PURPOSE: To provide a solid fuel having a high calorific value, generating only a small amount of smoke and exhibiting excellent ignitability, prepared by adding diatomaceous earth, soda ash, a specified adsorbent, a smoking inhibitor and a combustion promoter to peat.

CONSTITUTION: A naphthenic acid-based metal salt (e.g. cobalt naphthenate) as smoking inhibitor, a diphenyl carbonyl type metal compd. (e.g. diphenyl carbonyl magnesium) as combustion promoter and, when necessary, gypsum plaster are blended into a mixture of peat with a water content of 10W15%, diatomaceous earth, soda ash and waste oil or sludge as adsorbent, followed by granulation of the mixture.

EFFECT: The resultant solid fuel has a calorific value of 6,000Cal/kg in combustion.