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Using HVO as an alternative fuel choice in standby generator applications

Air Quality and Odour By Thomas Vaughan, Graduate Air Quality Consultant – 02 April 2024

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Thomas Vaughan

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What is HVO?

Hydrotreated or hydrogenated vegetable oil (HVO) is a biofuel made by hydrocracking or hydrogenating vegetable oil. Hydrocracking is the process of breaking down larger molecules using hydrogen, whereas hydrogenation is the process of adding hydrogen to vegetable oil molecules.

HVO can be produced from many kinds of vegetable oil and fats consisting of triglycerides (a type of fat found in the bloodstream) and fatty acids. Examples of feedstocks include rapeseed oil, sunflower oil, soybean oil, corn oil, palm oil, waste cooking oil, tall oil, and animal fats. Purpose-grown palm and soy plantations contribute to deforestation, whereas HVO produced from 100% waste-derived feedstock, such as used cooking oil, is considered the most sustainable. The resulting HVO is a renewable, paraffinic liquid fuel with comparable properties to fossil diesel but lower in carbon. It is classed as a renewable fuel as the materials used to create it can be easily replenished.

Although similar in its chemical and physical properties to diesel fuel, HVO has a lower carbon content, making it cleaner when used, with lower resulting emissions of CO2, nitrogen oxides (NOx) and particulates. One study, for example, found that the use of 100% HVO led to 6% lower NOx and 35% lower smoke compared with sulphur-free EN 590 diesel fuel (the current standard for all automotive diesel fuel sold in the European Union member states and other European countries).

Standby Generators

Standby generators are required as a backup option to supply power to a facility if the mains utility supply were to fail, but many have high emission rates of NOx, particulate matter and sulphur dioxide (SO2) associated with combustion of diesel. From market experience, cost effective options for the supply of low emission diesel generators are extremely limited.

Several solutions are available to reduce these emissions during generator use. One option is the use of selective catalytic reduction (SCR), which involves the incorporation of a catalyst into the exhaust system, promoting the conversion of NOx into nitrogen, water and CO2, significantly reducing total NOx emissions. However, this is an expensive option and only performs at full efficiency when a certain operating temperature is reached by the generator, typically from 300°C up to 600°C. These temperatures may not be reached when generators are required to operate over brief time periods, for example, for routine testing and maintenance.

The use of HVO offers a more affordable alternative as it can be blended with diesel in any proportion, allowing it to be easily integrated into many existing standby generator systems. It can be used in tandem with SCR to offer increased reductions in emissions of NOx and particulates.

Present and Future Use

The uptake of HVO has been promising, with increased demand worldwide, and several UK suppliers are now offering this as a standard product. This is boosted by its ability to be used in many existing generator systems, reducing upfront capital expenditure. Its adoption is currently limited by its geographically restricted supply chain and higher cost relative to standard diesel alternatives. Supply chains are developing to serve increased market demand, with this being a key requirement if the adoption of HVO becomes more commonplace in the journey towards reducing carbon emissions.

How can Cundall help?

The Cundall Air Quality team are experienced in conducting point source dispersion modelling of generator emissions to provide detailed assessments of operational impacts for both permitting and planning applications. Dispersion modelling of generator emissions to compare the use of diesel and HVO fuels, as well as considering the incorporation of SCR, can offer valuable insight into the expected reductions in NOx and particulate matter concentrations at nearby receptors. Cundall has experience in economic damage cost analysis to estimate societal costs associated with changes in pollutant emissions. Mitigation measures may be able to offset some of the damage costs, subject to agreement with the Local Authority. By demonstrating a reduction in emissions using HVO and/or application of SCR, and therefore agreeing on a lower damage cost, substantial cost savings can be delivered on behalf of the developer.

Please contact the Cundall Air Quality team for further information.