Life Cycle Assessment (LCA) of Microalgae Biofertilizer and Comparison of Scenarios for Its Application in Soil

The reliance on synthetic fertilizers in agriculture contributes significantly to greenhouse gas emissions and environmental degradation, highlighting the need for sustainable alternatives. This study assessed the environmental impacts of producing a biofertilizer based on the microalga Scenedesmus obliquus BR003 at pilot scale using Life Cycle Assessment (LCA). The cradle-to-gate system boundary included cultivation, harvesting, and processing. The functional unit was 1 kg of biofertilizer, with impacts quantified using the ReCiPe 2016 Midpoint (H) method in OpenLCA. Water consumption and global warming were the most impactful categories, with electricity as the main hotspot; the global warming potential was 17.6 kg CO2 eq/kg biofertilizer. A separate assessment was conducted to compare the environmental performance of six maize treatments based on their production of dry matter, extending the system boundary to cradle-to-farm-gate. T2 (microalgae biofertilizer supplemented with inorganic P and K) and T4 (conventional NPK fertilizer) showed the best agronomic performance and were selected for comparison. Under the deterministic model, T2 showed lower impacts than T4 across all categories evaluated, including a net negative global warming potential (−0.649 kg CO2 eq) versus a positive value for T4 (0.057 kg CO2 eq), reflecting urea replacement and increased soil carbon sequestration. These findings support microalgal biofertilizer as a lower-impact alternative to conventional fertilizers under the modeled conditions.