Life Cycle Assessment of Biogas: Evaluating Scenarios for Electricity Generation and Upgrading to Biomethane

Abstract

The energy use of biogas in Brazil still faces significant technological and logistical challenges, despite the high availability of raw materials. This study evaluates the environmental viability of biogas from cattle manure in a small-scale plant using a well-to-wheels life cycle assessment (LCA) approach. The motivation is to overcome barriers to biogas-to-biomethane conversion in Brazil. Comparing environmental impacts across scenarios helps identify key technological differences, strategies for broader adoption, and ways to integrate small-scale plants as viable producers. The benchmark scenario involves biogas for electricity and heat generation. In contrast, three biomethane upgrade scenarios were proposed, utilizing pressure swing adsorption (PSA), membrane separation (MS), and high-pressure water scrubbing (HPWS), with biomethane used as vehicle fuel. A fourth scenario assessed the direct application of manure as organic fertilizer. Results show that the benchmark performed better than biomethane in acidification (14%) and eutrophication (21%) but was less effective in climate change compared to manure application. Among upgrading technologies, HPWS had the lowest climate change impact (3.16 × 10⁻³ kg CO₂ eq./MJ), MS performed best in acidification (4.33 × 10⁻⁵ kg SO₂ eq./MJ), and PSA had the lowest eutrophication impact (3.61 × 10⁻⁶ kg PO₄ eq./MJ), 53% lower than MS and HPWS. Manure application had the lowest primary energy demand and negative GWP due to avoided synthetic fertilizers, but eutrophication was ten times higher than the benchmark (1.27 × 10⁻³ kg PO₄ eq./MJ), requiring optimized nutrient management. These findings provide insights into upgrading technologies and manure management to support sustainable strategies in Brazil’s energy transition.