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Introduction to Algae Biofuels and Crude Oil Production
First generation biofuels normally require a large plot of ground to grow the crops that produce the oils used in the process. This has led to the some of the world’s poorest nations having to decide on a livelihood of growing crops for this purpose, living on the minimum food sustainability or using all the crops as food.
However Second Generation bio-fuels use only non-food parts of plants such as stems, leaves and husks. Biofuels from algae fall into this category with modern methods cultivating algae for bio-fuels producing much more oil than other bio-crops.
Algae can be in the form of microscopic plankton which floats in water or the larger version of seaweed which clings to the rocks on our coasts.
I well remember when I was a lad growing up in Bangor Northern Ireland over fifty years ago. In those days we used to gather a few sackful of seaweed from the beach, especially after a storm, and put it round the potato beds in the garden. My father swore by it for fertilizing and keeping potato scab at bay.
On the way back home, walking along the sea wall at the harbor we purchased a bag of Dulse (a type of dried red seaweed) for a halfpenny. I suppose that was about a cent in USA money. This was chewed and swallowed with great relish, but because of the salt content you were gulping water the rest of the day.
Anyway I am rambling on, so we continue with a look at crude oil fuels. Conventional petrol and diesel is produced from crude oil which is extracted from underground reservoirs on land as well as offshore. Once the crude has been received at an oil refinery it can be processed into many products including diesel and petrol. (See my articles on Oil & Gas Production and Refining)
This is an article on fuels used in internal combustion engines, comparing biofuels obtained from algae with conventional fuels obtained from the refining of crude oil.
We begin by having a look at how both types of fuel are produced, and refined going on to examine other criteria such as costs involved in production and processing.
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Categories of Algae Cultivated for Algafuel
Algae can be divided into two categories, microalgae such as phytoplankton and, macroalgae with normal seaweed being example.
The algae within both groups have proved relatively hard to cultivate due to viruses and spores which they pick up from the ambient atmosphere. Therefore the best oil producing strains have been especially bred to be more resistant to cross-contamination.
There are three prominent types of algae used to produce biofuels:
- Brown Algae – Contains both Chlorophyll's a and c
- Green Algae - Contains both Chlorophyll's a and b
- Red Algae – Contains only Chlorophyll a.
The chlorophyll content is very important as this is the pigment that the algae use to capture light in the process of photosynthesis. Algae contain fatty acids, cellulose, carbohydrates and proteins, with the percentages of these properties varying within the different types of algae, and which can be extracted and processed into several types of algafuels.
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Algae Cultivation Methods
There are numerous methods of cultivation the two currently used ones listed below.
- Ponds and lakes
For the purpose of this article, we shall examine a vertical tubed photobioreactor algae cultivation system.
Photobioreactor Cultivation of Algae
A bioreactor consists of nest of vertical clear tubes constructed from acrylic, which has all the advantages of glass but with superior qualities.
The bioreactor is closed system that prevents the algae from cross contamination with other algae, but means that it has to be artificially fed with nutrients, CO2, and sterilized water.
The algae, water, and nutrients are stored in a feed tank and are continuously circulated through the bioreactor tubes by a diaphragm pump which also injects CO2 and/or air into the system.
There are two sensors built into the bioreactor system, one shows the amount of oxygen which has built up. The other one determining when the cultivation process is complete, the liquid then fed through the harvesting system to gather the algae.
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Harvesting Algae and Oil Extraction
Harvesting Algae and Oil Extraction
This starts with pretreatment using an algae filtering system which automatically removes the algae that is ready for harvesting, returning the unripe remainder back into the feed tank.
Following this the algae is separated from the water and this is normally achieved by using a centrifuge.
In the standard method, after dewatering, algae are dried and fed into a screw press, extracting their thick oil known as algafuel. This is too viscous to use as an additive or a replacement diesel fuel is converted to biodiesel by transesterification which basically involves adding a solution such as sodium hydroxide to the algafuel and letting the solution settle. This leaves biodiesel floating on top of glycerin from where the biodiesel is removed and filtered, while the glycerin is sold as a by-product with the profits going towards the conversion process.
Research and development of algae fuels has produced a biobutanol fuel known as Solagal Fuel. This biofuel has much the same fuel energy as (petrol 32MJ/l, biobutanol 29MJ/l) and can reputedly be used directly or as an additive to petrol engines.
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Microalgae are the preferred category for algaculture and these can be grown in a photobioreactor, which consists of a nest of acrylic tubes. These are formed in a closed circuit the nutrients, CO2, water and algae are supplied to the tubes from a storage tank being circulated by a pump. Sensors indicate when the algae are ready for harvesting and this is carried out by various filtration and centrifuging methods to separate the algae from the liquid. It is then dried and the resultant algae cake pressed to extract the oil. This undergoes transesterification to convert it to biodiesel and other biofuels depending on the type of algae and their component used.
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Fuels Produced From Crude Oil
Crude oil is extracted from reservoirs underground and subsea, using roughly the same methods, so below we shall look at the subsea extraction method.
Offshore oil is extracted from the reservoir via a well up to a production platform. Here it undergoes treatment to remove water, gas, sand and grit before being pumped ashore through subsea pipelines. From here it is transferred by pipe or tankers to an oil refinery where it undergoes many processes to produce numerous liquids used by today’s industries as well as petrol and diesel oil.
On arrival at the refinery, the crude is treated to remove any remaining salts, sediment, and water. It is then subjected to elevated temperatures before entering a vertical distillation unit where it flashes off into gases. The distillation unit consists of a vertical column containing numerous horizontal perforated trays. These trays are fixed at precise locations, drawing off and condensing different fractions from the gases as they pass upwards through the column.
Diesel is drawn off from one of these trays and undergoes hydrogen/catalytic processing to remove the sulphur and nitrogen contents. The diesel oil is then stored ready for distribution by tankers to the various fuel outlets.
Heavy and light naphtha are drawn off from the gases at the top trays of the distillation column, naphtha being the main fraction processed to produce petroleum as we know it.
The naphtha processes are quite complicated involving initially hydro-cracking to remove sulphur and nitrogen then catalytic/chloride treatment followed by scrubbing to remove acid, followed by final stabilization. It is fed into the petroleum blending and octane unit after which it is ready for distribution to the various fuel outlets.
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Comparison of Algafuel and Fossil Fuel by Criteria
In this section we shall compare fuel refined from crude oil to biofuel from algae, using the following criteria;
Fuel Produced from Crude
The extraction of crude oil from subsea reservoirs is a hazardous process, often carried out in a hostile environment, although modern methods have become more efficient and safety of personnel is one of the various oil companies’ priorities.
Notwithstanding, personnel are still being injured with loss of life through accidents on the platforms and in travelling to and from the structures by helicopter.
Once the oil reaches the refinery it is processed into numerous fuels and liquids used in industry which produce obnoxious and odorous fumes being slightly offset by the removal of sulphur and lead from domestic fuels to achieve low sulphur diesel and lead-free petrol.
There are always liquid and gas leaks no matter how good the plant maintenance is, so personnel are exposed to danger of burns from acids or breathing problems from gas inhalation.
Transportation of diesel and petrol to the pumps by tanker usually causes few problems although the tankers do carry hazardous mixture notice plates.
The production and transportation of crude oil in seagoing oil tankers is closely monitored for air and water pollution. However, accidents do happen causing oil spills around our coastlines which result in total devastation the local environment, flora and fauna.
Oil is now being extracted from unconventional sources such as shale and oil sands. This process can emit four times as much greenhouse gas to the atmosphere as conventional oil production, as well as leaving behind massive tailings of gangue.
Finally, oil has allegedly been found to exist under the ice in the Arctic Ocean with Russia, Denmark, Canada and USA lining up to make a claim on it.
Hopefully public opinion will prevent the exploitation of oil from this area as exploration, production and transporting crude oil from under the melting ice can only spell an environmental disaster.
The price of petrol and diesel we pay at the pumps is governed by the cost of a barrel of crude on the open market. Today it is around $80 a barrel, which reflects a price of $7 a gallon in the UK and $2.3 a gallon in the USA, the difference in price being the tax or duty levied by the respective governments.
However because of other government measures, vehicles are becoming more efficient, due to build methods and engine development, so higher MPG figures are being achieved, which offsets the cost of the fuels.
Crude oil has taken millions of years to develop, yet within a hundred short years we have exploited it to such an extent that according to oil experts, the world's conventional crude oil production is due to peak this decade. (USA oil production peaked as long ago as 1970 with the UK North Sea oil production peaking in 1999).
Many experts predict that oil will run out completely by 2050 and this includes the world’s top four oil producing nations; Iraq, Iran, Kuwait, and Saudi Arabia, as well as the new fields under development in the South China Seas.
This will make the production of oil from unconventional sources and the polar regions previously mentioned a more lucrative proposition with its associated damage to the environment.
Or will it? Maybe the production of biofuels from algae will enable the crude oil to be eked out a little longer; or eventually replace it. We shall be able to decide after we have a look at how the algafuel meets the same criteria in the following section.
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Oil reservoirs were formed millions of years ago from the bodies of miniature plankton which fell to the bottom of the sea. These layers were covered in sediment, compressed, heated and converted to hydrocarbons. When an oil reservoir is discovered offshore, a well is drilled into it, and a production platform is then erected and connected to the well. The oil is pushed up the well by reservoir pressure and is processed on the platform to remove water, sand and gas. It is then pumped ashore through subsea pipelines and transferred to an oil refinery. Here the crude oil is processed into many spirits used by today's industries, as well as the petrol and diesel fuels we use in our automobiles.
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Biofuels Produced from Algae
Biofuels have been traditionally produced from first generation crops such as maize or soybeans at the expense of the indigenous of the poorer nations who had to decide whether grow their crops for food or sell them to biofuel producers. However algae which is a second generation fuel (produced from crops not used as food supplies) is being commercially cultivated for the sole purpose of producing biofuels which can supplement conventional diesel and petrol supplies.
The current process combines the cultivation of microalgae with harvesting and extraction of the oil using a photobioreactor. This piece of equipment simulates photosynthesis by circulating algae, nutrients, (Phosphate and Nitrogen) water and CO2 through a set of clear tubes which allows the essential sun radiation to penetrate the liquid providing necessary energy.
The bioreactor absorbs CO2 into the system but because it is a totally closed circuit, any escape of liquid or gas to the environment is averted (apart from oxygen which is regularly bled off to atmosphere). Algae cultivation does not create any noxious fumes to harm the employees, although a wet earthy/seaweed odor is always present at the process plant. The only risk of pollution is in the transesterification process where acids are used, and in the filtration and cleaning of the biodiesel where water is used. However the water is recycled back to the system so risks to personnel and the environment are minimal.
The costs involved in production and distribution of biofuel from algae have been estimated at up to eight times that of fossil fuels, but experts believe with research and development, biofuels from algae can become competitive with the conventional fuels. However, recently in the USA, the Defense Advanced Research Projects Agency (DARPA) announced that it is to go ahead with production of jet fuel from algae which will cost between $2 and $5 per gallon.
Cultivation of algae for conversion to biofuels is a sustainable source of renewable energy.
It does require a certain amount of energy to operate the bioreactor and to produce the nutrients and CO2 required in a closed circuit system such as we have described. However this energy can minimized by cultivating the algae by an alternative method such an open pond process, although this is not as efficient as bioreactor cultivation.
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We have examined in detail two very different methods of producing fuels, comparing them using the same criteria.
The extraction of crude oil is a dangerous and hazardous occupation which can cause pollution to land and sea. However the fuels processed from crude are convenient, efficient and relatively affordable for use in our automobiles with air pollution being reduced by the removal of sulphur and lead at the refining stages, and by the use of catalytic converters in the vehicle exhaust system.
However, these hydrocarbon-derived fuels when combusted continue to exacerbate the already high volumes of greenhouse gasses, CO2 in particular, which cause global warming and lead to climate change.
The UK and USA have reached their oil production peak and are now dependent on importing oil from other countries, some of which not at all friendly and could cut supplies at any time. On top of this, according to geologists and oil experts, oil is due to run out before the end of this century.
So we should be looking towards developing a biofuel to replace the conventional fossil fuels.
The production of algae fuels can achieve this being a sustainable, renewable and safe biofuel which can be added to diesel and petrol and with recent research will soon be able to be used directly in spark and compression ignition engines.
Algae biofuels cause no pollution in processing- quite the opposite, by removing CO2 and adding oxygen to the atmosphere. Recent investigations into using algae cultivation as a means of removing CO2 from industrial fume emissions has been very well received by environmentalists worldwide.
So that just leaves the cost difference, which at present is a stumbling block, but in the light of rising crude oil prices, along with projected shortages, the change to using algae biofuels in our vehicles might not be too far away. It really is in all our interests to get involved in the algae biofuels vs. fossil fuels debate, and hopefully this article will have helped towards this end.
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