Environmental impacts
Land use
There is minimal land use associated with the culture of microalgae, especially if onshore production is located on marginal, non-arable lands.[1] Some microalgae production happens in fermenters, which require feedstocks for growth, including sugars, the production of which requires land.[2]
Macroalgae do not require land use except for onshore processing, which is minimal. For both sugar kelp and Spirulina or Chlorella, land use is lower to significantly lower than conventional sources of protein.[3]
Water use
The main use of freshwater for the production of microalgae is for cultivation – freshwater provides the environment in which microalgae grow – and washing the biomass acquired after filtration. This has been shown to consume only small amounts of freshwater per kilogram of product compared to beef meat production, which itself consumes more water than any other protein source.[4]
Macroalgae, by contrast, is grown in seawater, yet is washed and blanched in freshwater post-harvest, to clean it and reduce iodine content.[5] Blanching in seawater enables reducing iodine content too, and is being adopted by kelp producers in Europe.
While explicit comparisons with conventional sources are lacking, it is highly likely that freshwater use required for sugar kelp is less than for conventional proteins.
Greenhouse gas emissions
Emissions from macroalgae production vary greatly depending on the location, as they tend to be adapted to local conditions. They include the production of ropes and buoys, as well as operation of boat transportation and processing (drying and freezing).[6]
Current modes of protein-production have been shown to have a significantly greater global warming potential than soybean production, although the potential for lower impact than soybean production has been anticipated.[7]
Claims that seaweed supply chains could have a net negative carbon impact have been disputed.[8] However, as a food source, the production of microalgae or macroalgae currently results in fewer emissions than the animal-based conventional protein sources considered (beef, chicken, dairy).[9]
Waste
Minimal waste is generated from algae production. That consists principally of wastewater following cultivation (microalgae), washing (microalgae and macroalgae) and blanching (macroalgae).
[1] Tzachor et al., 2022.
[2] Araujo et al., 2021.
[3] Parodi A, Leip A, DeBoer IJM, Slegers PM, Ziegler F, Temme EHM, Herrero M, Tuomisto H, Valin H, Van Middelaar CE, Van Loon JJA and Van Zanten HHE, ‘The potential of future foods for sustainable and health diets,’ Nature Sust. 1: 782-789, 2018, https://doi.org/10.1038/x41893-018-0189-7.
[4] Tzachor A, Smidt-Jensen A, Ramel A, Geirsdottir M, ‘Environmental Impacts of Large-Scale Spirulina (Arthrospira platensis) Production in Hellisheidi Geothermal Park Iceland: Life Cycle Assessment’ Maritime Biotechnology 24: 991-1001, 2022, https://doi.org/10.1007/s10126-022-10162-8.
[5] Wirenfeldt CB et al, ‘Post-harvest quality changes and shelf-life determination of washed and blanched sugar kelp (Sacharina latissima)’ Sec. Food Biotechnology, 2, 2022, https://doi.org/10.3389/frfst.2022.1030229
[6] Hasselström L, Thomas J-BE ‘A critical review of the life cycle climate impact in seaweed value chains to support carbon accounting and blue carbon financing.’ Clean Environ Syst 6:100093, 2022. https://doi.org/10.1016/j.cesys.2022.100093.
[7] Koestling et al., 2021.
[8] Hasselström L, Thomas JBE, ‘A critical review of the life cylce climate impact in seaweed value chains to support carbon accounting and blue carbon financing’, Cleaner Environmental Systems, 6: 100093, 2022.
[9] Parodi et al 2018; Tzachor et al. 2022.