How to use Scotland’s whisky by-products
A key benefit of life cycle assessment (LCA) is its ability to take in the whole picture. LCAs examine incremental contributions to determine the entire impact of a decision over its lifetime. For a product or service this can be relatively straightforward. However, when we apply this to a policy, we often do not have a specific design in mind and want to pose a series of ‘what-if’ questions to understand how we can guide decision making to reach an environmentally sustainable outcome. This makes our work slightly more complex but yields fascinating results!
ClimateXChange approached us with a really interesting question and asked us to look at the entire lifecycle impacts of using some forms of whisky by-products in renewable energy, traditional animal feed or concentrated dark grains animal feed.
ClimateXChange is Scotland’s centre of expertise on climate change and publishes academic research to support policy making in Scotland. One of its areas of focus is renewable energy.
There are two core by-products from whisky distilleries in Scotland: draff (the wet grains which are no longer useful in the production of alcohol) and pot ale (liquid residue from the first distillation stage). These two substances can be used as a feed source for cattle, as fertilisers or as a source of renewable energy. The question posed by ClimateXChange was, in terms of global warming potential (GWP), what is the best option for using these by-products?
Our study focussed on the GWP of processing 1,000 tonnes of draff and 3,300 tonnes of pot ale, asking what-if we sent the by-product to one of three options:
- Renewable energy, in the form of combustion and anaerobic digestion
- Traditional animal feed
- Concentrated ‘dark grain’ animal feed
As with any LCA, we examined each scenario, building inventories of materials and processes (in the form of a mass and energy balance) to represent the different stages of its whole lifecycle. Taking the combustion stage of the renewable energy scenario as an example: the inventory mirrors a typical combustion facility, allocating capital burden impacts associated with the concrete and steel needed to build the facility, energy use at the facility, maintenance impacts and the output, in this instance renewable energy.
Future proofing model design
While the three core scenarios are relatively straightforward to compare, we wanted to enable ClimateXChange to pose further what-if questions as part of the sensitivity analysis and also ensure our model could accept wider questions as part of future studies. We created an interface whereby the user can choose the core three scenarios (renewable energy, animal feed and dark grains), but also transport scenarios, impact scenarios and sensitivities. This was all wrapped up in a what-if engine that could present the results of every combination together, enabling easy comparison.
This careful design enabled us to effectively incorporate questions raised at a stakeholder meeting facilitated by ClimateXChange with representatives from the Scottish Government, the Scotch Whisky Association and the Scottish Tennant Farmers’ Association. Questions included what would the impact be if the animal feed scenario offset soy meal rather than rape meal and what would the impact be of offsetting distilleries’ use of heavy fuel oil (HFO) rather than natural gas.
A further study then investigated what would the impact be if no pot-ale were produced as by-product? This is analogous to grain distilleries that only produce draff-like by-product.
It is important to state upfront that each scenario reduces greenhouse gas (GHG) emissions and would have a beneficial impact of GWP.
The renewable energy scenario was found to offset the largest amount of GHG emissions overall, when examining uses for draff and pot-ale by-products. A sensitivity analysis that examined offsetting soy meal animal feed, rather than rape meal, found an increased GWP benefit from the Animal Feed and Dark Grains scenarios. However, the renewable energy scenario was still found to be better in terms of GWP.
In contrast, when exploring uses for draff on its own, the study found a negligible difference between the renewable energy and animal feed scenarios. The two scenarios led to comparable reductions in GHG emissions via offsetting energy production or alternative animal feeds.
A key sensitivity concerned fuel use at the distilleries. The core study assumed that the renewable energy scenarios avoided the need to burn natural gas. However, many remote distilleries are not connected to the gas grid and tend to use heavy fuel oil (HFO) for their heating requirements. Under these circumstances, there was a significant benefit in using the draff for renewable energy rather than as an animal feed. This was true for the draff and pot-ale study and the draff only study.
“This was an important study that provides information which will help inform discussions on bio-energy moving forward. I was very pleased with the study that Ricardo delivered; its in-depth assessment of the different scenarios provides me with confidence in its results”.
Keith McWhinnie, Scottish Government
This was a really fascinating project and we are delighted that ClimateXChange are pleased with the robustness of our findings. We look forward to seeing how these results are used to support Scotland’s bio-energy policy.
If this article has resonated with you and you want to know more about how LCA can reveal hidden secrets to support your work, please contact one of our LCA experts. Our team is experienced in creating dynamic models that can help you:
- Test proposed policy or business decisions through a range of scenarios
- See where carbon or cost is embedded in an activity or product’s life cycle, enabling decisions to be targeted
- Pick the best green investment based on a range of environmental indicators
The report is published on the ClimateXChange website at https://www.climatexchange.org.uk/research/projects/whisky-by-products-in-renewable-energy/