Biofuels

 Biofuels

Introduction

Legislation now in force means fuel suppliers must ensure that a target percentage of their total road fuel sales are biofuels. The target percentage starts at 2.5% by volume in 2008/09 rising to 5% by volume in 2010/11

Standard petrol containing ethanol, or diesel are commonly referred to as E5 and B5 (for petrol and diesel blends respectively), but both can continued to be retailed as EN 228 and EN 590 diesel respectively. (I.e. as the current standard)

Things to be aware of...

 Although E5 and B5 remain within the requirements of EN 228 and EN 590 respectively, there are certain features of these fuels that need to be understood.

  Phase separation

 Unlike petrol, ethanol is highly soluble in water. When the water content of the E5 blend reaches a critical level the ethanol component and associated water will separate from the E5 blend and form an ethanol/water phase. This will accumulate at the bottom of a tank leaving petrol (without the ethanol component) in the upper layer. This is known as phase separation. If phase separation occurs the process is practically irreversible. In most cases all the tank contents will need to be scrapped and taken off site for appropriate handling as a hazardous waste.

Solvent properties

The solvent properties of E5 and B5 can have a cleaning effect on existing storage systems. This can cause a softening and loosening of any organic residues, dirt or scale present in the tank system. This loosening can bring this material into a suspended state, and can therefore increase the risk of filter blockage. This is particularly the case with B5, which contains chemicals used commonly as degreasing agents.

Electrical conductivity and corrosion

Because of the molecular composition of ethanol and FAME (fatty acid methyl esters) and their stronger association with water, E5 and B5 have a greater electrical conductivity than standard gasoline and diesel respectively (E5 more so than B5). The bio component present in the blend can increase the risk of corrosion in existing filling station systems form galvanic and electrolytic reactions where particular material combinations may be present. This can in addition increase the risk of pump filter blockage.

Microbial growth

Bacteria, yeasts and moulds can enter a filling station storage system through the distribution chain, via tanks, pipelines, filters, water and air. It is in the water phase that microbes survive, drawing nutrients from the fuel phase. With the addition of the FAME component in B5 blends, the nutrient sources available for microbes will increase and contamination may be more likely to occur. Microbial growth in the water phase can exacerbate localised corrosion, which may result in the blocking of dispense filters and fuel lines.

ESSENTIAL PREPARATION BEFORE THE INTRODUCTION OF E5 AND B5

Firstly, it is necessary to ensure all the materials and components used – tanks, lines, valves, flanges seals, gaskets are compatible with the new fuels. This MUST be checked and assurance provided by a competent person or the original equipment manufacturer.

It is advisable for the station operator to acquire an average flow rate for the associated pumps prior to the introduction of the new fuels to use as a bench mark to use as a comparison for any future pump issues.