Program Book - Master Brewers Association of the Americas

O-62
Bioconversion of brewer’s spent grains to bioethanol
GRAEME WALKER (1), Jane White (1), Biju Yohannan (1)
(1) University of Abertay, Dundee, Scotland
Spent grains (SG), the solid cereal residues remaining after
extraction of wort, represent a major by-product of brewing
and distilling industries. This lignocelluose-rich biomass may
provide a source of sugars for fuel ethanol fermentations and
may therefore offer potentially valuable alternatives to current
uses of SG as animal feedstock (Walker and White, 2007).
Bioethanol represents a renewable source of energy (as opposed
to synthetic ethanol obtained from crude oils), and it can replace
petroleum or can be used as an additive in car engines to increase
fuel combustion, octane number and to reduce the emissions of
toxic and greenhouse gases. This presentation will review the
challenges and opportunities regarding bioconversion of brewer’s
and distiller’s spent grains to biofuels and will also discuss recent
results on brewery SG hydrolysis and fermentation to bioethanol.
Dilute acid and enzyme treatments were developed to convert the
hemicellulose and cellulose fractions of SG from an ale production
process to glucose, xylose and arabinose. Pre-treatment of dried,
hammer-milled grains with 0.16 N HNO 3 at 121°C for 15 min was
chosen as the most suitable method for solubilizing grains prior to
enzymatic digestion with cellulase and hemicellulase preparations.
Solid loading concentrations (10, 15 and 20% w/v) were compared
and reducing sugar concentrations between 40 and 48 g (100 g SG) –1
were extracted. Hydrolysate, prepared from 20% SG, pre-treated
with 0.16 N HNO 3 , partially neutralized to pH 5–6 and digested with
enzymes for 18 h, contained 27 g L –1 glucose, 16.7 g L –1 xylose and
11.9 g L –1 arabinose. Fermentation of this hydrolysate for 48 h by
Pichia stipitis and Kluyveromyces marxianus resulted in ethanol
conversion yields of 0.25 and 0.18 g ethanol (g sugar) –1 , respectively.
These non-Saccharomyces yeasts can ferment C5 sugars, unlike
brewing yeast. The fermentation yields, however, were less
when compared with fermentation performance on glucose/
xylose mixtures in synthetic media, suggesting that inhibitory
compounds (possibly furfural) derived from SG were present in
the hydrolysate. Our research findings have revealed relatively
straightforward chemical and biotechnological approaches to
convert brewery and distillery spent grains to bioethanol. “Second
generation” bioethanol derived from biowaste material such as
SG represents one of the most interesting biofuel sources. Several
future challenges remain, however, regarding cost-efficiencies and
energy balances of such processes and they will be discussed in this
presentation. References: Walker, GM and White, JS (2007) Fuelling
the future. The science behind fuel alcohol yeast fermentations. The
Brewer & Distiller International 6: 23-27.
Graeme Walker graduated with a B.S. degree in brewing and
biochemistry in 1975 and completed his Ph.D. degree in yeast
physiology (1978) both from Heriot Watt University, Edinburgh. His
professional career has included Royal Society/NATO postdoctoral
fellow at Carlsberg Foundation, Copenhagen; lecturer (biochemistry)
at Otago University, New Zealand; lecturer (biotechnology) at
Dublin City University; visiting researcher at Case Western Reserve
University in Cleveland, OH; senior lecturer (microbiology) at
Dundee Institute of Technology; and reader (biotechnology) at the
University of Abertay Dundee, Scotland. He is currently professor
and divisional leader for biotechnology and forensic science
at Abertay University, where he directs a yeast research group
investigating growth, metabolism, and stress in industrial yeasts.
He is an active member of the Institute of Brewing & Distilling
and American Society of Brewing Chemists. Professor Walker has
published over 100 articles in journals, books, and conference
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proceedings and has also authored the textbook “Yeast Physiology
and Biotechnology” published by J. Wiley (1998). He acts in a
consulting capacity for international brewing and biotechnology
companies.
O-63
A financial and engineering analysis of energy conservation
strategies with respect to heat generation processes within the
brewing industry
JOHN MEAD (1)
(1) Emech Control Limited, Auckland, New Zealand
As the world moves into the era of high fossil fuel costs and the
carbon economy dictates minimization of a company’s carbon
footprint the need to reutilize valuable energy will become more
and more important. So far most breweries have under-utilized the
opportunities that their current plant and processes provide for
energy recycling. The most common energy recovery process to
date has been the wort cooling process used to heat hot liquor. The
cooling of wort is a brewing process, and the subsequent energy
recovery is a by-product of this process rather then a purpose of
the original activity. The purpose of this presentation is to explore
energy recovery techniques that may be applicable to the brewing
process and to provide an executive analysis of the engineering
fundamentals in light of financial limitations and expected returns.
The presentation will include examples of current technologies
available, a commentary on their potential applications and a
critique of their potential limitations. As breweries expand into
developing countries and existing breweries modify processes
to meet their new operating environments the opportunities to
incorporate these technologies into current processes will generate
results that have an immediate impact on the financial bottom line.
With the move toward triple bottom line reporting such innovations
will also provide positive results from an environmental standpoint
and allow the company to report on non-financial aspects of its
operation. It is my intention to discuss technologies that will be
applicable to the boiler, general brewing process, refrigeration,
bottling and CIP activates. Examples will be provided as to how such
activities are currently being conducted in both breweries and other
processing plants. I will also provide a decision-making framework
that can be utilized by conference attendees for assessing the
benefits of proposed energy recovery projects and the prioritizing of
their implementation.
John Mead has worked in the engineering field for 18 years, starting
as a mechanical engineer in the motor trade. He spent eight years at
Unilever’s Industrial Chemical division before taking up the national
sales managers role at Renold NZ. Currently John is employed as
the Australasian sales manager for Emech Control. Emech Control
is a specialized valve and actuation manufacturer who produces
a range of valves and controls for a variety of customers in process
industries. John’s area of expertise is heat and energy recovery. John
holds a number of engineering qualifications and has also completed
a BBS and postgraduate qualifications in accounting. He is currently
completing his masters degree in environmental accounting, and his
core area of research is in creating economic models that illustrate the
impact energy issues have on companies operating profitably and
their share price.