Scottish whisky is a truly iconic product, with Scotland the largest-producing nation of whisky worldwide. Production has increased by 30 percent in the last decade and more than five times in the last half-century. In 2011 more than 500 million litres of pure alcohol (lpa) of whisky were produced in the UK. As the whisky industry prospers, more attention is drawn to the by-products of whisky production. Whisky manufacture yields considerable amounts of by-products – which include liquid and solid components – alongside the main product. These materials contain significant amounts of proteins that are currently underutilised and are often perceived as a challenge rather than an opportunity for distillers.

1. I N C O R P O R AT I N G
f i s h far m ing t e c h no l og y
January | February 2014
Whisky by-products – a sustainable protein
source for aquaculture
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The International magazine for the aquaculture feed industry

3. FEATURE
Whisky by-products
– a sustainable protein source
for aquaculture
by Julio Traub, PhD student, Heriot-Watt University, Edinburgh, Scotland
S
cottish whisky is a truly iconic the development of sustainable methods for University in Edinburgh, Scotland. The team
product, with Scotland the largest- protein recovery suitable to the needs of both has been working on a protein recovery procproducing nation of whisky world- whisky and aquaculture producers, and a mas- ess from brewery and distillery by-products
wide. Production has increased by tery of the economics behind the process and since 2011. This article will focus on the
30 percent in the last decade and more product are essential to ensure a sustainable nutritional properties and quantities of protein
than five times in the last half-century. In large-scale protein supply to the aquaculture that could be potentially recovered from
whisky by-products and particularly pot ale
2011 more than 500 million litres of pure feed sector.
“Horizon Proteins” is a collaborative and draff, which are both produced during the
alcohol (lpa) of whisky were produced in
the UK. As the whisky industry prospers, research project based at Heriot-Watt manufacture of malt whisky.
more attention is drawn to the
by-products of whisky production.
Whisky and whisky
table 1. Malt and grain whisky by-products.
Whisky manufacture yields conby-products
siderable amounts of by-products
Whisky spirit is produced from
– which include liquid and solid Malt Whisky Pot ale: residues from first distillation, also known
either malted barley as the sole
components – alongside the main
cereal substrate or a mixture of
as “Burnt ale”. liquid substance that contains
typically 5% solids and at least 40% protein on dry
product. These materials contain
unmalted cereal grain together with
matter basis.
significant amounts of proteins
malted barley. It is important to
Spent lees: residual liquor after second distillation.
that are currently underutilised
distinguish between the two kinds
Mostly water, but also contains some volatile
and are often perceived as a chalof whisky (malt and grain) and the
components. nutritive value is negligible and
lenge rather than an opportunity
cereals used in the process, since
normally treated in bio-plants.
Draff: grain solids left after starch and enzyme
for distillers.
the properties of the whisky and its
extraction. Sometimes referred as distillers' grains
by-products differ substantially.
and used as animal feed. It contains typically
The salmon farming indusThe production of malt whisky
70-85% moisture and at least 20% protein on a dry
try, with a growing demand for
in Scotland requires only three raw
matter basis.
proteins to satisfy the nutritional
materials: barley, yeast and water.
Grain Whisky Spent Wash: liquid residue after distillation.
requirements of their fish stocks,
Nothing more, nothing less. This is
Comparable to pot ale from malt whisky production
could take advantage of the proa statutory requirement under the
Spent Grain: the equivalent of draff in grain
whisky production.
teins available from whisky byScottish Whisky Regulations 2009.
products. By reducing the reliance
Scottish malt whisky can only be
on wild fish and imported protein
made (and, since 2012, bottled) in
sources (e.g. soybean meal) to
Scotland so this holds worldwide.
meet the needs of an expandConsequently, the by-products
ing market, UK aquaculture could
from malt whisky originate from the
benefit economically from a locally
raw materials mentioned above.
sourced sustainable protein supply.
There are various types of bySymbiotic relationships such as this
products, but from a nutritional
can help to secure the long-term
perspective, two are of particular
sustainability of the aquaculture
importance. Draff (also known as
industry to meet the nutritional
spent grains) is a solid by-product
requirements of an expanding
typically containing 70-85 percent
world population.
moisture and at least 20 percent
An understanding of the
crude protein content on a dry
Figure 1: Historical malt whisky production in Scotland
nutritional, chemical and physical
matter basis. The other protein-rich
1946-2012 (Source: Scotch Whisky Association)
properties of whisky by-products,
by-product is pot ale. Pot ale is
20 | InternatIonal AquAFeed | January-February 2014

4. FEATURE
table 2. Chemical composition and feeding values of malt
distillery by-products. (2)
Draff
Pot ale
Dry Matter (g kg-1)
82
22
173
-
ash (g kg-1 DM)
33
105
Ca (g kg-1 DM)
processing technologies rely
on energy-intensive methods.
Hence, due to increasing energy
costs and increased competition, distiller’s by-products will
have a reduced potential value
to the whisky industry. Finding
alternative markets for these
by-products is important from
an economic and a sustainability
perspective.
350
Crude fibre (g kg-1 DM)
a liquid substance that contains typically 5
percent solids and at least 40 percent protein
on dry matter basis. A list of distilling byproducts and their definitions are presented
in Table 1. Figure 2 shows a simplified process diagram of malt whisky production, which
includes raw materials, by-products and the
main steps of the process.
Whilst whisky by-products have wellestablished markets in Scotland, current uses
do not specifically exploit the particular protein content of these materials. Currently,
draff and pot ale are used as food for cattle,
energy recovery, fertiliser and feedstock for
anaerobic digestion. However, in the medium-
to long-term, with bioethanol plants (which
also produce plentiful cereals by-products)
coming online, there will be an increasing
competition for distillers. Additionally, current
40
198
ether extract (g kg-1 DM)
1.7
1.6
P (g kg-1 DM)
3.7
22.0
Mg (g kg-1 DM)
1.4
6.6
na (g kg-1 DM)
0.9
1.1
K (g kg-1 DM)
Figure 2: Malt whisky production process
258
Crude protein (g kg-1 DM)
3.7
23.0
-
6.8
Cu (g kg-1 DM)
S (g kg-1 DM)
10
133
Mn (g kg-1 DM)
43
17
Zn (g kg-1 DM)
-
18
Co (g kg-1 DM)
0.02
0.11
Se (g kg-1 DM)
0.02
-
Metabolisable energy value (MJ kg-1 M)
10.8
14.2
Degradability of crude protein
0.80
0.95
Barley and yeast in
aquaculture feeds
To understand the nutritional properties
of the whisky by-products it is necessary to
review their components, specifically barley
and yeast. Barley has been incorporated in animal feed diets, but has not been widely used
in aquafeeds for several reasons. Economical
and nutritional considerations have played a
key role in these decisions.
Compared to other plant feedstuffs used
in aquafeeds (see Table 3), barley has a low
protein content (15 percent compared to 49
percent for soybean meal). However, a good
amino acid profile makes the barley protein
itself a suitable candidate for aquafeed diets.
take a
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January-February 2014 | InternatIonal AquAFeed | 21

5. FEATURE
table 3. typical composition (as-fed basis) of fish meal and various plants feedstuff .(3)
Protein
(%)
lipid
(%)
ash
(%)
lysine
(%)
Methionine
(%)
Cystine
(%)
Fish meal
72.0
8.4
10.4
5.57
2.08
0.74
Barley
14.9
2.1
2.9
0.44
0.16
0.24
Canola
38.0
3.8
6.8
2.27
0.70
0.47
Corn
8.5
3.6
1.3
0.25
0.17
0.22
Soya bean meal
48.5
0.9
5.8
3.08
0.68
0.75
Wheat
12.9
1.7
1.6
0.36
0.21
0.27
Ingredient
Malt whisky by-products: pot ale (left) and draff (right)
The other essential component in whisky
production is yeast. Although the volumes
of yeast compared to barley are substantially
smaller (typically a 60 to 1 ratio of barley to
yeast is used in malt whisky processing), the
nutritional properties of yeast are worth
considering.
Previous articles in International Aquafeed
have reviewed the nutritional properties of
yeast, but to summarise here, on a dry matter basis yeast can contain up to 50 percent
protein. Additionally, other components beneficial to aquaculture can be found in distillers
spent yeast such as nucleotides and β-glucans.
Potentially
tein output from UK malt whisky could offer
up to 70,000 tonnes per annum of proteins
to the animal and aquaculture feed markets.
Average outputs of whisky by-products
are reported in Table 4 below. Typically, solid
by-products from malt whisky distillation have
a bigger output per litre of pure alcohol than
grain whisky distillation, but it is the other way
round for liquid by-products. This is explained
by the fact that the quantity of starch convertible into glucose is greater in the cereals
used for grain whisky than those used for the
production of malt whisky.
Potentially
70k tonnes p.a.
£140m p.a.
of protein in malt
whisky by-products
across Scotland
worth of protein in
whisky by-products
across Scotland
Protein supply from
whisky by-products
Market value
The market value of whisky by-product will
depend on several factors including their protein
and moisture content. Ultimately however, their
price will be driven by international prices for
fish and soybean meal. Based on these factors
and current protein prices,
it could be estimated that
table 4. By products outputs per litre of pure alcohol (2)
protein recovery from malt
Malt
Grain
whisky co-products could
be worth up to £140m
Solid by-products
3.5-5.5 kg
1.0-1.25 kg
per annum across Scotland.
Other fermentation procliquid by-products
8.8-11.5 l
16-21 l
Considering all the malt whisky distilleries
in Scotland, proteins contained in pot ale
could potentially supply at least 40,000 tonnes
per annum. Including draff, the combined pro-
22 | InternatIonal AquAFeed | January-February 2014
esses with by-products similar to the malt whisky
industry, including grain distilleries, breweries and
biofuels, could represent a protein source worth
more than 200,000 tonnes annually, equivalent
to £150-450m in protein sales across the UK.
Protein demand for salmon farming
Worldwide, farmed salmon and trout production reached 2.5 million tonnes in 2009. The
main species cultured (Atlantic salmon, Rainbow
trout and Coho salmon) accounted for around
95 percent of total salmon and trout production.
The combined output of the top three producers (Norway, Chile and UK) represented more
than 70 percent of the world's total output of
the fish.
Protein requirements for the species mentioned above could include up to 50 percent
of their feed’s ingredients, which equates to a
protein demand of at least 1.3 million tonnes
globally on an annual basis. Protein demand for
salmon and trout feeds in the UK is approximately 85,000 tonnes per annum.
The aquaculture industry is set to expand
in the coming years and its protein demand
will consequently follow. In the UK alone, a 50
percent increase in salmon and trout production
is expected by 2020, which translates into a
protein consumption of at least 150,000 tonnes
annually.
Conclusion
Scotch whisky and Scottish aquaculture
could develop beneficial industrial synergies.
The proteins found in whisky by-products are
nutritionally comparable to proteins used in
the currently available fish feed ingredients, and
their potential volumes are enough to satisfy the
Scottish salmon farming industry and achieve
substantial protein sourcing benefits, in economical and sustainability terms. Whisky by-products
can offer a sustainable supply of suitable protein
to the aquaculture industry.
There is a need to identify appropriate and
sustainable techniques to obtain these proteins
on an industrial scale. At Horizon Proteins, a
Scottish research team is developing a sustainable process for protein recovery that could have
much more financial viability than traditional
treatment technologies for whisky by-products.
The savings are not only shown economically,
but through the significant reduction in energy
requirements in processing, reducing the increasingly important global warming impact of the
overall process.

6. FEATURE
FEATURE
EXCELLENCE IN YEAST –
EXCELLENT FOR FISH
Figure 2
erm
e
ad
G
in
in G e r m a n
y•
M
any • Made in
ad e
•M
Ge
y
farm is bound to produce 7,000 tonnes be grown in anothutilising an area of 57 hectares (see Figure 2). er unit in Portugal
Nevertheless, recent production problems recently acquired
that have arisen have unfortunately compro- for the purpose.
mised this turbot farm to attain full capacity Beginning production
in 1997, the Aquacria
production already this year.
The Acuinova layout is a double row of Piscícolas facility was
eight production units. Each production unit has the third flatfish
one juvenile pavilion and eight growth pavilions. unit constructed in
In the overhead shot of Figure 2, the juvenile Portugal. This highpavilions are coloured darker than the growth tech flatfish farm is
pavilions. Each juvenile pavilion (see Figure 3) located in Torreira in
has 30 40 m2 tanks for 10-100 g turbot, making the north of Portugal,
a total of 480 juvenile tanks, and each growth and is the only aquapavilion in turn has 20 113 m2 growth tanks for culture facility in the
fish from 100 gr. to commercial size in a total country operating
of 1,248 growth tanks (see Figure 4). At full with shallow raceway
capacity it will create more than 200 direct and system technology
in conjunction with
600 indirect jobs.
Ten-gram juvenile turbot are brought a recirculation aquaweekly from one of the Spanish company’s culture system (RAS)
turbot hatcheries to Acuinova Mira. Fish are for the growth out
automatically and manually fed, up to twelve phase of Senegalese
G er
y
ma
times daily with juveniles and up to four times sole • Made inproduction,
an
n
rm
daily in the grow-out phase, until they reach allowing L the fish
REA
BREWERS‘
the commercial size of 1-1.5 kg which may farm to substantially
YEA its
last between 600 and 750 days. Acuinova reduce ST environhas two pumping stations, the water intake is mental impact (see
located 2.4 km offshore, each one equipped Figures 6, 7).
In 2011, during
with nine 250 kW pumps providing a 10.8 m3
per second water flow, enough to provide a the management of
For Leiber`s specialty yeast products,
daily water supply for a city the size of Madrid. its previous own“Made in Germany” is afarm, ers, quality.farm
seal of the flatfish
Another Portuguese turbot
Piscicultura do Rio Alto, located in Estela in began its expansion
northern Portugal (see Figure 5), produced policy, which was
Multibiotic effect when it was already
turbot from 1993 to 2011, of Leiber yeast – concluded.
decided to abandon turbot production and Therefore, producvitality, health and performance
farm Senegalese sole instead. At present, this tion of Senegalese
for fish.
aquaculture unit is undergoing major modifica- sole will be substantions after being bought this year by a Spanish tially increased, with
company (Sea8 Porto) to be converted into an output of 350-400
a hatchery for Senegalese sole, which will tonnes estimated for
in G
ermany • M
a
de
Leiber GmbH
Hafenstraße 24
49565 Bramsche
Germany
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Figure 3
January-February 2014 InternatIonal AquAFeed 23
January-February 2014 || InternatIonal AquAFeed || 25

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