How We Make Biodiesel Fuel — Part 1
For my second entry in The Clean Air Journal, I thought it would be good to explain how my company makes this new cleaner, greener biodiesel fuel for the future. I’ll walk you through the entire process in a series of posts here. Follow us on our journey, as I share my insights, build my company, and create a greener footprint for the city of Columbus, Ohio.
Now let’s put on our lab coats and protective goggles, as I share with you how we take waste cooking oil used to make french fries, fried chicken and doughnuts — transforming it’s properties into biodiesel — waste to energy.
WHAT IS BIODIESEL?
Biodiesel can be run in any diesel engine without modification. It may be blended with regular dinosaur diesel at any percentage. Currently B20 is the most frequently sold blend at fuel stops worldwide. The B20 is 20 percent biodiesel and 80 percent dino diesel mixed together.
Biodiesel is an alternative fuel similar to conventional or dinosaur diesel. Biodiesel may be produced from straight vegetable oil, animal oil/fats, tallow, and waste cooking oil. The process used to convert these oils to Biodiesel is called transesterification.
This process is described in more detail later in the blog so keep reading. The largest possible source of suitable oil comes from oil crops such as canola, palm, or soy. In Ohio, where we are headquartered, the high availability soybean oil presents the greatest potential for biodiesel production.
However, most biodiesel is produced from waste vegetable oil sourced from restaurants, food trucks, and industrial food producers. Although oil direct from the agricultural industry represents the greatest potential source, raw oil is expensive so offsetting costs with used cooking oil is paramount to profitability.
After the cost of converting raw oil to biodiesel has been added on it is simply too expensive to compete with dinosaur diesel. Waste vegetable oil can often be sourced for free or sourced already treated for a minimal price. Waste cooking oil must be treated before conversion to biodiesel to remove impurities. The result is biodiesel produced from waste vegetable oil can compete with standard diesel.
Biodiesel has many environmentally beneficial properties. The main benefit of biodiesel is that it can be described as carbon neutral. This means that the fuel produces no net output of carbon in the form of carbon dioxide (CO2).
This effect occurs because when the oil crop grows it absorbs the same amount of CO2 as is released when the fuel is combusted. In fact, this is not completely accurate as CO2 is released during the production of the fertilizer required to fertilize the fields in which the oil crops are grown.
Fertilizer production is not the only source of pollution associated with the production of biodiesel, other sources include the esterification process, the solvent extraction of the oil, refining, drying, and transportation. All these processes require an energy input either in the form of electricity or from a fuel, both of which will generally result in the release of greenhouse gases.
To properly assess the impact of all these sources requires use of a technique called life cycle analysis. Biodiesel is rapidly biodegradable, and completely non-toxic, meaning spillages represent far less of a risk than dinosaur diesel spills. Biodiesel has a higher flash point than fossil diesel and so is safer in the event of a crash.
As mentioned above biodiesel can be produced from straight vegetable oil, animal oil/fats, tallow, and waste oils. There are three basic routes to biodiesel production from oils and fats:
- Base catalyzed transesterification of the oil.
- Direct acid catalyzed transesterification of the oil.
- Conversion of the oil to its fatty acids and then to biodiesel.
Almost all biodiesel is produced using base catalyzed transesterification as it is the most economical process requiring only low temperatures and pressures and producing a 98% conversion yield. For this reason, only this process will be described in this blog post.
The transesterification process is the reaction of a triglyceride (fat/oil) with an alcohol to form esters and glycerol. A triglyceride has a glycerin molecule as its base with three long chain fatty acids attached. The characteristics of the fat are determined by the nature of the fatty acids attached to the glycerin.
The nature of the fatty acids can in turn affect the characteristics of the biodiesel. During the esterification process, the triglyceride is reacted with alcohol in the presence of a catalyst, usually a strong alkaline like sodium hydroxide. The alcohol reacts with the fatty acids to form the mono-alkyl ester, or biodiesel and crude glycerol.
In most production methanol or ethanol is the alcohol used (methanol produces methyl esters, ethanol produces ethyl esters) and is base catalyzed by either potassium or sodium hydroxide. Potassium hydroxide has been found to be more suitable for the ethyl ester biodiesel production, either base can be used for the methyl ester.
The reaction between the fat or oil and the alcohol is a reversible reaction and so the alcohol must be added in excess to drive the reaction towards the right and ensure complete conversion. The result if the reaction is the biodiesel fuel itself, and the glycerol byproduct.
A successful transesterification reaction is signified by the separation of the ester and glycerol layers after the reaction time. The heavier, co-product, glycerol settles out and may be sold as it is or it may be purified for use in other industries, such as pharmaceuticals, cosmetics, etc. There is almost no waste from the production of this green biodiesel fuel.
In the next Clean Air Journal entry, I’ll share more about how we produce American Society for Testing and Materials (ASTM ) specification biodiesel by using ionized resins in a lead-lag setup of ion polishing towers. Please share, like and subscribe — Thank You 🙏🏻