USED COOKING OIL: FROM YOUR kitchen directly TO hitting up the road

All around the world, oil has been variously used for cooking purposes for centuries. Its major use, is as a medium for heat transfer when frying and of course as an additive for flavour and texture. There is a big variety of cooking oils derived from plants such as olive, sunflower and rapeseed that are mostly used in Europe, or soybean and palm oil that are widely used in south America and south-east Asia. In addition, butter and lard are considered as animal-based cooking oils. However, cooking oil does not stop being useful after being fried. Used cooking oil is considered a low-cost and renewable feedstock for the production of biodiesel and other biobased products.[8]

Europe and many individual countries have set goals regarding the climate change. Moreover, Sweden aims to be the first country that will become fossil free in the transportation sector by 2030. Thus, renewable fuels have become one of the main pillars to succeed such a goal. Vegetable oil is an already commercial used feedstock for the production of different renewable fuels such as biodiesel or hydrotreated vegetable oil (HVO). However, the use of such an edible feedstock is competing with food industry and poses the global dilemma of the need of feeding humanity versus the exploitation of land for agro-energy. Such a dilemma can be avoided with the use of used cooking oil (UCO) instead. Since the oil has already been used for cooking purposes it is considered a waste, hence the biofuels produced from UCO are as stated “second generation” biofuels.[3],[4]

During the last decade a significant increase in the usage of UCO has been reported in Europe. Even though rapeseed oil (RO) still remains the dominant biodiesel raw material, its share in the feedstock mix has decreased from 72% in 2008 to 47% in 2016. This is due to the use of recycled cooking oil that has become the second most important feedstock in Europe accounting to 18% in 2016. In Figure 1. a simplified process flow is illustrating the upgrade of waste oils to Hydrotreated Vegetable Oils (HVO) such as kerosene as a renewable jet fuel or green diesel as a renewable fuel used in the transport section. As it can be seen from the figure the UCO needs to be pretreated before the phase of hydrotreatment where hydrogen is added. Based on the feedstock green diesel could be classified as biodiesel, however, based on the processing technology and chemical formula green diesel and biodiesel are different products.[2],[5],[6]

Figure 1. Simplified process flow for HVO production from vegetable oil/ UCO

Overall, as presented UCO exploitation can involve large reductions in life cycle impacts, cutting the need for virgin vegetable oil for fuel production and promoting a way of waste management for this type of waste. Furthermore, some additional advantages of this biomass resource are that it can be found in abundance and since it is waste that is non-edible anymore it does not longer compete with food. Finally, it is a feedstock that depending on the chosen method can produce a variety of bio-products. Despite UCO seems to be an attractive choice of feedstock, there are some challenges that need to be overcome. Firstly, the supply chain plays a major role in the sustainability of the proposed production schemes, hence life cycle assessment of the feedstock must be done to examine the environmental impacts of the feedstock from its harvest to the collection point of UCO and it is necessary to deploy effective policies and regulated practices to enhance UCO recycling and collection rates, under multistakeholder considerations. Moreover, UCOs have a highly heterogenous nature, depending their origin, that make them having a big variety of different properties (i.e physicochemical, impurities, color, odor), thus the right pre-treatment method must be chosen.

References

  1. European Biomass Industry Association, 2020, “Used Cooking Oil”, ” https://www.eubia.org/cms/wiki-biomass/biomass-resources/challenges-related-to-biomass/used-cooking-oil-recycling/
  2. Dong-Shik Kim , Mohammadmatin Hanifzadeh, and Ashok Kumar, 2017, ”Trend of Biodiesel Feedstock and Its Impact on Biodiesel Emission Characteristics”, ”Environmental Progress & Sustainable Energy”, Volume 37, DOI 10.1002/ep.12800
  3. Swedish Environmental Protection Agency, 2019, ”Sweden’s Climate Act and Climate Policy Framework”, ” http://www.swedishepa.se/Environmental-objectives-and-cooperation/Swedish-environmental-work/Work-areas/Climate/Climate-Act-and-Climate-policy-framework-/
  4. Regis Rathmann, Alexandre Szklo, Roberto Schaeffer, 2008, “Land use competition for production of food and liquid biofuels:An analysis of the arguments in the current debate”, ”Renewable Energy: An International Journal”
  5. Radhika Singh, Stamatis Kalligeros, Jai Uppal, 2018, ”Advanced Biofuels in India: A comparative analysis between India and the EU for cooperation and investment”
  6. Wikipedia, ”Vegetable Oil refining”, ”https://en.wikipedia.org/wiki/Vegetable_oil_refining#Comparison_to_biodiesel”
  7. Alvaro Orjuela James Clark, 2020, ”Green chemicals from used cooking oils: Trends, challenges, and opportunities”, ”Current Opinion in Green and Sustainable Chemistry”, Volume 26
  8. Wikipedia, ”Cooking Oil”, ”https://en.wikipedia.org/wiki/Cooking_oil”

6 Comments on “USED COOKING OIL: FROM YOUR kitchen directly TO hitting up the road

  1. Hi! Your blog is very interesting. The idea of using waste vegetable oil instead of deiseal is amazing because it is not only an economical alternative of fossil fuel but it gives a waste management solution as well. However we should focus to develop such system that can efficiently processed the used oil into biodiesel at low cost.

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  2. Interesting topic which shows that there are alternatives for fossil fuels, especially when it can be extracted from “waste materials” but like you say it comes with the important question of sustainability and life cycle assessment to determine if it is alternative.
    An old memory also got back to my mind when reading this, I remember when I heard someone from my hometown had converted his old diesel car into a car driven by vegetable oil and I remember thinking that it sounded crazy. Just a little sidenote I thought I would share.

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  3. Great blog post. I think this is great, using used cooking oil as a fuel. I guess there is plenty of waste cooking oil from the food industry. My questions are, where does this oil go, if it is not used as a substrate for biofuel? Is it just dumped into landfills, or even into the drainage…?

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    • Dumping oil down the drain would be a very bad idea and also illegal. It’ll also cause sewage blockages and backwash, corrosion of metals and concrete degradation. Not to mention the smell. Landfilling of flammable and liquid waste is also illegal in the EU. It must be recovered, processed or recycled. Other uses for cooking oil is soap & cosmetic production and as a feedstock for stearic acid and methyl ester. It can also be used as food for livestock.

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  4. Circular economy in action. McDonald’s uses their waste cooking oil to power their delivery trucks. They even produce biodiesel made from left over grease contained in mops and cleaning cloths. They claim to recycle approximately 80% of the waste grease into biofuel.
    I don’t think we’ll stop eating fried food any time soon so this is a great transitional energy source.

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  5. Thank you for a great post! In my mind the quantity of used cooking oil must huge considering our diets, especially in EU and the US.
    To utilize it as a fuel istead on fossil fuel is an innovative idea. If fossil based fuels are going to be entirely replaced, all of the available resources for renewable fuels needs to be considerd, which this is a great example of.
    However, as you mention there are many obstacles to overcome regarding the sustainabillity processing and supply chain.

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