Supplementary memorandum submitted by
The Biosciences Federation and the Royal Society of Chemistry
(Bio 07a)
RENEWABLE ENERGY: THE POTENTIAL OF MARINE
BIOMASS
INTRODUCTION
1. We began to research seaweed cultivation
to investigate their potential for bioremediation, and in particular,
their potential to absorb some of the dissolved nitrogen that
results from intensive rearing of Atlantic salmon in sea cages
on the west coast of Scotland. This project REDWEED or "Reducing
the environmental impact of sea-cage farming through the cultivation
of seaweeds" showed that the seaweed do utilise farm origin
nitrogen and that a prodigious biomass of seaweed can be produced
as a result. One of the species we work with, the brown macroalgae
Laminaria saccharina increases from millimetres to meters
in size in a matter of months. (These macroalgae can take up nitrogen
from sea water at rates resulting in an increase in their biomass
of 10% day-1).
CULTURE
2. Seaweeds are collected from wild populations
at the time when they are known to be producing spores. Ripe fronds
are induced to shed their spores in controlled laboratory conditions.
The spores are allowed to settle and germinate on strings (1-2mm
diameter). Once the plants are large enough to withstand transport
these strings are suspended in the sea from a horizontal top rope
or long-line. Alternatively strings may be suspended from a floating
raft, anchored to the seafloor. The seaweeds are always situated
in the photic zone, the surface layers of the sea, to a depth
of less than 10 meters.
3. The methods for seaweed culture are well
developed; in terms of weight, more Laminaria japonica is
grown than any other aquaculture species. In fact world aquatic
plant production in 2002 was 11.6 million tonnes (US$6.2 billion),
of which 8.8 million tonnes (US$4.4 billion) originated from China,
0.89 million tonnes from the Philippines and 0.56 million tonnes
from Japan. Japanese kelp (Laminaria japonica—4.7
million tonnes) showed the highest production, followed by Nori
(Porphyra tenera—1.3 million tonnes) (statistics
from "SOFIA", The state of world fisheries and aquaculture,
2004. www.fao.org). The majority of this seaweed is cultured
for food, and also for the extraction of alginates, therefore
the technology for the large scale culture, harvest and processing
of seaweeds is well advanced.
4. I should stress that SAMS seaweed culture
is conducted on a research scale, but we do not perceive any major
technical challenges to scaling-up. Our industrial partner, the
salmon farming company Loch Duart Ltd., has committed to commercial
scale trials to test the economic viability of production for
human food.
5. Sea-cage aquaculture is only one example
of how seaweeds are used to ameliorate nutrient impact; they have
also been used with effect to treat human sewage and could be
grown in, and therefore used to "clean", other industrial
sources of nitrogenous waste.
POTENTIAL BIOFUEL
6. As long ago as 1974, the American Gas
Association decided to look for a renewable source of methane
(natural gas) from the seas and sponsored a project to produce
seaweed on farms in the ocean, harvest it and convert it to methane
by a process of biomass fermentation. Their research proved that
net energy can result from bioconversion, with good yields of
methane (approaching 71% (methane) per pound of kelp, greater
than any other known biomass source at the time. Methane production
varied with the species of seaweed and with their carbohydrate
and protein content. However the project suffered from catastrophic
losses of seaweeds farmed on exposed coastlines, highlighting
a lack of knowledge of marine farming in the US at the time. The
US research was scaled down until "a crisis threatens in
natural gas supplies".
7. The UK aquaculture industry (90% by value
and volume of which is conducted on the west coast of Scotland
can claim considerable expertise in marine farming. The knowledge
of seaweed culture gained at SAMS feeds in to this expertise.
Also, since that time there have been advances in anaerobic digestion
technology.
8. It is my observation, therefore, that
the time is right to re-visit this area of research and combine
our expertise in seaweed culture with the latest developments
in anaerobic digestion.
9. RESEARCH NEED: The immediate research
need is to test the indigenous seaweeds we can readily cultivate
for their suitability for methane production.
VISION
10. It terms of the future scale of the
seaweeds cultures, without assessing the methane yield for each
species, it is hard to visual the hectarage of seaweed farms required.
It is possible that offshore renewable energy installations such
as wind turbines, which require a hard substrate, might also provide
very suitable locations for culturing seaweeds, (see research
by Buck et al, Alfred Wegner Institute, Germany). However
our methods and perhaps the species we use would have to be adapted
from working in relatively sheltered Scottish sea lochs to working
in the more exposed off-shore environment.
11. However, seaweeds can also be grown
ashore in tumbling aerated cultures, contained in large vessels
and fed nutrients generated as waste from another process (terrestrial
agriculture or human sewage). In large scale cultures, a proportion
of the seaweed could be harvested at frequent intervals to feed
a digestor situated in the vicinity. The remaining seaweed would
stay in culture to form the basis of the next crop.
12. QUESTIONS RAISED IN ORAL EVIDENCE
Q220—Are we far away from the commercially
viable use of seaweed as a source of bioenergy?
A220—Anaerobic digestion is already used
to produce methane from plant biomass. Seaweeds have been trialled
in the past and are a good source of biogas. We have the expertise
to culture seaweeds. What is required now is a pilot project to
bring the two sciences together and trial the seaweeds available
for culture in the UK with the latest anaerobic digestion technology.
I am ready to initiate a partner search for a company or research
unit with the appropriate anaerobic digestion facility.
Q221—What level of funding are we talking
about to do this developmental work?
A221—I have not begun to cost the exercise,
either in terms of a large scale seaweed farm or for use of/construction
of an appropriate digestor. However, I would be happy to start
to collate figures for such a project. The first step is, as I
have said, to identify appropriate partners. I agree however,
with Professor Bridgewater that significant advances could be
achieved with a project at the lower end of the funding range
he mentioned (£5 million).
Q222—So are we working on guestimates
rather than an actually worked-out plan and programme?
A222—Absolutely. However a partner search
and provisional costing exercise is something we hope to achieve
fairly swiftly. I am currently attempting to identify a source
of funds to allow me to work on this topic in the coming months.
Q222—area occupied, planting, ownership.
I have already referred to your question as
to the size of area occupied/scale of sea farming. In short, without
testing the plants for methane production, we don't know. However,
I will throw a few facts into the mix which may help give perspective.
— The UK salmon farming industry produces
approximately 150,000 tonnes of salmon annually (although less
will be produced in 2006—120,000 tonnes) and this occupies
an area of approximately 345 hectares (my own calculation). This
is a tiny proportion of our coastal resource.
— For comparison, one, medium sized
terrestrial cereal farm is on average 240 hectares (Farm Business
census June 2003, DEFRA, 2003).
— A seaweed farm of 1 hectare (40,
100 meter longlines), might yield 100 tonnes of seaweed (conservative
estimate).
With regard to ownership the salmon and shellfish
farming companies lease an area of seafloor for production from
The Crown Estate, for which they pay rent. I would envisage that
a seaweed farm would operate in a similar way. As the seaweeds
are in suspended culture, and in a fixed place, one avoids any
issues over ownership.
13. FURTHER QUESTIONS RAISED IN WRITING
(a) What consideration has been given to
the effect on marine mammals of nets of seaweed off the coast?
The seaweeds hang in vertical strings or nets
suspended from a buoyed top-line or raft and would not extend
to a depth of more than 10 meters. If the seaweeds were cultured
in inshore areas, then I imagine the risk would be negligible,
as there are no reports of mussel farms (which operate a similar
system) causing harm to marine mammals. There is no formal impact
assessment, of which I am aware, as to the potential impact of
seaweeds cultures on marine mammals. Clearly an impact of assessment
of larger and offshore farms would be required, as for all types
of marine renewable energy. The fact that it might be possible
to link offshore seaweed farms and for example wind turbines,
would result in a more effective use of space at sea.
(b) Have key sites for such developments
been identified around our coast and what consideration has been
given to (a) shipping lanes; (b) strength of currents offshore,
in selecting/identifying sites?
It is too early in the process for offshore
sites to have been identified, or for inshore sites other than
those alongside existing aquaculture in western Scotland. However
salmon farm cages rarely occupy the whole of their leased areas
and these areas could be suited to seaweed production. The additional
nitrogen absorbed by the seaweeds would help balance nutrient
ratios in inshore waters.
(c) Is this proposal "blue sky thinking"
or has any research been undertaken to look at the practicalities
developing, harvesting, transporting and processing the seaweed?
In part, this question has been answered above,
however I should point out that while the technology is available
in other parts of the world where seaweed is harvested on a massive
scale (China), and despite a long history of the collection and
processing of seaweeds in the outer Isles and the west coast of
Scotland for both alginates and fertilisers, the practicalities
of large scale harvest of seaweed for methane production as not
been explored in the UK. I am however confident the skill base
to develop the relevant expertise exists within the UK aquaculture
industry.
References
Buck, B H, Buchholz, C M (2005). Response of
offshore cultivated Laminaria saccharina to hydrodynamic
forcing in the North Sea, Aquaculture, 250(3/4), 674-691.
Farm Business census June 2003, DEFRA, 2003:
http://statistics.defra.gov.uk/esg/publications/fab/2004/app1@mdash mdash@b.pdf
"SOFIA", The state of world fisheries
and aquaculture, 2004. www.fao.org.
Maeve S Kelly
Scottish Association for Marine Science
Biosciences Federation and the Royal Society of Chemistry
June 2006
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