Preface. Here are just a few of the dozens of reasons why seaweed can’t make a dent in energy supplies:

• A negative return on investment like corn ethanol
• No commercial biofuels are being made from it. Kelp is mainly used for food, animal feed, fertilizer, cosmetics, etc.
• As a monocrop it is just as vulnerable to pests as land crops and pesticides can’t be used to protect them
• The most desirable kelp is the massive brown variety which only grows in water 43 to 57 F where there are rocks to attach to and protected from storm waves and strong currents
• Like land biomass, it doesn’t scale up (Friedemann 2007). A U.S. Department of Energy study states that if we could increase world-wide production of seaweed 10.5 fold, we could produce 1% of United States domestic gasoline supply (Roesijadi)

And if Jehn et al (2024) is right, we’ll need all the seaweed we can get to survive after a nuclear war. This is because nuclear winter will block sunlight and prevent crops from growing.  But some plants may survive better than others, especially seaweed, which is also very nutritious. After all, do you want to eat, or drive?

Kelp in the news:

Bever (2021) Fighting climate change by farming kelp NPR:  An absurd  project to cash in on carbon sequestration funds to haul kelp out to sea until it’s so heavy the buoy sinks and the kelp CO2 is sequestered on the ocean floor. What could go wrong: whales entangled, ship propellers snarled, beaches fouled? The price and energy to do this? And why? As Life After Fossil Fuels explains, peak oil occurred in 2018 and the decline of emissions at 4% a year now that will exponentially increase dwarves all sequestration and renewable contraption dreams and schemes.

Alice Friedemann  www.energyskeptic.com  Author of Life After Fossil Fuels: A Reality Check on Alternative Energy; When Trucks Stop Running: Energy and the Future of Transportation”, Barriers to Making Algal Biofuels, & “Crunch! Whole Grain Artisan Chips and Crackers”.  Women in ecology  Podcasts: WGBH, Financial Sense, Jore, Planet: Critical, Crazy Town, Collapse Chronicles, Derrick Jensen, Practical Prepping, Kunstler 253 &278, Peak Prosperity,  Index of best energyskeptic posts

* * *

Fill ‘er up with kelp?

It’s easy to see why kelp looks like a great source of biofuel:

• Kelp are the most massive kind of seaweed. Kelp can grow up to 2 feet a day and up to 160 feet long.
• Kelp doesn’t need fresh water
• The photosynthetic efficiency of aquatic biomass is an amazing 6 to 8% (land plants average .5%)
• There’s no lignin, so sugars can be released by milling or crushing,which is much less energy-intensive than land plant pre-treatments and hydrolysis
• Kelp helps fisheries and biodiversity — many species depend on kelp for food and shelter

But kelp faces many of the same obstacles as land plants (see Peak soil: Why biofuels are not sustainable).

Much of the best underwater areas are already being to grow seaweed for the $5 billion dollar food industry in Asia. Kelp is also used for fertilizer, animal feed, cosmetics, food additives, and many other products.  These industries pay about $1.30 per kilogram, while going to all the trouble of making ethanol will only earn 75 cents per kilogram, plus the expenses of the conversion process  (Nielsen).

Kelp growth is can be blocked by the algae and other organisms that grow on its surface, which blocks sunlight.  Kelp blocks sunlight from reaching other plants, a potentially damaging ecological effect impacting life in deeper waters (Wren 2014).

Like land plants, kelp grown as a monocrop makes it more vulnerable to bacterial infection and disease, yet unlike land plants, seaweed can’t be doused in chemicals to prevent disease, fish, sea urchins, parasites, and other sea-pests from feasting on them.

Seaweed production is already being affected by climate change, with rising sea temperatures and ocean acidification reducing seaweed production.

The ocean is vast, but kelp needs to grow in water shallow enough for sunlight to penetrate, far from glitzy resorts and cities, but not so far that transport, harvest, and processing is  too expensive.

The really massive brown kelp most desired for biofuel production only grows in the wild.   And not just anywhere: there must be rocks for the kelp to attach to, the water can’t be too muddy, protected from large waves, a high water current, and enough phosphorous and other nutrients. Brown kelp likes cool temperatures between 43 and 57 F best (below 41 it can’t reproduce).  Above 68 F you seldom find kelp because warm temperatures reduce nutrients and increase mortality from black rot.   Kelp competes with other plants and animals for limited space

Which could be harvested at whatever rate Mother Nature produces it, but not energy efficiently enough to make biofuels (McHugh).

Not being able to cultivate brown seaweed is a problem because you can’t scale it up.   Brown algae are also hard to cultivate because you can’t use cuttings since brown algae propagates only with a reproductive cycle.  That hasn’t stopped people from trying though.  Here’s just a few of the cultivation costs and energy use required to attempt cultivation (Edwards).

• the hatchery must be on flat, low-lying land next to the ocean with a low pumping head, have 3-phase power, road access and sufficient space for tanks, a lab, an office and facilities.
• The room that grows the seaweed culture must be kept within 1 degree of 10 C (50 F).
• There must be a dedicated air blower in the water to get enough oxygen, lighting at different intensities to mimic day and night,  a warm lab for the workers, seawater pumping and filtration systems, prevention of algae in the water, provide nutrition, sterilized glassware

Scale

In Peak Soil it was clear land plants don’t scale up – burning every plant in America, including the roots, produces less energy than the U.S. burns a year (100 EJ).

A U.S. Department of Energy study states that if we could increase world-wide production of seaweed 10.5 fold, we could produce 1% of United States domestic gasoline supply (Roesijadi).  Let’s hope that doesn’t start any wars over seaweed, the world might resent us harvesting it all for ourselves.

How much brown kelp could be grown theoretically? 

Growing kelp for energy not only competes with seaweed grown for food and other products but with shipping lanes, recreation, marine sanctuaries, cities, military sites, wave and tidal power, and competition with the tourism industry for valuable coastal real estate.  Trying to move kelp growth far from shore to reduce competition hasn’t worked out, because structures and the attachment of kelp hasn’t worked out when large storms break them up — even extremely sturdy wave power equipment has been destroyed in storms. Additional energy needs to be used to mechanically upwell nutrient rich water to the offshore kelp structures, and additional diesel fuel to power boats out and back to shore with the harvest..

Land-based kelp would be great, but problematic for the same reasons growing kelp’s microscopic cousin algae is, such as finding fatter, oilier species, reducing energy to circulate water, construct ponds, keep water temperature within narrow boundaries.

Undaria, an invasive green kelp nominated one of the 100 worst invasive species in the world, is out-competing native kelp.  It has invaded California’s coast, and threatens native kelp because it crowds them out which deprives them of oxygen, which in turn ruins the natural habitat for native species of fish, shellfish, sea otters and other marine organisms, according to ecologist Chela Zabin (Kay, Perlman 2009)

Sunlight is essential to productivity, turbidity, cloudiness, shade, etc lower productivity.

Other factors that affect productivity are water circulation patterns and velocities, seasonal ocean temperature variation, atmospheric ozone at low tide, just the top 4 feet of some species can be harvested or it becomes unsustainable because below that are the reproductive parts.

Just because you can make kelp ethanol it in the lab doesn’t mean it will scale up to commercial level

The only place that attempted to build a smaller-scale pilot plant is Bio Architecture Lab, but in 2013 they gave up (Nielsen).

Resources

Is there enough shallow ocean to grow enough kelp to make 60 billion gallons of ethanol?  Wargacki estimates 19,000 liters of ethanol per hectare per year from 59 dry metric tons can be produced.  19,000 liters = 5,019 gallons.  60 billion gallons at 5019 per hectare is 11,954,573 hectares needed = 46,157 square miles, about the size of Pennsylvania.

Ecological considerations and damage

• Harm to fisheries and other wildlife.  Norway is also interested in biofuels from kelp, and recommends not removing more than 1% of kelp per year because kelp forests are an important nursery and feeding ground for a wide range of invertebrates and fish.
• Kelp appears to affect the weather by releasing large quantities of iodine oxide and volatile hydrocarbons when under stress which act as condensation nuclei for clouds, possibly part of why there’s longer lasting cloud cover in coastal regions.  Will that make coastal areas even more cloudy and what affect would that have on land ecosystems and agriculture?
• Kelp alters the availability of light, flow of ocean currents, and chemistry of ocean water.  What would happen to other ocean life and ocean chemistry if you grew a lot more kelp and harvested it?

Harvesting, delivery to and storage at bio-refinery

• Some metals in kelp can inhibit yeast fermentation at the bio-refinery, and growth is seasonal, with the highest carbohydrates produced and lowest metal levels means kelp is best only one month of the year, making year-round harvesting unlikely and year-round production difficult.  Nutrient levels are seasonal as well, further limiting harvest times.
• Harvesting giant pieces of slippery kelp is a challenge.
• Transporting the water weight of seaweed is another showstopper.  The water weight of corn stover needs to be reduced down to 6% water so trucks would burn less fuel hauling it to the biorefinery. Brown seaweed is 88% water.  Coasts are cool and often cloudy, making it difficult to dry, plus find the space alongshore to put it, and keep flies and other pests from eating or composting it.
• Kelp harvesting mechanized boats with 20 foot wide blades are (energy) expensive to build, operate, and maintain.
• Storage:  Unknown how much seaweed, for how long, could be stored without being consumed by pests or decomposing.

Bio-refinery

In addition to steps similar to land-based biorefineries above, seaweed has these pre-processing steps:

• To get rid of stones, sand, litter, adhering fauna, etc.
• to Mill seaweed to small particles (more efficiently processed).
• Drying the seaweed out in machines.
• Removing sulfur, nitrogen, salt, polyphenols, etc.

Energy Returned on Energy Invested (EROEI)

No studies have been done. As far as energy issues go (DOE):

• The juvenile grow-out phase, the marine grow-out phase and the distillation process were determined to be the most significant energy intensive phases of the process. The juvenile grow-out phase requires large quantities of water (i.e. pumping energy) and the marine grow-out phase requires much maintenance (i.e., fuel for transportation vessels). Distillation, which requires large amounts of steam, was identified as the greatest consumer of energy.
• Macroalgae cultivation farms require energy to sustain the cultivation and harvesting phases. In a study conducted for the Marine Biomass Program, energy usage for cultivation and harvesting for a 100,000 acre open-ocean kelp farm was reported to have fuel requirements for pumping deep water nutrients to the ocean surface in the range of 3.0-6.0 MMBtu/ wet metric ton seaweed for a yield of 10 metric ton/acre/year (mid-range analyzed). This method of providing nutrients has been identified to be prohibitively expensive in some situations because of the high energy requirements. Harvesting requirements were in the range of 0.6-2.1 MMBtu/wet metric ton. Location of kelp farms in natural upwelling areas with the use of passive, wave-driven pumps remains an option.

Conclusion  Fill ‘er up with gasoline.

 

Appendix A.  Miscellaneous.

United States potential brown macroalgae production

The pacific coastline, including offshore islands, sounds, bays, rivers, and creeks is 40,300 miles long. Alaska counts for a whopping 31,400 miles of that, and due to freezing temperatures preventing harvest and storage most of the year, high energy delivery costs to remote customers, and lack of hot sun to dry the kelp out, that limits USA production to 7,860 miles (also minus Hawaii due to delivery energy).  East coast kelp is limited to between Maine and Delaware, (the water gets too hot further south), which gains another 10,240 miles.  So roughly 18,100 miles or .2% of the shoreline we’d need, 923,140 miles, to be self-sufficient.

References       Also see Peak Soil references  

DOE. 2010. National Algal Biofuels Technology Roadmap. Washington, DC: U.S. Department of Energy, Energy Efficiency and Renewable Energy.

Edwards, M., et al. May 2011. Aquaculture Explained. No 26. Cultivating Laminaria digitata. Irish sea fisheries board.

Fingerman, K; Kammen, D, et al. Integrating Water Sustainability into the Low Carbon Fuel Standard. University of California, Berkeley

Friedemann, A. 2007. Peak soil: Why biofuels destroy ecosystems and civilizations. energyskeptic.com

Glennon, R. 2002. Water Follies. Groundwater Pumping and the Fate of America’s Fresh Waters.   Island Press.

Hall, C, et al. 20 Nov 2003. Hydrocarbons and the Evolution of Human Culture. Nature 426:318–22.

Hirsch, R. 2005. Peaking of World Oil Production: Impacts, Mitigation, & Risk Management. DOE NETL.

Jehn FU et al (2024) Seaweed as a resilient food solution after a nuclear war. Earth’s future. https://doi.org/10.1029/2023EF003710

Kay, J. 8 Jul 2009. Kelp among top 10 invasive seaweeds hits S.F.  San Francisco Chronicle.

McHugh, D. J. 2003. A guide to the seaweed industry. FAO FISHERIES TECHNICAL PAPER 441. Fisheries and Aquaculture Department of the FAO.

Montgomery, D. R.. 2007. Dirt: The Erosion of Civilizations.  Univ. of California Press.

Nielsen, S. May 15, 2013. Bio gives up on seaweed-to-ethanol effort in Chile. Bloomberg.

Opie, J. 2000. Ogallala: Water for a Dry Land.  University of Nebraska Press.

Patzek, T. Nov 5, 2006. Why cellulosic ethanol will not save us.  Venturebeat.com

Patzek, T. 26 Jun 2006. The Real Biofuels Cycles.Online supporting material for Science Vol 312: 1747.

Patzek, T. Dec 2006. A Statistical Analysis of the Theoretical Yield of Ethanol from Corn Starch. Natural Resources Research, Vol 15/4.

Perlman, D. 10 Jul 2009. Divers battle fast-growing alien kelp in bay. San Francisco Chronicle.

Perlman, D.  20 Jan 2012.  Bio Architecture Lab sees seaweed in biofuels. San Francisco Chronicle.

Pimentel D. 2003. Ethanol fuels: Energy balance, economics and environmental impacts are negative. Natural Resources Research. 12:127–134.

Pimentel, D. et al. March 2005. Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower.  Natural Resources Research, Vol 14:1

Roesijadi, G. et al. Sep 2010. Macroalgae as a Biomass Feedstock: A Preliminary Analysis. U.S. Department of Energy.

Wargacki, A.J. et al.  20 Jan 2012. An Engineered Microbial Platform for Direct Biofuel Production from Brown Macroalgae. Science Vol 335 #6066 pp. 308-313.

Wren, K. October 31, 2014. Can algae make the big time in renewable energy? Science vol 346: 562-563.