-to-oxygen ratios on zinc removal efficiency and productivity.

Results

SMS reduced zinc removal temperature by approximately 150°C compared to coke (achieving 95% removal at 1100°C versus 1250°C for coke). Volatile matter in SMS generated hydrogen that enhanced reduction efficiency, allowing C/O ratios as low as 0.16 while maintaining 98% zinc removal. Torrefied SMS at 500°C achieved nearly equivalent zinc productivity to coke at 1200°C. CO2 emissions were reduced by 23,000 tons annually when processing 120,000 tons of EAFD.

Conclusion

SMS is a viable renewable alternative to metallurgical coke for EAFD recycling, achieving high zinc recovery at lower temperatures with significantly reduced CO2 emissions. The volatile matter content in SMS provides additional reducing capacity, and torrefaction improves efficiency. This approach creates a circular economy solution for both agricultural and industrial waste streams.

Published in:Materials (Basel),
Study Type:Experimental Research,
Source: 10.3390/ma15072639, PMID: 35407972