Beyond animal feed? 115
chemicals, pharmaceuticals, packaging materials and energy resources (biogas,
ethanol), along with the by- products (e.g. fertiliser) of these processes. Below
we briefly discuss alternative valorisation options, drawing on the waste
pyramid presented in Chapter 3: disposal, energy recovery, recycling, reuse
and waste prevention. We do not assess whether one option is more sustainable than another, as this would require detailed life cycle analyses and also
depend on local- specific factors.
Disposal. A key issue in handling spent grain is its high moisture levels.
Spent grain consists of 70–80% water (Lynch et al., 2016; Thomas &
Rahman, 2006), meaning that transporting spent grain is costly per kg of dry
matter. Second, the rich polysaccharide and protein contents of spent grain
make it susceptible to fast deterioration and spoilage (Thomas & Rahman,
2006), with associated health and smell hazards. Hence disposing of spent
grain as a waste requires constant effort and can be expensive for the brewery,
so this option is the least preferred.
Energy recovery. Spent grain can also be used in energy production, as it can
show net calorific values of 18.64 MJ per kg dry mass and is thus interesting as
raw material for combustion (Keller- Reinspach, 1989). Spent grain can also
be used as a substrate for biogas or second generation- ethanol production,
replacing natural gas and gasoline respectively (Mussatto, 2014).
Recycling. Using spent grain in animal feed has several positive benefits,
including increasing milk production by cows and improving the meat quality
of livestock (Thomas & Rahman, 2006). Spent grain can also be recycled as a
soil conditioner. Combining spent grain with sludge or woodchips can
improve soil fertility (ibid.).
Reuse as human food. Spent grain has high contents of fibre, protein and
minerals, making it potentially attractive for human consumption. Experiments have improved properties in various food products including increased
levels of protein and fibres in cookies (Öztürk, Özboy, Cavidoğlu & Köksel,
2002), bread and processed meat products (Thomas & Rahman, 2006).
However, consumer acceptance and the quality of the final product need
more attention (Mussatto, 2014).
Reuse in chemical processes. Applying spent grain in chemical processes has
also been tested. Spent grain is rich in cellulose, polysaccharides and natural
antioxidants, all compounds adding value to industrial applications. Furthermore, spent grain can be used in the production of paper- based products such
as paper towels, business cards and coasters (Mussatto et al., 2006; Thomas &
Rahman, 2006). The most promising use of spent grain in chemical processes
is as an adsorbent for organic compounds from waste gas or dye from wastewater (Mussatto, 2014). Spent grain has also proved useful in biotechnical
processes (ibid.).
Waste prevention. The amount of spent grain by- product generated per
volume of beer produced depends on the brewing equipment; the type and
quality of the vessel that separates the wort from the spent grain is especially
significant when it comes to the efficient use of malt and water and hence for
chemicals, pharmaceuticals, packaging materials and energy resources (biogas,
ethanol), along with the by- products (e.g. fertiliser) of these processes. Below
we briefly discuss alternative valorisation options, drawing on the waste
pyramid presented in Chapter 3: disposal, energy recovery, recycling, reuse
and waste prevention. We do not assess whether one option is more sustainable than another, as this would require detailed life cycle analyses and also
depend on local- specific factors.
Disposal. A key issue in handling spent grain is its high moisture levels.
Spent grain consists of 70–80% water (Lynch et al., 2016; Thomas &
Rahman, 2006), meaning that transporting spent grain is costly per kg of dry
matter. Second, the rich polysaccharide and protein contents of spent grain
make it susceptible to fast deterioration and spoilage (Thomas & Rahman,
2006), with associated health and smell hazards. Hence disposing of spent
grain as a waste requires constant effort and can be expensive for the brewery,
so this option is the least preferred.
Energy recovery. Spent grain can also be used in energy production, as it can
show net calorific values of 18.64 MJ per kg dry mass and is thus interesting as
raw material for combustion (Keller- Reinspach, 1989). Spent grain can also
be used as a substrate for biogas or second generation- ethanol production,
replacing natural gas and gasoline respectively (Mussatto, 2014).
Recycling. Using spent grain in animal feed has several positive benefits,
including increasing milk production by cows and improving the meat quality
of livestock (Thomas & Rahman, 2006). Spent grain can also be recycled as a
soil conditioner. Combining spent grain with sludge or woodchips can
improve soil fertility (ibid.).
Reuse as human food. Spent grain has high contents of fibre, protein and
minerals, making it potentially attractive for human consumption. Experiments have improved properties in various food products including increased
levels of protein and fibres in cookies (Öztürk, Özboy, Cavidoğlu & Köksel,
2002), bread and processed meat products (Thomas & Rahman, 2006).
However, consumer acceptance and the quality of the final product need
more attention (Mussatto, 2014).
Reuse in chemical processes. Applying spent grain in chemical processes has
also been tested. Spent grain is rich in cellulose, polysaccharides and natural
antioxidants, all compounds adding value to industrial applications. Furthermore, spent grain can be used in the production of paper- based products such
as paper towels, business cards and coasters (Mussatto et al., 2006; Thomas &
Rahman, 2006). The most promising use of spent grain in chemical processes
is as an adsorbent for organic compounds from waste gas or dye from wastewater (Mussatto, 2014). Spent grain has also proved useful in biotechnical
processes (ibid.).
Waste prevention. The amount of spent grain by- product generated per
volume of beer produced depends on the brewing equipment; the type and
quality of the vessel that separates the wort from the spent grain is especially
significant when it comes to the efficient use of malt and water and hence for