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Biofuels Production
24 October 2008
Biofuels is an important factor in an active energy policy which seeks to optimise energy use. It does this by safeguarding the energy supplies needed to ensure socioeconomic growth and to promote sustainability.
Renewable energy sources and energy efficiency both play a significant role in the safeguarding of the world’s energy supplies. Many countries worldwide have adopted a series of directives to promote renewable energy sources and to encourage energy efficiency. These directives set legislative framework action to meet a range of energy objectives in sectors such as heating, electricity and transport.
The biofuels directive aims to promote the substitution of conventional transport fuels such as diesel and petrol (derived from oil), with biofuels such as biodiesel and bioethanol (derived from agricultural crops). Because of their non-fossil origin, biofuels are better for the environment and they help countries to meet their climate change commitments. The EU biofuels directive sets indicative targets for the biofuel share of all transport fuels at 2% by 2005 and 5.75% by 2010. Member States have to set their own targets for biofuel substitution that take account of the overall European targets. Achieving the biofuels targets will affect many other policy areas, such as agriculture, fiscal policy, international trade and employment.
Biodiesel is a substitution for conventional diesel fuel derived from vegetable oils by esterification. Bioethanol is a substitution for a conventional petrol derived from starch or sugar containing raw materials by fermentation and distillation.
Biodiesel Production
In principle, all edible oils and fats (vegetable and animal) can be transformed to biodiesel with the help of specific pumping processes. For fuel-specific properties, pretreated oils from rapeseeds and sunflower seeds are preferred in Europe. However other oils like soya oil, palm and palm kernel oil, coconut oil, cottonseed oil and animal fats are also applicable.
Transesterification is based on the chemical reaction of triglycerides with methanol to form methylesters (biodiesel) and glycerine in the presence of an alkaline catalyst. It takes place in the mixing section, while the subsequent settling section allows for the separation of methylesters (the light phase) from glycerine water (the heavy phase).
A subsequent washing step for the methylester removes minute by-product components and gives a biodiesel which is ready for use after the final drying stage. The surplus methanol contained in the glycerine water is removed in a rectification column, which yields methanol in a condition and purity ready for use.
To achieve pharmaceutical grade or technical grade glycerine further stages are needed, including chemical treatment, evaporation, distillation and bleaching.
The biodiesel production process involves the following steps:
Transesterification
Pump type needed: Centrifugal
Before transesterification, methanol is mixed with the catalyst. Oil and methanol then react in several stages to fatty acid methyl ester.
Separating biodiesel/glycerine
Pump type needed: Centrifugal
With the process of neutralisation, the watery state is separated from the organic state. The watery state is pumped to the glycerine processing.
Biodiesel washing
Pump type needed: Centrifugal
Biodiesel is washed with water several times in order to remove traces of methanol, sulphuric acid, catalyst and glycerine.
Biodiesel drying
Pump type needed: Centrifugal
During the drying phase the surplus water is removed by distillation. Water-free biodiesel is then pumped to the storage tank.
Glycerine processing
Pump type needed: Centrifugal
Glycerine is purified by evaporation and distillation in order to achieve the required qualities.
Methanol recovery
Pump type needed: Centrifugal
The methanol inside the wash water is recovered by distillation and is then pumped back into the methanol storage tank.
Bioethanol Production
Bioethanol is made by fermentation of renewable feedstocks, followed by distillation and dehydration processes. Typical feedstock materials include (i) starches and cereals e.g. wheat, corn, rye, cassava, potatoes and rice; and (ii) sugars e.g. cane molasses, beet molasses, sugar syrup, fructose and whey.
Raw material for bioethanol is sugar derived in an enzymatic reaction from starch. The fermentation generates ethyl alcohol with the help of yeast. This ethyl alcohol (bioethanol) is then separated by distillation. For petrol-grade bioethanol, the alcohol must be dehydrated raising the concentration of bioethanol to more than 99%.
The by-product of the ethanol process is stillage. It can be used to fuel biogas plants for energy generation, or it can be converted in DDGS – a protein-rich food for animals.
The bioethanol production process involves the following steps:
Slurrification
Pump type needed: Centrifugal
After milling, the mash is liquefied with water and steam, and starch is enzymatically transformed into sugars.
Fermentation
Pump type needed: Centrifugal
The mash is mixed with yeast. The yeast ferments the sugar into alcohol and CO2.
Distillation
Pump type needed: Liquid ring
The mash is cooked and the alcohol evaporates in the column.
Rectification
Pump type needed: Liquid ring
The rectifier concentrates the alcohol.
Dehydration
Pump type needed: Complete vacuum systems
The concentrated bioethanol is dehydrated to an ethanol content of more than 99.9%.
CO2 recovery
Pump type needed: Side channel
The CO2 from fermentation is collected, washed, liquefied and then pumped into a storage tank.
Stillage treatment
Pump type needed: Centrifugal
The remaining stillage is evaporated and then dried.
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