A BREATH OF FRESH AIR SAY CHEESE WAR ON ... - GEA Group

UK AGRICULTURE
PRODUCES ROUGHLY
90 MILLION TONNES
OF SLURRY AND
MANURES EACH YEAR.
in the form of gas. AD facilities are relatively
quick and cheap to construct and can be
scaled to local feedstock availability.
Methane is also one of the few renewable
fuels suitable for heavy goods vehicles.
The UK Government estimates that if five of
the seven million tonnes of food waste sent to
landfill were digested, it would save 386,000
tonnes of CO 2 equivalent in greenhouse
gas emissions.
UK agriculture produces roughly 90 million
tonnes of slurry and manures each year.
According to a UK Government report half of
this, combined with the food waste digestion,
has the potential to generate approximately
3.5 TWh of electricity: enough to supply over
900,000 households and saving 1.8 million
tonnes of CO 2 equivalent from grid-based
electricity production.
However, there are several ‘ifs’ in this vision,
not least of which is to ensure that local
authorities provide weekly collections of food
waste. At the moment these cover three
million households in England out of 22.5
million – or just 13 per cent.
convErtinG biomAss to hEAt And powEr
In the anaerobic digestion process, plant and animal
material (biomass) is mixed with water and put inside
sealed tanks where, in the absence of air, naturally
occurring micro-organisms digest it. They generate
methane which can be used to provide heat and power.
The material left over at the end of the fermentation
process is also valuable, but needs to be dried before
it can be used.
GEA Mechanical Equipment has supplied decanters
for dewatering fermented biomass to fermentation
plants in Germany, Luxembourg, Spain, Sweden, the
Netherlands and Portugal.
The digested left-overs are supplied in suspension to
a continuously operating scroll-type centrifuge, and
are decanted at between 3,000 to 4,000 times gravity.
The machine removes the solid particles and dewaters
them to a dry consistency.
The separated solids are used as a nutrient-rich
compost in gardening and agriculture, and the clear
water is recycled back into the process.
cApturinG cArbon
Carbon dioxide (CO 2) is a waste product from many
industries – and a damaging greenhouse gas. Around the
world there are projects seeking to use algae to capture
industrially generated CO 2 and put it to good use.
In Queensland, Australia, for example, the MBD Energy
company is using flue gases from the Tarong power
station as ‘food’ for its algal synthesizer plant. The CO 2
allows the algal biomass to double every 24 to 48 hours
– which means it can be harvested daily.
It can be used as a fertilizer, be converted into solid fuel
briquettes, or used as a feedstock for the production
of biodiesel.
Another project, at the Glenturret Distillery in Scotland
– home to The Famous Grouse whisky – percolates CO 2
made during the whisky distillation process through a
microalgae bioreactor. Each tonne of microalgae absorbs
two tonnes of CO 2.
Scottish Bioenergy, who run the project, sell the
microalgae as high value, protein-rich food for
aquaculture (fish farms) and for the dairy cattle market. In
the future, they will also use the algae residues to produce
renewable energy through anaerobic digesters.
But in order to extract the value from the algae, it needs
to be separated from the water that it is grown in, and
GEA Mechanical Equipment has a new generation of
separators specifically designed for algal biotechnology.
These separators can be used for processing small to
medium capacities of farmed algae suspension (up to
24,000 liters an hour), and producing very high levels of
dry matter.
GEA Process Engineering supplies GEA Niro Soavi
homogenizers for use in algal processing and GEA Niro
and GEA Barr-Rosin equipment for drying algae.
GENERATE MAGAZINE ISSUE 15 15