What is Biofuel?
A biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases. Biofuels are gaining increased public and scientific attention, driven by factors such as oil price hikes and the need for increased energy security. However, according to the European Environment Agency, biofuels do not address global warming concerns.
Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn or sugarcane. Cellulosic biomass, derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Current plant design does not provide for converting the lignin portion of plant raw materials to fuel components by fermentation.
Biodiesel is made from vegetable oils and animal fats. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using trans-esterification and is the most common biofuel in Europe.
In 2010, worldwide biofuel production reached 105 billion litres (28 billion gallons US), up 17% from 2009, and biofuels provided 2.7% of the world’s fuels for road transport, a contribution largely made up of ethanol and biodiesel. Global ethanol fuel production reached 86 billion litres (23 billion gallons US) in 2010, with the United States and Brazil as the world’s top producers, accounting together for 90% of global production. The world’s largest biodiesel producer is the European Union, accounting for 53% of all biodiesel production in 2010. As of 2011, mandates for blending biofuels exist in 31 countries at the national level and in 29 states or provinces. According to the International Energy Agency, biofuels have the potential to meet more than a quarter of world demand for transportation fuels by 2050.
In a report by Robert J. Simon (http://www.allenfiltersinc.com/howtocontrolmicroorganismsindieselfuel.cfm) in regards to bacteria corrosion and the problems relating to internal steel within storage tanks, the author highlights the problem:
“Microbes in petrodiesel and biodiesel products can mean serious problems. They can cause product deterioration, sludge formation, and corrosion of tanks and pipework. The fuel that presents the most serious problems in terms of microbiological growth is diesel fuel, whether it is petrodiesel or worse, biodiesel. Conditions in diesel fuel storage containers are ideal for significant and rapid growth. Biodiesel is subject to even more microbial contamination than petrodiesel.
Contamination in Storage Tanks
Even in the best maintained tanks, microbial contamination can be a problem. Tanks that hold strategic reserves are particularly vulnerable and large quantities of microbial growth have been reported. One of the essential substances for microbiological growth is water:
- Water that is dissolved in the fuel will condense on tank walls
- Moisture in the air that enters through vents or floating tank lids
- Poorly designed tanks that do not drain properly allow water to remain in the bottom
- High water content of “new” diesel fuel that is delivered
Even the allowable amount of moisture in new diesel is enough to start a microbiological colony growing. The resulting cell metabolism then produces more water and the cycle continues. Since oxygen is usually present, all ingredients needed for rapid microbiological growth are present including the carbon source from diesel.
The equation of life and evolution is:
Bacteria + Water + Oxygen –> More Bacteria + Carbon Dioxide + More water
Even if oxygen were not present, such facultative organisms such as Bacillus and anaerobes such as sulfur-reducing bacteria (SRB) continue to thrive and corrode tank material.
When microorganisms are subjected to a strong magnetic flux field, the ability of the protein channels that maintain the electrical and chemical potential across the cell membrane is torn apart and the microorganism is destroyed. The resulting debris settles to the bottom of the tank or can be filtered out. This is an expensive and often impractical method.
Biocides are expensive and highly toxic chemicals that have potential for serious environmental contamination. The fallout of dead cells creates sludge in the bottom of the tank, clogging fuel lines and filters alike. Over time, the microorganisms develop a resistance to any biocide through the process of evolution and other toxins must be brought to bear.”
Robert J. Simpson
Biofuel by its nature is biodegradeable – and the same characteristics that make biofuel attractive to biodegrading organisms, also make biofuel attractive to Sulphate Reducing Bacteria (SRB’s). Sulphate Reducing Bacteria are the cause of damage to many fuel storage tanks.
Biofuel Contamination from Bacterial or Fungal growth can have serious consequences for any system running on Biofuels. Primarily the contamination can cause damage to internal steel within storage tanks. Damage can become exponentially worse given increases in water content and climatic conditions.
The introduction of the FAME standard has meant a steady rise in the ubiquity of biofuels. The nature of biofuel increases the likelihood of microbial contamination due to the nature of its contents. When put into bunkering terminals and marine environments, the prevalence of water and heat from engines, components and fuel delivery systems creates almost perfect environmental conditions for bacterial and fungal colony production.
The solution to this age old problem of bacterial corrosion is to apply a solvent free resin resistant to the stored fuel. Solvent free resin can be applied from 1000 microns to 4000 microns in one application however when applied to blasted steel a nominal thickness of 1000 microns (1mm) is sufficient to protect the steel and additional resin makes no difference to chemical resistance within the internal surface of the storage tank. Statements in regard to structural strength of a 4mm thick coating of known solvent free resin is questionable (and could be considered a waste of funds) as the resin cannot replace the strength of the existing steel tank, however the resin applied up to 1mm nominal thickness will achieve full chemical resistance necessary and also reduce bacteria corrosion attack internally to zero.
Once storage tank(s) have been fully protected de-watering can be performed to remove any excess water which has separated at the lower level of the tank as required, care should be taken not to mechanically damage the existing coating and where possible only plastic hoses without metal edges should be inserted internally to remove excess water which may have built up over time.
Additional protection can be achieved by installing a double skin liner once the original steel has been refurbished and coated with a solvent free resin. The space created between the original steel wall and the new liner installed is called an interstice and this space can be monitored by use of a vacuum or pressure gauge / unit.
The term “pressure” is used to describe either negative (below atmospheric) or positive (above atmospheric) pressure. Positive pressure is called “gauge pressure”. The term “vacuum” is used to describe the region of pressure below one atmosphere of pressure, also referred to as negative pressure. When speaking of vacuum, one must remember it as the opposite of pressure; high vacuum means low pressure.
The purpose of monitoring storage tanks is good management and provides environmental control; clients can influence and contain a potential disaster. If internal damage of the double skin liner is sustained or the external steel eroded/corroded the vacuum pressure in the interstice would dissipate and initiate an alarm to alert the client of an issue with that particular tank ensuring action is taken to ensure stored fuel does not leak into ground soil or water ways.
Leak detection hardware and software can be linked to send a response if an alarm initiated to most locations nominated by client (World Wide) depending on what system is purchased and installed. Monitoring gauges and units can link to most known systems already installed on forecourts or within tank storage depots, refineries etc.
Biofuels are here to stay for the foreseeable future therefore storage tank protection is necessary to protect the environment and client’s assets.
Tank replacement is costly without the downtime necessary to remove and install new, however it is a relatively simple process to ensure the internal of the tank are fully protected using 21st Century technology (solvent free resins applied through plural component heated spray pump equipment) and experienced and trusted companies such as Fuelvac, a division of ABFAD Ltd who have perfected the application of these resins since 2001.