Sustainable use of Baltic Sea natural resources based on ecological engineering and biogas production - a good example on land and water management

Sustainabel use of Baltic Sea natural resources
based on ecological engineering and biogas
production - a good exampel on land and water
management

Fredrik Gröndahl,
Industrial Ecology, KTH SE-100 44 Stockholm, Sweden

Fredrik Gröndahl (fgro@kth.se)
Industrial Ecology
KTH, Stockholm, Sweden

Fredrik Gröndahl, Industrial Ecology, KTH

• Eutrophication – the most serious
environmental problem of the Baltic Sea

• Action plan by the Helsinki Comission
(HELCOM)
– 21 000 tonnes N, 290 tonnes P
– Good ecological status 2021


Sustainable use of Baltic sea biomass resources based on ecological retrieval of biomass (reed and algae)
for production of energy and new innovative products (including fertilizers) with an associated waste stream.
Blue squares indicate technology dependent processes and the yellow clouds shows the sustainability and
feasibility aspects. Gröndahl et. al. 2008


Objectives of the study
• Compare the efficiency of reed and macro
algae harvesting and mussel farming with
respect to nutrient removal from the Baltic
Sea.
• Provide and compare energy budgets for the
full process chain from harvesting of biomass
to biogas production for reed, macro algae
and mussels.


Rivers
706 000 tons/y
Agriculture
Traffic

Atmospheric
N-Fixation by
deposit
Cyanobacteria
264 000 tons/y
400 000 tons/y Baltic Sea Traffic
909 000 tons/y
Sediments and
Biomass

Point Sources Loss
39 000 tons/y Denitriphication
Waste water 500 000 tons/y
treatment

Figure 1: Nodularia spumigena
(Helcom, 2004)

dw 16 - OP dw 16 - N dw 22 - GPT dw 19 - N dw 20 - OPB

Figure 11: The forming fabrics after being pulled through algal rich water

Forming fabric

Figure 7: Forming fabric is
Figure 6: Outline of an oil boom with attached to the oil boom skirt
forming fabric attached

Reed
• Grows as large
monospecific stands
along the Baltic coast
of Sweden
• Swedish total reed
area: 100 000 ha
• Biomass above
ground in the middle,
and south of Sweden
in august: 1 kg dw/m2

Aquatic Plant Harvester RS 2000

• Floating device with front
conveyors
• Makes harvest of water
plants possible (i.e. both
algae and reed)


Algae
• Heavy algal blooms and growth
due to surplus of nutrients, and
internal distribution of N and P.
• Harvestable amount of algae
along the South coast of Sweden:
43 000 tonnes dry weight
• Collection take place in the water
(within an area 100 m from the
coastline)
• Assumptions of quantities per
hectare is based on the present
collection performed by the
municipality of Trelleborg


Mussels
• Grow on hard substrates down to
dephts of 30 m, prefers salinity
above 18 PSU.

• Reduced growth rate, and size
compared to the North Sea (3 cm
in Baltic Sea).

• Dominate the Baltic Sea
– 90 % of the animal biomass
growing on hard bottoms

• Clean water
– Filter feeding through their gills
– Feed on phytoplankton
– Filtration rate: 1-4 liters per hour


Long line mussel farming

• Rope wires are held up by
floating barrels

• Mussel lines are hanged from the
rope wires

• The larvae settle on the mussel
rigs from where they feed on
foodstuffs that naturally exists in
the surrounding water.

• The mussels are harvested
through scraping the mussels off
the lines by a machine


Kalmarsund, 14 month

The biomass after 1 year was 4 kg m-1
or 16 kg for a long line.


Fritt val av foder

Kokt musselkött Vanligt foder

Biogas
• Biogas is formed when volatile solids are broken down anaerobically by
methane forming microorganisms.

• Biogas mainly consists of methane (50-60 volume-%) and CO2 (25-40
volume-%) (hydrogen gas, sulphur-hydrogen, and steam)

• Formation occurs in four steps
– Methane formation
• Sensitive step
• High concentration of ammonia, phosphorus, potassium, heavy
metals, sulphur and certain fatty acids can restrain the sensitive
methane forming bacteria

• Different factors have influence on the biogas production, such as
temperature and technique of the biogas production process, pre-
treatment of the substrate and chemical composition of the
substrate


System boundaries


Nutrient removal efficiency
• Comparison of nutrient
contents of the three
biomasses, based on living
weight
• Nitrogen content of mussels
> 3 times higher
• Phosphorus content of
mussels > 2 times higher
• Harvest of mussels is most
efficient according to
nutrient removal


2500
En erg y co n ten t [M J/to n n e w w ]
2000

1500

1000

500

0
Algae Reed Mussels Sludge


Energy demands
600
Energy demands [MJ/tonne ww]
500

400

300

200

100

0
Algae Reed Mussels


Energy balance

6.E+05
Net energy benefit [MJ/tonne N]
5.E+05

4.E+05

3.E+05

2.E+05

1.E+05

0.E+00
Algae Reed Mussels


Conclusions
• Reed has the highest net energy benefit,
followed by macro algae.
• Blue mussels are not suitable for biogas
production, but are better than reed or algae
when the ambition is to remove nitrogen or
phosphorus from the Baltic Sea.
• Biogas production from reed and macro algae
may be important in the future but need
further investigations.


Advantage with Biomanupulation and the
production of Biogas
• Biogas means less CO2 and is thus an important contributor to decreasing
climate change.
• The establishment of wetlands will stimulate biological diversity in the
region and will deal with the nutrient load from surrounding farm land.
• Harvesting of the reed belt will remove the nutrients from the wetland
area.
• Harvesting of macro algae will remove nutrients and heavy metals from
the Baltic Sea and improve local beaches for recreation purposes.
• The removal of Cyanobacteria will remove nutrients from the Baltic Sea,
but perhaps the most important contribution is that it will improve
recreational value in the region.
• When the shallow coastal waters are cleansed from oxygen-depleting,
decaying accumulated macro algae, large areas will again become
available to sustain the growth of juvenile fish.

Sustainable use of Baltic Sea natural resources based on ecological engineering and biogas production - a good example on land and water management

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Sustainable use of Baltic Sea natural resources based on ecological engineering and biogas production - a good example on land and water management