Seaweeds, the coming revolution

Seaweeds, the coming revolution
Ignored yet potentially top players in the bioenergy vs. food game.

Ricardo Radulovich

Climate change and bioenergy agriculture and photosynthesis have placed back into the main stage. Besides the opportunities, looking like some cream on top of a glamorous and subsidized market, many questions remain unanswered. These are being addressed by many with a discourse that envisions "a world of clean fuels in lush fields produced by prosperous farmers" (1), forging an energy-independent "bio-economy" based on "multifunctional" agriculture (2). All of this supported by a detailed accounting of biomass sources, including animal dung and coconut husks together with corn and sugarcane (3).

Others, however, are more cautious. New and old problems have been rapidly evidenced by this change in the traditional purpose of agriculture and pressure to expand. Of particular relevance are environmental costs, including deforestation, water and greenhouse gases, energy-efficiency limitations, and food and nutrition issues affecting poor people the most. For example, an OECD-FAO joint panel views biofuel technologies and policies as uncertainties that could dramatically impact food prices (4) (and they have risen), while IFPRI's models predict that expanded biofuel production will also be accompanied by "a net decrease in the availability of and access to food, "adding that" subsidies for biofuels that use agricultural production resources are extremely anti-poor. "(5)

Yet, and save for a brief mention in a recent paper by the Royal Society (6), the main potential player in this race bioenergy, biomass production at sea, is ignored (1,2,3,4,5,7). However, the oceans, the largest active carbon sink in the planet, cover over 70% of its surface area (predicted to grow with rising sea levels), and receive an even larger proportion of photosynthetically active radiation (due to an even larger coverage is at the tropical and subtropical belts) which goes largely unused for this purpose since, it is estimated, only 50% of the world's photosynthesis takes place naturally there, mostly through phytoplankton (8)-in other words, to the eyes of an agriculturalist, the oceans should be seen as vast and grossly underutilized fields well provided with water and insolation.

While humanity evolved millennia ago from hunting-gathering into agriculture, the cultivation of the Seas had to wait until recent years, when aquaculture, mariculture and within it something in the term "blue revolution", entered an exponential phase of growth as its potential begun to unfold (coincidentally with reaching and surpassing the limits of sustainable fisheries).

According to FAO (9), aquaculture production moved from less than a million tonnes in the early 1950s to 59.4 million tonnes, with a value close to U.S. $ 70 billion in 2004. However, 91.5% of this production came from Asia and the Pacific region, while the European region contributed 3.9%, Latin America and the Caribbean 2.3%, 1.3% North America, and the Near East and Africa 1.1%. Of this, 99.8% of cultured aquatic plants, with a market of billions of U.S. $ and million tonnes of seaweed biomass produced per year, come from Asia and the Pacific region, mostly from China, Japan and Korea (10).

Thus, agriculture, based on the systematic use of plants to harvest solar energy, has already evolved to the sea, though not in the Western hemisphere.

Currently, only macro-algae (seaweeds) are cultivated at sea, for which very simple mechanisms are used (mainly tying them to anchored floating lines). Intensive and CO2-enriched micro-algae culture for energy in saltwater tanks on land is a very different and specialized niche. Seaweeds resemble higher plants in many ways, including appearance and size, while not in others since they do not require soil (nor its cultivation), and are already provided with all the water they need (in itself a major advantage since water is the most limiting factor for the expansion and, faced with climate change, even the survival of agriculture, a view upheld by the CGIAR to the point of saying "is about gas mitigation, adaptation is about water" (7)-which is also the reason why I turned to the sea years ago).

Seaweeds are classified into three broad groups based on pigmentation and other characteristics: brown (Phaeophyceae), red (Rhodophyceae) and green (Chlorophyceae). Many species are known evidencing a vast potential, though only a few are currently harvested or cultivated to any extent (9.10). Historically, seaweeds have been valued around the world for a variety of uses, mainly for food, but also for fertilizer, feed, and a growing phycocolloid industry currently valued at billions of U.S. $. Though harvesting from the wild is significant and hard to quantify, the FAO estimates that a large percentage of world production is from cultivation (10). This is important since harvesting massive amounts of naturally occurring seaweed populations (eg, the Sargasso Sea) could be equivalent to large scale deforestation in terms of atmospheric CO2 addition and habitat loss and fragmentation.

Early attempts to Cultivate seaweeds for biofuels date back to the 1970s, particularly in the USA through what came to be known as the Giant Kelp Project, apparently with a counterpart in Japan (11), and sought to produce methane from biomass. Such efforts faced several seaweed and energy production problems and were filed as unfeasible. Given that seaweed cultivation and biofuel production techniques have greatly advanced in recent years, and for the many reasons already presented, it is obvious that not only feasibility but most likely the need is now at hand. At least us in Costa Rica and others in Japan (11) are restarting the production of seaweeds for energy.

Energy applications from seaweed biomass are similar to those from land vegetation. The simplest option is direct burning for electricity and heat generation, such as it is currently done with bagasse from sugarcane and not unlike coal-fired power plants in principle-in fact, co-firing biomass together with coal is already implemented, partly to reduce net CO2 emissions in the electrical power sector. Next is the production of biofuels like ethanol, biodiesel and methane. Current biofuel production technologies may suffice for some cases, while next generation technologies will come to improve biofuel yields.

However, even if only for burning to generate electricity, seaweed cultivation can quickly begin yielding large amounts of net carbon-neutral biomass which could be burnt directly or after extracting compounds of high market value (including some for biofuels), a process that should include pressing out its cold liquids, plus perhaps some drying taking advantage of high insolation where available. A speculative direct quantification based on seaweed biomass burning follows.

Taking a modest production of combustible solids (dry matter minus ash) of 30 t / ha / yr, and assuming a specific energy density of 15 MJ / kg for dry seaweed biomass (common for whole plant biomass) to gross energy yield of 450 GJ / ha / yr could be obtained. This is approximately 10 tonnes of oil equivalent (toe) in terms of energy or more than 70 barrels of oil / ha / yr. At $ 100 per barrel of oil, the gross profit would be over $ 7000/ha/yr-if energy that could be used as cost-efficiently as oil. For 10 Gtoe of world's annual fossil fuel consumption and 10 toe / ha / yr from seaweed biomass to GHA or 10 [7] km [2] of sea area would be needed to grow seaweeds. This an area similar to a large country, less than 3% of the world's Oceans, and about 20% of the land area currently in agriculture (70% of which is in pasture). Considering the rather modest biomass and biofuel goals set for the coming years in the USA and the EU, a small fraction of that area as would be needed to fully substitute for biofuel production in land.

Such estimated energy from seaweed biomass yields could be greatly increased when placed in the proper hands (eg, the kind that achieved a five-fold increase in corn yields in the USA during the past century, and the kind that currently extensive farm land areas around the world), advancing biofuel and biomass productivity, partly through the selection and development of seaweed varieties with desired traits.

Moreover, 30 Gt of biomass production from GHA 1 of seaweed farms weigh on CO2 balance. Assuming a standing-rather, floating-biomass between Harvests of 10 Gt, that by itself represents several Gt of atmospheric CO2 permanently sequestered. However, the largest contribution to CO2 reduction comes from cutting net additions from CO2 equivalent decreases in fossil fuel combustion, at the upper mentioned Gtoe goal of 10 per year. With a carbon market currently paying U.S. $ 30 per tonne of CO2 equivalent, there is an Astronomical amount of money just in selling carbon sequestration through seaweed cultivation and the use of biomass for energy. Some of that money could surely be used as start-up funds for experimental seaweed farming at the proper scale.

Once adequate ocean areas for each region are identified, the main external input to implementing large scale seaweed farming for energy will be the addition of nutrients, as evidenced by so many ocean iron fertilization efforts to promote micro-algal growth. However, agriculture-like production requires large quantities of all the plant nutrients because large quantities are removed at harvest. Common agricultural fertilization, besides being costly and energy consuming, would add large amounts of nutrients to the oceans with unknown results. There is, nonetheless, a great and grossly misuse nutritional resource: domestic wastewaters. Their application grown on large seaweed fields for energy-an option already explored (12)-could find economically-sound use for the millions of tonnes of untreated wastewaters dumped daily direct into the sea through submarine outfalls or "emissaries" everywhere in the world. The service fee to be charged for properly disposing of wastewaters would come to lower nutrient handling costs.

Besides bioenergy, and climate-change considering growing limitations to agriculture, seaweed used as food should be established as a world priority. China is already leading the way consuming 5 billion tonnes per year, taking advantage of excellent seaweed nutritional composition, which is naturally high in protein9. Moreover, to better suit preferences, and many other organoleptic characteristics could be altered through genetic manipulation and food science technology-nothing new to agricultural scientists.

Thus, seaweed cultivation for energy, food and other uses can bring about large and ecologically friendly planetary improvements, extending our lease on Earth on the hope that eventually we will mature as a species and a society. For this, and given the fact that as waters, particularly those within exclusive economic zones of each country, are still in the hands of governments, this new set of activities may as well constitute the basis for generating a new wealth more equitably distributed.

Ricardo Radulovich
Sea Gardens Project Director
University of Costa Rica

1.Childs, B. & Bradley, R. Plants at the Pump (World Resources Institute, Washington, DC, 2007).

2. Jordan, N. et al. Science 316, 1570-1571 (2007).

3. World Energy Council 2007 Survey of Energy Sources (WEC, London, 2007).

4. OECD-FAO Agricultural Outlook 2007-2016 (OECD, Paris, 2007).

5. Von Braun, J. The World Food Situation. IFPRI's Biannual Overview of the World Food Situation (IFPRI, Washington DC, 2007).

6. The Royal Society, Sustainable biofuels: prospects and challenges (The Royal Society, London, 2008).

7. IWMI (International Water Management Institute) Water: Key for adapting to climate change (IWMI, Colombo, 2007).

8. Beardall, J. & Raven, JA Phycologia 43, 26-40 (2004).

9. FAO State of World Aquaculture. Fisheries Technical Paper 500 (FAO, Rome, 2006).

10. FAO A Guide to the Seaweed Industry. Fisheries Technical Paper 441 (FAO, Rome, 2003).

11. Yokoyama, S. et al. IJECSE 1, 168-171 (2007).

12. Edwards, P. Reuse of Human Wastes in Aquaculture (UNDP-World Bank, Washington DC, 1992).