Integration of biochar in psychrophilic anaerobic digestion: effects on the digestate quality

• Biochar improves digestate stability by reducing soluble organic compounds by 50%. • Organic carbon and nitrogen in the digestate increased by 150% and 30%, respectively. • Biochar digestate matches urea performance for lettuce growth. • Ammonium and phosphate leaching were reduced by 67% and 50% during fertigation. • Biochar in psychrophilic AD improves digestate agronomic and environmental value.