Biogas production through co-digestion of cattle waste and agricultural residues of tomato cultivation (Solanum lycopersicum l.)

Abstract

Anaerobic digestion is an alternative to reduce pollution problems due to the open sky disposal of waste, such as manures and agricultural residues; besides, it is an option for the generation of alternative energies due to biogas production. The aim of this work was to evaluate the co-digestion of cattle waste with tomato crop residues. The experimental design was completely randomized under a 2 × 2 factorial arrangement, considering two levels of manure (20 and 50 %) and two pH initial levels (6.8 and 7.5). It was found that by adjusting the pH to 7.5 using 20 or 50 % manure, the total production of biogas and methane increased 100 %, compared to that obtained in di-gesters starting at pH 6.8. In digesters where 50 % of manure and 50 % of tomato crop residues were used, the methane content reached 45 %, which is the minimum to be used as combustible. The use of 20 % manure and 80% tomato crop residues produced 35 to 37 % methane. The 50:50 proportion manure:tomato residues best treatment was in with pH adjust at 7.5 . The resulting digestate did not present phytotoxicity in the test with lettuce seeds, and its coliform and salmonella was below those indicated in standard NOM 004-SEMARNAT.