Estimation of environmental impact of conversion to organic agriculture in Hamburg using the Life-Cycle-Assessment method

Summary

Commissioned by the Ministry of Environment of Hamburg, Germany, an environmental impact assessment using the Life-Cycle Assessment (LCA) method was carried out during 1995 and 1996. In a scenario, the effect of a complete transition from conventional to organic agriculture of about 5,674 ha and 4,669 livestock units in a rural part of Hamburg was investigated using 9 impact categories. The study was based on the analysis of 15 farms representative of the farms in the region, mainly dairy and beef cattle farms with some cash crops, in close cooperation with local advisers and other experts. Several workshops were held to integrate the local public, in particular the experts and administrative staff related to farming and nature protection.
It was estimated for the study area for the year 1995 that through the conversion to organic agriculture, the eutrophication potential could be lowered by reducing the nitrogen (N) surplus by 75% (from 311 t to 77 t) and turning the phosphate (P) surplus of 47 t into a deficit of 19 t. The ammonia emission decreased to 69% of the conventional level (from 238 t to 165 t) resulting in a similar reduction of the acidification potential (from 474 t to 328 t SO2-equivalents). Compared to conventional farming, 55% of the primary energy was saved by organic agriculture (38,540 instead of 84,760 GJ), which also lowered the global warming potential by 31% from 26,365 t to 18,271 t CO2-equivalents. No pesticides were used, thus saving about 22.7 t of chemical agents. This would lead to positive effects in the impact categories drinking water quality, human toxicity and ecotoxicity, especially as most pesti¬cides were applied illegally and not in compliance with the regulations regarding minimum distance to surface water. The biodiversity impact assessed by evaluating several indicators during field visits showed a clear improvement for arable land, permanent grassland and landscape structures (such as ditches and field boundaries). No differences were determined for the categories soil protection and landscape image due to specific site conditions and cropping system effects. The study confirmed the suitability of the LCA approach for com¬paring different farming systems. However, the results led to strong reactions from some experts and particularly farmers and their representatives.