Research into biofuels has been rampant over the last decade largely driven by two factors. First, the ever-increasing specter of global warming demands that the world reduce emissions including those from the transportation sector. Second, regardless of when it occurs and there are a wide range of predictions, oil reserves will run out and a viable alternative infrastructure needs to be in place to ensure a smooth transition between oil/gasoline and these alternatives. Although it may be possible to ease the burden of this transition through mass deployment of electrical and hybrid vehicles, the prospects of mass distribution of electrical airplanes or ships are unlikely. Therefore, the pursuit of the next generation of liquid based fuel remains important.
Currently there are three major avenues of biofuel production each with their own strengths and weaknesses. Proper objective analysis of these strengths and weaknesses in relation to how the world transportation structure will develop in the future is critical to avoiding wasted time, money and effort. Issues that must be weighed are, but not limited to: emission reduction potential, cost, environmental damage, longevity, scalability and technological demands.
Food Stuffs Strengths:
• Technology already exists for production and scale-up;
• Limited energy required;
• Useful by-products such as dried distiller’s grain, bagasse and high quality (not crude) glycerin that can be used in other processes;
Food Stuffs Weaknesses:
• Requires quality soil and cultivated land;
• Due to the land requirement competes with food stock which can increase food prices;
• Inefficient process based on the total amount of energy absorbed by feed stock;
• Based on processing and production method, it may actually increase carbon emissions vs. gasoline when considering a lifecycle analysis;
• Profitability largely based on feed stock price;
• Synthesis ceiling determined by feed stock availability;
• Land requirement reduces longevity;
• Largest efficiency rating of the three methodologies (oil per acre of land);
• High emission reduction potential due to CO2 consumption in addition to fuel replacement;
• Easy growth management;
• Low overhead;
• Low fresh water consumption;
• Increased potential through the use of waste water;
• Depending on the catalyst, potential to produce useful by-products, although does not appear to be in a quantity similar to food stuffs;
• Limited growth and scale-up potential due to heavy CO2 feed requirement to maintain efficiency of production;
• Co-localization requirement for sound economics reduces longevity;
• Limited suitable and cost-effective locations for large processing facilities;
• Lack of scale-up potential for photobioreactors;
• Questions regarding oil extraction technique (although this issue is not a large concern);
• Lots of talk, but no viable commercial level processing scale yet;
• Near limitless feed stock supply;
• Potential to grow feed stock supplies in poor soil on otherwise unusable agricultural land;
• Potential to recycle lignin by-product to reduce initial energy inputs, reducing overall CO2 required for production;
• Exceedingly high energy costs which translate to higher production costs;
• Potential problems with ground cover harvesting with regards to erosion and soil replenishment;
• Very large capital costs for developed scale-up mass development infrastructure;
• Possible questions regarding CO2 reduction due to necessity of feed stock transport;
• No viable commercial level processing scale yet;
General Problems Across the Biofuel Spectrum:
• A vast majority of current and future vehicles would need to be retrofitted with additional accessories to properly operate higher than 20-25% biofuel/gasoline blends; biofuel cars are not currently mass marketed;
• Biofuels possess less energy than gasoline, thus higher biofuel blends will result in lower gas mileage;
• Current gasoline/oil transfer pipeline infrastructure is inappropriate to transport biofuels due to their tendency to absorb moisture dissolving impurities leading to corrosion of the pipe;
When weighing all of the pros and cons for the three different methodologies for biofuel production three conclusions, one for each methodology, can be drawn concerning its use on a global level.
For food stock based biofuels using corn, soybean or sugar beet/cane the process itself may be viable and even widely successful in countries like Brazil, but it does not appear to be sustainable in the long-term. Long-term sustainability is threatened largely by the requirement of high quality soil and agriculture to provide the necessary feedstock for the production of the biofuel. In addition the strain placed on modern fertilizer stocks also raises questions regarding production over the long-term from both a quantity and a cost standpoint.
In short food stock derived biofuels only appear viable in regions where motor vehicle use is small. The fact that mounting evidence demonstrating that biofuels produced from such food stocks may in fact result in a greater release of CO2 and other greenhouse gases begs the question, why continue production at all?
For algae based biofuels, the immediate future looks very promising with advantages in efficiency of production, additional CO2 consumption and low freshwater requirements for processing. However, the chief problem plaguing the future of algae based biofuels is their longevity in an emission-reducing environment. Currently the only viable means to generate economically acceptable biofuels from algae is to co-locate the algae growth region within an environment with excess CO2 far beyond what is currently the average atmospheric concentration. If the location could also provide waste heat and wastewater all the better. The best location has been identified as a coal plant.
Unfortunately in a future environment of emission reduction that excess CO2 from that coal plant will be short-lived as either the plant will be decommissioned to abide by future emission caps or the CO2 will be captured and sequestered. If such action occurs the coal plant is no longer a useful environment for enhanced algae growth limiting the total scale-up potential relative to associated cost. Some have proposed positioning the algae in the coal plant flue instead of using chemical sequestration, but such a process theoretically significantly hampers the total product that can be acquired from that biofuel.
Use of fertilizer to provide essential growth elements to algae is also a concern for the present and the future. Currently algae based biofuel is actually carbon positive instead of carbon neutral or negative because of the fertilizer requirements to stimulate enough growth for profitable scale-up. Although the demands for fertilizer can be somewhat eased by locating the growth region near a waste water facilities, at the moment it is unlikely to conclude that scale-up will be successful if fertilizer is removed to the point of carbon neutrality.
For cellulose-based biofuels, the chief problem is discovering and processing the necessary enzymes to facilitate the breakdown of the cellulose in the feedstock. However, even if those enzymes are discovered and can be produced at economically competitive rates, the question regarding the acquisition of feedstock still remains. Despite the proclamations of vast quantities of potential feedstock for a cellulose-based system, these statements only describe the potential not the feasible. Dedicated collection methodologies will have to be developed and carried out to ensure a continuous and environmental friendly amount of feedstock.
Although there is a fourth method for biofuel production, genetically engineering bacteria most notably E.Coli, both cost and efficiency elements of the process are still in the interim stages, despite initial successes, thus it would be unsuitable to discuss it on equal ground to the above three methodologies. On a side note this method of genetic engineering most closely mirrors the cellulose production pathway. Returning to the three major methodologies overall although there are still some sufficient obstacles ahead, from both longevity and emission reduction standpoints it appears that cellulose-based biofuel production has measure of superiority over the other two methodologies.