Abstract
Fresh vegetables available on Northern European markets usually originate from a high number of sources. Environmental impacts for these goods typically arise from the resources used in production and the long-distance transport in air-conditioned trucks. As such, environmental impacts are mainly attributed to direct energy consumption, water use and nutrient supply. The aim of this paper was therefore to investigate and evaluate possible solutions to reduce the environmental impacts of vegetables available on urban markets in Northern Europe. We hypothesise that for the production of lettuce and tomatoes in Northern Europe, a 4-step solution, i.e. 1) local production, 2) climate-controlled efficient greenhouses, 3) decoupled aquaponics, and 4) combined building architecture with waste heat and green waste reuse, will enable a low environmental impact. We defined the metropole Berlin as case example, and used simulation results from a proven greenhouse simulator as input to a comparing life cycle assessment of fresh lettuce and tomato. The assessment included a list of 12 midpoint environmental impact categories, e.g. global warming potential with 100 year horizon (GWP100; kg CO2 eq.), depletion of fossil fuel reserves (FRS; kg oil eq.), and water use (WCO; m3 water). Most impact categories decreased systematically when increasing the complexity of the local vegetable production. Compared to the mix of vegetables from different locations available on the market, the complete 4-step solution reduced WCO from water consumption to water saving: i.e. from 14.2 L or 3.3 L to −10.1 L or −0.21 L per package of 500 g tomatoes or 150 g lettuce, respectively. GWP100 and FRS were below the values of the available market mix, e.g. GWP100 decreased with 8.7% in tomatoes and 49.9% in lettuce. In conclusion, with the right set-up, local vegetable productions in urban regions can surpass the imported mix on environmental performance in Northern Europe.
Highlights
Aquaponics is the combined cultivation of fish in recirculating aquaculture systems (RAS) and plant hydroponics (HP)
A comparative LCA of tomato or lettuce produced in decoupled aquaponic systems (DAPS) or produced in HP was performed with different benchmark scenarios (Table 1)
For tomatoes produced in Germany, heating has a total consumption of 1.38 GJ m− 2 per year, which is more than eight times higher than that in Spain
Summary
Aquaponics is the combined cultivation of fish in recirculating aquaculture systems (RAS) and plant hydroponics (HP). In these com bined systems, two products are produced simultaneously with almost the same amount of resource input when the system is optimally balanced (Goddek and Korner, 2019). Additional advantages are syn ergistic effects with substantially increased crop production that have been observed in some crops (e.g., in lettuce) (Delaide et al, 2016; Goddek and Vermeulen, 2018), decreased energy use (Korner et al, 2017), and a lower environmental impact compared to production in independent systems (Ghamkhar et al, 2020). Compared to CAPS, where RAS water is directly recirculated via the HP subsystem, decoupled aquaponic sys tems treat the water by adjusting the quantity and quality to the actual crop demands. Since not all nutrients required by the crop are available from the RAS subsystem (Kloas et al, 2015), decoupled aquaponic
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