Using brewery waste to grow yeast

Using brewery waste to grow yeast

Spent grain amounts to as much as 85% of a brewery’s waste. Researchers at Nanyang Technological University in Singapore found a way to convert this brewery waste into a valuable feedstock for yeast. We interviewed Professor William Chen, director of NTU’s Food Science and Technology Programme.

What are the current uses of spent grains as a waste product from breweries?

Currently, spent grains are used mainly for animal feeds.


Can you give an estimate of the size of this waste stream worldwide?

In Singapore alone, more than 23,000 tonnes of spent grains are generated every year.


You developed a process to turn the spent grains into a feedstock to grow beer yeast. How does this process work?

It’s a fermentation process, with food grade and non GM microbes, which break down the macromolecules (lipids, proteins and carbohydrates).


How much of the waste stream can be converted using your process?

Our process contains a second part which allows extraction of cellulose from the post-fermented solid waste. As a whole, there is no waste left behind after fermentation and cellulose extraction.


Has the process already been applied on a production scale?

We are in discussion to make our technology at industry level (more than 100 tonnes scale).


What do you consider to be the main advantages for the brewer?

Sustainable and low cost culture medium for the yeast growth. The surplus yeast culture from our technology can be used for other food applications (bakery for example).


Are there other industrial processes where the conversion process can be applied?

Our technology platform has been successfully applied to our side-streams of food processing industry, including soy bean residues.



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Grow Smarter Stockholm

Grow Smarter Stockholm

The GrowSmarter project brings together cities and industry to integrate and demonstrate 12 smart city solutions in energy, infrastructure and transport, to provide other cities with valuable insights on how they work in practice and opportunities for replication. We interviewed Gustaf Landahl, the coordinator for GrowSmarter in Stockholm.

What are the goals that Stockholm uses when it comes to sustainability?

We have a city vision that comprises 4 main areas: ecological, social, economic and democratic sustainability. In our environmental programme we have 6 main goals and 30 sub-goals in the areas of:

  1. Sustainable energy use
  2. Environmentally friendly transport
  3. Sustainable land and water use
  4. Resource-efficient recycling
  5. A non-toxic Stockholm
  6. A healthy indoor environment

And what is your current position regarding these goals?

The city asseses the goals annually through the integrated management system. The environmental goals are monitored the same way as all other progress and the budget for each administration in the city. Last year’s assessment showed that we are doing fine.

My role for the process was setting up the programme for the City administrative board  I was temporarily detached to the city hall a couple of years ago to produce this programme and also the Climate strategy to be fossil fuel free by 2040.

Around the world we see a trend where cities are more ambitious than national governments when it comes to climate change and pollution. Does that also apply for Stockholm?

In many ways I can agree on that. We have for example reduced the climate gas emissions in Stockholm per capita, from all activities both private and public, within the municipal border by 50 % between the years 1995 and 2015. Although we also need to mention that the Swedish national carbon tax introduced in the 1990’s has been of great help supporting this work.

The GrowSmarter project combines measures in the areas of energy, mobility and infrastructure. What is the advantage of this approach?

When I applied for the project my main aim was to go further with our climate work using smart solutions to reach further than we can do by just picking the low-hanging fruits. The smart measures include more behaviour change among the citizens with other modes of mobility and also changing habits for the use of energy for hot-water and electricity. As we only build passive houses we need active tenants to reach further.

Can you name some successful measures that Stockholm is implementing in the area of low energy buildings?

In the GrowSmarter project we focus on retrofitting buildings. In Stockholm especially those built during the “million unit programme” in 1960’s and 1970’s.

We are retrofitting 6 buildings from that period. We are including energy efficiency measures that reduce the energy use by 60 %. This includes measures like quadruple glazed window, but where the mobile-phones can transmit without interferences. Thermal insulation of façades. Heat recovery of ventilation air. Better control systems of heat but also of electricity with smart home systems and metering.

When it comes to energy efficient buildings there is often the effect that the owner of the building is not inclined to invest because the energy savings don’t accrue to him but to the renter of the house. How does Stockholm try to tackle this incentive problem?

In Sweden heat and hot water is included in the rent you pay for your apartment. So all measures that reduce the energy use can give savings to the building owner.

What are the measures in the area of smart mobility?

Several. Both building logistics at the retrofitting site saving transports and moving around goods at the site thus making working conditions better as well as saving money and emissions.

Delivery rooms in the retrofitted buildings so that good bought on the internet can be delivered to the buildings instead of to some other store or delivery point thus improving the quality of life for the tenants but also saving emission from transport.

Electrical vehicle car pools are built into the area as well as charging facilities for these and also bike-pools.

Do you also use environmental zones in the city and what is your experience with the effects of this?

We have environmental zone setting requirements on vehicles weighing more than 3.5 ton. These vehicles  must be of  EURO Class 5 or later to be permitted in the zone. The zone comprised the inner-city area of Stockholm. The legislation sets up the rules but it is up to the municipality to designate a certain area an environmental zone.

The national government is now also considering passing new legislation making environmental zones for cars also possible. This will have an effect on especially diesel cars.

The cities that participate in the GrowSmarter project have different starting points and infrastructures. Do you still feel that you can learn from each other’s successes and failures?

We can absolutely learn from each other and we do. Both between the Lighthouse cities of Stockholm, Cologne and Barcelona, but especially with our five follower cities: Cork, Porto, Valetta, Graz and Suceava.

The whole idea of GrowSmarter is to help create a market for our 12 smart solutions thus helping other cities to reduce their emissions, Help create new jobs among the 20 industrial partners in the project and finally to help improve the quality of life for our citizens.

They say that energy efficiency is the first fuel. Would you agree with this?

To reach the climate goals we need to save energy but also change fuel from fossil to renewable. We need both!

What inspires you to work on a transition project like GrowSmarter?

I set up the project to reach further in our climate work. By demonstrating and showing new solutions we can inspire others to follow these examples. We can also help induce change in our own cities. That is why I chose to apply and that is what I hope we can do to help Europe grow smarter!

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Photo’s: courtesy of Grow Smarter Stockholm

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