Used cooking oils from restaurant chains and food producers have become a useful commodity. The forecasted growth of the global usage of cooking oil increases year after year. Waste cooking oil is recycled and utilized for a number of purposes, such as industrial burner fuel and additives in manufactured products – but creating biodiesel is the largest use of waste cooking oil.
Biofuel refers to a type of fuel that is derived from renewable biological resources, such as plants, crops, or organic waste. It is considered an alternative to traditional fossil fuels, as it has the potential to reduce greenhouse gas emissions and dependence on finite fossil fuel reserves. Biodiesel is a type of biofuel produced from vegetable oils, animal fats, or recycled cooking oils through a process called transesterification.
Transesterification is a chemical reaction that involves the exchange of ester groups between an ester compound and an alcohol compound. It typically occurs in the presence of a catalyst, such as an acid or a base. The process results in the formation of a new ester compound and an alcohol compound as byproducts. Transesterification is commonly used in various industries, such as biodiesel production, where it is utilized to convert vegetable oils or animal fats into biodiesel fuel. It is often used as a substitute for diesel fuel in vehicles and machinery.
Producing biodiesel from used cooking oils
The US Dept. of Agriculture reports that the state of Alaska, alone, produces over 250,000 gallons of biodiesel annually from using recycled cooking oil gathered from local restaurants. The American Soybean Association reported that the largest increase in imports of the feedstock used to produce biomass-based diesel is from used cooking oil, which has gone from less than 300 million pounds in 2021 to over 3 billion pounds in 2023.
The US Department of Energy explains on its website that biodiesel is produced from vegetable oils, yellow grease, used cooking oils, or animal fats. The fuel is produced via the transesterification process which converts fats and oils into biodiesel and glycerin (a coproduct). ”Raw or refined plant oil, or recycled greases that have not been processed into biodiesel, are not biodiesel and should not be used as a vehicle fuel,” the site warns. “Fats and oils (triglycerides) are much more viscous than biodiesel, and low-level vegetable oil blends can cause long-term engine deposits, ring sticking, lube-oil gelling, and other maintenance problems that can reduce engine life.”
The Soybean Association also noted that the EPA requires that biofuel producers maintain chain of custody data for every gallon of used cooking oil, both domestic and imported origin, most likely to ensure the product meets standards.
Ensuring Waste Cooking Oil Meets Standards
Waste cooking oil collection companies can utilize X-ray fluorescence (XRF) analysis and EDXRF (energy-dispersive XRF) in particular to help ensure deliveries will meet the set standards.
In the case of used cooking oil analysis, EDXRF can provide information about the presence and concentration of various elements, such as phosphorus, sulfur, calcium, potassium, and heavy metals. These elements can be indicative of the quality and potential contaminants in the used cooking oil. By analyzing the elemental composition, EDXRF can help assess the suitability of the oil for further use or identify any potential adulteration or contamination.
XRF and EDXRF Analysis
X-ray fluorescence (XRF) analysis is a technology that utilizes the interaction between X-rays and matter. Atoms consist of a nucleus surrounded by electrons in shells, balancing the positive charge of the nucleus. When high-energy X-rays strike an atom, an electron in the inner shell is ejected, creating a vacancy. An electron from a higher shell then fills this vacancy, emitting secondary X-rays with an energy difference between the electron’s quantum states. Each element emits unique X-ray signals, forming an elemental fingerprint or spectrum during XRF analysis.
EDXRF (energy-dispersive XRF) enables quick and easy analysis of even irregular samples with little-to-no sample preparation. In EDXRF analysis, the characteristic X-rays of different elements present in a reading are separated into a complete fluorescence energy spectrum using either direct excitation (2D optics) or indirect excitation (3D optics). EDXRF technology is engineered to simultaneously process whole groups of elements for qualitative or quantitative analysis and can be used in portable and laboratory-based formats. As a result, EDXRF can accommodate samples of almost any shape and size.
An EDXRF Spectrometer can provide major, minor, and trace element quantification across the broadest range of samples, including bulk solids, granules, loose or pressed powders, fused beads, thin films, pastes, and liquids.
Summary
The exact amount of used cooking oil generated per year can vary depending on various factors such as population size, dietary habits, and cooking practices – and of course may differ in different countries and regions. However, the final product must be processed correctly, and analyzed to help ensure it is free of contaminants. EDXRF spectrometers can help safeguard the biodiesel supply, help reduce greenhouse gas emissions, and dependence on finite fossil fuel reserves.
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