Scientific Article for Students

Introduction What does “environmentally friendly” mean to you? You might think of recycling programs, reusable bags, or windmills. You probably didn’t picture seaweed! There are lots of things to like about seaweed. Seaweed can be delicious, like the nori used for sushi and maki rolls. Kelp forests in coastal oceans are home to animals like otters and porpoises. Seaweed can even help clean up the ocean by absorbing pollution from farm runoff! People have been talking lately about seaweed farming as a way to help fight climate change. The amount of carbon dioxide (CO2) in the atmosphere has gone up and up. This is because people burn so many fossil fuels for energy, like coal, gasoline, and oil. CO2 traps heat in the atmosphere, causing the Earth to warm up. That makes it harder for plants and animals to survive. So what can we do? We need to lower CO2 emissions. And we need to find ways to remove CO2 from the air. Seaweed farming could help with both of these things! A lot of the CO2 in the air is absorbed by the ocean. When seaweed grows, it absorbs CO2 from the water and turns it into biomass. This biomass can then be used in a variety of ways to remove the carbon from the environment. One thing people have proposed is sinking the biomass deep into the ocean. Others are working on seaweed-based products which have lower carbon footprints than many current products. Could using more seaweed products lower CO2 emissions? What are the best things we could do with seaweed biomass to lower emissions? We think these are important questions to answer! Methods Our study focused on seaweed farming in British Columbia, Canada. Its long coastline has lots of areas and native kelp species suitable for farming. We labeled these places on a map (Figure 1). We came up with five scenarios to explore. Each scenario examined different combinations of answers to the questions: Where can we farm seaweed? Only in shallow water, or in deep water too? Close to towns, or far away? How fast do we expect the seaweed to grow? Slowly, like in real seaweed farms near British Columbia? Quickly, imagining creative farmers come up with new techniques? What do we do with the seaweed after it’s grown? Let it sink and decompose? Drag it to the deep ocean and sink it? Sell the seaweed to make useful products? We developed a mathematical model to explore these questions. It uses a set of equations to track how much carbon seaweed removes from the ocean when it grows. The model also tracks the carbon emissions from running the farm, processing the harvest, and transporting it. With our five scenarios, we looked at how seaweed could be used in different ways, like being stored in the deep ocean or making various replacement products like fertilizer, biofuel, and food. By comparing how much carbon is stored or replaced, we can calculate the carbon emissions avoided with the farmed seaweed. Results Is growing seaweed in the ocean a good method for CO2 removal? It turns out that it’s not. In all our scenarios, the amount of carbon removed was less than the carbon emissions from seaweed farming (Figure 2). Growing seaweed and letting it sink in place can remove a little bit of carbon dioxide from the water, but not enough. We checked whether growing seaweed in more places on the map would help. We also looked at increasing the growth rate, imagining the seaweed could grow more than 10 times as fast. We even tested the idea of dragging seaweed out to the deep ocean and sinking it there. That removes a bit more. But none of these things were enough to make up for emissions from production and transportation. Could using more seaweed products lower CO2 emissions? Yes, indeed! By far the biggest impacts come from avoiding CO2 emissions. Using seaweed to replace more carbon-intensive products leads to much lower carbon emissions in the future. In our best scenario, using seaweed to replace other products avoids 10 times more CO2 than just sinking it in the ocean! Discussion Our study shows that growing and harvesting seaweed can help with climate change and its impacts on the oceans. But it’s not as simple as just growing more seaweed. Instead, the best thing we can do with seaweed to make a positive impact is to use it to replace other products. Why is that? Growing seaweed does not generate very much CO2. So using seaweed instead of another product made with fossil fuels means that the total CO2 emissions can be lowered. Seaweed has many uses as a food. You can make pickles, dry it to make snacks, put it in soups, or even make cooking oils from it. It’s not yet a common ingredient in Canada or the US, but it’s a major crop in many Asian countries. Growing plants for animal feed is a big source of carbon emissions worldwide. The right kinds of seaweed can be healthy for many farm animals. Using seaweed for animal feed would also make it so that less land would need to be used for farms. And the uses of seaweed aren’t limited to foods! It can be used to make fertilizer, plastic, shampoo, and even fuel. Conclusion There are lots of exciting ideas for how we slow down climate change. Renewable energy like windmills and solar panels let us make electricity without burning fossil fuels. Electric cars make it possible to drive without burning gasoline. From our study, we’ve learned that seaweed products can be a good way to help lower CO2 emissions. But as with any new product, it’s going to take a lot of creativity for people to find the best ways to use seaweed in their daily lives. Think about your day-to-day activities at home and at school. How many things can you find that could be replaced with seaweed products?