Biofuel Potential from Orange Peel

(Polytech University of Madrid (Google Translation)) Researchers from the Polytechnic University of Madrid are part of a scientific team that has managed to produce a biofuel from orange peels that emits 55% less soot, which represents a promising advance in reducing emissions both in aviation and in automotive.

Currently, there is a worrying need to seek environmentally sustainable alternatives to replace fossil fuels, especially in the transport sector, whose current dependence on these non-renewable fuels is over 97% in the European Union. For this reason, the use of the native resources of each country favors the security of supply compared to imported raw materials and increases industrial and economic development at the regional level. A team of researchers from the Polytechnic University of Madrid (UPM) and the University of Castilla-La Mancha (UCLM) have used waste from the fruit industry to extract orange oil and analyze its potential as a fuel for bioreactors. The results obtained show that said oil is a viable alternative to be mixed up to 15% with jet fuel, without any significant inconvenience for their performance, and complying with all the requirements of aviation standards. Biofuel has been treated to reduce its tendency to form soot, so its use would help reduce polluting emissions from current fuels.

Tendency to soot formation against conversion of orange oil and limonene.
Source: Own elaboration (pexels.com, cleanpng.com).

The fruit industry and, specifically, the orange juice industry generates a large amount of by-products and waste, up to 30 million tons annually, which need to be managed to avoid serious economic and environmental problems. These residues have a high content of terpenes, the transformation of which makes it possible to obtain suitable biofuels to be mixed with conventional fuels, both in aviation and in the automotive industry. Among these residues, orange peels contain orange oil, which can be extracted by pressing or using solvents.

Orange oil, mainly made up of D-limonene, could be used as a biofuel in aviation and automotive due to its excellent density and calorific value (together, they indicate the amount of energy stored in the vehicle's tank) and cold flow properties. (that is, the behavior of the biofuel at low temperatures). However, the high tendency of orange oil to form soot during its combustion makes it necessary to transform it through the chemical process of hydrogenation. "The main advantage of this process is that the complete hydrogenation of the fuel allows it to reduce its soot emission by 55%, as we have verified in our study," says David Donoso, a researcher at the ETS of Industrial Engineering at the University of Castilla-La Stain.

The fruit industry is consolidated in various productive sectors, so the use of the vast majority of its by-products increases its competitiveness. For example, residual orange oil is used in various applications: food, cosmetics and pharmacy. However, the residues derived from the food consumption of oranges and the waste of oranges in poor condition in the cultivation fields could also be used. In addition, there are other citrus fruits (lemon, grapefruit, lime, citron, yuzu, bergamot or combava) from which terpenes can be extracted, such as the D-limonene present in oranges or tangerines, in different proportions. Therefore, "the introduction of orange oil (and other citrus-derived terpenes) into a new market, such as fuels for transportation,

Orange oil derived from the juice industry could replace 0.1% or 0.02% of the kerosene and diesel consumed in Spain in 2019, respectively. Clearly, the incorporation of orange oil into the biofuels market would not be enough to meet the targets for reducing polluting emissions to mitigate the effects of climate change, but it would help. "In the future energy scenario, multiple sources of biofuels will have to be used to replace fossil fuels," the researchers conclude. READ MORE

Donoso, D., Bolonio, D., Ballesteros, R., Lapuerta, M., Canoira, L. Hydrogenated orange oil: A waste derived drop-in biojet fuel. Renewable Energy 2022, 188, 1049–1058. https://doi.org/10.1016/j.renene.2022.02.078.