Sustainable scale-up of Irish seaweed production: Quantifying potential environmental, economic, and social impacts of wild harvesting and cultivation pathways

Seaweed is a versatile bioresource which can be used as a source of food, feed, fertilizer, and higher-value products. Countries with extensive sea areas such as Ireland have the potential to produce significant volumes domestically, but limitations and consequences to this potential should be considered. This study aims to capture the environmental, economic, and social consequences of different pathways for scaling up Irish seaweed production using a life cycle sustainability assessment (LCSA) framework. Six pathways are considered: manual wild harvesting by foot, manual wild harvesting by boat, mechanical wild harvesting by trawler, and three longline cultivation systems. Environmental, economic, and social impacts are considered through quantifying exergy extraction (MJex), global warming potential (kg CO2-eq), minimum selling price (MSP), and improvements in human wellbeing (HP). Finally, limitations to scale-up are assessed. The results demonstrate that manual wild harvesting has a relatively low climate impact (0.03–0.04 kg CO2-eq/kg fresh seaweed), resource intensity (1.75–2.00 MJex/kg fresh seaweed), and MSP (0.10–0.12 €/kg fresh seaweed), but a low increase in wellbeing (5.01–5.45 HP/kg fresh seaweed), while mechanical wild harvesting has a worse performance than manual harvesting in every dimension (0.14 kg CO2-eq/kg fresh seaweed, 3.50 MJex/kg fresh seaweed, 0.16 €/kg fresh seaweed, 0.60 HP/kg fresh seaweed). The impacts of cultivation pathways vary significantly, but generally perform better than wild harvesting for social impacts (18.53–20.59 HP/kg fresh seaweed) and worse for environmental and economic (MSP) impacts (0.12–0.35 kg CO2-eq/kg fresh seaweed; 2.30–5.95 MJex/kg fresh seaweed; 1.05–1.80 €/kg fresh seaweed). Nonetheless, limitations to upscaling manual wild harvesting (max 8.4 % of a future production target of 900,000 t fresh seaweed) determine that both mechanical wild harvesting and cultivation pathways will be needed to achieve future targets. It is therefore important that steps be taken to optimize each of these pathways based on the overall priorities of society.