A chemical mixture for treating biodegradable materials which when subjected to anaerobic decomposition generate environmentally harmful gases such as methane and hydrogen sulfide. The chemical mixture includes chemicals for inhibiting the production of methane and hydrogen sulfide (H2S). The mixture may be formed by: (a) combining compound(s) which inhibit the production of methane gas with compound(s) which inhibit the generation of hydrogen sulfide; and/or (b) using one or more compounds which can perform both functions. The biodegradable materials include all types of paper products. A liquid may be added to the chemical mixture to form a solution which may be applied, in any suitable manner, to biodegradable materials at any point during the manufacture of the materials and/or after the biodegradable materials are disposed of and ready for decomposition.