Life Cycle Assessment of Lettuce Production Systems : A Case Study Performed at Hollbium

Sammanfattning: Agriculture is one of the most carbon-intensive sectors in today’s world. With demand for food soaring to feed an ever-increasing population, many methods are employed to produce food, ranging from open-field to greenhouse systems. However, due to their large environmental footprint, urban agriculture methods such as soilless culture systems are increasingly becoming a preferred method for food production. A case study has been performed at Hollbium in Stockholm, Sweden for the purpose of evaluating potential environmental impacts of Hollbium Loop, a vertical hydroponic system used for food production. This is achieved by carrying out a stand-alone assessment of Hollbium Loop, to identify potential environmental hotspots over the product’s lifetime of 10 years. Furthermore, Hollbium Loop’s system is compared to the production of lettuce in a horizontal open-field, a greenhouse farming system and nutrient film technique located in Spain, to identify potential trade-offs. Attributional life cycle assessment (ALCA) has been employed as a methodology with an explicit focus on eight impact categories at a midpoint level. The results of the study indicate that hotspots of environmental impacts in Hollbium Loop’s life cycle are due to the use of an internal combustion engine vehicle for maintenance, production of electronic components and the consumption of electricity in the use phase. In contrast, the results from the comparative scenarios indicated that Hollbium Loop from a life cycle perspective had the highest impacts under all impact categories in relation to the other three systems of food production. When the distance for transportation within the maintenance phase is reduced to a reasonable figure, Hollbium Loop no longer had the highest impacts within global warming and fossil resource scarcity, showing that the distance traversed plays a key role in mitigating the impacts. Other aspects and assumptions are also analyzed further using a sensitivity analysis, which shows that there is scope for decreasing Hollbium Loop’s environmental footprint. It is therefore recommended that Hollbium puts its efforts into optimizing the distance and modes of transport utilized and increasing the outer frame thickness of the Loop to make it sturdy and robust. Finally, it is also advised to increase the Loop’s vertical length to increase the yield per cycle, thereby reducing the overall impacts per kilogram of lettuce produced.