Emergy evaluation of organic and conventional marine shrimp farms in Guaraíra Lagoon, Brazil

Organic products are often appreciated by the consumers as being more environmentally friendly and sustainable compared to their conventional counterparts. However, in the case of aquaculture, scientific information regarding environmental impacts and costs of conventional and organic farming systems is scarce. Scientific methods able to measure the sustainability of production systems are of great relevance to identify best management practices and ensure consumers the sustainability of the production process of aquaculture products. The objective of this study was to compare organic and conventional marine shrimp farms located in Guaraíra Lagoon, Brazil, using emergy analysis. The principle of emergy analysis is to express all costs of a process or product in solar energy units (sej), making it possible to compare systems with different inputs, outputs and environmental impacts. Emergy accounting was used at this study to integrate ecological and human dimensions of conventional and organic marine shrimp farms systems located at Brazilian northeast in order to better discuss and understand the multiple dimensions of the sustainability in such systems. The results showed several emergy indicators in favor of organic farming system: the renewability indicator, the emergy yield ratio indicator and the emergy investment ratio indicator. Both systems (organic and conventional) showed large flows of concentrated non-renewable emergy. Further improvements of the organic system are needed to increase the efficiency and to ensure its economic sustainability.