Highlights
•Biogas production from rice husks (RH) was investigated using cow rumen fluid as a source of inoculums.
•Feedstock to water dilution ratio of 1:6 w/v gave the best biogas yield.
•Initial pH of 7 gave the maximum biogas yield.
•Addition of heavy metals (Ni2+, Zn2+, and Cu2+) improved biogas production.
•The use of poultry droppings (PD) as nitrogen supplements encouraged biogas generation.