According to the Biomass Handbook, cultivated seaweed can yield close to 130 tons per ha per year. Fast growing willow may yield just above 10 tonnes per ha per year. And miscanthus grass can yield 15 tonnes dry mass per ha per year. Giant King Grass (PDF) may produce 5 X or more yield than miscanthus, in tropical climates.
Those are rough figures which are subject to change as faster-growing strains are developed via several means. Besides rapid growth and 6 X a year harvesting, seaweed takes advantage of large areas of the Earth's surface which cannot be utilised to grow land trees or land grass for biomass. Seaweed essentially doubles available biomass growing area -- or more -- which throws conventional calculations for biomass potential out the window. Some problems must be worked out, but by the time humans truly need the massive quantities of biomass they can get from seaweed (and special grasses and trees), the problems should have been solved.
Seaweeds, a macro form of algae, hold great promise because of their potential for very high yields and high oil production while thriving on non-arable land. Another benefit is that they grow well in saline water. Traditionally crops will not excel in salt water and in some areas of the country valuable agricultural land has been taken out of production due to high concentrations of salt.
But as all researchers know, not all algae is created equal. There are strains of seaweeds that hold great promise for bio-energy and others that hold great promise for producing other products such as high protein meals for replacing non-sustainable ocean-caught fishmeals in aquaculture and other animal diets.
In fact, many algae companies that began with the mission of producing algal fuels have now refocused on producing algae products for the pharmaceutical, plastics, health, and agricultural feed industries. For example, there are strains of seaweeds that UCSD-SIO has been studying that grow well inland and can be used to recycle artificial seawater and waste nutrients from chicken ranches or pig farms. Algae has also been used in farm fish operations from cleaning the ponds to providing feed.
...Yet with all the research focused on algae, there are still several major hurdles that need to be overcome before algal biofuels will become commercially viable. The cost of production must be significantly reduced, elite strains of algae and seaweeds optimized for fuel production need to be developed and test facilities need to scale up to large production areas of several hundred acres.
Mitchell believes the timeline for this to occur spans more than 10 years. To date, all research projects are small and need to be brought to commercial scale levels. “We need several hundred acre demos that would take three years to design, permit and build. Then we need at least two years to get data and improve design,” said Mitchell. “Then we’ll roll out commercial scale over the following five years. We can do all this now at pilot scale but its not yet economically viable. So I see 10 years for this to be turned to economic viability.”
The result, Mitchell believes, will be a multi-trillion dollar industry that will disrupt the use of fossil fuels. _DomesticFuel
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