Assessing biochar impact on earthworms: Implications for soil quality promotion

Area of Science:

• Environmental Science
• Soil Science
• Ecotoxicology

Background:

• Spent coffee grounds (SCGs) are a waste product with potential for biochar production.
• Biochar application to soils can alter soil properties and affect soil organisms.
• The ecotoxicological effects of SCG-biochar on earthworms (Lumbricus terrestris) require investigation.

Purpose of the Study:

• To investigate the potential harmful effects of SCG-derived biochar on earthworms.
• To assess earthworm avoidance responses to biochar-amended soils.
• To evaluate the impact of biochar on earthworm oxidative stress biomarkers and digestive enzymes.

Main Methods:

• Two experiments were conducted: one assessing earthworm avoidance behavior and another analyzing physiological responses.
• Earthworm avoidance response to varying biochar concentrations (1% and 5% w/w) in soil was measured.
• Oxidative stress biomarkers and digestive enzyme activities in earthworms and soil extracellular enzymes were analyzed.

Main Results:

• A significant avoidance response (75%) was observed in earthworms at the highest biochar dose (5% w/w).
• Early signs of oxidative stress were detected in earthworms exposed to 1% and 5% biochar.
• Digestive enzyme activities increased in earthworms after 30 days of exposure, and soil extracellular enzyme activities were higher in the 1% biochar treatment.

Conclusions:

• SCG-biochar can induce avoidance and physiological stress in earthworms at higher concentrations.
• Earthworms may develop antioxidant defense mechanisms, indicating potential for biochar tolerance.
• The combined use of SCG-biochar and earthworms shows promise for soil biochemical improvement, despite potential short-term stress.