Biofuels Development at Stellenbosch University

Recently we were involved with the development of an online interactive site to help broaden the public understanding of biofuels in South Africa and our involvement with this particular field here at Stellenbosch University. If you are interested in looking at the site to see what we are doing please click on either the link or picture below to take you to the site.

Click here to go to interactive website

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Comparison between Bio-ethanol and gasoline

In November 2010 I visited Brazil and was interested to see their use of Bio-ethanol as a fuel for transport. I was amazed to see ethanol fuel pumps at all the petrol stations and to see so many flexi-fuel vehicles driving around (Flexi-fuel vehicles are able to run on both gasoline and fuel ethanol at varying mixtures depending on the particular flex engine in the motor car). For me this was very interesting as here at home in South Africa we have only the option of running our cars on Diesel and gasoline/petrol.

So how does fuel ethanol (bio-ethanol) compare to gasoline? Well Bio-ethanol has a higher octane number, broader flammability limits, higher flame speeds and higher heats of vaporisation than gasoline. These properties allow for a higher compression ratio, shorter burn time, and an engine which burns much leaner. These all suggest that ethanol should be better than gasoline in an internal combustion engine (Balat M. et al, 2007)

Disadvantages of bioethanol include its lower energy density than gasoline (Bioethanol has 66% the energy of gasoline), its corrosiveness, low flame luminosity, low vapor pressure (which makes cold starts difficult), miscibility with water, and toxicity to ecosystems (Balat M., et al, 2007)

So what did the locals have to say about ethanol as a fuel? Well I met many people in Brazil who use ethanol in their cars and for them the major drawcard is that it is much cheaper to purchase than gasoline. Although on the down side many of them said that their cars did not perform as well on ethanol as on gasoline. They found that there cars consumed slightly more fuel per 100km and that there was sligthly less power available for acceleration when they used ethanol instead of gasoline.

So the question for me as to whether I would use ethanol over gasoline based on the above thoughts above is one that requires some more thought. I think I would most definately use ethanol based on the fact that it is much cheaper and it is theoretically better for my cars engine. I think most people would be prepared to sacrifice a lower petrol consumption and less power because of this but my main concern with the use of Bio-ethanol would be whether it is a more sustainable fuel than gasoline. But since sustainability is another entire question I will leave that for another post.

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Raw Materials for Lignofuels

Raw materials for lignocellulosic ethanol currently fall into four basic categories. These include hardwoods, softwoods, grasses and agricultural residues. The benefit of these over fossil fuels is that they can be found in abundance.

For me agricultural residues are the most promising as they are already available in large quantities mainly as a byproduct from agricultural farming practices and would not require further agricultural land to produce. They also do not compete with food crops, which is one of the biggest concerns that biofuel production faces. Examples of these residues include corn stover, sugarcane bagasse, wheat straw and sweet sorghum bagasse to name a few.

In many cases agricultural residues are normally burnt directly in boilers to provide energy for steam generation. Although this is a cheap form of energy, the conversion of these residues to bio-ethanol (for example) would add value to the residue which would mean that the residue could then be sold as a value added by-product by farmers alongside the crop being grown. In South Africa for example, where farmers are currently giving up on farming due to the fact that it costs more to produce their crop than what they are being offered for it, they would benefit from value being added to one of their waste products.

Triticale (Hyrbid between wheat and rye)

Triticale - a hybrid of wheat and rye

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What is Lignocellulose

What is lignocellulose? Lignocellulose refers to the specific structure of biomass. The main constituents of lignocellulosic biomass comprises lignin, hemicellulose and cellulose. This is a complex structure in which the cellulose is surrounded by a monolayer of hemicellulose and embedded in a matrix of hemicellulose and lignin. Furthermore lignin specifically creates a barrier to enzymatic attack while the highly crystalline structure of cellulose is insoluble in water while the hemicellulose and lignin create a protective sheath around the cellulose. This structure can be seen in the image below.
This structure of lignocellulose therefore plays a huge role in inhibiting degradation of the hemicellulose and cellulose structure to monomeric sugars which is necessary to effectively convert biomass into ethanol. Processing of lignocellulose is therefore essential for the conversion of lignocellulosic biomass to biofuel such as bio-ethanol.

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Steam Gun Arrival

Steamgun? What is that? This is a piece of equipment that is used in preatreatment of biomass so that Bio-ethanol can be produced. We have one arriving here early next week which is to be incorparated into our lignocellulosic research facilites.

So how does it work and what is its purpose? Let me start with its purpose. As I’ve mentioned it is used in pretreatment which in short opens up the biomass structure to  enzymatic attcack. Once pretreated, enzymes are able to efficiently attack the structure of the biomass and convert it into fermentable sugars. The fermentable sugars can then be fermented into bio-ethanol. Without pretreatment the structure of the biomass is basically inpenetrable and immune to enzymatic attack which results in extremely low ethanol yields.

So how does the steamgun pretreat the biomass material? It achieves this by placing the biomass under high pressure and temperature through steam addition to the material for a certain period of time. At the end of the pretreatment the pressure is suddenly released which cause the material to explode making it more accessible to enzymatic attack. This is in short how the steamgun works but I will have to explain it a bit more in detail the effect and advantages of pretreatment technologies. Hopefully soon I will upload pictures of our new steamgun.

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Biofuel Technology

Currently biofuel falls into two general technology cateregories. These are first and second generation biofuels. First generation biofuel’s are produced from food or energy crops such as sugarcane, corn, maize and sorghum and compete directly with food production. Second generation biofuel on the otherhand is primarily produced from biomass that is not used for food production. For example, the biomass used  in second generation bio-ethanol production comes from agricultural residues, hardwoods, softwoods and grasses. These are what are known as lignocellulosic materials which is the scientific  name refering to the structure of these sources.

These types of materials are the way forward for bio-ethanol production as they do not compete with food and energy crops. Agricultural residues specifically are interesting to me as they are the residues left over after processing. An example of this is bagasse which is the residue from sucar cane processing which is typically burnt to supply energy to a sugar cane plant and which results in large releases of CO2. Producing bio-ethanol from bagasse is therefore an interesting and important alternative which needs to be looked at.

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South Africa vs. Brazil

So what are the factors that have contributed to Brazil being the second largest producer of Bio-ethanol (they currently produce 30-35% of the world’s ethanol) after the USA. I mean they have a similar climate to us here in South Africa, they are also a third world country and have an economy that is similar to ours. And yet South Africa is far behind Brazil in terms of Bio-ethanol production.

The main reason for their success come during the oil crisis in 1973 when the Brazilian government implemented what was known as the “Proalcohol” or “National alcohol program”, which was hoped to move Brazil towards energy independance. This program was extremely effective in that today bio-ethanol accounts for around 50% of their gasoline/petrol consumption.

So what made this program so successful:
1. Tax incentives and government subsidies for bioethanol producers.
2. Mandatory mixing of ethanol with petrol, which today is set at 1:3 (E25)
3. Development of flexi-fuel vehicles which can run on any proportion of ethanol:petrol

Interestly enough I was reading the other day on the Department of Minerals and Energy’s website and was suprised to find that bio-ethanol producers in South Africa qualify for a 100% tax return on there bio-ethanol sales which works out to around R1.20 per litre of bio-ethanol sold. I was also interested to find out that in their white paper on renewable energy for 2013, they aim at making it mandatory for petrol to contain 8 – 10% bio-ethanol.

So where does that leave South Africa’s Bio-ethanol economy? Personally taking Brazil as an example, I think in a extremely promising situation and I am looking forward to seeing what happens. A move towards independance from fossil fuels and the price of oil is in my opinion a good one.

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