Biogas production using biomass from tree branches and sewage sludge in the municipality of Recife (PE)

Abstract

Adequate management of urban solid waste makes a better municipal administration of these materials. The production of biogas from the anaerobic biodigestion from the pruning of tree biomass with sludge as inoculum is analyzed. Chemical characteristics of fertilizers acquired by aerobic and anaerobic processes are compared. Raw material used as substrate comprised sewage sludge from the effluent treatment plant of the Camará Reserve, in Camaragibe, Brazil, and biomass from tree pruning in Recife PE Brazil. Experiments were carried out in a laboratory and evaluated different compositions of pruning biomass, sewage sludge and water to determine the best efficiency for biogas production. The gases released were analyzed on a chromatograph to determine methane contents. Fertilizer from the composting process by EMLURB and the organic fertilizer of anaerobic digestion were chemically analyzed with regard to macronutrients, carbon and C/N ratio. Under such conditions, 40.2 MWh of electricity could be generated from the biodigestion of pruning biomass, with gross income of approximately R$ 29.6 thousand per year in electricity expenditures in the municipality. In the case of the production of fertilizer, the composting and anaerobic digestion processes showed compounds with C/N ratio of 9.7 and 18.6, respectively, not differing in N, K, P and Ca levels.