Ash in composting of source-separated catering waste

Area of Science:

• Environmental Science
• Waste Management
• Soil Science

Background:

• Previous studies indicated positive effects of co-incineration ash on composting small batches of catering waste.
• Catering waste composting is crucial for waste reduction and resource recovery.

Purpose of the Study:

• To evaluate the feasibility of using fuel ash as an additive in large-scale (10 m3) composting of source-separated catering waste.
• To assess the impact of varying fuel ash concentrations on the composting process and compost quality.

Main Methods:

• Composting of catering waste mixed with peat, wood chips, and 0%, 10%, or 20% (wt.%) fuel ash in a 10-m3 drum composter.
• Monitoring of temperature, oxygen concentration, and gas emissions (H2S) during drum composting and subsequent curing.
• Analysis of compost for heavy metals, total nitrogen, organic matter mineralization, and humic acid content over two years.

Main Results:

• Fuel ash addition significantly increased compost temperatures, reaching up to 80°C, and accelerated organic matter breakdown (mineralization).
• Ash amendment improved oxygen availability in the drum composter and effectively reduced the formation of hydrogen sulfide (H2S) and other odors.
• Compost with 10-20% ash showed decreased total nitrogen loss over two years and increased humic acid content, while heavy metal levels remained suitable for use.

Conclusions:

• Fuel ash is a beneficial additive for large-scale catering waste composting, enhancing thermal and biological activity.
• Ash amendment improves compost quality by reducing nitrogen loss and increasing humic acid formation, with no adverse odor or heavy metal issues.
• The use of fuel ash in composting offers a sustainable approach to waste management and soil improvement.